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< ol class = "chapter" > < li class = "chapter-item expanded affix " > < a href = "index.html" > chainerror< / a > < / li > < li class = "chapter-item expanded " > < a href = "tutorial1.html" > < strong aria-hidden = "true" > 1.< / strong > Simple String Errors< / a > < / li > < li class = "chapter-item expanded " > < a href = "tutorial2.html" > < strong aria-hidden = "true" > 2.< / strong > Simple Chained String Errors< / a > < / li > < li class = "chapter-item expanded " > < a href = "tutorial3.html" > < strong aria-hidden = "true" > 3.< / strong > Mapping Errors< / a > < / li > < li class = "chapter-item expanded " > < a href = "tutorial4.html" > < strong aria-hidden = "true" > 4.< / strong > More Information< / a > < / li > < li class = "chapter-item expanded " > < a href = "tutorial5.html" > < strong aria-hidden = "true" > 5.< / strong > The source() of Errors< / a > < / li > < li class = "chapter-item expanded " > < a href = "tutorial6.html" > < strong aria-hidden = "true" > 6.< / strong > Downcast the Errors< / a > < / li > < li class = "chapter-item expanded " > < a href = "tutorial7.html" > < strong aria-hidden = "true" > 7.< / strong > The root cause of all Errors< / a > < / li > < li class = "chapter-item expanded " > < a href = "tutorial8.html" > < strong aria-hidden = "true" > 8.< / strong > Finding an Error cause< / a > < / li > < li class = "chapter-item expanded " > < a href = "tutorial9.html" > < strong aria-hidden = "true" > 9.< / strong > Selective Error Handling< / a > < / li > < li class = "chapter-item expanded " > < a href = "tutorial10.html" > < strong aria-hidden = "true" > 10.< / strong > ErrorKind to the rescue< / a > < / li > < li class = "chapter-item expanded " > < a href = "tutorial11.html" > < strong aria-hidden = "true" > 11.< / strong > Debug for the ErrorKind< / a > < / li > < li class = "chapter-item expanded " > < a href = "tutorial12.html" > < strong aria-hidden = "true" > 12.< / strong > Deref for the ErrorKind< / a > < / li > < li class = "chapter-item expanded " > < a href = "tutorial13.html" > < strong aria-hidden = "true" > 13.< / strong > Writing a library< / a > < / li > < li class = "chapter-item expanded " > < a href = "tutorial14.html" > < strong aria-hidden = "true" > 14.< / strong > Going back to std< / a > < / li > < li class = "chapter-item expanded affix " > < a href = "end.html" > The End< / a > < / li > < / ol >
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< main >
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< p > < a href = "https://crates.io/crates/chainerror" > < img src = "https://img.shields.io/crates/v/chainerror.svg" alt = "Crate" / > < / a >
< a href = "https://docs.rs/chainerror/" > < img src = "https://img.shields.io/badge/api-rustdoc-blue.svg" alt = "Rust Documentation" / > < / a >
< a href = "https://coveralls.io/github/haraldh/chainerror?branch=master" > < img src = "https://coveralls.io/repos/github/haraldh/chainerror/badge.svg?branch=master" alt = "Coverage Status" / > < / a >
< a href = "https://github.com/haraldh/chainerror/actions?query=workflow%3A%22Rust%22" > < img src = "https://github.com/haraldh/chainerror/workflows/Rust/badge.svg" alt = "Workflow Status" / > < / a >
< a href = "https://isitmaintained.com/project/haraldh/chainerror" title = "Average time to resolve an issue" > < img src = "https://isitmaintained.com/badge/resolution/haraldh/chainerror.svg" alt = "Average time to resolve an issue" / > < / a >
< a href = "https://isitmaintained.com/project/haraldh/chainerror" title = "Percentage of issues still open" > < img src = "https://isitmaintained.com/badge/open/haraldh/chainerror.svg" alt = "Percentage of issues still open" / > < / a >
< img src = "https://img.shields.io/badge/maintenance-activly--developed-brightgreen.svg" alt = "Maintenance" / > < / p >
< h1 > < a class = "header" href = "#chainerror" id = "chainerror" > chainerror< / a > < / h1 >
< p > < code > chainerror< / code > provides an error backtrace without doing a real backtrace, so even after you < code > strip< / code > your
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binaries, you still have the error backtrace.< / p >
< p > < code > chainerror< / code > has no dependencies!< / p >
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< p > < code > chainerror< / code > uses < code > .source()< / code > of < code > std::error::Error< / code > along with < code > #[track_caller]< / code > and < code > Location< / code > to provide a nice debug error backtrace.
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It encapsulates all types, which have < code > Display + Debug< / code > and can store the error cause internally.< / p >
< p > Along with the < code > ChainError< T> < / code > struct, < code > chainerror< / code > comes with some useful helper macros to save a lot of typing.< / p >
< p > Debug information is worth it!< / p >
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< h3 > < a class = "header" href = "#features" id = "features" > Features< / a > < / h3 >
< p > < code > display-cause< / code >
: turn on printing a backtrace of the errors in < code > Display< / code > < / p >
< h2 > < a class = "header" href = "#tutorial" id = "tutorial" > Tutorial< / a > < / h2 >
< p > Read the < a href = "https://haraldh.github.io/chainerror/tutorial1.html" > Tutorial< / a > < / p >
< h2 > < a class = "header" href = "#examples" id = "examples" > Examples< / a > < / h2 >
< p > examples/example.rs:< / p >
< pre > < pre class = "playground" > < code class = "language-rust" > // […]
fn main() {
if let Err(e) = func1() {
eprintln!(" \nDebug Error {{:?}}:\n{:?}" , e);
eprintln!(" \nAlternative Debug Error {{:#?}}:\n{:#?}\n" , e);
// […]
}
}
< / code > < / pre > < / pre >
< pre > < code class = "language-console" > $ cargo run -q --example example
Debug Error {:?}:
examples/example.rs:46:13: func1 error calling func2
Caused by:
examples/example.rs:21:13: Func2Error(func2 error: calling func3)
Caused by:
examples/example.rs:14:18: Error reading 'foo.txt'
Caused by:
Kind(NotFound)
Alternative Debug Error {:#?}:
ChainError< example::Func1Error> {
occurrence: Some(
" examples/example.rs:46:13" ,
),
kind: func1 error calling func2,
source: Some(
ChainError< example::Func2Error> {
occurrence: Some(
" examples/example.rs:21:13" ,
),
kind: Func2Error(func2 error: calling func3),
source: Some(
ChainError< alloc::string::String> {
occurrence: Some(
" examples/example.rs:14:18" ,
),
kind: " Error reading \'foo.txt\'" ,
source: Some(
Kind(
NotFound,
),
),
},
),
},
),
}
< / code > < / pre >
< pre > < pre class = "playground" > < code class = "language-rust" >
< span class = "boring" > #![allow(unused)]
< / span > < span class = "boring" > fn main() {
< / span > use chainerror::prelude::v1::*;
use std::error::Error;
use std::io;
use std::result::Result;
fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
Err(io::Error::from(io::ErrorKind::NotFound))?;
Ok(())
}
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fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
let filename = " foo.txt" ;
do_some_io().context(format!(" Error reading '{}'" , filename))?;
Ok(())
}
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fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
func2().context(" func1 error" )?;
Ok(())
}
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if let Err(e) = func1() {
#[cfg(not(windows))]
assert_eq!(
format!(" \n{:?}\n" , e),
r#"
src/lib.rs:21:13: func1 error
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Caused by:
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src/lib.rs:16:18: Error reading 'foo.txt'
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Caused by:
Kind(NotFound)
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" #
);
}
< span class = "boring" > }
< / span > < / code > < / pre > < / pre >
< pre > < pre class = "playground" > < code class = "language-rust" >
< span class = "boring" > #![allow(unused)]
< / span > < span class = "boring" > fn main() {
< / span > use chainerror::prelude::v1::*;
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use std::error::Error;
use std::io;
use std::result::Result;
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fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
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Err(io::Error::from(io::ErrorKind::NotFound))?;
Ok(())
}
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fn func3() -> Result< (), Box< dyn Error + Send + Sync> > {
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let filename = " foo.txt" ;
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do_some_io().context(format!(" Error reading '{}'" , filename))?;
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Ok(())
}
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derive_str_context!(Func2Error);
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fn func2() -> ChainResult< (), Func2Error> {
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func3().context(Func2Error(" func2 error: calling func3" .into()))?;
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Ok(())
}
enum Func1Error {
Func2,
IO(String),
}
impl ::std::fmt::Display for Func1Error {
fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
match self {
Func1Error::Func2 => write!(f, " func1 error calling func2" ),
Func1Error::IO(filename) => write!(f, " Error reading '{}'" , filename),
}
}
}
impl ::std::fmt::Debug for Func1Error {
fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
write!(f, " {}" , self)
}
}
fn func1() -> ChainResult< (), Func1Error> {
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func2().context(Func1Error::Func2)?;
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let filename = String::from(" bar.txt" );
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do_some_io().context(Func1Error::IO(filename))?;
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Ok(())
}
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if let Err(e) = func1() {
assert!(match e.kind() {
Func1Error::Func2 => {
eprintln!(" Main Error Report: func1 error calling func2" );
true
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}
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Func1Error::IO(filename) => {
eprintln!(" Main Error Report: func1 error reading '{}'" , filename);
false
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}
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});
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assert!(e.find_chain_cause::< Func2Error> ().is_some());
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if let Some(e) = e.find_chain_cause::< Func2Error> () {
eprintln!(" \nError reported by Func2Error: {}" , e)
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}
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assert!(e.root_cause().is_some());
if let Some(e) = e.root_cause() {
let io_error = e.downcast_ref::< io::Error> ().unwrap();
eprintln!(" \nThe root cause was: std::io::Error: {:#?}" , io_error);
}
#[cfg(not(windows))]
assert_eq!(
format!(" \n{:?}\n" , e),
r#"
src/lib.rs:48:13: func1 error calling func2
Caused by:
src/lib.rs:23:13: Func2Error(func2 error: calling func3)
Caused by:
src/lib.rs:16:18: Error reading 'foo.txt'
Caused by:
Kind(NotFound)
" #
);
}
< span class = "boring" > }
< / span > < / code > < / pre > < / pre >
< h2 > < a class = "header" href = "#license" id = "license" > License< / a > < / h2 >
< p > Licensed under either of< / p >
< ul >
< li > Apache License, Version 2.0, (< a href = "LICENSE-APACHE" > LICENSE-APACHE< / a > or https://www.apache.org/licenses/LICENSE-2.0)< / li >
< li > MIT license (< a href = "LICENSE-MIT" > LICENSE-MIT< / a > or https://opensource.org/licenses/MIT)< / li >
< / ul >
< p > at your option.< / p >
< h3 > < a class = "header" href = "#contribution" id = "contribution" > Contribution< / a > < / h3 >
< p > Unless you explicitly state otherwise, any contribution intentionally
submitted for inclusion in the work by you, as defined in the Apache-2.0
license, shall be dual licensed as above, without any additional terms or
conditions.< / p >
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< h1 > < a class = "header" href = "#simple-string-errors" id = "simple-string-errors" > Simple String Errors< / a > < / h1 >
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< p > An easy way of doing error handling in rust is by returning < code > String< / code > as a < code > Box< std::error::Error> < / code > .< / p >
< p > If the rust < code > main< / code > function returns an < code > Err()< / code > , this < code > Err()< / code > will be displayed with < code > std::fmt::Debug< / code > .< / p >
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< p > As you can see by running the example (by pressing the " Play" button in upper right of the code block),
this only
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prints out the last < code > Error< / code > .< / p >
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< pre > < code > Error: " func1 error"
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< / code > < / pre >
< p > The next chapters of this tutorial show how < code > chainerror< / code > adds more information
and improves inspecting the sources of an error.< / p >
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< p > You can also run the tutorial examples in the checked out
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< a href = "https://github.com/haraldh/chainerror" > chainerror git repo< / a > .< / p >
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< pre > < code class = "language-console" > $ cargo run -q --example tutorial1
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< / code > < / pre >
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< pre > < pre class = "playground" > < code class = "language-rust" > use std::error::Error;
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use std::io;
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use std::result::Result;
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fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
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Err(io::Error::from(io::ErrorKind::NotFound))?;
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Ok(())
}
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fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
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if let Err(_) = do_some_io() {
Err(" func2 error" )?;
}
Ok(())
}
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fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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if let Err(_) = func2() {
Err(" func1 error" )?;
}
Ok(())
}
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fn main() -> Result< (), Box< dyn Error + Send + Sync> > {
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func1()
}
< / code > < / pre > < / pre >
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< h1 > < a class = "header" href = "#simple-chained-string-errors" id = "simple-chained-string-errors" > Simple Chained String Errors< / a > < / h1 >
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< p > With relatively small changes and the help of the < code > context()< / code > method of the < code > chainerror< / code > crate
the < code > & str< / code > errors are now chained together.< / p >
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< p > Press the play button in the upper right corner and see the nice debug output.< / p >
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< pre > < pre class = "playground" > < code class = "language-rust" > use chainerror::prelude::v1::*;
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use std::error::Error;
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use std::io;
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use std::result::Result;
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fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
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Err(io::Error::from(io::ErrorKind::NotFound))?;
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Ok(())
}
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fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
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if let Err(e) = do_some_io() {
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Err(e).context(" func2 error" )?;
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}
Ok(())
}
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fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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if let Err(e) = func2() {
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Err(e).context(" func1 error" )?;
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}
Ok(())
}
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fn main() -> Result< (), Box< dyn Error + Send + Sync> > {
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func1()
}
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< span class = "boring" > #[allow(dead_code)]
< / span > < span class = "boring" > mod chainerror {
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< / span > < span class = "boring" > //! `chainerror` provides an error backtrace without doing a real backtrace, so even after you `strip` your
< / span > < span class = "boring" > //! binaries, you still have the error backtrace.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `chainerror` has no dependencies!
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
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< / span > < span class = "boring" > //! It encapsulates all types, which have `Display + Debug` and can store the error cause internally.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Along with the `ChainError< T> ` struct, `chainerror` comes with some useful helper macros to save a lot of typing.
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! Debug information is worth it!
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ## Features
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `display-cause`
< / span > < span class = "boring" > //! : turn on printing a backtrace of the errors in `Display`
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Tutorial
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Read the [Tutorial](https://haraldh.github.io/chainerror/tutorial1.html)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Examples
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! examples/example.rs:
< / span > < span class = "boring" > //! ```rust,ignore
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! fn main() {
< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! eprintln!(" \nDebug Error {{:?}}:\n{:?}" , e);
< / span > < span class = "boring" > //! eprintln!(" \nAlternative Debug Error {{:#?}}:\n{:#?}\n" , e);
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```console
< / span > < span class = "boring" > //! $ cargo run -q --example example
< / span > < span class = "boring" > //! Debug Error {:?}:
< / span > < span class = "boring" > //! examples/example.rs:46:13: func1 error calling func2
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:21:13: Func2Error(func2 error: calling func3)
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:14:18: Error reading 'foo.txt'
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Alternative Debug Error {:#?}:
< / span > < span class = "boring" > //! ChainError< example::Func1Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:46:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: func1 error calling func2,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< example::Func2Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:21:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: Func2Error(func2 error: calling func3),
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< alloc::string::String> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:14:18" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: " Error reading \'foo.txt\'" ,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! Kind(
< / span > < span class = "boring" > //! NotFound,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > //! func2().context(" func1 error" )?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:21:13: func1 error
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func3() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! derive_str_context!(Func2Error);
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> ChainResult< (), Func2Error> {
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< / span > < span class = "boring" > //! func3().context(Func2Error(" func2 error: calling func3" .into()))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! enum Func1Error {
< / span > < span class = "boring" > //! Func2,
< / span > < span class = "boring" > //! IO(String),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Display for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! match self {
< / span > < span class = "boring" > //! Func1Error::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > //! Func1Error::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Debug for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! write!(f, " {}" , self)
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> ChainResult< (), Func1Error> {
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< / span > < span class = "boring" > //! func2().context(Func1Error::Func2)?;
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< / span > < span class = "boring" > //! let filename = String::from(" bar.txt" );
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< / span > < span class = "boring" > //! do_some_io().context(Func1Error::IO(filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! assert!(match e.kind() {
< / span > < span class = "boring" > //! Func1Error::Func2 => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error calling func2" );
< / span > < span class = "boring" > //! true
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< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! Func1Error::IO(filename) => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error reading '{}'" , filename);
< / span > < span class = "boring" > //! false
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! });
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! assert!(e.find_chain_cause::< Func2Error> ().is_some());
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Some(e) = e.find_chain_cause::< Func2Error> () {
< / span > < span class = "boring" > //! eprintln!(" \nError reported by Func2Error: {}" , e)
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! assert!(e.root_cause().is_some());
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Some(e) = e.root_cause() {
< / span > < span class = "boring" > //! let io_error = e.downcast_ref::< io::Error> ().unwrap();
< / span > < span class = "boring" > //! eprintln!(" \nThe root cause was: std::io::Error: {:#?}" , io_error);
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:48:13: func1 error calling func2
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:23:13: Func2Error(func2 error: calling func3)
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" >
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< / span > < span class = "boring" > #![deny(clippy::all)]
< / span > < span class = "boring" > #![deny(clippy::integer_arithmetic)]
< / span > < span class = "boring" > #![deny(missing_docs)]
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< / span > < span class = "boring" >
< / span > < span class = "boring" > use std::any::TypeId;
< / span > < span class = "boring" > use std::error::Error;
< / span > < span class = "boring" > use std::fmt::{Debug, Display, Formatter, Result};
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< / span > < span class = "boring" > use std::panic::Location;
< / span > < span class = "boring" >
< / span > < span class = "boring" > pub mod prelude {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub mod v1 {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub use super::super::ChainErrorDown as _;
< / span > < span class = "boring" > pub use super::super::ResultTrait as _;
< / span > < span class = "boring" > pub use super::super::{ChainError, ChainResult};
< / span > < span class = "boring" > pub use crate::{derive_err_kind, derive_str_context};
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > /// chains an inner error kind `T` with a causing error
< / span > < span class = "boring" > pub struct ChainError< T> {
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// convenience type alias
< / span > < span class = "boring" > pub type ChainResult< O, E> = std::result::Result< O, ChainError< E> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> ChainError< T> {
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< / span > < span class = "boring" > /// Use the `context()` or `map_context()` Result methods instead of calling this directly
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< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn new(
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > ) -> Self {
< / span > < span class = "boring" > Self {
< / span > < span class = "boring" > occurrence,
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > error_cause,
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// return the root cause of the error chain, if any exists
< / span > < span class = "boring" > pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.iter().last()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type U, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// assert!(f1err.find_cause::< io::Error> ().is_some());
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< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter().filter_map(Error::downcast_ref::< U> ).next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> `, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooError);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooError> > ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooError> implementation detail
< / span > < span class = "boring" > /// err.find_chain_cause::< FooError> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(Error::downcast_ref::< ChainError< U> > )
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> ` or `U`, if any exists and return `U`
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause` and `find_chain_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooErrorKind);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooErrorKind> > ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_chain_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_cause::< FooErrorKind> ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooErrorKind> implementation detail
< / span > < span class = "boring" > /// err.find_kind_or_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_kind_or_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(|e| {
< / span > < span class = "boring" > e.downcast_ref::< ChainError< U> > ()
< / span > < span class = "boring" > .map(|e| e.kind())
< / span > < span class = "boring" > .or_else(|| e.downcast_ref::< U> ())
< / span > < span class = "boring" > })
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Return a reference to T of `ChainError< T> `
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug)]
< / span > < span class = "boring" > /// enum Func1ErrorKind {
< / span > < span class = "boring" > /// Func2,
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// /// impl ::std::fmt::Display for Func1ErrorKind {…}
< / span > < span class = "boring" > /// # impl ::std::fmt::Display for Func1ErrorKind {
< / span > < span class = "boring" > /// # fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > /// # match self {
< / span > < span class = "boring" > /// # Func1ErrorKind::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > /// # Func1ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> ChainResult< (), Func1ErrorKind> {
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< / span > < span class = "boring" > /// func2().context(Func1ErrorKind::Func2)?;
< / span > < span class = "boring" > /// do_some_io().context(Func1ErrorKind::IO(" bar.txt" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// Func1ErrorKind::Func2 => {}
< / span > < span class = "boring" > /// Func1ErrorKind::IO(filename) => panic!(),
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn kind(& self) -> & T {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Returns an Iterator over all error causes/sources
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Example
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn iter(& self) -> impl Iterator< Item = & (dyn Error + 'static)> {
< / span > < span class = "boring" > ErrorIter {
< / span > < span class = "boring" > current: Some(self),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > /// Convenience methods for `Result< > ` to turn the error into a decorated ChainError
< / span > < span class = "boring" > pub trait ResultTrait< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > {
< / span > < span class = "boring" > /// Decorate the error with a `kind` of type `T` and the source `Location`
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Decorate the `error` with a `kind` of type `T` produced with a `FnOnce(& error)` and the source `Location`
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > ResultTrait< O, E>
< / span > < span class = "boring" > for std::result::Result< O, E>
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > )),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => {
< / span > < span class = "boring" > let kind = op(& error_cause);
< / span > < span class = "boring" > Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// An iterator over all error causes/sources
< / span > < span class = "boring" > pub struct ErrorIter< 'a> {
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< / span > < span class = "boring" > current: Option< & 'a (dyn Error + 'static)> ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< 'a> Iterator for ErrorIter< 'a> {
< / span > < span class = "boring" > type Item = & 'a (dyn Error + 'static);
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn next(& mut self) -> Option< Self::Item> {
< / span > < span class = "boring" > let current = self.current;
< / span > < span class = "boring" > self.current = self.current.and_then(Error::source);
< / span > < span class = "boring" > current
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> std::ops::Deref for ChainError< T> {
< / span > < span class = "boring" > type Target = T;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn deref(& self) -> & Self::Target {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience trait to hide the `ChainError< T> ` implementation internals
< / span > < span class = "boring" > pub trait ChainErrorDown {
< / span > < span class = "boring" > /// Test if of type `ChainError< T> `
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
< / span > < span class = "boring" > /// Downcast to a reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to a mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to T of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> ;
< / span > < span class = "boring" > /// Downcast to T mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< U: 'static + Display + Debug> ChainErrorDown for ChainError< U> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > TypeId::of::< T> () == TypeId::of::< U> ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& *(self as *const dyn Error as *const & ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& (*(self as *const dyn Error as *const & ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut (*(self as *mut dyn Error as *mut & mut ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send + Sync {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Display for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
< / span > < span class = "boring" > write!(f, " {}" , self.kind)?;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[cfg(feature = " display-cause" )]
< / span > < span class = "boring" > {
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Display::fmt(& e, f)?;
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > Ok(())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Debug for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
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< / span > < span class = "boring" > if f.alternate() {
< / span > < span class = "boring" > let mut f = f.debug_struct(& format!(" ChainError< {}> " , std::any::type_name::< T> ()));
< / span > < span class = "boring" >
< / span > < span class = "boring" > let f = f
< / span > < span class = "boring" > .field(" occurrence" , & self.occurrence)
< / span > < span class = "boring" > .field(" kind" , & self.kind)
< / span > < span class = "boring" > .field(" source" , & self.source());
< / span > < span class = "boring" >
< / span > < span class = "boring" > f.finish()
< / span > < span class = "boring" > } else {
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< / span > < span class = "boring" > if let Some(ref o) = self.occurrence {
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< / span > < span class = "boring" > write!(f, " {}: " , o)?;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > if TypeId::of::< String> () == TypeId::of::< T> ()
< / span > < span class = "boring" > || TypeId::of::< & str> () == TypeId::of::< T> ()
< / span > < span class = "boring" > {
< / span > < span class = "boring" > Display::fmt(& self.kind, f)?;
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > Debug::fmt(& self.kind, f)?;
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Debug::fmt(& e, f)?;
< / span > < span class = "boring" > }
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< / span > < span class = "boring" > Ok(())
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< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `ChainErrorFrom< T> ` is similar to `From< T> `
< / span > < span class = "boring" > pub trait ChainErrorFrom< T> : Sized {
< / span > < span class = "boring" > /// similar to From< T> ::from()
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< / span > < span class = "boring" > fn chain_error_from(from: T, line_filename: Option< String> ) -> ChainError< Self> ;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `IntoChainError< T> ` is similar to `Into< T> `
< / span > < span class = "boring" > pub trait IntoChainError< T> : Sized {
< / span > < span class = "boring" > /// similar to Into< T> ::into()
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< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< T> ;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> IntoChainError< U> for T
< / span > < span class = "boring" > where
< / span > < span class = "boring" > U: ChainErrorFrom< T> ,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
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< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< U> {
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< / span > < span class = "boring" > U::chain_error_from(self, line_filename)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> ChainErrorFrom< T> for U
< / span > < span class = "boring" > where
< / span > < span class = "boring" > T: Into< U> ,
< / span > < span class = "boring" > U: 'static + Display + Debug,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
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< / span > < span class = "boring" > fn chain_error_from(t: T, line_filename: Option< String> ) -> ChainError< Self> {
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< / span > < span class = "boring" > let e: U = t.into();
< / span > < span class = "boring" > ChainError::new(e, None, line_filename)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > /// Convenience macro to create a " new type" T(String) and implement Display + Debug for T
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
< / span > < span class = "boring" > /// # use crate::chainerror::*;
< / span > < span class = "boring" > /// # use std::error::Error;
< / span > < span class = "boring" > /// # use std::io;
< / span > < span class = "boring" > /// # use std::result::Result;
< / span > < span class = "boring" > /// # fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// # Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// # Ok(())
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// fn func2() -> ChainResult< (), Func2Error> {
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< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error> > {
< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// # if let Err(e) = func1() {
< / span > < span class = "boring" > /// # if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// # assert!(f1err.find_cause::< ChainError< Func2Error> > ().is_some());
< / span > < span class = "boring" > /// # assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
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< / span > < span class = "boring" > macro_rules! derive_str_context {
< / span > < span class = "boring" > ($e:ident) => {
< / span > < span class = "boring" > #[derive(Clone)]
< / span > < span class = "boring" > pub struct $e(pub String);
< / span > < span class = "boring" > impl ::std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}" , self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}({})" , stringify!($e), self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::error::Error for $e {}
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Derive an Error for an ErrorKind, which wraps a `ChainError` and implements a `kind()` method
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// It basically hides `ChainError` to the outside and only exposes the `kind()`
< / span > < span class = "boring" > /// method.
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Error::kind() returns the ErrorKind
< / span > < span class = "boring" > /// Error::source() returns the parent error
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// use std::io;
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< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// fn do_some_io(_f: & str) -> std::result::Result< (), io::Error> {
< / span > < span class = "boring" > /// return Err(io::Error::from(io::ErrorKind::NotFound));
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< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug, Clone)]
< / span > < span class = "boring" > /// pub enum ErrorKind {
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// FatalError(String),
< / span > < span class = "boring" > /// Unknown,
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// derive_err_kind!(Error, ErrorKind);
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl std::fmt::Display for ErrorKind {
< / span > < span class = "boring" > /// fn fmt(& self, f: & mut ::std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > /// match self {
< / span > < span class = "boring" > /// ErrorKind::FatalError(e) => write!(f, " fatal error {}" , e),
< / span > < span class = "boring" > /// ErrorKind::Unknown => write!(f, " unknown error" ),
< / span > < span class = "boring" > /// ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl ErrorKind {
< / span > < span class = "boring" > /// fn from_io_error(e: & io::Error, f: String) -> Self {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// io::ErrorKind::BrokenPipe => panic!(" Should not happen" ),
< / span > < span class = "boring" > /// io::ErrorKind::ConnectionReset => {
< / span > < span class = "boring" > /// ErrorKind::FatalError(format!(" While reading `{}`: {}" , f, e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// _ => ErrorKind::IO(f),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl From< & io::Error> for ErrorKind {
< / span > < span class = "boring" > /// fn from(e: & io::Error) -> Self {
< / span > < span class = "boring" > /// ErrorKind::IO(format!(" {}" , e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// pub fn func1() -> std::result::Result< (), Error> {
< / span > < span class = "boring" > /// let filename = " bar.txt" ;
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from_io_error(e, filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::IO(filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from(e))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
< / span > < span class = "boring" > macro_rules! derive_err_kind {
< / span > < span class = "boring" > ($e:ident, $k:ident) => {
< / span > < span class = "boring" > pub struct $e($crate::ChainError< $k> );
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl $e {
< / span > < span class = "boring" > pub fn kind(& self) -> & $k {
< / span > < span class = "boring" > self.0.kind()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< $k> for $e {
< / span > < span class = "boring" > fn from(e: $k) -> Self {
< / span > < span class = "boring" > $e($crate::ChainError::new(e, None, None))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< ChainError< $k> > for $e {
< / span > < span class = "boring" > fn from(e: $crate::ChainError< $k> ) -> Self {
< / span > < span class = "boring" > $e(e)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< & $e> for $k
< / span > < span class = "boring" > where
< / span > < span class = "boring" > $k: Clone,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > fn from(e: & $e) -> Self {
< / span > < span class = "boring" > e.kind().clone()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::error::Error for $e {
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn std::error::Error + 'static)> {
< / span > < span class = "boring" > self.0.source()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Display::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Debug::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < / code > < / pre > < / pre >
< h3 > < a class = "header" href = "#what-did-we-do-here" id = "what-did-we-do-here" > What did we do here?< / a > < / h3 >
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< pre > < code class = "language-rust ignore" > if let Err(e) = do_some_io() {
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Err(e).context(" func2 error" )?;
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}
< / code > < / pre >
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< p > The function < code > context(newerror)< / code > stores < code > olderror< / code > as the source/cause of < code > newerror< / code >
along with the < code > Location< / code > of the < code > context()< / code > call and returns < code > Err(newerror)< / code > .< / p >
< p > < code > ?< / code > then returns the inner error applying < code > .into()< / code > , so that we
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again have a < code > Err(Box< Error + Send + Sync> )< / code > as a result.< / p >
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< p > The < code > Debug< / code > implementation of < code > ChainError< T> < / code > (which is returned by < code > context()< / code > )
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prints the < code > Debug< / code > of < code > T< / code > prefixed with the stored filename and line number.< / p >
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< p > < code > ChainError< T> < / code > in our case is < code > ChainError< & str> < / code > .< / p >
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< h1 > < a class = "header" href = "#mapping-errors" id = "mapping-errors" > Mapping Errors< / a > < / h1 >
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< p > Now let's get more rust idiomatic by using < code > .context()< / code > directly on the previous < code > Result< / code > .< / p >
< pre > < pre class = "playground" > < code class = "language-rust" > use chainerror::prelude::v1::*;
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use std::error::Error;
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use std::io;
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use std::result::Result;
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fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
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Err(io::Error::from(io::ErrorKind::NotFound))?;
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Ok(())
}
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fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
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do_some_io().context(" func2 error" )?;
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Ok(())
}
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fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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func2().context(" func1 error" )?;
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Ok(())
}
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fn main() -> Result< (), Box< dyn Error + Send + Sync> > {
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if let Err(e) = func1() {
eprintln!(" {:?}" , e);
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std::process::exit(1);
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}
Ok(())
}
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< span class = "boring" > #[allow(dead_code)]
< / span > < span class = "boring" > mod chainerror {
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< / span > < span class = "boring" > //! `chainerror` provides an error backtrace without doing a real backtrace, so even after you `strip` your
< / span > < span class = "boring" > //! binaries, you still have the error backtrace.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `chainerror` has no dependencies!
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
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< / span > < span class = "boring" > //! It encapsulates all types, which have `Display + Debug` and can store the error cause internally.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Along with the `ChainError< T> ` struct, `chainerror` comes with some useful helper macros to save a lot of typing.
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! Debug information is worth it!
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ## Features
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `display-cause`
< / span > < span class = "boring" > //! : turn on printing a backtrace of the errors in `Display`
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Tutorial
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Read the [Tutorial](https://haraldh.github.io/chainerror/tutorial1.html)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Examples
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! examples/example.rs:
< / span > < span class = "boring" > //! ```rust,ignore
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! fn main() {
< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! eprintln!(" \nDebug Error {{:?}}:\n{:?}" , e);
< / span > < span class = "boring" > //! eprintln!(" \nAlternative Debug Error {{:#?}}:\n{:#?}\n" , e);
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```console
< / span > < span class = "boring" > //! $ cargo run -q --example example
< / span > < span class = "boring" > //! Debug Error {:?}:
< / span > < span class = "boring" > //! examples/example.rs:46:13: func1 error calling func2
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:21:13: Func2Error(func2 error: calling func3)
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:14:18: Error reading 'foo.txt'
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Alternative Debug Error {:#?}:
< / span > < span class = "boring" > //! ChainError< example::Func1Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:46:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: func1 error calling func2,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< example::Func2Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:21:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: Func2Error(func2 error: calling func3),
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< alloc::string::String> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:14:18" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: " Error reading \'foo.txt\'" ,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! Kind(
< / span > < span class = "boring" > //! NotFound,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > //! func2().context(" func1 error" )?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:21:13: func1 error
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func3() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! derive_str_context!(Func2Error);
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> ChainResult< (), Func2Error> {
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< / span > < span class = "boring" > //! func3().context(Func2Error(" func2 error: calling func3" .into()))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! enum Func1Error {
< / span > < span class = "boring" > //! Func2,
< / span > < span class = "boring" > //! IO(String),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Display for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! match self {
< / span > < span class = "boring" > //! Func1Error::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > //! Func1Error::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Debug for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! write!(f, " {}" , self)
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> ChainResult< (), Func1Error> {
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< / span > < span class = "boring" > //! func2().context(Func1Error::Func2)?;
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< / span > < span class = "boring" > //! let filename = String::from(" bar.txt" );
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< / span > < span class = "boring" > //! do_some_io().context(Func1Error::IO(filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! assert!(match e.kind() {
< / span > < span class = "boring" > //! Func1Error::Func2 => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error calling func2" );
< / span > < span class = "boring" > //! true
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! Func1Error::IO(filename) => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error reading '{}'" , filename);
< / span > < span class = "boring" > //! false
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< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! });
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! assert!(e.find_chain_cause::< Func2Error> ().is_some());
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Some(e) = e.find_chain_cause::< Func2Error> () {
< / span > < span class = "boring" > //! eprintln!(" \nError reported by Func2Error: {}" , e)
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! assert!(e.root_cause().is_some());
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Some(e) = e.root_cause() {
< / span > < span class = "boring" > //! let io_error = e.downcast_ref::< io::Error> ().unwrap();
< / span > < span class = "boring" > //! eprintln!(" \nThe root cause was: std::io::Error: {:#?}" , io_error);
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:48:13: func1 error calling func2
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:23:13: Func2Error(func2 error: calling func3)
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" >
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< / span > < span class = "boring" > #![deny(clippy::all)]
< / span > < span class = "boring" > #![deny(clippy::integer_arithmetic)]
< / span > < span class = "boring" > #![deny(missing_docs)]
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< / span > < span class = "boring" >
< / span > < span class = "boring" > use std::any::TypeId;
< / span > < span class = "boring" > use std::error::Error;
< / span > < span class = "boring" > use std::fmt::{Debug, Display, Formatter, Result};
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< / span > < span class = "boring" > use std::panic::Location;
< / span > < span class = "boring" >
< / span > < span class = "boring" > pub mod prelude {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub mod v1 {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub use super::super::ChainErrorDown as _;
< / span > < span class = "boring" > pub use super::super::ResultTrait as _;
< / span > < span class = "boring" > pub use super::super::{ChainError, ChainResult};
< / span > < span class = "boring" > pub use crate::{derive_err_kind, derive_str_context};
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > /// chains an inner error kind `T` with a causing error
< / span > < span class = "boring" > pub struct ChainError< T> {
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// convenience type alias
< / span > < span class = "boring" > pub type ChainResult< O, E> = std::result::Result< O, ChainError< E> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> ChainError< T> {
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< / span > < span class = "boring" > /// Use the `context()` or `map_context()` Result methods instead of calling this directly
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< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn new(
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > ) -> Self {
< / span > < span class = "boring" > Self {
< / span > < span class = "boring" > occurrence,
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > error_cause,
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// return the root cause of the error chain, if any exists
< / span > < span class = "boring" > pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.iter().last()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type U, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// assert!(f1err.find_cause::< io::Error> ().is_some());
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< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter().filter_map(Error::downcast_ref::< U> ).next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> `, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooError);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooError> > ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooError> implementation detail
< / span > < span class = "boring" > /// err.find_chain_cause::< FooError> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(Error::downcast_ref::< ChainError< U> > )
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> ` or `U`, if any exists and return `U`
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause` and `find_chain_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooErrorKind);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooErrorKind> > ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_chain_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_cause::< FooErrorKind> ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooErrorKind> implementation detail
< / span > < span class = "boring" > /// err.find_kind_or_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_kind_or_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(|e| {
< / span > < span class = "boring" > e.downcast_ref::< ChainError< U> > ()
< / span > < span class = "boring" > .map(|e| e.kind())
< / span > < span class = "boring" > .or_else(|| e.downcast_ref::< U> ())
< / span > < span class = "boring" > })
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Return a reference to T of `ChainError< T> `
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug)]
< / span > < span class = "boring" > /// enum Func1ErrorKind {
< / span > < span class = "boring" > /// Func2,
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// /// impl ::std::fmt::Display for Func1ErrorKind {…}
< / span > < span class = "boring" > /// # impl ::std::fmt::Display for Func1ErrorKind {
< / span > < span class = "boring" > /// # fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > /// # match self {
< / span > < span class = "boring" > /// # Func1ErrorKind::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > /// # Func1ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> ChainResult< (), Func1ErrorKind> {
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< / span > < span class = "boring" > /// func2().context(Func1ErrorKind::Func2)?;
< / span > < span class = "boring" > /// do_some_io().context(Func1ErrorKind::IO(" bar.txt" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// Func1ErrorKind::Func2 => {}
< / span > < span class = "boring" > /// Func1ErrorKind::IO(filename) => panic!(),
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn kind(& self) -> & T {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Returns an Iterator over all error causes/sources
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Example
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn iter(& self) -> impl Iterator< Item = & (dyn Error + 'static)> {
< / span > < span class = "boring" > ErrorIter {
< / span > < span class = "boring" > current: Some(self),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > /// Convenience methods for `Result< > ` to turn the error into a decorated ChainError
< / span > < span class = "boring" > pub trait ResultTrait< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > {
< / span > < span class = "boring" > /// Decorate the error with a `kind` of type `T` and the source `Location`
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Decorate the `error` with a `kind` of type `T` produced with a `FnOnce(& error)` and the source `Location`
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > ResultTrait< O, E>
< / span > < span class = "boring" > for std::result::Result< O, E>
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > )),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => {
< / span > < span class = "boring" > let kind = op(& error_cause);
< / span > < span class = "boring" > Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// An iterator over all error causes/sources
< / span > < span class = "boring" > pub struct ErrorIter< 'a> {
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< / span > < span class = "boring" > current: Option< & 'a (dyn Error + 'static)> ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< 'a> Iterator for ErrorIter< 'a> {
< / span > < span class = "boring" > type Item = & 'a (dyn Error + 'static);
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn next(& mut self) -> Option< Self::Item> {
< / span > < span class = "boring" > let current = self.current;
< / span > < span class = "boring" > self.current = self.current.and_then(Error::source);
< / span > < span class = "boring" > current
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> std::ops::Deref for ChainError< T> {
< / span > < span class = "boring" > type Target = T;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn deref(& self) -> & Self::Target {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience trait to hide the `ChainError< T> ` implementation internals
< / span > < span class = "boring" > pub trait ChainErrorDown {
< / span > < span class = "boring" > /// Test if of type `ChainError< T> `
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
< / span > < span class = "boring" > /// Downcast to a reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to a mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to T of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> ;
< / span > < span class = "boring" > /// Downcast to T mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< U: 'static + Display + Debug> ChainErrorDown for ChainError< U> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > TypeId::of::< T> () == TypeId::of::< U> ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& *(self as *const dyn Error as *const & ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& (*(self as *const dyn Error as *const & ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut (*(self as *mut dyn Error as *mut & mut ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send + Sync {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Display for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
< / span > < span class = "boring" > write!(f, " {}" , self.kind)?;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[cfg(feature = " display-cause" )]
< / span > < span class = "boring" > {
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Display::fmt(& e, f)?;
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > Ok(())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Debug for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
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< / span > < span class = "boring" > if f.alternate() {
< / span > < span class = "boring" > let mut f = f.debug_struct(& format!(" ChainError< {}> " , std::any::type_name::< T> ()));
< / span > < span class = "boring" >
< / span > < span class = "boring" > let f = f
< / span > < span class = "boring" > .field(" occurrence" , & self.occurrence)
< / span > < span class = "boring" > .field(" kind" , & self.kind)
< / span > < span class = "boring" > .field(" source" , & self.source());
< / span > < span class = "boring" >
< / span > < span class = "boring" > f.finish()
< / span > < span class = "boring" > } else {
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< / span > < span class = "boring" > if let Some(ref o) = self.occurrence {
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< / span > < span class = "boring" > write!(f, " {}: " , o)?;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > if TypeId::of::< String> () == TypeId::of::< T> ()
< / span > < span class = "boring" > || TypeId::of::< & str> () == TypeId::of::< T> ()
< / span > < span class = "boring" > {
< / span > < span class = "boring" > Display::fmt(& self.kind, f)?;
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > Debug::fmt(& self.kind, f)?;
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Debug::fmt(& e, f)?;
< / span > < span class = "boring" > }
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< / span > < span class = "boring" > Ok(())
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< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `ChainErrorFrom< T> ` is similar to `From< T> `
< / span > < span class = "boring" > pub trait ChainErrorFrom< T> : Sized {
< / span > < span class = "boring" > /// similar to From< T> ::from()
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< / span > < span class = "boring" > fn chain_error_from(from: T, line_filename: Option< String> ) -> ChainError< Self> ;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `IntoChainError< T> ` is similar to `Into< T> `
< / span > < span class = "boring" > pub trait IntoChainError< T> : Sized {
< / span > < span class = "boring" > /// similar to Into< T> ::into()
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< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< T> ;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> IntoChainError< U> for T
< / span > < span class = "boring" > where
< / span > < span class = "boring" > U: ChainErrorFrom< T> ,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
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< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< U> {
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< / span > < span class = "boring" > U::chain_error_from(self, line_filename)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> ChainErrorFrom< T> for U
< / span > < span class = "boring" > where
< / span > < span class = "boring" > T: Into< U> ,
< / span > < span class = "boring" > U: 'static + Display + Debug,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn chain_error_from(t: T, line_filename: Option< String> ) -> ChainError< Self> {
< / span > < span class = "boring" > let e: U = t.into();
< / span > < span class = "boring" > ChainError::new(e, None, line_filename)
< / span > < span class = "boring" > }
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience macro to create a " new type" T(String) and implement Display + Debug for T
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
< / span > < span class = "boring" > /// # use crate::chainerror::*;
< / span > < span class = "boring" > /// # use std::error::Error;
< / span > < span class = "boring" > /// # use std::io;
< / span > < span class = "boring" > /// # use std::result::Result;
< / span > < span class = "boring" > /// # fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// # Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// # Ok(())
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> ChainResult< (), Func2Error> {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// # if let Err(e) = func1() {
< / span > < span class = "boring" > /// # if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// # assert!(f1err.find_cause::< ChainError< Func2Error> > ().is_some());
< / span > < span class = "boring" > /// # assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
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< / span > < span class = "boring" > macro_rules! derive_str_context {
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< / span > < span class = "boring" > ($e:ident) => {
< / span > < span class = "boring" > #[derive(Clone)]
< / span > < span class = "boring" > pub struct $e(pub String);
< / span > < span class = "boring" > impl ::std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}" , self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}({})" , stringify!($e), self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::error::Error for $e {}
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Derive an Error for an ErrorKind, which wraps a `ChainError` and implements a `kind()` method
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// It basically hides `ChainError` to the outside and only exposes the `kind()`
< / span > < span class = "boring" > /// method.
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Error::kind() returns the ErrorKind
< / span > < span class = "boring" > /// Error::source() returns the parent error
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io(_f: & str) -> std::result::Result< (), io::Error> {
< / span > < span class = "boring" > /// return Err(io::Error::from(io::ErrorKind::NotFound));
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug, Clone)]
< / span > < span class = "boring" > /// pub enum ErrorKind {
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// FatalError(String),
< / span > < span class = "boring" > /// Unknown,
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// derive_err_kind!(Error, ErrorKind);
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl std::fmt::Display for ErrorKind {
< / span > < span class = "boring" > /// fn fmt(& self, f: & mut ::std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > /// match self {
< / span > < span class = "boring" > /// ErrorKind::FatalError(e) => write!(f, " fatal error {}" , e),
< / span > < span class = "boring" > /// ErrorKind::Unknown => write!(f, " unknown error" ),
< / span > < span class = "boring" > /// ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl ErrorKind {
< / span > < span class = "boring" > /// fn from_io_error(e: & io::Error, f: String) -> Self {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// io::ErrorKind::BrokenPipe => panic!(" Should not happen" ),
< / span > < span class = "boring" > /// io::ErrorKind::ConnectionReset => {
< / span > < span class = "boring" > /// ErrorKind::FatalError(format!(" While reading `{}`: {}" , f, e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// _ => ErrorKind::IO(f),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl From< & io::Error> for ErrorKind {
< / span > < span class = "boring" > /// fn from(e: & io::Error) -> Self {
< / span > < span class = "boring" > /// ErrorKind::IO(format!(" {}" , e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// pub fn func1() -> std::result::Result< (), Error> {
< / span > < span class = "boring" > /// let filename = " bar.txt" ;
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from_io_error(e, filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::IO(filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from(e))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
< / span > < span class = "boring" > macro_rules! derive_err_kind {
< / span > < span class = "boring" > ($e:ident, $k:ident) => {
< / span > < span class = "boring" > pub struct $e($crate::ChainError< $k> );
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl $e {
< / span > < span class = "boring" > pub fn kind(& self) -> & $k {
< / span > < span class = "boring" > self.0.kind()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< $k> for $e {
< / span > < span class = "boring" > fn from(e: $k) -> Self {
< / span > < span class = "boring" > $e($crate::ChainError::new(e, None, None))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< ChainError< $k> > for $e {
< / span > < span class = "boring" > fn from(e: $crate::ChainError< $k> ) -> Self {
< / span > < span class = "boring" > $e(e)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< & $e> for $k
< / span > < span class = "boring" > where
< / span > < span class = "boring" > $k: Clone,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > fn from(e: & $e) -> Self {
< / span > < span class = "boring" > e.kind().clone()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::error::Error for $e {
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn std::error::Error + 'static)> {
< / span > < span class = "boring" > self.0.source()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Display::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Debug::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < / code > < / pre > < / pre >
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< p > If you compare the output to the previous example, you will see,
that:< / p >
< pre > < code > Error: src/main.rs:19: " func1 error"
< / code > < / pre >
< p > changed to just:< / p >
< pre > < code > src/main.rs:16: " func1 error"
< / code > < / pre >
< p > This is, because we caught the error of < code > func1()< / code > in < code > main()< / code > and print it out ourselves.< / p >
< p > We can now control, whether to output in < code > Debug< / code > or < code > Display< / code > mode.
Maybe depending on < code > --debug< / code > as a CLI argument.< / p >
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< h1 > < a class = "header" href = "#more-information" id = "more-information" > More information< / a > < / h1 >
< p > To give more context to the error, you want to use < code > format!< / code >
to extend the information in the context string.< / p >
< pre > < pre class = "playground" > < code class = "language-rust" > use chainerror::prelude::v1::*;
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use std::error::Error;
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use std::io;
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use std::result::Result;
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fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
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Err(io::Error::from(io::ErrorKind::NotFound))?;
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Ok(())
}
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fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
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let filename = " foo.txt" ;
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do_some_io().context(format!(" Error reading '{}'" , filename))?;
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Ok(())
}
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fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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func2().context(" func1 error" )?;
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Ok(())
}
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fn main() -> Result< (), Box< dyn Error + Send + Sync> > {
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if let Err(e) = func1() {
eprintln!(" {:?}" , e);
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std::process::exit(1);
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}
Ok(())
}
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< span class = "boring" > #[allow(dead_code)]
< / span > < span class = "boring" > mod chainerror {
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< / span > < span class = "boring" > //! `chainerror` provides an error backtrace without doing a real backtrace, so even after you `strip` your
< / span > < span class = "boring" > //! binaries, you still have the error backtrace.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `chainerror` has no dependencies!
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
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< / span > < span class = "boring" > //! It encapsulates all types, which have `Display + Debug` and can store the error cause internally.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Along with the `ChainError< T> ` struct, `chainerror` comes with some useful helper macros to save a lot of typing.
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! Debug information is worth it!
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ## Features
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `display-cause`
< / span > < span class = "boring" > //! : turn on printing a backtrace of the errors in `Display`
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Tutorial
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Read the [Tutorial](https://haraldh.github.io/chainerror/tutorial1.html)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Examples
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! examples/example.rs:
< / span > < span class = "boring" > //! ```rust,ignore
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! fn main() {
< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! eprintln!(" \nDebug Error {{:?}}:\n{:?}" , e);
< / span > < span class = "boring" > //! eprintln!(" \nAlternative Debug Error {{:#?}}:\n{:#?}\n" , e);
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```console
< / span > < span class = "boring" > //! $ cargo run -q --example example
< / span > < span class = "boring" > //! Debug Error {:?}:
< / span > < span class = "boring" > //! examples/example.rs:46:13: func1 error calling func2
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:21:13: Func2Error(func2 error: calling func3)
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:14:18: Error reading 'foo.txt'
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Alternative Debug Error {:#?}:
< / span > < span class = "boring" > //! ChainError< example::Func1Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:46:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: func1 error calling func2,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< example::Func2Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:21:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: Func2Error(func2 error: calling func3),
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< alloc::string::String> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:14:18" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: " Error reading \'foo.txt\'" ,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! Kind(
< / span > < span class = "boring" > //! NotFound,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > //! func2().context(" func1 error" )?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:21:13: func1 error
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func3() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! derive_str_context!(Func2Error);
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> ChainResult< (), Func2Error> {
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< / span > < span class = "boring" > //! func3().context(Func2Error(" func2 error: calling func3" .into()))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! enum Func1Error {
< / span > < span class = "boring" > //! Func2,
< / span > < span class = "boring" > //! IO(String),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Display for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! match self {
< / span > < span class = "boring" > //! Func1Error::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > //! Func1Error::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Debug for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! write!(f, " {}" , self)
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> ChainResult< (), Func1Error> {
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< / span > < span class = "boring" > //! func2().context(Func1Error::Func2)?;
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< / span > < span class = "boring" > //! let filename = String::from(" bar.txt" );
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< / span > < span class = "boring" > //! do_some_io().context(Func1Error::IO(filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! assert!(match e.kind() {
< / span > < span class = "boring" > //! Func1Error::Func2 => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error calling func2" );
< / span > < span class = "boring" > //! true
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< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! Func1Error::IO(filename) => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error reading '{}'" , filename);
< / span > < span class = "boring" > //! false
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! });
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! assert!(e.find_chain_cause::< Func2Error> ().is_some());
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Some(e) = e.find_chain_cause::< Func2Error> () {
< / span > < span class = "boring" > //! eprintln!(" \nError reported by Func2Error: {}" , e)
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! assert!(e.root_cause().is_some());
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Some(e) = e.root_cause() {
< / span > < span class = "boring" > //! let io_error = e.downcast_ref::< io::Error> ().unwrap();
< / span > < span class = "boring" > //! eprintln!(" \nThe root cause was: std::io::Error: {:#?}" , io_error);
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:48:13: func1 error calling func2
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:23:13: Func2Error(func2 error: calling func3)
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" >
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< / span > < span class = "boring" > #![deny(clippy::all)]
< / span > < span class = "boring" > #![deny(clippy::integer_arithmetic)]
< / span > < span class = "boring" > #![deny(missing_docs)]
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< / span > < span class = "boring" >
< / span > < span class = "boring" > use std::any::TypeId;
< / span > < span class = "boring" > use std::error::Error;
< / span > < span class = "boring" > use std::fmt::{Debug, Display, Formatter, Result};
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< / span > < span class = "boring" > use std::panic::Location;
< / span > < span class = "boring" >
< / span > < span class = "boring" > pub mod prelude {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub mod v1 {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub use super::super::ChainErrorDown as _;
< / span > < span class = "boring" > pub use super::super::ResultTrait as _;
< / span > < span class = "boring" > pub use super::super::{ChainError, ChainResult};
< / span > < span class = "boring" > pub use crate::{derive_err_kind, derive_str_context};
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > /// chains an inner error kind `T` with a causing error
< / span > < span class = "boring" > pub struct ChainError< T> {
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// convenience type alias
< / span > < span class = "boring" > pub type ChainResult< O, E> = std::result::Result< O, ChainError< E> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> ChainError< T> {
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< / span > < span class = "boring" > /// Use the `context()` or `map_context()` Result methods instead of calling this directly
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< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn new(
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > ) -> Self {
< / span > < span class = "boring" > Self {
< / span > < span class = "boring" > occurrence,
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > error_cause,
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// return the root cause of the error chain, if any exists
< / span > < span class = "boring" > pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.iter().last()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type U, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// assert!(f1err.find_cause::< io::Error> ().is_some());
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< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter().filter_map(Error::downcast_ref::< U> ).next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> `, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooError);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooError> > ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooError> implementation detail
< / span > < span class = "boring" > /// err.find_chain_cause::< FooError> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(Error::downcast_ref::< ChainError< U> > )
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> ` or `U`, if any exists and return `U`
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause` and `find_chain_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooErrorKind);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooErrorKind> > ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_chain_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_cause::< FooErrorKind> ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooErrorKind> implementation detail
< / span > < span class = "boring" > /// err.find_kind_or_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_kind_or_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(|e| {
< / span > < span class = "boring" > e.downcast_ref::< ChainError< U> > ()
< / span > < span class = "boring" > .map(|e| e.kind())
< / span > < span class = "boring" > .or_else(|| e.downcast_ref::< U> ())
< / span > < span class = "boring" > })
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Return a reference to T of `ChainError< T> `
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug)]
< / span > < span class = "boring" > /// enum Func1ErrorKind {
< / span > < span class = "boring" > /// Func2,
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// /// impl ::std::fmt::Display for Func1ErrorKind {…}
< / span > < span class = "boring" > /// # impl ::std::fmt::Display for Func1ErrorKind {
< / span > < span class = "boring" > /// # fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > /// # match self {
< / span > < span class = "boring" > /// # Func1ErrorKind::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > /// # Func1ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> ChainResult< (), Func1ErrorKind> {
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< / span > < span class = "boring" > /// func2().context(Func1ErrorKind::Func2)?;
< / span > < span class = "boring" > /// do_some_io().context(Func1ErrorKind::IO(" bar.txt" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// Func1ErrorKind::Func2 => {}
< / span > < span class = "boring" > /// Func1ErrorKind::IO(filename) => panic!(),
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn kind(& self) -> & T {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Returns an Iterator over all error causes/sources
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Example
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn iter(& self) -> impl Iterator< Item = & (dyn Error + 'static)> {
< / span > < span class = "boring" > ErrorIter {
< / span > < span class = "boring" > current: Some(self),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > /// Convenience methods for `Result< > ` to turn the error into a decorated ChainError
< / span > < span class = "boring" > pub trait ResultTrait< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > {
< / span > < span class = "boring" > /// Decorate the error with a `kind` of type `T` and the source `Location`
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Decorate the `error` with a `kind` of type `T` produced with a `FnOnce(& error)` and the source `Location`
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > ResultTrait< O, E>
< / span > < span class = "boring" > for std::result::Result< O, E>
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > )),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => {
< / span > < span class = "boring" > let kind = op(& error_cause);
< / span > < span class = "boring" > Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// An iterator over all error causes/sources
< / span > < span class = "boring" > pub struct ErrorIter< 'a> {
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< / span > < span class = "boring" > current: Option< & 'a (dyn Error + 'static)> ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< 'a> Iterator for ErrorIter< 'a> {
< / span > < span class = "boring" > type Item = & 'a (dyn Error + 'static);
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn next(& mut self) -> Option< Self::Item> {
< / span > < span class = "boring" > let current = self.current;
< / span > < span class = "boring" > self.current = self.current.and_then(Error::source);
< / span > < span class = "boring" > current
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> std::ops::Deref for ChainError< T> {
< / span > < span class = "boring" > type Target = T;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn deref(& self) -> & Self::Target {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience trait to hide the `ChainError< T> ` implementation internals
< / span > < span class = "boring" > pub trait ChainErrorDown {
< / span > < span class = "boring" > /// Test if of type `ChainError< T> `
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
< / span > < span class = "boring" > /// Downcast to a reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to a mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to T of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> ;
< / span > < span class = "boring" > /// Downcast to T mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< U: 'static + Display + Debug> ChainErrorDown for ChainError< U> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > TypeId::of::< T> () == TypeId::of::< U> ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& *(self as *const dyn Error as *const & ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& (*(self as *const dyn Error as *const & ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut (*(self as *mut dyn Error as *mut & mut ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send + Sync {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Display for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
< / span > < span class = "boring" > write!(f, " {}" , self.kind)?;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[cfg(feature = " display-cause" )]
< / span > < span class = "boring" > {
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Display::fmt(& e, f)?;
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > Ok(())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Debug for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
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< / span > < span class = "boring" > if f.alternate() {
< / span > < span class = "boring" > let mut f = f.debug_struct(& format!(" ChainError< {}> " , std::any::type_name::< T> ()));
< / span > < span class = "boring" >
< / span > < span class = "boring" > let f = f
< / span > < span class = "boring" > .field(" occurrence" , & self.occurrence)
< / span > < span class = "boring" > .field(" kind" , & self.kind)
< / span > < span class = "boring" > .field(" source" , & self.source());
< / span > < span class = "boring" >
< / span > < span class = "boring" > f.finish()
< / span > < span class = "boring" > } else {
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< / span > < span class = "boring" > if let Some(ref o) = self.occurrence {
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< / span > < span class = "boring" > write!(f, " {}: " , o)?;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > if TypeId::of::< String> () == TypeId::of::< T> ()
< / span > < span class = "boring" > || TypeId::of::< & str> () == TypeId::of::< T> ()
< / span > < span class = "boring" > {
< / span > < span class = "boring" > Display::fmt(& self.kind, f)?;
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > Debug::fmt(& self.kind, f)?;
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Debug::fmt(& e, f)?;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" > Ok(())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `ChainErrorFrom< T> ` is similar to `From< T> `
< / span > < span class = "boring" > pub trait ChainErrorFrom< T> : Sized {
< / span > < span class = "boring" > /// similar to From< T> ::from()
< / span > < span class = "boring" > fn chain_error_from(from: T, line_filename: Option< String> ) -> ChainError< Self> ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `IntoChainError< T> ` is similar to `Into< T> `
< / span > < span class = "boring" > pub trait IntoChainError< T> : Sized {
< / span > < span class = "boring" > /// similar to Into< T> ::into()
< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< T> ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> IntoChainError< U> for T
< / span > < span class = "boring" > where
< / span > < span class = "boring" > U: ChainErrorFrom< T> ,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< U> {
< / span > < span class = "boring" > U::chain_error_from(self, line_filename)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> ChainErrorFrom< T> for U
< / span > < span class = "boring" > where
< / span > < span class = "boring" > T: Into< U> ,
< / span > < span class = "boring" > U: 'static + Display + Debug,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn chain_error_from(t: T, line_filename: Option< String> ) -> ChainError< Self> {
< / span > < span class = "boring" > let e: U = t.into();
< / span > < span class = "boring" > ChainError::new(e, None, line_filename)
< / span > < span class = "boring" > }
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience macro to create a " new type" T(String) and implement Display + Debug for T
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
< / span > < span class = "boring" > /// # use crate::chainerror::*;
< / span > < span class = "boring" > /// # use std::error::Error;
< / span > < span class = "boring" > /// # use std::io;
< / span > < span class = "boring" > /// # use std::result::Result;
< / span > < span class = "boring" > /// # fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// # Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// # Ok(())
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> ChainResult< (), Func2Error> {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// # if let Err(e) = func1() {
< / span > < span class = "boring" > /// # if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// # assert!(f1err.find_cause::< ChainError< Func2Error> > ().is_some());
< / span > < span class = "boring" > /// # assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
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< / span > < span class = "boring" > macro_rules! derive_str_context {
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< / span > < span class = "boring" > ($e:ident) => {
< / span > < span class = "boring" > #[derive(Clone)]
< / span > < span class = "boring" > pub struct $e(pub String);
< / span > < span class = "boring" > impl ::std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}" , self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}({})" , stringify!($e), self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::error::Error for $e {}
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Derive an Error for an ErrorKind, which wraps a `ChainError` and implements a `kind()` method
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// It basically hides `ChainError` to the outside and only exposes the `kind()`
< / span > < span class = "boring" > /// method.
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Error::kind() returns the ErrorKind
< / span > < span class = "boring" > /// Error::source() returns the parent error
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io(_f: & str) -> std::result::Result< (), io::Error> {
< / span > < span class = "boring" > /// return Err(io::Error::from(io::ErrorKind::NotFound));
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug, Clone)]
< / span > < span class = "boring" > /// pub enum ErrorKind {
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// FatalError(String),
< / span > < span class = "boring" > /// Unknown,
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// derive_err_kind!(Error, ErrorKind);
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl std::fmt::Display for ErrorKind {
< / span > < span class = "boring" > /// fn fmt(& self, f: & mut ::std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > /// match self {
< / span > < span class = "boring" > /// ErrorKind::FatalError(e) => write!(f, " fatal error {}" , e),
< / span > < span class = "boring" > /// ErrorKind::Unknown => write!(f, " unknown error" ),
< / span > < span class = "boring" > /// ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl ErrorKind {
< / span > < span class = "boring" > /// fn from_io_error(e: & io::Error, f: String) -> Self {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// io::ErrorKind::BrokenPipe => panic!(" Should not happen" ),
< / span > < span class = "boring" > /// io::ErrorKind::ConnectionReset => {
< / span > < span class = "boring" > /// ErrorKind::FatalError(format!(" While reading `{}`: {}" , f, e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// _ => ErrorKind::IO(f),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl From< & io::Error> for ErrorKind {
< / span > < span class = "boring" > /// fn from(e: & io::Error) -> Self {
< / span > < span class = "boring" > /// ErrorKind::IO(format!(" {}" , e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// pub fn func1() -> std::result::Result< (), Error> {
< / span > < span class = "boring" > /// let filename = " bar.txt" ;
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from_io_error(e, filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::IO(filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from(e))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
< / span > < span class = "boring" > macro_rules! derive_err_kind {
< / span > < span class = "boring" > ($e:ident, $k:ident) => {
< / span > < span class = "boring" > pub struct $e($crate::ChainError< $k> );
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl $e {
< / span > < span class = "boring" > pub fn kind(& self) -> & $k {
< / span > < span class = "boring" > self.0.kind()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< $k> for $e {
< / span > < span class = "boring" > fn from(e: $k) -> Self {
< / span > < span class = "boring" > $e($crate::ChainError::new(e, None, None))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< ChainError< $k> > for $e {
< / span > < span class = "boring" > fn from(e: $crate::ChainError< $k> ) -> Self {
< / span > < span class = "boring" > $e(e)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< & $e> for $k
< / span > < span class = "boring" > where
< / span > < span class = "boring" > $k: Clone,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > fn from(e: & $e) -> Self {
< / span > < span class = "boring" > e.kind().clone()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::error::Error for $e {
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn std::error::Error + 'static)> {
< / span > < span class = "boring" > self.0.source()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Display::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Debug::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < / code > < / pre > < / pre >
< h1 > < a class = "header" href = "#the-source-of-errors" id = "the-source-of-errors" > The source() of Errors< / a > < / h1 >
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< p > Sometimes you want to inspect the < code > source()< / code > of an < code > Error< / code > .
< code > chainerror< / code > implements < code > std::error::Error::source()< / code > , so you can get the cause of an error.< / p >
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< pre > < pre class = "playground" > < code class = "language-rust" > use chainerror::prelude::v1::*;
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use std::error::Error;
use std::io;
use std::result::Result;
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fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
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Err(io::Error::from(io::ErrorKind::NotFound))?;
Ok(())
}
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fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
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let filename = " foo.txt" ;
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do_some_io().context(format!(" Error reading '{}'" , filename))?;
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Ok(())
}
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fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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if let Err(e) = func2() {
if let Some(s) = e.source() {
eprintln!(" func2 failed because of '{}'" , s);
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Err(e).context(" func1 error" )?;
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}
}
Ok(())
}
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fn main() -> Result< (), Box< dyn Error + Send + Sync> > {
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if let Err(e) = func1() {
eprintln!(" {}" , e);
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std::process::exit(1);
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}
Ok(())
}
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< span class = "boring" > #[allow(dead_code)]
< / span > < span class = "boring" > mod chainerror {
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< / span > < span class = "boring" > //! `chainerror` provides an error backtrace without doing a real backtrace, so even after you `strip` your
< / span > < span class = "boring" > //! binaries, you still have the error backtrace.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `chainerror` has no dependencies!
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
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< / span > < span class = "boring" > //! It encapsulates all types, which have `Display + Debug` and can store the error cause internally.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Along with the `ChainError< T> ` struct, `chainerror` comes with some useful helper macros to save a lot of typing.
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! Debug information is worth it!
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ## Features
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `display-cause`
< / span > < span class = "boring" > //! : turn on printing a backtrace of the errors in `Display`
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Tutorial
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Read the [Tutorial](https://haraldh.github.io/chainerror/tutorial1.html)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Examples
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! examples/example.rs:
< / span > < span class = "boring" > //! ```rust,ignore
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! fn main() {
< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! eprintln!(" \nDebug Error {{:?}}:\n{:?}" , e);
< / span > < span class = "boring" > //! eprintln!(" \nAlternative Debug Error {{:#?}}:\n{:#?}\n" , e);
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```console
< / span > < span class = "boring" > //! $ cargo run -q --example example
< / span > < span class = "boring" > //! Debug Error {:?}:
< / span > < span class = "boring" > //! examples/example.rs:46:13: func1 error calling func2
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:21:13: Func2Error(func2 error: calling func3)
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:14:18: Error reading 'foo.txt'
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Alternative Debug Error {:#?}:
< / span > < span class = "boring" > //! ChainError< example::Func1Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:46:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: func1 error calling func2,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< example::Func2Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:21:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: Func2Error(func2 error: calling func3),
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< alloc::string::String> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:14:18" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: " Error reading \'foo.txt\'" ,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! Kind(
< / span > < span class = "boring" > //! NotFound,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > //! func2().context(" func1 error" )?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:21:13: func1 error
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func3() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! derive_str_context!(Func2Error);
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> ChainResult< (), Func2Error> {
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< / span > < span class = "boring" > //! func3().context(Func2Error(" func2 error: calling func3" .into()))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! enum Func1Error {
< / span > < span class = "boring" > //! Func2,
< / span > < span class = "boring" > //! IO(String),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Display for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! match self {
< / span > < span class = "boring" > //! Func1Error::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > //! Func1Error::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Debug for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! write!(f, " {}" , self)
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> ChainResult< (), Func1Error> {
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< / span > < span class = "boring" > //! func2().context(Func1Error::Func2)?;
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< / span > < span class = "boring" > //! let filename = String::from(" bar.txt" );
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< / span > < span class = "boring" > //! do_some_io().context(Func1Error::IO(filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! assert!(match e.kind() {
< / span > < span class = "boring" > //! Func1Error::Func2 => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error calling func2" );
< / span > < span class = "boring" > //! true
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! Func1Error::IO(filename) => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error reading '{}'" , filename);
< / span > < span class = "boring" > //! false
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< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! });
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! assert!(e.find_chain_cause::< Func2Error> ().is_some());
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Some(e) = e.find_chain_cause::< Func2Error> () {
< / span > < span class = "boring" > //! eprintln!(" \nError reported by Func2Error: {}" , e)
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! assert!(e.root_cause().is_some());
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Some(e) = e.root_cause() {
< / span > < span class = "boring" > //! let io_error = e.downcast_ref::< io::Error> ().unwrap();
< / span > < span class = "boring" > //! eprintln!(" \nThe root cause was: std::io::Error: {:#?}" , io_error);
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:48:13: func1 error calling func2
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:23:13: Func2Error(func2 error: calling func3)
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" >
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< / span > < span class = "boring" > #![deny(clippy::all)]
< / span > < span class = "boring" > #![deny(clippy::integer_arithmetic)]
< / span > < span class = "boring" > #![deny(missing_docs)]
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< / span > < span class = "boring" >
< / span > < span class = "boring" > use std::any::TypeId;
< / span > < span class = "boring" > use std::error::Error;
< / span > < span class = "boring" > use std::fmt::{Debug, Display, Formatter, Result};
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< / span > < span class = "boring" > use std::panic::Location;
< / span > < span class = "boring" >
< / span > < span class = "boring" > pub mod prelude {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub mod v1 {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub use super::super::ChainErrorDown as _;
< / span > < span class = "boring" > pub use super::super::ResultTrait as _;
< / span > < span class = "boring" > pub use super::super::{ChainError, ChainResult};
< / span > < span class = "boring" > pub use crate::{derive_err_kind, derive_str_context};
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > /// chains an inner error kind `T` with a causing error
< / span > < span class = "boring" > pub struct ChainError< T> {
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// convenience type alias
< / span > < span class = "boring" > pub type ChainResult< O, E> = std::result::Result< O, ChainError< E> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> ChainError< T> {
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< / span > < span class = "boring" > /// Use the `context()` or `map_context()` Result methods instead of calling this directly
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< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn new(
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > ) -> Self {
< / span > < span class = "boring" > Self {
< / span > < span class = "boring" > occurrence,
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > error_cause,
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// return the root cause of the error chain, if any exists
< / span > < span class = "boring" > pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.iter().last()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type U, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// assert!(f1err.find_cause::< io::Error> ().is_some());
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< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter().filter_map(Error::downcast_ref::< U> ).next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> `, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooError);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooError> > ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooError> implementation detail
< / span > < span class = "boring" > /// err.find_chain_cause::< FooError> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(Error::downcast_ref::< ChainError< U> > )
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> ` or `U`, if any exists and return `U`
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause` and `find_chain_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooErrorKind);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooErrorKind> > ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_chain_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_cause::< FooErrorKind> ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooErrorKind> implementation detail
< / span > < span class = "boring" > /// err.find_kind_or_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_kind_or_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(|e| {
< / span > < span class = "boring" > e.downcast_ref::< ChainError< U> > ()
< / span > < span class = "boring" > .map(|e| e.kind())
< / span > < span class = "boring" > .or_else(|| e.downcast_ref::< U> ())
< / span > < span class = "boring" > })
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Return a reference to T of `ChainError< T> `
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug)]
< / span > < span class = "boring" > /// enum Func1ErrorKind {
< / span > < span class = "boring" > /// Func2,
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// /// impl ::std::fmt::Display for Func1ErrorKind {…}
< / span > < span class = "boring" > /// # impl ::std::fmt::Display for Func1ErrorKind {
< / span > < span class = "boring" > /// # fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > /// # match self {
< / span > < span class = "boring" > /// # Func1ErrorKind::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > /// # Func1ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> ChainResult< (), Func1ErrorKind> {
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< / span > < span class = "boring" > /// func2().context(Func1ErrorKind::Func2)?;
< / span > < span class = "boring" > /// do_some_io().context(Func1ErrorKind::IO(" bar.txt" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// Func1ErrorKind::Func2 => {}
< / span > < span class = "boring" > /// Func1ErrorKind::IO(filename) => panic!(),
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn kind(& self) -> & T {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Returns an Iterator over all error causes/sources
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Example
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn iter(& self) -> impl Iterator< Item = & (dyn Error + 'static)> {
< / span > < span class = "boring" > ErrorIter {
< / span > < span class = "boring" > current: Some(self),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > /// Convenience methods for `Result< > ` to turn the error into a decorated ChainError
< / span > < span class = "boring" > pub trait ResultTrait< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > {
< / span > < span class = "boring" > /// Decorate the error with a `kind` of type `T` and the source `Location`
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Decorate the `error` with a `kind` of type `T` produced with a `FnOnce(& error)` and the source `Location`
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > ResultTrait< O, E>
< / span > < span class = "boring" > for std::result::Result< O, E>
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > )),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => {
< / span > < span class = "boring" > let kind = op(& error_cause);
< / span > < span class = "boring" > Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// An iterator over all error causes/sources
< / span > < span class = "boring" > pub struct ErrorIter< 'a> {
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< / span > < span class = "boring" > current: Option< & 'a (dyn Error + 'static)> ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< 'a> Iterator for ErrorIter< 'a> {
< / span > < span class = "boring" > type Item = & 'a (dyn Error + 'static);
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn next(& mut self) -> Option< Self::Item> {
< / span > < span class = "boring" > let current = self.current;
< / span > < span class = "boring" > self.current = self.current.and_then(Error::source);
< / span > < span class = "boring" > current
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> std::ops::Deref for ChainError< T> {
< / span > < span class = "boring" > type Target = T;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn deref(& self) -> & Self::Target {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience trait to hide the `ChainError< T> ` implementation internals
< / span > < span class = "boring" > pub trait ChainErrorDown {
< / span > < span class = "boring" > /// Test if of type `ChainError< T> `
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
< / span > < span class = "boring" > /// Downcast to a reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to a mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to T of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> ;
< / span > < span class = "boring" > /// Downcast to T mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< U: 'static + Display + Debug> ChainErrorDown for ChainError< U> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > TypeId::of::< T> () == TypeId::of::< U> ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& *(self as *const dyn Error as *const & ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& (*(self as *const dyn Error as *const & ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut (*(self as *mut dyn Error as *mut & mut ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send + Sync {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Display for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
< / span > < span class = "boring" > write!(f, " {}" , self.kind)?;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[cfg(feature = " display-cause" )]
< / span > < span class = "boring" > {
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Display::fmt(& e, f)?;
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > Ok(())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Debug for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
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< / span > < span class = "boring" > if f.alternate() {
< / span > < span class = "boring" > let mut f = f.debug_struct(& format!(" ChainError< {}> " , std::any::type_name::< T> ()));
< / span > < span class = "boring" >
< / span > < span class = "boring" > let f = f
< / span > < span class = "boring" > .field(" occurrence" , & self.occurrence)
< / span > < span class = "boring" > .field(" kind" , & self.kind)
< / span > < span class = "boring" > .field(" source" , & self.source());
< / span > < span class = "boring" >
< / span > < span class = "boring" > f.finish()
< / span > < span class = "boring" > } else {
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< / span > < span class = "boring" > if let Some(ref o) = self.occurrence {
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< / span > < span class = "boring" > write!(f, " {}: " , o)?;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > if TypeId::of::< String> () == TypeId::of::< T> ()
< / span > < span class = "boring" > || TypeId::of::< & str> () == TypeId::of::< T> ()
< / span > < span class = "boring" > {
< / span > < span class = "boring" > Display::fmt(& self.kind, f)?;
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > Debug::fmt(& self.kind, f)?;
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Debug::fmt(& e, f)?;
< / span > < span class = "boring" > }
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< / span > < span class = "boring" > Ok(())
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< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `ChainErrorFrom< T> ` is similar to `From< T> `
< / span > < span class = "boring" > pub trait ChainErrorFrom< T> : Sized {
< / span > < span class = "boring" > /// similar to From< T> ::from()
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< / span > < span class = "boring" > fn chain_error_from(from: T, line_filename: Option< String> ) -> ChainError< Self> ;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `IntoChainError< T> ` is similar to `Into< T> `
< / span > < span class = "boring" > pub trait IntoChainError< T> : Sized {
< / span > < span class = "boring" > /// similar to Into< T> ::into()
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< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< T> ;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> IntoChainError< U> for T
< / span > < span class = "boring" > where
< / span > < span class = "boring" > U: ChainErrorFrom< T> ,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
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< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< U> {
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< / span > < span class = "boring" > U::chain_error_from(self, line_filename)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> ChainErrorFrom< T> for U
< / span > < span class = "boring" > where
< / span > < span class = "boring" > T: Into< U> ,
< / span > < span class = "boring" > U: 'static + Display + Debug,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn chain_error_from(t: T, line_filename: Option< String> ) -> ChainError< Self> {
< / span > < span class = "boring" > let e: U = t.into();
< / span > < span class = "boring" > ChainError::new(e, None, line_filename)
< / span > < span class = "boring" > }
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience macro to create a " new type" T(String) and implement Display + Debug for T
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
< / span > < span class = "boring" > /// # use crate::chainerror::*;
< / span > < span class = "boring" > /// # use std::error::Error;
< / span > < span class = "boring" > /// # use std::io;
< / span > < span class = "boring" > /// # use std::result::Result;
< / span > < span class = "boring" > /// # fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// # Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// # Ok(())
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> ChainResult< (), Func2Error> {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// # if let Err(e) = func1() {
< / span > < span class = "boring" > /// # if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// # assert!(f1err.find_cause::< ChainError< Func2Error> > ().is_some());
< / span > < span class = "boring" > /// # assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
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< / span > < span class = "boring" > macro_rules! derive_str_context {
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< / span > < span class = "boring" > ($e:ident) => {
< / span > < span class = "boring" > #[derive(Clone)]
< / span > < span class = "boring" > pub struct $e(pub String);
< / span > < span class = "boring" > impl ::std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}" , self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}({})" , stringify!($e), self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::error::Error for $e {}
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Derive an Error for an ErrorKind, which wraps a `ChainError` and implements a `kind()` method
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// It basically hides `ChainError` to the outside and only exposes the `kind()`
< / span > < span class = "boring" > /// method.
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Error::kind() returns the ErrorKind
< / span > < span class = "boring" > /// Error::source() returns the parent error
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io(_f: & str) -> std::result::Result< (), io::Error> {
< / span > < span class = "boring" > /// return Err(io::Error::from(io::ErrorKind::NotFound));
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug, Clone)]
< / span > < span class = "boring" > /// pub enum ErrorKind {
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// FatalError(String),
< / span > < span class = "boring" > /// Unknown,
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// derive_err_kind!(Error, ErrorKind);
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl std::fmt::Display for ErrorKind {
< / span > < span class = "boring" > /// fn fmt(& self, f: & mut ::std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > /// match self {
< / span > < span class = "boring" > /// ErrorKind::FatalError(e) => write!(f, " fatal error {}" , e),
< / span > < span class = "boring" > /// ErrorKind::Unknown => write!(f, " unknown error" ),
< / span > < span class = "boring" > /// ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl ErrorKind {
< / span > < span class = "boring" > /// fn from_io_error(e: & io::Error, f: String) -> Self {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// io::ErrorKind::BrokenPipe => panic!(" Should not happen" ),
< / span > < span class = "boring" > /// io::ErrorKind::ConnectionReset => {
< / span > < span class = "boring" > /// ErrorKind::FatalError(format!(" While reading `{}`: {}" , f, e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// _ => ErrorKind::IO(f),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl From< & io::Error> for ErrorKind {
< / span > < span class = "boring" > /// fn from(e: & io::Error) -> Self {
< / span > < span class = "boring" > /// ErrorKind::IO(format!(" {}" , e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// pub fn func1() -> std::result::Result< (), Error> {
< / span > < span class = "boring" > /// let filename = " bar.txt" ;
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from_io_error(e, filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::IO(filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from(e))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
< / span > < span class = "boring" > macro_rules! derive_err_kind {
< / span > < span class = "boring" > ($e:ident, $k:ident) => {
< / span > < span class = "boring" > pub struct $e($crate::ChainError< $k> );
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl $e {
< / span > < span class = "boring" > pub fn kind(& self) -> & $k {
< / span > < span class = "boring" > self.0.kind()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< $k> for $e {
< / span > < span class = "boring" > fn from(e: $k) -> Self {
< / span > < span class = "boring" > $e($crate::ChainError::new(e, None, None))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< ChainError< $k> > for $e {
< / span > < span class = "boring" > fn from(e: $crate::ChainError< $k> ) -> Self {
< / span > < span class = "boring" > $e(e)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< & $e> for $k
< / span > < span class = "boring" > where
< / span > < span class = "boring" > $k: Clone,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > fn from(e: & $e) -> Self {
< / span > < span class = "boring" > e.kind().clone()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::error::Error for $e {
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn std::error::Error + 'static)> {
< / span > < span class = "boring" > self.0.source()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Display::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Debug::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < / code > < / pre > < / pre >
< p > Note, that because we changed the output of the error in < code > main()< / code > from
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< code > Debug< / code > to < code > Display< / code > , we don't see the error backtrace with filename and line number.< / p >
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< p > To enable the < code > Display< / code > backtrace, you have to enable the feature < code > display-cause< / code > for < code > chainerror< / code > .< / p >
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< h1 > < a class = "header" href = "#downcast-the-errors" id = "downcast-the-errors" > Downcast the Errors< / a > < / h1 >
< p > < code > std::error::Error< / code > comes with some helper methods to get to the original object of the
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< code > & (dyn Error + 'static)< / code > returned by < code > .source()< / code > .< / p >
< pre > < code class = "language-rust ignore" > pub fn downcast_ref< T: Error + 'static> (& self) -> Option< & T>
pub fn downcast_mut< T: Error + 'static> (& mut self) -> Option< & mut T>
< / code > < / pre >
< p > This is how it looks like, when using those:< / p >
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< pre > < pre class = "playground" > < code class = "language-rust" > use chainerror::prelude::v1::*;
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use std::error::Error;
use std::io;
use std::result::Result;
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fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
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Err(io::Error::from(io::ErrorKind::NotFound))?;
Ok(())
}
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fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
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let filename = " foo.txt" ;
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do_some_io().context(format!(" Error reading '{}'" , filename))?;
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Ok(())
}
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fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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func2().context(" func1 error" )?;
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Ok(())
}
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fn main() -> Result< (), Box< dyn Error + Send + Sync> > {
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if let Err(e) = func1() {
eprintln!(" Error: {}" , e);
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let mut s: & (dyn Error) = e.as_ref();
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while let Some(c) = s.source() {
if let Some(ioerror) = c.downcast_ref::< io::Error> () {
eprintln!(" caused by: std::io::Error: {}" , ioerror);
match ioerror.kind() {
io::ErrorKind::NotFound => eprintln!(" of kind: std::io::ErrorKind::NotFound" ),
_ => {}
}
} else {
eprintln!(" caused by: {}" , c);
}
s = c;
}
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std::process::exit(1);
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}
Ok(())
}
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< span class = "boring" > #[allow(dead_code)]
< / span > < span class = "boring" > mod chainerror {
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< / span > < span class = "boring" > //! `chainerror` provides an error backtrace without doing a real backtrace, so even after you `strip` your
< / span > < span class = "boring" > //! binaries, you still have the error backtrace.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `chainerror` has no dependencies!
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
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< / span > < span class = "boring" > //! It encapsulates all types, which have `Display + Debug` and can store the error cause internally.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Along with the `ChainError< T> ` struct, `chainerror` comes with some useful helper macros to save a lot of typing.
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! Debug information is worth it!
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ## Features
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `display-cause`
< / span > < span class = "boring" > //! : turn on printing a backtrace of the errors in `Display`
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Tutorial
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Read the [Tutorial](https://haraldh.github.io/chainerror/tutorial1.html)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Examples
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! examples/example.rs:
< / span > < span class = "boring" > //! ```rust,ignore
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! fn main() {
< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! eprintln!(" \nDebug Error {{:?}}:\n{:?}" , e);
< / span > < span class = "boring" > //! eprintln!(" \nAlternative Debug Error {{:#?}}:\n{:#?}\n" , e);
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```console
< / span > < span class = "boring" > //! $ cargo run -q --example example
< / span > < span class = "boring" > //! Debug Error {:?}:
< / span > < span class = "boring" > //! examples/example.rs:46:13: func1 error calling func2
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:21:13: Func2Error(func2 error: calling func3)
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:14:18: Error reading 'foo.txt'
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Alternative Debug Error {:#?}:
< / span > < span class = "boring" > //! ChainError< example::Func1Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:46:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: func1 error calling func2,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< example::Func2Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:21:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: Func2Error(func2 error: calling func3),
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< alloc::string::String> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:14:18" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: " Error reading \'foo.txt\'" ,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! Kind(
< / span > < span class = "boring" > //! NotFound,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > //! func2().context(" func1 error" )?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:21:13: func1 error
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func3() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! derive_str_context!(Func2Error);
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> ChainResult< (), Func2Error> {
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< / span > < span class = "boring" > //! func3().context(Func2Error(" func2 error: calling func3" .into()))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! enum Func1Error {
< / span > < span class = "boring" > //! Func2,
< / span > < span class = "boring" > //! IO(String),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Display for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! match self {
< / span > < span class = "boring" > //! Func1Error::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > //! Func1Error::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Debug for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! write!(f, " {}" , self)
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> ChainResult< (), Func1Error> {
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< / span > < span class = "boring" > //! func2().context(Func1Error::Func2)?;
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< / span > < span class = "boring" > //! let filename = String::from(" bar.txt" );
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< / span > < span class = "boring" > //! do_some_io().context(Func1Error::IO(filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! assert!(match e.kind() {
< / span > < span class = "boring" > //! Func1Error::Func2 => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error calling func2" );
< / span > < span class = "boring" > //! true
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< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! Func1Error::IO(filename) => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error reading '{}'" , filename);
< / span > < span class = "boring" > //! false
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! });
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! assert!(e.find_chain_cause::< Func2Error> ().is_some());
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Some(e) = e.find_chain_cause::< Func2Error> () {
< / span > < span class = "boring" > //! eprintln!(" \nError reported by Func2Error: {}" , e)
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! assert!(e.root_cause().is_some());
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Some(e) = e.root_cause() {
< / span > < span class = "boring" > //! let io_error = e.downcast_ref::< io::Error> ().unwrap();
< / span > < span class = "boring" > //! eprintln!(" \nThe root cause was: std::io::Error: {:#?}" , io_error);
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:48:13: func1 error calling func2
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:23:13: Func2Error(func2 error: calling func3)
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" >
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< / span > < span class = "boring" > #![deny(clippy::all)]
< / span > < span class = "boring" > #![deny(clippy::integer_arithmetic)]
< / span > < span class = "boring" > #![deny(missing_docs)]
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< / span > < span class = "boring" >
< / span > < span class = "boring" > use std::any::TypeId;
< / span > < span class = "boring" > use std::error::Error;
< / span > < span class = "boring" > use std::fmt::{Debug, Display, Formatter, Result};
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< / span > < span class = "boring" > use std::panic::Location;
< / span > < span class = "boring" >
< / span > < span class = "boring" > pub mod prelude {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub mod v1 {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub use super::super::ChainErrorDown as _;
< / span > < span class = "boring" > pub use super::super::ResultTrait as _;
< / span > < span class = "boring" > pub use super::super::{ChainError, ChainResult};
< / span > < span class = "boring" > pub use crate::{derive_err_kind, derive_str_context};
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > /// chains an inner error kind `T` with a causing error
< / span > < span class = "boring" > pub struct ChainError< T> {
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// convenience type alias
< / span > < span class = "boring" > pub type ChainResult< O, E> = std::result::Result< O, ChainError< E> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> ChainError< T> {
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< / span > < span class = "boring" > /// Use the `context()` or `map_context()` Result methods instead of calling this directly
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< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn new(
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > ) -> Self {
< / span > < span class = "boring" > Self {
< / span > < span class = "boring" > occurrence,
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > error_cause,
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// return the root cause of the error chain, if any exists
< / span > < span class = "boring" > pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.iter().last()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type U, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// assert!(f1err.find_cause::< io::Error> ().is_some());
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< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter().filter_map(Error::downcast_ref::< U> ).next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> `, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooError);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooError> > ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooError> implementation detail
< / span > < span class = "boring" > /// err.find_chain_cause::< FooError> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(Error::downcast_ref::< ChainError< U> > )
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> ` or `U`, if any exists and return `U`
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause` and `find_chain_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooErrorKind);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooErrorKind> > ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_chain_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_cause::< FooErrorKind> ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooErrorKind> implementation detail
< / span > < span class = "boring" > /// err.find_kind_or_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_kind_or_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(|e| {
< / span > < span class = "boring" > e.downcast_ref::< ChainError< U> > ()
< / span > < span class = "boring" > .map(|e| e.kind())
< / span > < span class = "boring" > .or_else(|| e.downcast_ref::< U> ())
< / span > < span class = "boring" > })
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Return a reference to T of `ChainError< T> `
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug)]
< / span > < span class = "boring" > /// enum Func1ErrorKind {
< / span > < span class = "boring" > /// Func2,
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// /// impl ::std::fmt::Display for Func1ErrorKind {…}
< / span > < span class = "boring" > /// # impl ::std::fmt::Display for Func1ErrorKind {
< / span > < span class = "boring" > /// # fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > /// # match self {
< / span > < span class = "boring" > /// # Func1ErrorKind::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > /// # Func1ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> ChainResult< (), Func1ErrorKind> {
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< / span > < span class = "boring" > /// func2().context(Func1ErrorKind::Func2)?;
< / span > < span class = "boring" > /// do_some_io().context(Func1ErrorKind::IO(" bar.txt" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// Func1ErrorKind::Func2 => {}
< / span > < span class = "boring" > /// Func1ErrorKind::IO(filename) => panic!(),
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn kind(& self) -> & T {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Returns an Iterator over all error causes/sources
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Example
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn iter(& self) -> impl Iterator< Item = & (dyn Error + 'static)> {
< / span > < span class = "boring" > ErrorIter {
< / span > < span class = "boring" > current: Some(self),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > /// Convenience methods for `Result< > ` to turn the error into a decorated ChainError
< / span > < span class = "boring" > pub trait ResultTrait< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > {
< / span > < span class = "boring" > /// Decorate the error with a `kind` of type `T` and the source `Location`
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Decorate the `error` with a `kind` of type `T` produced with a `FnOnce(& error)` and the source `Location`
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > ResultTrait< O, E>
< / span > < span class = "boring" > for std::result::Result< O, E>
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > )),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => {
< / span > < span class = "boring" > let kind = op(& error_cause);
< / span > < span class = "boring" > Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// An iterator over all error causes/sources
< / span > < span class = "boring" > pub struct ErrorIter< 'a> {
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< / span > < span class = "boring" > current: Option< & 'a (dyn Error + 'static)> ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< 'a> Iterator for ErrorIter< 'a> {
< / span > < span class = "boring" > type Item = & 'a (dyn Error + 'static);
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn next(& mut self) -> Option< Self::Item> {
< / span > < span class = "boring" > let current = self.current;
< / span > < span class = "boring" > self.current = self.current.and_then(Error::source);
< / span > < span class = "boring" > current
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> std::ops::Deref for ChainError< T> {
< / span > < span class = "boring" > type Target = T;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn deref(& self) -> & Self::Target {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience trait to hide the `ChainError< T> ` implementation internals
< / span > < span class = "boring" > pub trait ChainErrorDown {
< / span > < span class = "boring" > /// Test if of type `ChainError< T> `
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
< / span > < span class = "boring" > /// Downcast to a reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to a mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to T of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> ;
< / span > < span class = "boring" > /// Downcast to T mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< U: 'static + Display + Debug> ChainErrorDown for ChainError< U> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > TypeId::of::< T> () == TypeId::of::< U> ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& *(self as *const dyn Error as *const & ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& (*(self as *const dyn Error as *const & ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut (*(self as *mut dyn Error as *mut & mut ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send + Sync {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Display for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
< / span > < span class = "boring" > write!(f, " {}" , self.kind)?;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[cfg(feature = " display-cause" )]
< / span > < span class = "boring" > {
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Display::fmt(& e, f)?;
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > Ok(())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Debug for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
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< / span > < span class = "boring" > if f.alternate() {
< / span > < span class = "boring" > let mut f = f.debug_struct(& format!(" ChainError< {}> " , std::any::type_name::< T> ()));
< / span > < span class = "boring" >
< / span > < span class = "boring" > let f = f
< / span > < span class = "boring" > .field(" occurrence" , & self.occurrence)
< / span > < span class = "boring" > .field(" kind" , & self.kind)
< / span > < span class = "boring" > .field(" source" , & self.source());
< / span > < span class = "boring" >
< / span > < span class = "boring" > f.finish()
< / span > < span class = "boring" > } else {
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< / span > < span class = "boring" > if let Some(ref o) = self.occurrence {
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< / span > < span class = "boring" > write!(f, " {}: " , o)?;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > if TypeId::of::< String> () == TypeId::of::< T> ()
< / span > < span class = "boring" > || TypeId::of::< & str> () == TypeId::of::< T> ()
< / span > < span class = "boring" > {
< / span > < span class = "boring" > Display::fmt(& self.kind, f)?;
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > Debug::fmt(& self.kind, f)?;
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Debug::fmt(& e, f)?;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" > Ok(())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `ChainErrorFrom< T> ` is similar to `From< T> `
< / span > < span class = "boring" > pub trait ChainErrorFrom< T> : Sized {
< / span > < span class = "boring" > /// similar to From< T> ::from()
< / span > < span class = "boring" > fn chain_error_from(from: T, line_filename: Option< String> ) -> ChainError< Self> ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `IntoChainError< T> ` is similar to `Into< T> `
< / span > < span class = "boring" > pub trait IntoChainError< T> : Sized {
< / span > < span class = "boring" > /// similar to Into< T> ::into()
< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< T> ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> IntoChainError< U> for T
< / span > < span class = "boring" > where
< / span > < span class = "boring" > U: ChainErrorFrom< T> ,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< U> {
< / span > < span class = "boring" > U::chain_error_from(self, line_filename)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> ChainErrorFrom< T> for U
< / span > < span class = "boring" > where
< / span > < span class = "boring" > T: Into< U> ,
< / span > < span class = "boring" > U: 'static + Display + Debug,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn chain_error_from(t: T, line_filename: Option< String> ) -> ChainError< Self> {
< / span > < span class = "boring" > let e: U = t.into();
< / span > < span class = "boring" > ChainError::new(e, None, line_filename)
< / span > < span class = "boring" > }
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience macro to create a " new type" T(String) and implement Display + Debug for T
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
< / span > < span class = "boring" > /// # use crate::chainerror::*;
< / span > < span class = "boring" > /// # use std::error::Error;
< / span > < span class = "boring" > /// # use std::io;
< / span > < span class = "boring" > /// # use std::result::Result;
< / span > < span class = "boring" > /// # fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// # Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// # Ok(())
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> ChainResult< (), Func2Error> {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// # if let Err(e) = func1() {
< / span > < span class = "boring" > /// # if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// # assert!(f1err.find_cause::< ChainError< Func2Error> > ().is_some());
< / span > < span class = "boring" > /// # assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
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< / span > < span class = "boring" > macro_rules! derive_str_context {
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< / span > < span class = "boring" > ($e:ident) => {
< / span > < span class = "boring" > #[derive(Clone)]
< / span > < span class = "boring" > pub struct $e(pub String);
< / span > < span class = "boring" > impl ::std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}" , self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}({})" , stringify!($e), self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::error::Error for $e {}
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Derive an Error for an ErrorKind, which wraps a `ChainError` and implements a `kind()` method
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// It basically hides `ChainError` to the outside and only exposes the `kind()`
< / span > < span class = "boring" > /// method.
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Error::kind() returns the ErrorKind
< / span > < span class = "boring" > /// Error::source() returns the parent error
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io(_f: & str) -> std::result::Result< (), io::Error> {
< / span > < span class = "boring" > /// return Err(io::Error::from(io::ErrorKind::NotFound));
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug, Clone)]
< / span > < span class = "boring" > /// pub enum ErrorKind {
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// FatalError(String),
< / span > < span class = "boring" > /// Unknown,
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// derive_err_kind!(Error, ErrorKind);
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl std::fmt::Display for ErrorKind {
< / span > < span class = "boring" > /// fn fmt(& self, f: & mut ::std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > /// match self {
< / span > < span class = "boring" > /// ErrorKind::FatalError(e) => write!(f, " fatal error {}" , e),
< / span > < span class = "boring" > /// ErrorKind::Unknown => write!(f, " unknown error" ),
< / span > < span class = "boring" > /// ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl ErrorKind {
< / span > < span class = "boring" > /// fn from_io_error(e: & io::Error, f: String) -> Self {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// io::ErrorKind::BrokenPipe => panic!(" Should not happen" ),
< / span > < span class = "boring" > /// io::ErrorKind::ConnectionReset => {
< / span > < span class = "boring" > /// ErrorKind::FatalError(format!(" While reading `{}`: {}" , f, e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// _ => ErrorKind::IO(f),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl From< & io::Error> for ErrorKind {
< / span > < span class = "boring" > /// fn from(e: & io::Error) -> Self {
< / span > < span class = "boring" > /// ErrorKind::IO(format!(" {}" , e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// pub fn func1() -> std::result::Result< (), Error> {
< / span > < span class = "boring" > /// let filename = " bar.txt" ;
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from_io_error(e, filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::IO(filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from(e))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
< / span > < span class = "boring" > macro_rules! derive_err_kind {
< / span > < span class = "boring" > ($e:ident, $k:ident) => {
< / span > < span class = "boring" > pub struct $e($crate::ChainError< $k> );
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl $e {
< / span > < span class = "boring" > pub fn kind(& self) -> & $k {
< / span > < span class = "boring" > self.0.kind()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< $k> for $e {
< / span > < span class = "boring" > fn from(e: $k) -> Self {
< / span > < span class = "boring" > $e($crate::ChainError::new(e, None, None))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< ChainError< $k> > for $e {
< / span > < span class = "boring" > fn from(e: $crate::ChainError< $k> ) -> Self {
< / span > < span class = "boring" > $e(e)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< & $e> for $k
< / span > < span class = "boring" > where
< / span > < span class = "boring" > $k: Clone,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > fn from(e: & $e) -> Self {
< / span > < span class = "boring" > e.kind().clone()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::error::Error for $e {
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn std::error::Error + 'static)> {
< / span > < span class = "boring" > self.0.source()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Display::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Debug::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < / code > < / pre > < / pre >
< h1 > < a class = "header" href = "#the-root-cause-of-all-errors" id = "the-root-cause-of-all-errors" > The root cause of all Errors< / a > < / h1 >
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< p > < code > chainerror< / code > also has some helper methods:< / p >
< pre > < code class = "language-rust ignore" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool
fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> >
fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> >
fn root_cause(& self) -> Option< & (dyn Error + 'static)>
fn find_cause< U: Error + 'static> (& self) -> Option< & U>
fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> >
fn kind< 'a> (& 'a self) -> & 'a T
< / code > < / pre >
< p > Using < code > downcast_chain_ref::< String> ()< / code > gives a < code > ChainError< String> < / code > , which can be used
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to call < code > .find_cause::< io::Error> ()< / code > . < / p >
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< pre > < code class = "language-rust ignore" > if let Some(s) = e.downcast_chain_ref::< String> () {
if let Some(ioerror) = s.find_cause::< io::Error> () {
< / code > < / pre >
< p > or to use < code > .root_cause()< / code > , which of course can be of any type implementing < code > std::error::Error< / code > .< / p >
< pre > < code class = "language-rust ignore" > if let Some(e) = s.root_cause() {
< / code > < / pre >
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< pre > < pre class = "playground" > < code class = "language-rust" > use chainerror::prelude::v1::*;
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use std::error::Error;
use std::io;
use std::result::Result;
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fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
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Err(io::Error::from(io::ErrorKind::NotFound))?;
Ok(())
}
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fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
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let filename = " foo.txt" ;
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do_some_io().context(format!(" Error reading '{}'" , filename))?;
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Ok(())
}
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fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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func2().context(format!(" func1 error" ))?;
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Ok(())
}
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fn main() -> Result< (), Box< dyn Error + Send + Sync> > {
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if let Err(e) = func1() {
eprintln!(" Error: {}" , e);
if let Some(s) = e.downcast_chain_ref::< String> () {
if let Some(ioerror) = s.find_cause::< io::Error> () {
eprintln!(" caused by: std::io::Error: {}" , ioerror);
match ioerror.kind() {
io::ErrorKind::NotFound => eprintln!(" of kind: std::io::ErrorKind::NotFound" ),
_ => {}
}
}
if let Some(e) = s.root_cause() {
let ioerror = e.downcast_ref::< io::Error> ().unwrap();
eprintln!(" The root cause was: std::io::Error: {:#?}" , ioerror);
}
}
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std::process::exit(1);
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}
Ok(())
}
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< span class = "boring" > #[allow(dead_code)]
< / span > < span class = "boring" > mod chainerror {
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< / span > < span class = "boring" > //! `chainerror` provides an error backtrace without doing a real backtrace, so even after you `strip` your
< / span > < span class = "boring" > //! binaries, you still have the error backtrace.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `chainerror` has no dependencies!
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
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< / span > < span class = "boring" > //! It encapsulates all types, which have `Display + Debug` and can store the error cause internally.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Along with the `ChainError< T> ` struct, `chainerror` comes with some useful helper macros to save a lot of typing.
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! Debug information is worth it!
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ## Features
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `display-cause`
< / span > < span class = "boring" > //! : turn on printing a backtrace of the errors in `Display`
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Tutorial
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Read the [Tutorial](https://haraldh.github.io/chainerror/tutorial1.html)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Examples
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! examples/example.rs:
< / span > < span class = "boring" > //! ```rust,ignore
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! fn main() {
< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! eprintln!(" \nDebug Error {{:?}}:\n{:?}" , e);
< / span > < span class = "boring" > //! eprintln!(" \nAlternative Debug Error {{:#?}}:\n{:#?}\n" , e);
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```console
< / span > < span class = "boring" > //! $ cargo run -q --example example
< / span > < span class = "boring" > //! Debug Error {:?}:
< / span > < span class = "boring" > //! examples/example.rs:46:13: func1 error calling func2
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:21:13: Func2Error(func2 error: calling func3)
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:14:18: Error reading 'foo.txt'
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Alternative Debug Error {:#?}:
< / span > < span class = "boring" > //! ChainError< example::Func1Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:46:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: func1 error calling func2,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< example::Func2Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:21:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: Func2Error(func2 error: calling func3),
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< alloc::string::String> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:14:18" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: " Error reading \'foo.txt\'" ,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! Kind(
< / span > < span class = "boring" > //! NotFound,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > //! func2().context(" func1 error" )?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:21:13: func1 error
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func3() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! derive_str_context!(Func2Error);
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> ChainResult< (), Func2Error> {
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< / span > < span class = "boring" > //! func3().context(Func2Error(" func2 error: calling func3" .into()))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! enum Func1Error {
< / span > < span class = "boring" > //! Func2,
< / span > < span class = "boring" > //! IO(String),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Display for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! match self {
< / span > < span class = "boring" > //! Func1Error::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > //! Func1Error::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Debug for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! write!(f, " {}" , self)
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> ChainResult< (), Func1Error> {
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< / span > < span class = "boring" > //! func2().context(Func1Error::Func2)?;
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< / span > < span class = "boring" > //! let filename = String::from(" bar.txt" );
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< / span > < span class = "boring" > //! do_some_io().context(Func1Error::IO(filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! assert!(match e.kind() {
< / span > < span class = "boring" > //! Func1Error::Func2 => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error calling func2" );
< / span > < span class = "boring" > //! true
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! Func1Error::IO(filename) => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error reading '{}'" , filename);
< / span > < span class = "boring" > //! false
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< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! });
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! assert!(e.find_chain_cause::< Func2Error> ().is_some());
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Some(e) = e.find_chain_cause::< Func2Error> () {
< / span > < span class = "boring" > //! eprintln!(" \nError reported by Func2Error: {}" , e)
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! assert!(e.root_cause().is_some());
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Some(e) = e.root_cause() {
< / span > < span class = "boring" > //! let io_error = e.downcast_ref::< io::Error> ().unwrap();
< / span > < span class = "boring" > //! eprintln!(" \nThe root cause was: std::io::Error: {:#?}" , io_error);
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:48:13: func1 error calling func2
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:23:13: Func2Error(func2 error: calling func3)
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" >
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< / span > < span class = "boring" > #![deny(clippy::all)]
< / span > < span class = "boring" > #![deny(clippy::integer_arithmetic)]
< / span > < span class = "boring" > #![deny(missing_docs)]
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< / span > < span class = "boring" >
< / span > < span class = "boring" > use std::any::TypeId;
< / span > < span class = "boring" > use std::error::Error;
< / span > < span class = "boring" > use std::fmt::{Debug, Display, Formatter, Result};
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< / span > < span class = "boring" > use std::panic::Location;
< / span > < span class = "boring" >
< / span > < span class = "boring" > pub mod prelude {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub mod v1 {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub use super::super::ChainErrorDown as _;
< / span > < span class = "boring" > pub use super::super::ResultTrait as _;
< / span > < span class = "boring" > pub use super::super::{ChainError, ChainResult};
< / span > < span class = "boring" > pub use crate::{derive_err_kind, derive_str_context};
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > /// chains an inner error kind `T` with a causing error
< / span > < span class = "boring" > pub struct ChainError< T> {
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// convenience type alias
< / span > < span class = "boring" > pub type ChainResult< O, E> = std::result::Result< O, ChainError< E> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> ChainError< T> {
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< / span > < span class = "boring" > /// Use the `context()` or `map_context()` Result methods instead of calling this directly
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< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn new(
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > ) -> Self {
< / span > < span class = "boring" > Self {
< / span > < span class = "boring" > occurrence,
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > error_cause,
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// return the root cause of the error chain, if any exists
< / span > < span class = "boring" > pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.iter().last()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type U, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// assert!(f1err.find_cause::< io::Error> ().is_some());
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< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter().filter_map(Error::downcast_ref::< U> ).next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> `, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooError);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooError> > ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooError> implementation detail
< / span > < span class = "boring" > /// err.find_chain_cause::< FooError> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(Error::downcast_ref::< ChainError< U> > )
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> ` or `U`, if any exists and return `U`
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause` and `find_chain_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooErrorKind);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooErrorKind> > ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_chain_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_cause::< FooErrorKind> ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooErrorKind> implementation detail
< / span > < span class = "boring" > /// err.find_kind_or_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_kind_or_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(|e| {
< / span > < span class = "boring" > e.downcast_ref::< ChainError< U> > ()
< / span > < span class = "boring" > .map(|e| e.kind())
< / span > < span class = "boring" > .or_else(|| e.downcast_ref::< U> ())
< / span > < span class = "boring" > })
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Return a reference to T of `ChainError< T> `
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug)]
< / span > < span class = "boring" > /// enum Func1ErrorKind {
< / span > < span class = "boring" > /// Func2,
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// /// impl ::std::fmt::Display for Func1ErrorKind {…}
< / span > < span class = "boring" > /// # impl ::std::fmt::Display for Func1ErrorKind {
< / span > < span class = "boring" > /// # fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > /// # match self {
< / span > < span class = "boring" > /// # Func1ErrorKind::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > /// # Func1ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> ChainResult< (), Func1ErrorKind> {
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< / span > < span class = "boring" > /// func2().context(Func1ErrorKind::Func2)?;
< / span > < span class = "boring" > /// do_some_io().context(Func1ErrorKind::IO(" bar.txt" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// Func1ErrorKind::Func2 => {}
< / span > < span class = "boring" > /// Func1ErrorKind::IO(filename) => panic!(),
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn kind(& self) -> & T {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Returns an Iterator over all error causes/sources
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Example
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn iter(& self) -> impl Iterator< Item = & (dyn Error + 'static)> {
< / span > < span class = "boring" > ErrorIter {
< / span > < span class = "boring" > current: Some(self),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > /// Convenience methods for `Result< > ` to turn the error into a decorated ChainError
< / span > < span class = "boring" > pub trait ResultTrait< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > {
< / span > < span class = "boring" > /// Decorate the error with a `kind` of type `T` and the source `Location`
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Decorate the `error` with a `kind` of type `T` produced with a `FnOnce(& error)` and the source `Location`
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > ResultTrait< O, E>
< / span > < span class = "boring" > for std::result::Result< O, E>
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > )),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => {
< / span > < span class = "boring" > let kind = op(& error_cause);
< / span > < span class = "boring" > Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// An iterator over all error causes/sources
< / span > < span class = "boring" > pub struct ErrorIter< 'a> {
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< / span > < span class = "boring" > current: Option< & 'a (dyn Error + 'static)> ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< 'a> Iterator for ErrorIter< 'a> {
< / span > < span class = "boring" > type Item = & 'a (dyn Error + 'static);
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn next(& mut self) -> Option< Self::Item> {
< / span > < span class = "boring" > let current = self.current;
< / span > < span class = "boring" > self.current = self.current.and_then(Error::source);
< / span > < span class = "boring" > current
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> std::ops::Deref for ChainError< T> {
< / span > < span class = "boring" > type Target = T;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn deref(& self) -> & Self::Target {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience trait to hide the `ChainError< T> ` implementation internals
< / span > < span class = "boring" > pub trait ChainErrorDown {
< / span > < span class = "boring" > /// Test if of type `ChainError< T> `
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
< / span > < span class = "boring" > /// Downcast to a reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to a mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to T of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> ;
< / span > < span class = "boring" > /// Downcast to T mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< U: 'static + Display + Debug> ChainErrorDown for ChainError< U> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > TypeId::of::< T> () == TypeId::of::< U> ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& *(self as *const dyn Error as *const & ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& (*(self as *const dyn Error as *const & ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut (*(self as *mut dyn Error as *mut & mut ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send + Sync {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Display for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
< / span > < span class = "boring" > write!(f, " {}" , self.kind)?;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[cfg(feature = " display-cause" )]
< / span > < span class = "boring" > {
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Display::fmt(& e, f)?;
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > Ok(())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Debug for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
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< / span > < span class = "boring" > if f.alternate() {
< / span > < span class = "boring" > let mut f = f.debug_struct(& format!(" ChainError< {}> " , std::any::type_name::< T> ()));
< / span > < span class = "boring" >
< / span > < span class = "boring" > let f = f
< / span > < span class = "boring" > .field(" occurrence" , & self.occurrence)
< / span > < span class = "boring" > .field(" kind" , & self.kind)
< / span > < span class = "boring" > .field(" source" , & self.source());
< / span > < span class = "boring" >
< / span > < span class = "boring" > f.finish()
< / span > < span class = "boring" > } else {
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< / span > < span class = "boring" > if let Some(ref o) = self.occurrence {
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< / span > < span class = "boring" > write!(f, " {}: " , o)?;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > if TypeId::of::< String> () == TypeId::of::< T> ()
< / span > < span class = "boring" > || TypeId::of::< & str> () == TypeId::of::< T> ()
< / span > < span class = "boring" > {
< / span > < span class = "boring" > Display::fmt(& self.kind, f)?;
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > Debug::fmt(& self.kind, f)?;
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Debug::fmt(& e, f)?;
< / span > < span class = "boring" > }
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< / span > < span class = "boring" > Ok(())
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< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `ChainErrorFrom< T> ` is similar to `From< T> `
< / span > < span class = "boring" > pub trait ChainErrorFrom< T> : Sized {
< / span > < span class = "boring" > /// similar to From< T> ::from()
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< / span > < span class = "boring" > fn chain_error_from(from: T, line_filename: Option< String> ) -> ChainError< Self> ;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `IntoChainError< T> ` is similar to `Into< T> `
< / span > < span class = "boring" > pub trait IntoChainError< T> : Sized {
< / span > < span class = "boring" > /// similar to Into< T> ::into()
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< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< T> ;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> IntoChainError< U> for T
< / span > < span class = "boring" > where
< / span > < span class = "boring" > U: ChainErrorFrom< T> ,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
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< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< U> {
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< / span > < span class = "boring" > U::chain_error_from(self, line_filename)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> ChainErrorFrom< T> for U
< / span > < span class = "boring" > where
< / span > < span class = "boring" > T: Into< U> ,
< / span > < span class = "boring" > U: 'static + Display + Debug,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn chain_error_from(t: T, line_filename: Option< String> ) -> ChainError< Self> {
< / span > < span class = "boring" > let e: U = t.into();
< / span > < span class = "boring" > ChainError::new(e, None, line_filename)
< / span > < span class = "boring" > }
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience macro to create a " new type" T(String) and implement Display + Debug for T
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
< / span > < span class = "boring" > /// # use crate::chainerror::*;
< / span > < span class = "boring" > /// # use std::error::Error;
< / span > < span class = "boring" > /// # use std::io;
< / span > < span class = "boring" > /// # use std::result::Result;
< / span > < span class = "boring" > /// # fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// # Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// # Ok(())
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> ChainResult< (), Func2Error> {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// # if let Err(e) = func1() {
< / span > < span class = "boring" > /// # if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// # assert!(f1err.find_cause::< ChainError< Func2Error> > ().is_some());
< / span > < span class = "boring" > /// # assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
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< / span > < span class = "boring" > macro_rules! derive_str_context {
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< / span > < span class = "boring" > ($e:ident) => {
< / span > < span class = "boring" > #[derive(Clone)]
< / span > < span class = "boring" > pub struct $e(pub String);
< / span > < span class = "boring" > impl ::std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}" , self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}({})" , stringify!($e), self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::error::Error for $e {}
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Derive an Error for an ErrorKind, which wraps a `ChainError` and implements a `kind()` method
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// It basically hides `ChainError` to the outside and only exposes the `kind()`
< / span > < span class = "boring" > /// method.
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Error::kind() returns the ErrorKind
< / span > < span class = "boring" > /// Error::source() returns the parent error
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io(_f: & str) -> std::result::Result< (), io::Error> {
< / span > < span class = "boring" > /// return Err(io::Error::from(io::ErrorKind::NotFound));
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug, Clone)]
< / span > < span class = "boring" > /// pub enum ErrorKind {
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// FatalError(String),
< / span > < span class = "boring" > /// Unknown,
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// derive_err_kind!(Error, ErrorKind);
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl std::fmt::Display for ErrorKind {
< / span > < span class = "boring" > /// fn fmt(& self, f: & mut ::std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > /// match self {
< / span > < span class = "boring" > /// ErrorKind::FatalError(e) => write!(f, " fatal error {}" , e),
< / span > < span class = "boring" > /// ErrorKind::Unknown => write!(f, " unknown error" ),
< / span > < span class = "boring" > /// ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl ErrorKind {
< / span > < span class = "boring" > /// fn from_io_error(e: & io::Error, f: String) -> Self {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// io::ErrorKind::BrokenPipe => panic!(" Should not happen" ),
< / span > < span class = "boring" > /// io::ErrorKind::ConnectionReset => {
< / span > < span class = "boring" > /// ErrorKind::FatalError(format!(" While reading `{}`: {}" , f, e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// _ => ErrorKind::IO(f),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl From< & io::Error> for ErrorKind {
< / span > < span class = "boring" > /// fn from(e: & io::Error) -> Self {
< / span > < span class = "boring" > /// ErrorKind::IO(format!(" {}" , e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// pub fn func1() -> std::result::Result< (), Error> {
< / span > < span class = "boring" > /// let filename = " bar.txt" ;
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from_io_error(e, filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::IO(filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from(e))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
< / span > < span class = "boring" > macro_rules! derive_err_kind {
< / span > < span class = "boring" > ($e:ident, $k:ident) => {
< / span > < span class = "boring" > pub struct $e($crate::ChainError< $k> );
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl $e {
< / span > < span class = "boring" > pub fn kind(& self) -> & $k {
< / span > < span class = "boring" > self.0.kind()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< $k> for $e {
< / span > < span class = "boring" > fn from(e: $k) -> Self {
< / span > < span class = "boring" > $e($crate::ChainError::new(e, None, None))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< ChainError< $k> > for $e {
< / span > < span class = "boring" > fn from(e: $crate::ChainError< $k> ) -> Self {
< / span > < span class = "boring" > $e(e)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< & $e> for $k
< / span > < span class = "boring" > where
< / span > < span class = "boring" > $k: Clone,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > fn from(e: & $e) -> Self {
< / span > < span class = "boring" > e.kind().clone()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::error::Error for $e {
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn std::error::Error + 'static)> {
< / span > < span class = "boring" > self.0.source()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Display::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Debug::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < / code > < / pre > < / pre >
< h1 > < a class = "header" href = "#finding-an-error-cause" id = "finding-an-error-cause" > Finding an Error cause< / a > < / h1 >
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< p > To distinguish the errors occuring in various places, we can define named string errors with the
" new type" pattern.< / p >
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< pre > < code class = "language-rust ignore" > derive_str_context!(Func2Error);
derive_str_context!(Func1Error);
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< / code > < / pre >
< p > Instead of < code > ChainError< String> < / code > we now have < code > struct Func1Error(String)< / code > and < code > ChainError< Func1Error> < / code > .< / p >
< p > In the < code > main< / code > function you can see, how we can match the different errors.< / p >
< p > Also see:< / p >
< pre > < code class = "language-rust ignore" > if let Some(f2err) = f1err.find_chain_cause::< Func2Error> () {
< / code > < / pre >
< p > as a shortcut to< / p >
< pre > < code class = "language-rust ignore" > if let Some(f2err) = f1err.find_cause::< ChainError< Func2Error> > () {
< / code > < / pre >
< p > hiding the < code > ChainError< T> < / code > implementation detail.< / p >
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< pre > < pre class = "playground" > < code class = "language-rust" > use chainerror::prelude::v1::*;
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use std::error::Error;
use std::io;
use std::result::Result;
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fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
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Err(io::Error::from(io::ErrorKind::NotFound))?;
Ok(())
}
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derive_str_context!(Func2Error);
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fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
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let filename = " foo.txt" ;
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do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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Ok(())
}
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derive_str_context!(Func1Error);
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fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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func2().context(Func1Error(format!(" func1 error" )))?;
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Ok(())
}
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fn main() -> Result< (), Box< dyn Error + Send + Sync> > {
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if let Err(e) = func1() {
if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
eprintln!(" Func1Error: {}" , f1err);
if let Some(f2err) = f1err.find_cause::< ChainError< Func2Error> > () {
eprintln!(" Func2Error: {}" , f2err);
}
if let Some(f2err) = f1err.find_chain_cause::< Func2Error> () {
eprintln!(" Debug Func2Error:\n{:?}" , f2err);
}
}
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std::process::exit(1);
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}
Ok(())
}
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< span class = "boring" > #[allow(dead_code)]
< / span > < span class = "boring" > mod chainerror {
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< / span > < span class = "boring" > //! `chainerror` provides an error backtrace without doing a real backtrace, so even after you `strip` your
< / span > < span class = "boring" > //! binaries, you still have the error backtrace.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `chainerror` has no dependencies!
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
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< / span > < span class = "boring" > //! It encapsulates all types, which have `Display + Debug` and can store the error cause internally.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Along with the `ChainError< T> ` struct, `chainerror` comes with some useful helper macros to save a lot of typing.
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! Debug information is worth it!
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ## Features
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `display-cause`
< / span > < span class = "boring" > //! : turn on printing a backtrace of the errors in `Display`
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Tutorial
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Read the [Tutorial](https://haraldh.github.io/chainerror/tutorial1.html)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Examples
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! examples/example.rs:
< / span > < span class = "boring" > //! ```rust,ignore
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! fn main() {
< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! eprintln!(" \nDebug Error {{:?}}:\n{:?}" , e);
< / span > < span class = "boring" > //! eprintln!(" \nAlternative Debug Error {{:#?}}:\n{:#?}\n" , e);
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```console
< / span > < span class = "boring" > //! $ cargo run -q --example example
< / span > < span class = "boring" > //! Debug Error {:?}:
< / span > < span class = "boring" > //! examples/example.rs:46:13: func1 error calling func2
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:21:13: Func2Error(func2 error: calling func3)
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:14:18: Error reading 'foo.txt'
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Alternative Debug Error {:#?}:
< / span > < span class = "boring" > //! ChainError< example::Func1Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:46:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: func1 error calling func2,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< example::Func2Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:21:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: Func2Error(func2 error: calling func3),
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< alloc::string::String> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:14:18" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: " Error reading \'foo.txt\'" ,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! Kind(
< / span > < span class = "boring" > //! NotFound,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > //! func2().context(" func1 error" )?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:21:13: func1 error
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func3() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! derive_str_context!(Func2Error);
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> ChainResult< (), Func2Error> {
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< / span > < span class = "boring" > //! func3().context(Func2Error(" func2 error: calling func3" .into()))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! enum Func1Error {
< / span > < span class = "boring" > //! Func2,
< / span > < span class = "boring" > //! IO(String),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Display for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! match self {
< / span > < span class = "boring" > //! Func1Error::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > //! Func1Error::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Debug for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! write!(f, " {}" , self)
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> ChainResult< (), Func1Error> {
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< / span > < span class = "boring" > //! func2().context(Func1Error::Func2)?;
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< / span > < span class = "boring" > //! let filename = String::from(" bar.txt" );
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< / span > < span class = "boring" > //! do_some_io().context(Func1Error::IO(filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! assert!(match e.kind() {
< / span > < span class = "boring" > //! Func1Error::Func2 => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error calling func2" );
< / span > < span class = "boring" > //! true
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< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! Func1Error::IO(filename) => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error reading '{}'" , filename);
< / span > < span class = "boring" > //! false
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! });
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! assert!(e.find_chain_cause::< Func2Error> ().is_some());
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Some(e) = e.find_chain_cause::< Func2Error> () {
< / span > < span class = "boring" > //! eprintln!(" \nError reported by Func2Error: {}" , e)
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! assert!(e.root_cause().is_some());
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Some(e) = e.root_cause() {
< / span > < span class = "boring" > //! let io_error = e.downcast_ref::< io::Error> ().unwrap();
< / span > < span class = "boring" > //! eprintln!(" \nThe root cause was: std::io::Error: {:#?}" , io_error);
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:48:13: func1 error calling func2
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:23:13: Func2Error(func2 error: calling func3)
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" >
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< / span > < span class = "boring" > #![deny(clippy::all)]
< / span > < span class = "boring" > #![deny(clippy::integer_arithmetic)]
< / span > < span class = "boring" > #![deny(missing_docs)]
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< / span > < span class = "boring" >
< / span > < span class = "boring" > use std::any::TypeId;
< / span > < span class = "boring" > use std::error::Error;
< / span > < span class = "boring" > use std::fmt::{Debug, Display, Formatter, Result};
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< / span > < span class = "boring" > use std::panic::Location;
< / span > < span class = "boring" >
< / span > < span class = "boring" > pub mod prelude {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub mod v1 {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub use super::super::ChainErrorDown as _;
< / span > < span class = "boring" > pub use super::super::ResultTrait as _;
< / span > < span class = "boring" > pub use super::super::{ChainError, ChainResult};
< / span > < span class = "boring" > pub use crate::{derive_err_kind, derive_str_context};
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > /// chains an inner error kind `T` with a causing error
< / span > < span class = "boring" > pub struct ChainError< T> {
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// convenience type alias
< / span > < span class = "boring" > pub type ChainResult< O, E> = std::result::Result< O, ChainError< E> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> ChainError< T> {
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< / span > < span class = "boring" > /// Use the `context()` or `map_context()` Result methods instead of calling this directly
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< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn new(
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > ) -> Self {
< / span > < span class = "boring" > Self {
< / span > < span class = "boring" > occurrence,
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > error_cause,
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// return the root cause of the error chain, if any exists
< / span > < span class = "boring" > pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.iter().last()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type U, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// assert!(f1err.find_cause::< io::Error> ().is_some());
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< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter().filter_map(Error::downcast_ref::< U> ).next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> `, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooError);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooError> > ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooError> implementation detail
< / span > < span class = "boring" > /// err.find_chain_cause::< FooError> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(Error::downcast_ref::< ChainError< U> > )
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> ` or `U`, if any exists and return `U`
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause` and `find_chain_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooErrorKind);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooErrorKind> > ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_chain_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_cause::< FooErrorKind> ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooErrorKind> implementation detail
< / span > < span class = "boring" > /// err.find_kind_or_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_kind_or_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(|e| {
< / span > < span class = "boring" > e.downcast_ref::< ChainError< U> > ()
< / span > < span class = "boring" > .map(|e| e.kind())
< / span > < span class = "boring" > .or_else(|| e.downcast_ref::< U> ())
< / span > < span class = "boring" > })
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Return a reference to T of `ChainError< T> `
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug)]
< / span > < span class = "boring" > /// enum Func1ErrorKind {
< / span > < span class = "boring" > /// Func2,
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// /// impl ::std::fmt::Display for Func1ErrorKind {…}
< / span > < span class = "boring" > /// # impl ::std::fmt::Display for Func1ErrorKind {
< / span > < span class = "boring" > /// # fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > /// # match self {
< / span > < span class = "boring" > /// # Func1ErrorKind::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > /// # Func1ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> ChainResult< (), Func1ErrorKind> {
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< / span > < span class = "boring" > /// func2().context(Func1ErrorKind::Func2)?;
< / span > < span class = "boring" > /// do_some_io().context(Func1ErrorKind::IO(" bar.txt" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// Func1ErrorKind::Func2 => {}
< / span > < span class = "boring" > /// Func1ErrorKind::IO(filename) => panic!(),
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn kind(& self) -> & T {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Returns an Iterator over all error causes/sources
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Example
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn iter(& self) -> impl Iterator< Item = & (dyn Error + 'static)> {
< / span > < span class = "boring" > ErrorIter {
< / span > < span class = "boring" > current: Some(self),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > /// Convenience methods for `Result< > ` to turn the error into a decorated ChainError
< / span > < span class = "boring" > pub trait ResultTrait< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > {
< / span > < span class = "boring" > /// Decorate the error with a `kind` of type `T` and the source `Location`
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Decorate the `error` with a `kind` of type `T` produced with a `FnOnce(& error)` and the source `Location`
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > ResultTrait< O, E>
< / span > < span class = "boring" > for std::result::Result< O, E>
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > )),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => {
< / span > < span class = "boring" > let kind = op(& error_cause);
< / span > < span class = "boring" > Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// An iterator over all error causes/sources
< / span > < span class = "boring" > pub struct ErrorIter< 'a> {
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< / span > < span class = "boring" > current: Option< & 'a (dyn Error + 'static)> ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< 'a> Iterator for ErrorIter< 'a> {
< / span > < span class = "boring" > type Item = & 'a (dyn Error + 'static);
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn next(& mut self) -> Option< Self::Item> {
< / span > < span class = "boring" > let current = self.current;
< / span > < span class = "boring" > self.current = self.current.and_then(Error::source);
< / span > < span class = "boring" > current
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> std::ops::Deref for ChainError< T> {
< / span > < span class = "boring" > type Target = T;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn deref(& self) -> & Self::Target {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience trait to hide the `ChainError< T> ` implementation internals
< / span > < span class = "boring" > pub trait ChainErrorDown {
< / span > < span class = "boring" > /// Test if of type `ChainError< T> `
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
< / span > < span class = "boring" > /// Downcast to a reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to a mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to T of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> ;
< / span > < span class = "boring" > /// Downcast to T mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< U: 'static + Display + Debug> ChainErrorDown for ChainError< U> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > TypeId::of::< T> () == TypeId::of::< U> ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& *(self as *const dyn Error as *const & ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& (*(self as *const dyn Error as *const & ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut (*(self as *mut dyn Error as *mut & mut ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send + Sync {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Display for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
< / span > < span class = "boring" > write!(f, " {}" , self.kind)?;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[cfg(feature = " display-cause" )]
< / span > < span class = "boring" > {
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Display::fmt(& e, f)?;
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > Ok(())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Debug for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
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< / span > < span class = "boring" > if f.alternate() {
< / span > < span class = "boring" > let mut f = f.debug_struct(& format!(" ChainError< {}> " , std::any::type_name::< T> ()));
< / span > < span class = "boring" >
< / span > < span class = "boring" > let f = f
< / span > < span class = "boring" > .field(" occurrence" , & self.occurrence)
< / span > < span class = "boring" > .field(" kind" , & self.kind)
< / span > < span class = "boring" > .field(" source" , & self.source());
< / span > < span class = "boring" >
< / span > < span class = "boring" > f.finish()
< / span > < span class = "boring" > } else {
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< / span > < span class = "boring" > if let Some(ref o) = self.occurrence {
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< / span > < span class = "boring" > write!(f, " {}: " , o)?;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > if TypeId::of::< String> () == TypeId::of::< T> ()
< / span > < span class = "boring" > || TypeId::of::< & str> () == TypeId::of::< T> ()
< / span > < span class = "boring" > {
< / span > < span class = "boring" > Display::fmt(& self.kind, f)?;
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > Debug::fmt(& self.kind, f)?;
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Debug::fmt(& e, f)?;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" > Ok(())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `ChainErrorFrom< T> ` is similar to `From< T> `
< / span > < span class = "boring" > pub trait ChainErrorFrom< T> : Sized {
< / span > < span class = "boring" > /// similar to From< T> ::from()
< / span > < span class = "boring" > fn chain_error_from(from: T, line_filename: Option< String> ) -> ChainError< Self> ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `IntoChainError< T> ` is similar to `Into< T> `
< / span > < span class = "boring" > pub trait IntoChainError< T> : Sized {
< / span > < span class = "boring" > /// similar to Into< T> ::into()
< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< T> ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> IntoChainError< U> for T
< / span > < span class = "boring" > where
< / span > < span class = "boring" > U: ChainErrorFrom< T> ,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< U> {
< / span > < span class = "boring" > U::chain_error_from(self, line_filename)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> ChainErrorFrom< T> for U
< / span > < span class = "boring" > where
< / span > < span class = "boring" > T: Into< U> ,
< / span > < span class = "boring" > U: 'static + Display + Debug,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn chain_error_from(t: T, line_filename: Option< String> ) -> ChainError< Self> {
< / span > < span class = "boring" > let e: U = t.into();
< / span > < span class = "boring" > ChainError::new(e, None, line_filename)
< / span > < span class = "boring" > }
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience macro to create a " new type" T(String) and implement Display + Debug for T
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
< / span > < span class = "boring" > /// # use crate::chainerror::*;
< / span > < span class = "boring" > /// # use std::error::Error;
< / span > < span class = "boring" > /// # use std::io;
< / span > < span class = "boring" > /// # use std::result::Result;
< / span > < span class = "boring" > /// # fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// # Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// # Ok(())
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> ChainResult< (), Func2Error> {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// # if let Err(e) = func1() {
< / span > < span class = "boring" > /// # if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// # assert!(f1err.find_cause::< ChainError< Func2Error> > ().is_some());
< / span > < span class = "boring" > /// # assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
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< / span > < span class = "boring" > macro_rules! derive_str_context {
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< / span > < span class = "boring" > ($e:ident) => {
< / span > < span class = "boring" > #[derive(Clone)]
< / span > < span class = "boring" > pub struct $e(pub String);
< / span > < span class = "boring" > impl ::std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}" , self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}({})" , stringify!($e), self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::error::Error for $e {}
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Derive an Error for an ErrorKind, which wraps a `ChainError` and implements a `kind()` method
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// It basically hides `ChainError` to the outside and only exposes the `kind()`
< / span > < span class = "boring" > /// method.
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Error::kind() returns the ErrorKind
< / span > < span class = "boring" > /// Error::source() returns the parent error
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io(_f: & str) -> std::result::Result< (), io::Error> {
< / span > < span class = "boring" > /// return Err(io::Error::from(io::ErrorKind::NotFound));
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug, Clone)]
< / span > < span class = "boring" > /// pub enum ErrorKind {
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// FatalError(String),
< / span > < span class = "boring" > /// Unknown,
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// derive_err_kind!(Error, ErrorKind);
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl std::fmt::Display for ErrorKind {
< / span > < span class = "boring" > /// fn fmt(& self, f: & mut ::std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > /// match self {
< / span > < span class = "boring" > /// ErrorKind::FatalError(e) => write!(f, " fatal error {}" , e),
< / span > < span class = "boring" > /// ErrorKind::Unknown => write!(f, " unknown error" ),
< / span > < span class = "boring" > /// ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl ErrorKind {
< / span > < span class = "boring" > /// fn from_io_error(e: & io::Error, f: String) -> Self {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// io::ErrorKind::BrokenPipe => panic!(" Should not happen" ),
< / span > < span class = "boring" > /// io::ErrorKind::ConnectionReset => {
< / span > < span class = "boring" > /// ErrorKind::FatalError(format!(" While reading `{}`: {}" , f, e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// _ => ErrorKind::IO(f),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl From< & io::Error> for ErrorKind {
< / span > < span class = "boring" > /// fn from(e: & io::Error) -> Self {
< / span > < span class = "boring" > /// ErrorKind::IO(format!(" {}" , e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// pub fn func1() -> std::result::Result< (), Error> {
< / span > < span class = "boring" > /// let filename = " bar.txt" ;
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from_io_error(e, filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::IO(filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from(e))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
< / span > < span class = "boring" > macro_rules! derive_err_kind {
< / span > < span class = "boring" > ($e:ident, $k:ident) => {
< / span > < span class = "boring" > pub struct $e($crate::ChainError< $k> );
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl $e {
< / span > < span class = "boring" > pub fn kind(& self) -> & $k {
< / span > < span class = "boring" > self.0.kind()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< $k> for $e {
< / span > < span class = "boring" > fn from(e: $k) -> Self {
< / span > < span class = "boring" > $e($crate::ChainError::new(e, None, None))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< ChainError< $k> > for $e {
< / span > < span class = "boring" > fn from(e: $crate::ChainError< $k> ) -> Self {
< / span > < span class = "boring" > $e(e)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< & $e> for $k
< / span > < span class = "boring" > where
< / span > < span class = "boring" > $k: Clone,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > fn from(e: & $e) -> Self {
< / span > < span class = "boring" > e.kind().clone()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::error::Error for $e {
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn std::error::Error + 'static)> {
< / span > < span class = "boring" > self.0.source()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Display::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Debug::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < / code > < / pre > < / pre >
< h1 > < a class = "header" href = "#selective-error-handling" id = "selective-error-handling" > Selective Error Handling< / a > < / h1 >
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< p > What about functions returning different Error types?< / p >
< p > In this example < code > func1()< / code > can return either < code > Func1ErrorFunc2< / code > or < code > Func1ErrorIO< / code > .< / p >
< p > We might want to < code > match< / code > on < code > func1()< / code > with something like:< / p >
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< pre > < code class = "language-rust ignore" > fn main() -> Result< (), Box< Error + Send + Sync> > {
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match func1() {
Err(e) if let Some(s) = e.downcast_chain_ref::< Func1ErrorIO> () =>
eprintln!(" Func1ErrorIO:\n{:?}" , s),
Err(e) if let Some(s) = e.downcast_chain_ref::< Func1ErrorFunc2> () =>
eprintln!(" Func1ErrorFunc2:\n{:?}" , s),
Ok(_) => {},
}
Ok(())
}
< / code > < / pre >
< p > but this is not valid rust code, so we end up doing it the hard way.
In the next chapter, we will see, how to solve this more elegantly.< / p >
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< pre > < pre class = "playground" > < code class = "language-rust" > use chainerror::prelude::v1::*;
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use std::error::Error;
use std::io;
use std::result::Result;
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fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
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Err(io::Error::from(io::ErrorKind::NotFound))?;
Ok(())
}
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derive_str_context!(Func2Error);
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fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
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let filename = " foo.txt" ;
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do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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Ok(())
}
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derive_str_context!(Func1ErrorFunc2);
derive_str_context!(Func1ErrorIO);
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fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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func2().context(Func1ErrorFunc2(format!(" func1 error calling func2" )))?;
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let filename = " bar.txt" ;
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do_some_io().context(Func1ErrorIO(format!(" Error reading '{}'" , filename)))?;
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Ok(())
}
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fn main() -> Result< (), Box< dyn Error + Send + Sync> > {
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if let Err(e) = func1() {
if let Some(s) = e.downcast_ref::< ChainError< Func1ErrorIO> > () {
eprintln!(" Func1ErrorIO:\n{:?}" , s);
}
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if let Some(s) = e.downcast_chain_ref::< Func1ErrorFunc2> () {
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eprintln!(" Func1ErrorFunc2:\n{:?}" , s);
}
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std::process::exit(1);
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}
Ok(())
}
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< span class = "boring" > #[allow(dead_code)]
< / span > < span class = "boring" > mod chainerror {
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< / span > < span class = "boring" > //! `chainerror` provides an error backtrace without doing a real backtrace, so even after you `strip` your
< / span > < span class = "boring" > //! binaries, you still have the error backtrace.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `chainerror` has no dependencies!
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
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< / span > < span class = "boring" > //! It encapsulates all types, which have `Display + Debug` and can store the error cause internally.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Along with the `ChainError< T> ` struct, `chainerror` comes with some useful helper macros to save a lot of typing.
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! Debug information is worth it!
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ## Features
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `display-cause`
< / span > < span class = "boring" > //! : turn on printing a backtrace of the errors in `Display`
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Tutorial
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Read the [Tutorial](https://haraldh.github.io/chainerror/tutorial1.html)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Examples
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! examples/example.rs:
< / span > < span class = "boring" > //! ```rust,ignore
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! fn main() {
< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! eprintln!(" \nDebug Error {{:?}}:\n{:?}" , e);
< / span > < span class = "boring" > //! eprintln!(" \nAlternative Debug Error {{:#?}}:\n{:#?}\n" , e);
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```console
< / span > < span class = "boring" > //! $ cargo run -q --example example
< / span > < span class = "boring" > //! Debug Error {:?}:
< / span > < span class = "boring" > //! examples/example.rs:46:13: func1 error calling func2
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:21:13: Func2Error(func2 error: calling func3)
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:14:18: Error reading 'foo.txt'
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Alternative Debug Error {:#?}:
< / span > < span class = "boring" > //! ChainError< example::Func1Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:46:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: func1 error calling func2,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< example::Func2Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:21:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: Func2Error(func2 error: calling func3),
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< alloc::string::String> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:14:18" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: " Error reading \'foo.txt\'" ,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! Kind(
< / span > < span class = "boring" > //! NotFound,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > //! func2().context(" func1 error" )?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:21:13: func1 error
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func3() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! derive_str_context!(Func2Error);
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> ChainResult< (), Func2Error> {
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< / span > < span class = "boring" > //! func3().context(Func2Error(" func2 error: calling func3" .into()))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! enum Func1Error {
< / span > < span class = "boring" > //! Func2,
< / span > < span class = "boring" > //! IO(String),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Display for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! match self {
< / span > < span class = "boring" > //! Func1Error::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > //! Func1Error::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Debug for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! write!(f, " {}" , self)
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> ChainResult< (), Func1Error> {
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< / span > < span class = "boring" > //! func2().context(Func1Error::Func2)?;
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< / span > < span class = "boring" > //! let filename = String::from(" bar.txt" );
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< / span > < span class = "boring" > //! do_some_io().context(Func1Error::IO(filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! assert!(match e.kind() {
< / span > < span class = "boring" > //! Func1Error::Func2 => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error calling func2" );
< / span > < span class = "boring" > //! true
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! Func1Error::IO(filename) => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error reading '{}'" , filename);
< / span > < span class = "boring" > //! false
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< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! });
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! assert!(e.find_chain_cause::< Func2Error> ().is_some());
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Some(e) = e.find_chain_cause::< Func2Error> () {
< / span > < span class = "boring" > //! eprintln!(" \nError reported by Func2Error: {}" , e)
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! assert!(e.root_cause().is_some());
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Some(e) = e.root_cause() {
< / span > < span class = "boring" > //! let io_error = e.downcast_ref::< io::Error> ().unwrap();
< / span > < span class = "boring" > //! eprintln!(" \nThe root cause was: std::io::Error: {:#?}" , io_error);
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:48:13: func1 error calling func2
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:23:13: Func2Error(func2 error: calling func3)
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" >
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< / span > < span class = "boring" > #![deny(clippy::all)]
< / span > < span class = "boring" > #![deny(clippy::integer_arithmetic)]
< / span > < span class = "boring" > #![deny(missing_docs)]
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< / span > < span class = "boring" >
< / span > < span class = "boring" > use std::any::TypeId;
< / span > < span class = "boring" > use std::error::Error;
< / span > < span class = "boring" > use std::fmt::{Debug, Display, Formatter, Result};
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< / span > < span class = "boring" > use std::panic::Location;
< / span > < span class = "boring" >
< / span > < span class = "boring" > pub mod prelude {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub mod v1 {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub use super::super::ChainErrorDown as _;
< / span > < span class = "boring" > pub use super::super::ResultTrait as _;
< / span > < span class = "boring" > pub use super::super::{ChainError, ChainResult};
< / span > < span class = "boring" > pub use crate::{derive_err_kind, derive_str_context};
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > /// chains an inner error kind `T` with a causing error
< / span > < span class = "boring" > pub struct ChainError< T> {
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// convenience type alias
< / span > < span class = "boring" > pub type ChainResult< O, E> = std::result::Result< O, ChainError< E> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> ChainError< T> {
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< / span > < span class = "boring" > /// Use the `context()` or `map_context()` Result methods instead of calling this directly
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< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn new(
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > ) -> Self {
< / span > < span class = "boring" > Self {
< / span > < span class = "boring" > occurrence,
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > error_cause,
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// return the root cause of the error chain, if any exists
< / span > < span class = "boring" > pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.iter().last()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type U, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// assert!(f1err.find_cause::< io::Error> ().is_some());
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< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter().filter_map(Error::downcast_ref::< U> ).next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> `, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooError);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooError> > ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooError> implementation detail
< / span > < span class = "boring" > /// err.find_chain_cause::< FooError> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(Error::downcast_ref::< ChainError< U> > )
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> ` or `U`, if any exists and return `U`
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause` and `find_chain_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooErrorKind);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooErrorKind> > ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_chain_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_cause::< FooErrorKind> ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooErrorKind> implementation detail
< / span > < span class = "boring" > /// err.find_kind_or_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_kind_or_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(|e| {
< / span > < span class = "boring" > e.downcast_ref::< ChainError< U> > ()
< / span > < span class = "boring" > .map(|e| e.kind())
< / span > < span class = "boring" > .or_else(|| e.downcast_ref::< U> ())
< / span > < span class = "boring" > })
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Return a reference to T of `ChainError< T> `
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug)]
< / span > < span class = "boring" > /// enum Func1ErrorKind {
< / span > < span class = "boring" > /// Func2,
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// /// impl ::std::fmt::Display for Func1ErrorKind {…}
< / span > < span class = "boring" > /// # impl ::std::fmt::Display for Func1ErrorKind {
< / span > < span class = "boring" > /// # fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > /// # match self {
< / span > < span class = "boring" > /// # Func1ErrorKind::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > /// # Func1ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> ChainResult< (), Func1ErrorKind> {
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< / span > < span class = "boring" > /// func2().context(Func1ErrorKind::Func2)?;
< / span > < span class = "boring" > /// do_some_io().context(Func1ErrorKind::IO(" bar.txt" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// Func1ErrorKind::Func2 => {}
< / span > < span class = "boring" > /// Func1ErrorKind::IO(filename) => panic!(),
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn kind(& self) -> & T {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Returns an Iterator over all error causes/sources
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Example
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn iter(& self) -> impl Iterator< Item = & (dyn Error + 'static)> {
< / span > < span class = "boring" > ErrorIter {
< / span > < span class = "boring" > current: Some(self),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > /// Convenience methods for `Result< > ` to turn the error into a decorated ChainError
< / span > < span class = "boring" > pub trait ResultTrait< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > {
< / span > < span class = "boring" > /// Decorate the error with a `kind` of type `T` and the source `Location`
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Decorate the `error` with a `kind` of type `T` produced with a `FnOnce(& error)` and the source `Location`
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > ResultTrait< O, E>
< / span > < span class = "boring" > for std::result::Result< O, E>
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > )),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => {
< / span > < span class = "boring" > let kind = op(& error_cause);
< / span > < span class = "boring" > Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// An iterator over all error causes/sources
< / span > < span class = "boring" > pub struct ErrorIter< 'a> {
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< / span > < span class = "boring" > current: Option< & 'a (dyn Error + 'static)> ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< 'a> Iterator for ErrorIter< 'a> {
< / span > < span class = "boring" > type Item = & 'a (dyn Error + 'static);
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn next(& mut self) -> Option< Self::Item> {
< / span > < span class = "boring" > let current = self.current;
< / span > < span class = "boring" > self.current = self.current.and_then(Error::source);
< / span > < span class = "boring" > current
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> std::ops::Deref for ChainError< T> {
< / span > < span class = "boring" > type Target = T;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn deref(& self) -> & Self::Target {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience trait to hide the `ChainError< T> ` implementation internals
< / span > < span class = "boring" > pub trait ChainErrorDown {
< / span > < span class = "boring" > /// Test if of type `ChainError< T> `
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
< / span > < span class = "boring" > /// Downcast to a reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to a mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to T of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> ;
< / span > < span class = "boring" > /// Downcast to T mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< U: 'static + Display + Debug> ChainErrorDown for ChainError< U> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > TypeId::of::< T> () == TypeId::of::< U> ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& *(self as *const dyn Error as *const & ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& (*(self as *const dyn Error as *const & ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut (*(self as *mut dyn Error as *mut & mut ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send + Sync {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Display for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
< / span > < span class = "boring" > write!(f, " {}" , self.kind)?;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[cfg(feature = " display-cause" )]
< / span > < span class = "boring" > {
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Display::fmt(& e, f)?;
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > Ok(())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Debug for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
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< / span > < span class = "boring" > if f.alternate() {
< / span > < span class = "boring" > let mut f = f.debug_struct(& format!(" ChainError< {}> " , std::any::type_name::< T> ()));
< / span > < span class = "boring" >
< / span > < span class = "boring" > let f = f
< / span > < span class = "boring" > .field(" occurrence" , & self.occurrence)
< / span > < span class = "boring" > .field(" kind" , & self.kind)
< / span > < span class = "boring" > .field(" source" , & self.source());
< / span > < span class = "boring" >
< / span > < span class = "boring" > f.finish()
< / span > < span class = "boring" > } else {
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< / span > < span class = "boring" > if let Some(ref o) = self.occurrence {
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< / span > < span class = "boring" > write!(f, " {}: " , o)?;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > if TypeId::of::< String> () == TypeId::of::< T> ()
< / span > < span class = "boring" > || TypeId::of::< & str> () == TypeId::of::< T> ()
< / span > < span class = "boring" > {
< / span > < span class = "boring" > Display::fmt(& self.kind, f)?;
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > Debug::fmt(& self.kind, f)?;
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Debug::fmt(& e, f)?;
< / span > < span class = "boring" > }
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< / span > < span class = "boring" > Ok(())
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< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `ChainErrorFrom< T> ` is similar to `From< T> `
< / span > < span class = "boring" > pub trait ChainErrorFrom< T> : Sized {
< / span > < span class = "boring" > /// similar to From< T> ::from()
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< / span > < span class = "boring" > fn chain_error_from(from: T, line_filename: Option< String> ) -> ChainError< Self> ;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `IntoChainError< T> ` is similar to `Into< T> `
< / span > < span class = "boring" > pub trait IntoChainError< T> : Sized {
< / span > < span class = "boring" > /// similar to Into< T> ::into()
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< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< T> ;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> IntoChainError< U> for T
< / span > < span class = "boring" > where
< / span > < span class = "boring" > U: ChainErrorFrom< T> ,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
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< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< U> {
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< / span > < span class = "boring" > U::chain_error_from(self, line_filename)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> ChainErrorFrom< T> for U
< / span > < span class = "boring" > where
< / span > < span class = "boring" > T: Into< U> ,
< / span > < span class = "boring" > U: 'static + Display + Debug,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn chain_error_from(t: T, line_filename: Option< String> ) -> ChainError< Self> {
< / span > < span class = "boring" > let e: U = t.into();
< / span > < span class = "boring" > ChainError::new(e, None, line_filename)
< / span > < span class = "boring" > }
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience macro to create a " new type" T(String) and implement Display + Debug for T
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
< / span > < span class = "boring" > /// # use crate::chainerror::*;
< / span > < span class = "boring" > /// # use std::error::Error;
< / span > < span class = "boring" > /// # use std::io;
< / span > < span class = "boring" > /// # use std::result::Result;
< / span > < span class = "boring" > /// # fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// # Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// # Ok(())
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> ChainResult< (), Func2Error> {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// # if let Err(e) = func1() {
< / span > < span class = "boring" > /// # if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// # assert!(f1err.find_cause::< ChainError< Func2Error> > ().is_some());
< / span > < span class = "boring" > /// # assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
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< / span > < span class = "boring" > macro_rules! derive_str_context {
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< / span > < span class = "boring" > ($e:ident) => {
< / span > < span class = "boring" > #[derive(Clone)]
< / span > < span class = "boring" > pub struct $e(pub String);
< / span > < span class = "boring" > impl ::std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}" , self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}({})" , stringify!($e), self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::error::Error for $e {}
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Derive an Error for an ErrorKind, which wraps a `ChainError` and implements a `kind()` method
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// It basically hides `ChainError` to the outside and only exposes the `kind()`
< / span > < span class = "boring" > /// method.
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Error::kind() returns the ErrorKind
< / span > < span class = "boring" > /// Error::source() returns the parent error
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io(_f: & str) -> std::result::Result< (), io::Error> {
< / span > < span class = "boring" > /// return Err(io::Error::from(io::ErrorKind::NotFound));
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug, Clone)]
< / span > < span class = "boring" > /// pub enum ErrorKind {
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// FatalError(String),
< / span > < span class = "boring" > /// Unknown,
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// derive_err_kind!(Error, ErrorKind);
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl std::fmt::Display for ErrorKind {
< / span > < span class = "boring" > /// fn fmt(& self, f: & mut ::std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > /// match self {
< / span > < span class = "boring" > /// ErrorKind::FatalError(e) => write!(f, " fatal error {}" , e),
< / span > < span class = "boring" > /// ErrorKind::Unknown => write!(f, " unknown error" ),
< / span > < span class = "boring" > /// ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl ErrorKind {
< / span > < span class = "boring" > /// fn from_io_error(e: & io::Error, f: String) -> Self {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// io::ErrorKind::BrokenPipe => panic!(" Should not happen" ),
< / span > < span class = "boring" > /// io::ErrorKind::ConnectionReset => {
< / span > < span class = "boring" > /// ErrorKind::FatalError(format!(" While reading `{}`: {}" , f, e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// _ => ErrorKind::IO(f),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl From< & io::Error> for ErrorKind {
< / span > < span class = "boring" > /// fn from(e: & io::Error) -> Self {
< / span > < span class = "boring" > /// ErrorKind::IO(format!(" {}" , e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// pub fn func1() -> std::result::Result< (), Error> {
< / span > < span class = "boring" > /// let filename = " bar.txt" ;
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from_io_error(e, filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::IO(filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from(e))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
< / span > < span class = "boring" > macro_rules! derive_err_kind {
< / span > < span class = "boring" > ($e:ident, $k:ident) => {
< / span > < span class = "boring" > pub struct $e($crate::ChainError< $k> );
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl $e {
< / span > < span class = "boring" > pub fn kind(& self) -> & $k {
< / span > < span class = "boring" > self.0.kind()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< $k> for $e {
< / span > < span class = "boring" > fn from(e: $k) -> Self {
< / span > < span class = "boring" > $e($crate::ChainError::new(e, None, None))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< ChainError< $k> > for $e {
< / span > < span class = "boring" > fn from(e: $crate::ChainError< $k> ) -> Self {
< / span > < span class = "boring" > $e(e)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< & $e> for $k
< / span > < span class = "boring" > where
< / span > < span class = "boring" > $k: Clone,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > fn from(e: & $e) -> Self {
< / span > < span class = "boring" > e.kind().clone()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::error::Error for $e {
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn std::error::Error + 'static)> {
< / span > < span class = "boring" > self.0.source()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Display::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Debug::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < / code > < / pre > < / pre >
< h1 > < a class = "header" href = "#errorkind-to-the-rescue" id = "errorkind-to-the-rescue" > ErrorKind to the rescue< / a > < / h1 >
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< p > To cope with different kind of errors, we introduce the kind of an error < code > Func1ErrorKind< / code > with an enum.< / p >
< p > Because we derive < code > Debug< / code > and implement < code > Display< / code > our < code > Func1ErrorKind< / code > enum, this enum can be used as
a < code > std::error::Error< / code > .< / p >
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< p > Only returning < code > Func1ErrorKind< / code > in < code > func1()< / code > now let us get rid of < code > Result< (), Box< Error + Send + Sync> > < / code > and we can
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use < code > ChainResult< (), Func1ErrorKind> < / code > .< / p >
< p > In < code > main< / code > we can now directly use the methods of < code > ChainError< T> < / code > without downcasting the error first.< / p >
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< p > Also a nice < code > match< / code > on < code > ChainError< T> .kind()< / code > is now possible, which returns < code > & T< / code > , meaning
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< code > & Func1ErrorKind< / code > here.< / p >
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< pre > < pre class = "playground" > < code class = "language-rust" > use chainerror::prelude::v1::*;
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use std::error::Error;
use std::io;
use std::result::Result;
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fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
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Err(io::Error::from(io::ErrorKind::NotFound))?;
Ok(())
}
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derive_str_context!(Func2Error);
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fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
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let filename = " foo.txt" ;
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do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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Ok(())
}
#[derive(Debug)]
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enum Func1ErrorKind {
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Func2,
IO(String),
}
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impl ::std::fmt::Display for Func1ErrorKind {
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fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
match self {
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Func1ErrorKind::Func2 => write!(f, " func1 error calling func2" ),
Func1ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
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}
}
}
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impl ::std::error::Error for Func1ErrorKind {}
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fn func1() -> ChainResult< (), Func1ErrorKind> {
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func2().context(Func1ErrorKind::Func2)?;
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let filename = String::from(" bar.txt" );
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do_some_io().context(Func1ErrorKind::IO(filename))?;
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Ok(())
}
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fn main() -> Result< (), Box< dyn Error + Send + Sync> > {
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if let Err(e) = func1() {
match e.kind() {
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Func1ErrorKind::Func2 => eprintln!(" Main Error Report: func1 error calling func2" ),
Func1ErrorKind::IO(filename) => {
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eprintln!(" Main Error Report: func1 error reading '{}'" , filename)
}
}
if let Some(e) = e.find_chain_cause::< Func2Error> () {
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eprintln!(" \nError reported by Func2Error: {}" , e)
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}
eprintln!(" \nDebug Error:\n{:?}" , e);
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std::process::exit(1);
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}
Ok(())
}
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< span class = "boring" > #[allow(dead_code)]
< / span > < span class = "boring" > mod chainerror {
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< / span > < span class = "boring" > //! `chainerror` provides an error backtrace without doing a real backtrace, so even after you `strip` your
< / span > < span class = "boring" > //! binaries, you still have the error backtrace.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `chainerror` has no dependencies!
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
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< / span > < span class = "boring" > //! It encapsulates all types, which have `Display + Debug` and can store the error cause internally.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Along with the `ChainError< T> ` struct, `chainerror` comes with some useful helper macros to save a lot of typing.
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! Debug information is worth it!
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ## Features
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `display-cause`
< / span > < span class = "boring" > //! : turn on printing a backtrace of the errors in `Display`
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Tutorial
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Read the [Tutorial](https://haraldh.github.io/chainerror/tutorial1.html)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Examples
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! examples/example.rs:
< / span > < span class = "boring" > //! ```rust,ignore
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! fn main() {
< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! eprintln!(" \nDebug Error {{:?}}:\n{:?}" , e);
< / span > < span class = "boring" > //! eprintln!(" \nAlternative Debug Error {{:#?}}:\n{:#?}\n" , e);
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```console
< / span > < span class = "boring" > //! $ cargo run -q --example example
< / span > < span class = "boring" > //! Debug Error {:?}:
< / span > < span class = "boring" > //! examples/example.rs:46:13: func1 error calling func2
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:21:13: Func2Error(func2 error: calling func3)
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:14:18: Error reading 'foo.txt'
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Alternative Debug Error {:#?}:
< / span > < span class = "boring" > //! ChainError< example::Func1Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:46:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: func1 error calling func2,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< example::Func2Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:21:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: Func2Error(func2 error: calling func3),
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< alloc::string::String> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:14:18" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: " Error reading \'foo.txt\'" ,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! Kind(
< / span > < span class = "boring" > //! NotFound,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > //! func2().context(" func1 error" )?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:21:13: func1 error
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func3() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! derive_str_context!(Func2Error);
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> ChainResult< (), Func2Error> {
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< / span > < span class = "boring" > //! func3().context(Func2Error(" func2 error: calling func3" .into()))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! enum Func1Error {
< / span > < span class = "boring" > //! Func2,
< / span > < span class = "boring" > //! IO(String),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Display for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! match self {
< / span > < span class = "boring" > //! Func1Error::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > //! Func1Error::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Debug for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! write!(f, " {}" , self)
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> ChainResult< (), Func1Error> {
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< / span > < span class = "boring" > //! func2().context(Func1Error::Func2)?;
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< / span > < span class = "boring" > //! let filename = String::from(" bar.txt" );
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< / span > < span class = "boring" > //! do_some_io().context(Func1Error::IO(filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! assert!(match e.kind() {
< / span > < span class = "boring" > //! Func1Error::Func2 => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error calling func2" );
< / span > < span class = "boring" > //! true
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! Func1Error::IO(filename) => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error reading '{}'" , filename);
< / span > < span class = "boring" > //! false
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< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! });
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! assert!(e.find_chain_cause::< Func2Error> ().is_some());
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Some(e) = e.find_chain_cause::< Func2Error> () {
< / span > < span class = "boring" > //! eprintln!(" \nError reported by Func2Error: {}" , e)
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! assert!(e.root_cause().is_some());
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! if let Some(e) = e.root_cause() {
< / span > < span class = "boring" > //! let io_error = e.downcast_ref::< io::Error> ().unwrap();
< / span > < span class = "boring" > //! eprintln!(" \nThe root cause was: std::io::Error: {:#?}" , io_error);
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:48:13: func1 error calling func2
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:23:13: Func2Error(func2 error: calling func3)
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" >
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< / span > < span class = "boring" > #![deny(clippy::all)]
< / span > < span class = "boring" > #![deny(clippy::integer_arithmetic)]
< / span > < span class = "boring" > #![deny(missing_docs)]
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< / span > < span class = "boring" >
< / span > < span class = "boring" > use std::any::TypeId;
< / span > < span class = "boring" > use std::error::Error;
< / span > < span class = "boring" > use std::fmt::{Debug, Display, Formatter, Result};
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< / span > < span class = "boring" > use std::panic::Location;
< / span > < span class = "boring" >
< / span > < span class = "boring" > pub mod prelude {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub mod v1 {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub use super::super::ChainErrorDown as _;
< / span > < span class = "boring" > pub use super::super::ResultTrait as _;
< / span > < span class = "boring" > pub use super::super::{ChainError, ChainResult};
< / span > < span class = "boring" > pub use crate::{derive_err_kind, derive_str_context};
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > /// chains an inner error kind `T` with a causing error
< / span > < span class = "boring" > pub struct ChainError< T> {
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// convenience type alias
< / span > < span class = "boring" > pub type ChainResult< O, E> = std::result::Result< O, ChainError< E> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> ChainError< T> {
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< / span > < span class = "boring" > /// Use the `context()` or `map_context()` Result methods instead of calling this directly
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< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn new(
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > ) -> Self {
< / span > < span class = "boring" > Self {
< / span > < span class = "boring" > occurrence,
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > error_cause,
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// return the root cause of the error chain, if any exists
< / span > < span class = "boring" > pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.iter().last()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type U, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// assert!(f1err.find_cause::< io::Error> ().is_some());
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< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter().filter_map(Error::downcast_ref::< U> ).next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> `, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooError);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooError> > ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooError> implementation detail
< / span > < span class = "boring" > /// err.find_chain_cause::< FooError> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(Error::downcast_ref::< ChainError< U> > )
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> ` or `U`, if any exists and return `U`
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause` and `find_chain_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooErrorKind);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooErrorKind> > ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_chain_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_cause::< FooErrorKind> ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooErrorKind> implementation detail
< / span > < span class = "boring" > /// err.find_kind_or_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_kind_or_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(|e| {
< / span > < span class = "boring" > e.downcast_ref::< ChainError< U> > ()
< / span > < span class = "boring" > .map(|e| e.kind())
< / span > < span class = "boring" > .or_else(|| e.downcast_ref::< U> ())
< / span > < span class = "boring" > })
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Return a reference to T of `ChainError< T> `
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug)]
< / span > < span class = "boring" > /// enum Func1ErrorKind {
< / span > < span class = "boring" > /// Func2,
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// /// impl ::std::fmt::Display for Func1ErrorKind {…}
< / span > < span class = "boring" > /// # impl ::std::fmt::Display for Func1ErrorKind {
< / span > < span class = "boring" > /// # fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > /// # match self {
< / span > < span class = "boring" > /// # Func1ErrorKind::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > /// # Func1ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> ChainResult< (), Func1ErrorKind> {
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< / span > < span class = "boring" > /// func2().context(Func1ErrorKind::Func2)?;
< / span > < span class = "boring" > /// do_some_io().context(Func1ErrorKind::IO(" bar.txt" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// Func1ErrorKind::Func2 => {}
< / span > < span class = "boring" > /// Func1ErrorKind::IO(filename) => panic!(),
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn kind(& self) -> & T {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Returns an Iterator over all error causes/sources
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Example
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn iter(& self) -> impl Iterator< Item = & (dyn Error + 'static)> {
< / span > < span class = "boring" > ErrorIter {
< / span > < span class = "boring" > current: Some(self),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > /// Convenience methods for `Result< > ` to turn the error into a decorated ChainError
< / span > < span class = "boring" > pub trait ResultTrait< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > {
< / span > < span class = "boring" > /// Decorate the error with a `kind` of type `T` and the source `Location`
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Decorate the `error` with a `kind` of type `T` produced with a `FnOnce(& error)` and the source `Location`
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > ResultTrait< O, E>
< / span > < span class = "boring" > for std::result::Result< O, E>
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > )),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => {
< / span > < span class = "boring" > let kind = op(& error_cause);
< / span > < span class = "boring" > Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// An iterator over all error causes/sources
< / span > < span class = "boring" > pub struct ErrorIter< 'a> {
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< / span > < span class = "boring" > current: Option< & 'a (dyn Error + 'static)> ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< 'a> Iterator for ErrorIter< 'a> {
< / span > < span class = "boring" > type Item = & 'a (dyn Error + 'static);
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn next(& mut self) -> Option< Self::Item> {
< / span > < span class = "boring" > let current = self.current;
< / span > < span class = "boring" > self.current = self.current.and_then(Error::source);
< / span > < span class = "boring" > current
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> std::ops::Deref for ChainError< T> {
< / span > < span class = "boring" > type Target = T;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn deref(& self) -> & Self::Target {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience trait to hide the `ChainError< T> ` implementation internals
< / span > < span class = "boring" > pub trait ChainErrorDown {
< / span > < span class = "boring" > /// Test if of type `ChainError< T> `
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
< / span > < span class = "boring" > /// Downcast to a reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to a mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to T of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> ;
< / span > < span class = "boring" > /// Downcast to T mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< U: 'static + Display + Debug> ChainErrorDown for ChainError< U> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > TypeId::of::< T> () == TypeId::of::< U> ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& *(self as *const dyn Error as *const & ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& (*(self as *const dyn Error as *const & ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut (*(self as *mut dyn Error as *mut & mut ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send + Sync {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Display for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
< / span > < span class = "boring" > write!(f, " {}" , self.kind)?;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[cfg(feature = " display-cause" )]
< / span > < span class = "boring" > {
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Display::fmt(& e, f)?;
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > Ok(())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Debug for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
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< / span > < span class = "boring" > if f.alternate() {
< / span > < span class = "boring" > let mut f = f.debug_struct(& format!(" ChainError< {}> " , std::any::type_name::< T> ()));
< / span > < span class = "boring" >
< / span > < span class = "boring" > let f = f
< / span > < span class = "boring" > .field(" occurrence" , & self.occurrence)
< / span > < span class = "boring" > .field(" kind" , & self.kind)
< / span > < span class = "boring" > .field(" source" , & self.source());
< / span > < span class = "boring" >
< / span > < span class = "boring" > f.finish()
< / span > < span class = "boring" > } else {
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< / span > < span class = "boring" > if let Some(ref o) = self.occurrence {
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< / span > < span class = "boring" > write!(f, " {}: " , o)?;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > if TypeId::of::< String> () == TypeId::of::< T> ()
< / span > < span class = "boring" > || TypeId::of::< & str> () == TypeId::of::< T> ()
< / span > < span class = "boring" > {
< / span > < span class = "boring" > Display::fmt(& self.kind, f)?;
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > Debug::fmt(& self.kind, f)?;
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Debug::fmt(& e, f)?;
< / span > < span class = "boring" > }
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< / span > < span class = "boring" > Ok(())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `ChainErrorFrom< T> ` is similar to `From< T> `
< / span > < span class = "boring" > pub trait ChainErrorFrom< T> : Sized {
< / span > < span class = "boring" > /// similar to From< T> ::from()
< / span > < span class = "boring" > fn chain_error_from(from: T, line_filename: Option< String> ) -> ChainError< Self> ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `IntoChainError< T> ` is similar to `Into< T> `
< / span > < span class = "boring" > pub trait IntoChainError< T> : Sized {
< / span > < span class = "boring" > /// similar to Into< T> ::into()
< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< T> ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> IntoChainError< U> for T
< / span > < span class = "boring" > where
< / span > < span class = "boring" > U: ChainErrorFrom< T> ,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< U> {
< / span > < span class = "boring" > U::chain_error_from(self, line_filename)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> ChainErrorFrom< T> for U
< / span > < span class = "boring" > where
< / span > < span class = "boring" > T: Into< U> ,
< / span > < span class = "boring" > U: 'static + Display + Debug,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn chain_error_from(t: T, line_filename: Option< String> ) -> ChainError< Self> {
< / span > < span class = "boring" > let e: U = t.into();
< / span > < span class = "boring" > ChainError::new(e, None, line_filename)
< / span > < span class = "boring" > }
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience macro to create a " new type" T(String) and implement Display + Debug for T
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
< / span > < span class = "boring" > /// # use crate::chainerror::*;
< / span > < span class = "boring" > /// # use std::error::Error;
< / span > < span class = "boring" > /// # use std::io;
< / span > < span class = "boring" > /// # use std::result::Result;
< / span > < span class = "boring" > /// # fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// # Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// # Ok(())
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> ChainResult< (), Func2Error> {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// # if let Err(e) = func1() {
< / span > < span class = "boring" > /// # if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// # assert!(f1err.find_cause::< ChainError< Func2Error> > ().is_some());
< / span > < span class = "boring" > /// # assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
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< / span > < span class = "boring" > macro_rules! derive_str_context {
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< / span > < span class = "boring" > ($e:ident) => {
< / span > < span class = "boring" > #[derive(Clone)]
< / span > < span class = "boring" > pub struct $e(pub String);
< / span > < span class = "boring" > impl ::std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}" , self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}({})" , stringify!($e), self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::error::Error for $e {}
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Derive an Error for an ErrorKind, which wraps a `ChainError` and implements a `kind()` method
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// It basically hides `ChainError` to the outside and only exposes the `kind()`
< / span > < span class = "boring" > /// method.
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Error::kind() returns the ErrorKind
< / span > < span class = "boring" > /// Error::source() returns the parent error
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io(_f: & str) -> std::result::Result< (), io::Error> {
< / span > < span class = "boring" > /// return Err(io::Error::from(io::ErrorKind::NotFound));
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug, Clone)]
< / span > < span class = "boring" > /// pub enum ErrorKind {
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// FatalError(String),
< / span > < span class = "boring" > /// Unknown,
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// derive_err_kind!(Error, ErrorKind);
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl std::fmt::Display for ErrorKind {
< / span > < span class = "boring" > /// fn fmt(& self, f: & mut ::std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > /// match self {
< / span > < span class = "boring" > /// ErrorKind::FatalError(e) => write!(f, " fatal error {}" , e),
< / span > < span class = "boring" > /// ErrorKind::Unknown => write!(f, " unknown error" ),
< / span > < span class = "boring" > /// ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl ErrorKind {
< / span > < span class = "boring" > /// fn from_io_error(e: & io::Error, f: String) -> Self {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// io::ErrorKind::BrokenPipe => panic!(" Should not happen" ),
< / span > < span class = "boring" > /// io::ErrorKind::ConnectionReset => {
< / span > < span class = "boring" > /// ErrorKind::FatalError(format!(" While reading `{}`: {}" , f, e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// _ => ErrorKind::IO(f),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl From< & io::Error> for ErrorKind {
< / span > < span class = "boring" > /// fn from(e: & io::Error) -> Self {
< / span > < span class = "boring" > /// ErrorKind::IO(format!(" {}" , e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// pub fn func1() -> std::result::Result< (), Error> {
< / span > < span class = "boring" > /// let filename = " bar.txt" ;
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from_io_error(e, filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::IO(filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from(e))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
< / span > < span class = "boring" > macro_rules! derive_err_kind {
< / span > < span class = "boring" > ($e:ident, $k:ident) => {
< / span > < span class = "boring" > pub struct $e($crate::ChainError< $k> );
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl $e {
< / span > < span class = "boring" > pub fn kind(& self) -> & $k {
< / span > < span class = "boring" > self.0.kind()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< $k> for $e {
< / span > < span class = "boring" > fn from(e: $k) -> Self {
< / span > < span class = "boring" > $e($crate::ChainError::new(e, None, None))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< ChainError< $k> > for $e {
< / span > < span class = "boring" > fn from(e: $crate::ChainError< $k> ) -> Self {
< / span > < span class = "boring" > $e(e)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< & $e> for $k
< / span > < span class = "boring" > where
< / span > < span class = "boring" > $k: Clone,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > fn from(e: & $e) -> Self {
< / span > < span class = "boring" > e.kind().clone()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::error::Error for $e {
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn std::error::Error + 'static)> {
< / span > < span class = "boring" > self.0.source()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Display::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Debug::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < / code > < / pre > < / pre >
< h1 > < a class = "header" href = "#debug-for-the-errorkind" id = "debug-for-the-errorkind" > Debug for the ErrorKind< / a > < / h1 >
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< p > One small improvement is to fix the debug output of
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< code > Func1ErrorKind< / code > . As you probably noticed, the output doesn't say much of the enum.< / p >
< pre > < code > Debug Error:
src/main.rs:35: Func2
[…]
< / code > < / pre >
< p > As a lazy shortcut, we implement < code > Debug< / code > by calling < code > Display< / code > and end up with< / p >
< pre > < code > Debug Error:
src/main.rs:40: func1 error calling func2
[…}
< / code > < / pre >
< p > which gives us a lot more detail.< / p >
< p > To create your own Errors, you might find < a href = "https://crates.io" > crates< / a > which create enum < code > Display+Debug< / code > via derive macros.< / p >
< p > Also noteworthy is < a href = "https://crates.io/crates/custom_error" > custom_error< / a > to define your custom errors,
which can then be used with < code > chainerror< / code > .< / p >
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< pre > < pre class = "playground" > < code class = "language-rust" > use chainerror::prelude::v1::*;
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use std::error::Error;
use std::io;
use std::result::Result;
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fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
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Err(io::Error::from(io::ErrorKind::NotFound))?;
Ok(())
}
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derive_str_context!(Func2Error);
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fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
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let filename = " foo.txt" ;
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do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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Ok(())
}
enum Func1ErrorKind {
Func2,
IO(String),
}
impl ::std::fmt::Display for Func1ErrorKind {
fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
match self {
Func1ErrorKind::Func2 => write!(f, " func1 error calling func2" ),
Func1ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
}
}
}
impl ::std::fmt::Debug for Func1ErrorKind {
fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
write!(f, " {}" , self)
}
}
impl ::std::error::Error for Func1ErrorKind {}
fn func1() -> ChainResult< (), Func1ErrorKind> {
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func2().context(Func1ErrorKind::Func2)?;
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let filename = String::from(" bar.txt" );
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do_some_io().context(Func1ErrorKind::IO(filename))?;
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Ok(())
}
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fn main() -> Result< (), Box< dyn Error + Send + Sync> > {
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if let Err(e) = func1() {
match e.kind() {
Func1ErrorKind::Func2 => eprintln!(" Main Error Report: func1 error calling func2" ),
Func1ErrorKind::IO(filename) => {
eprintln!(" Main Error Report: func1 error reading '{}'" , filename)
}
}
if let Some(e) = e.find_chain_cause::< Func2Error> () {
eprintln!(" \nError reported by Func2Error: {}" , e)
}
eprintln!(" \nDebug Error:\n{:?}" , e);
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std::process::exit(1);
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}
Ok(())
}
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< span class = "boring" > #[allow(dead_code)]
< / span > < span class = "boring" > mod chainerror {
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< / span > < span class = "boring" > //! `chainerror` provides an error backtrace without doing a real backtrace, so even after you `strip` your
< / span > < span class = "boring" > //! binaries, you still have the error backtrace.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `chainerror` has no dependencies!
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
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< / span > < span class = "boring" > //! It encapsulates all types, which have `Display + Debug` and can store the error cause internally.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Along with the `ChainError< T> ` struct, `chainerror` comes with some useful helper macros to save a lot of typing.
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! Debug information is worth it!
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ## Features
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `display-cause`
< / span > < span class = "boring" > //! : turn on printing a backtrace of the errors in `Display`
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Tutorial
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Read the [Tutorial](https://haraldh.github.io/chainerror/tutorial1.html)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Examples
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! examples/example.rs:
< / span > < span class = "boring" > //! ```rust,ignore
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! fn main() {
< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! eprintln!(" \nDebug Error {{:?}}:\n{:?}" , e);
< / span > < span class = "boring" > //! eprintln!(" \nAlternative Debug Error {{:#?}}:\n{:#?}\n" , e);
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```console
< / span > < span class = "boring" > //! $ cargo run -q --example example
< / span > < span class = "boring" > //! Debug Error {:?}:
< / span > < span class = "boring" > //! examples/example.rs:46:13: func1 error calling func2
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:21:13: Func2Error(func2 error: calling func3)
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:14:18: Error reading 'foo.txt'
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Alternative Debug Error {:#?}:
< / span > < span class = "boring" > //! ChainError< example::Func1Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:46:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: func1 error calling func2,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< example::Func2Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:21:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: Func2Error(func2 error: calling func3),
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< alloc::string::String> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:14:18" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: " Error reading \'foo.txt\'" ,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! Kind(
< / span > < span class = "boring" > //! NotFound,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > //! func2().context(" func1 error" )?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:21:13: func1 error
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func3() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! derive_str_context!(Func2Error);
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> ChainResult< (), Func2Error> {
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< / span > < span class = "boring" > //! func3().context(Func2Error(" func2 error: calling func3" .into()))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! enum Func1Error {
< / span > < span class = "boring" > //! Func2,
< / span > < span class = "boring" > //! IO(String),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Display for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! match self {
< / span > < span class = "boring" > //! Func1Error::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > //! Func1Error::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Debug for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! write!(f, " {}" , self)
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> ChainResult< (), Func1Error> {
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< / span > < span class = "boring" > //! func2().context(Func1Error::Func2)?;
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< / span > < span class = "boring" > //! let filename = String::from(" bar.txt" );
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< / span > < span class = "boring" > //! do_some_io().context(Func1Error::IO(filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! assert!(match e.kind() {
< / span > < span class = "boring" > //! Func1Error::Func2 => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error calling func2" );
< / span > < span class = "boring" > //! true
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! Func1Error::IO(filename) => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error reading '{}'" , filename);
< / span > < span class = "boring" > //! false
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< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! });
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! assert!(e.find_chain_cause::< Func2Error> ().is_some());
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Some(e) = e.find_chain_cause::< Func2Error> () {
< / span > < span class = "boring" > //! eprintln!(" \nError reported by Func2Error: {}" , e)
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! assert!(e.root_cause().is_some());
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Some(e) = e.root_cause() {
< / span > < span class = "boring" > //! let io_error = e.downcast_ref::< io::Error> ().unwrap();
< / span > < span class = "boring" > //! eprintln!(" \nThe root cause was: std::io::Error: {:#?}" , io_error);
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:48:13: func1 error calling func2
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:23:13: Func2Error(func2 error: calling func3)
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" >
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< / span > < span class = "boring" > #![deny(clippy::all)]
< / span > < span class = "boring" > #![deny(clippy::integer_arithmetic)]
< / span > < span class = "boring" > #![deny(missing_docs)]
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< / span > < span class = "boring" >
< / span > < span class = "boring" > use std::any::TypeId;
< / span > < span class = "boring" > use std::error::Error;
< / span > < span class = "boring" > use std::fmt::{Debug, Display, Formatter, Result};
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< / span > < span class = "boring" > use std::panic::Location;
< / span > < span class = "boring" >
< / span > < span class = "boring" > pub mod prelude {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub mod v1 {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub use super::super::ChainErrorDown as _;
< / span > < span class = "boring" > pub use super::super::ResultTrait as _;
< / span > < span class = "boring" > pub use super::super::{ChainError, ChainResult};
< / span > < span class = "boring" > pub use crate::{derive_err_kind, derive_str_context};
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > /// chains an inner error kind `T` with a causing error
< / span > < span class = "boring" > pub struct ChainError< T> {
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// convenience type alias
< / span > < span class = "boring" > pub type ChainResult< O, E> = std::result::Result< O, ChainError< E> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> ChainError< T> {
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< / span > < span class = "boring" > /// Use the `context()` or `map_context()` Result methods instead of calling this directly
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< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn new(
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > ) -> Self {
< / span > < span class = "boring" > Self {
< / span > < span class = "boring" > occurrence,
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > error_cause,
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// return the root cause of the error chain, if any exists
< / span > < span class = "boring" > pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.iter().last()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type U, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// assert!(f1err.find_cause::< io::Error> ().is_some());
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< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter().filter_map(Error::downcast_ref::< U> ).next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> `, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooError);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooError> > ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooError> implementation detail
< / span > < span class = "boring" > /// err.find_chain_cause::< FooError> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(Error::downcast_ref::< ChainError< U> > )
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> ` or `U`, if any exists and return `U`
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause` and `find_chain_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooErrorKind);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooErrorKind> > ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_chain_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_cause::< FooErrorKind> ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooErrorKind> implementation detail
< / span > < span class = "boring" > /// err.find_kind_or_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_kind_or_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(|e| {
< / span > < span class = "boring" > e.downcast_ref::< ChainError< U> > ()
< / span > < span class = "boring" > .map(|e| e.kind())
< / span > < span class = "boring" > .or_else(|| e.downcast_ref::< U> ())
< / span > < span class = "boring" > })
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Return a reference to T of `ChainError< T> `
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug)]
< / span > < span class = "boring" > /// enum Func1ErrorKind {
< / span > < span class = "boring" > /// Func2,
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// /// impl ::std::fmt::Display for Func1ErrorKind {…}
< / span > < span class = "boring" > /// # impl ::std::fmt::Display for Func1ErrorKind {
< / span > < span class = "boring" > /// # fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > /// # match self {
< / span > < span class = "boring" > /// # Func1ErrorKind::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > /// # Func1ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> ChainResult< (), Func1ErrorKind> {
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< / span > < span class = "boring" > /// func2().context(Func1ErrorKind::Func2)?;
< / span > < span class = "boring" > /// do_some_io().context(Func1ErrorKind::IO(" bar.txt" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// Func1ErrorKind::Func2 => {}
< / span > < span class = "boring" > /// Func1ErrorKind::IO(filename) => panic!(),
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn kind(& self) -> & T {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Returns an Iterator over all error causes/sources
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Example
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn iter(& self) -> impl Iterator< Item = & (dyn Error + 'static)> {
< / span > < span class = "boring" > ErrorIter {
< / span > < span class = "boring" > current: Some(self),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > /// Convenience methods for `Result< > ` to turn the error into a decorated ChainError
< / span > < span class = "boring" > pub trait ResultTrait< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > {
< / span > < span class = "boring" > /// Decorate the error with a `kind` of type `T` and the source `Location`
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Decorate the `error` with a `kind` of type `T` produced with a `FnOnce(& error)` and the source `Location`
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > ResultTrait< O, E>
< / span > < span class = "boring" > for std::result::Result< O, E>
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > )),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => {
< / span > < span class = "boring" > let kind = op(& error_cause);
< / span > < span class = "boring" > Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// An iterator over all error causes/sources
< / span > < span class = "boring" > pub struct ErrorIter< 'a> {
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< / span > < span class = "boring" > current: Option< & 'a (dyn Error + 'static)> ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< 'a> Iterator for ErrorIter< 'a> {
< / span > < span class = "boring" > type Item = & 'a (dyn Error + 'static);
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn next(& mut self) -> Option< Self::Item> {
< / span > < span class = "boring" > let current = self.current;
< / span > < span class = "boring" > self.current = self.current.and_then(Error::source);
< / span > < span class = "boring" > current
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> std::ops::Deref for ChainError< T> {
< / span > < span class = "boring" > type Target = T;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn deref(& self) -> & Self::Target {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience trait to hide the `ChainError< T> ` implementation internals
< / span > < span class = "boring" > pub trait ChainErrorDown {
< / span > < span class = "boring" > /// Test if of type `ChainError< T> `
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
< / span > < span class = "boring" > /// Downcast to a reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to a mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to T of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> ;
< / span > < span class = "boring" > /// Downcast to T mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< U: 'static + Display + Debug> ChainErrorDown for ChainError< U> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > TypeId::of::< T> () == TypeId::of::< U> ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& *(self as *const dyn Error as *const & ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& (*(self as *const dyn Error as *const & ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut (*(self as *mut dyn Error as *mut & mut ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send + Sync {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Display for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
< / span > < span class = "boring" > write!(f, " {}" , self.kind)?;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[cfg(feature = " display-cause" )]
< / span > < span class = "boring" > {
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Display::fmt(& e, f)?;
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > Ok(())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Debug for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
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< / span > < span class = "boring" > if f.alternate() {
< / span > < span class = "boring" > let mut f = f.debug_struct(& format!(" ChainError< {}> " , std::any::type_name::< T> ()));
< / span > < span class = "boring" >
< / span > < span class = "boring" > let f = f
< / span > < span class = "boring" > .field(" occurrence" , & self.occurrence)
< / span > < span class = "boring" > .field(" kind" , & self.kind)
< / span > < span class = "boring" > .field(" source" , & self.source());
< / span > < span class = "boring" >
< / span > < span class = "boring" > f.finish()
< / span > < span class = "boring" > } else {
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< / span > < span class = "boring" > if let Some(ref o) = self.occurrence {
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< / span > < span class = "boring" > write!(f, " {}: " , o)?;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > if TypeId::of::< String> () == TypeId::of::< T> ()
< / span > < span class = "boring" > || TypeId::of::< & str> () == TypeId::of::< T> ()
< / span > < span class = "boring" > {
< / span > < span class = "boring" > Display::fmt(& self.kind, f)?;
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > Debug::fmt(& self.kind, f)?;
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Debug::fmt(& e, f)?;
< / span > < span class = "boring" > }
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< / span > < span class = "boring" > Ok(())
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< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `ChainErrorFrom< T> ` is similar to `From< T> `
< / span > < span class = "boring" > pub trait ChainErrorFrom< T> : Sized {
< / span > < span class = "boring" > /// similar to From< T> ::from()
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< / span > < span class = "boring" > fn chain_error_from(from: T, line_filename: Option< String> ) -> ChainError< Self> ;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `IntoChainError< T> ` is similar to `Into< T> `
< / span > < span class = "boring" > pub trait IntoChainError< T> : Sized {
< / span > < span class = "boring" > /// similar to Into< T> ::into()
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< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< T> ;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> IntoChainError< U> for T
< / span > < span class = "boring" > where
< / span > < span class = "boring" > U: ChainErrorFrom< T> ,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
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< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< U> {
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< / span > < span class = "boring" > U::chain_error_from(self, line_filename)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> ChainErrorFrom< T> for U
< / span > < span class = "boring" > where
< / span > < span class = "boring" > T: Into< U> ,
< / span > < span class = "boring" > U: 'static + Display + Debug,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn chain_error_from(t: T, line_filename: Option< String> ) -> ChainError< Self> {
< / span > < span class = "boring" > let e: U = t.into();
< / span > < span class = "boring" > ChainError::new(e, None, line_filename)
< / span > < span class = "boring" > }
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience macro to create a " new type" T(String) and implement Display + Debug for T
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
< / span > < span class = "boring" > /// # use crate::chainerror::*;
< / span > < span class = "boring" > /// # use std::error::Error;
< / span > < span class = "boring" > /// # use std::io;
< / span > < span class = "boring" > /// # use std::result::Result;
< / span > < span class = "boring" > /// # fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// # Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// # Ok(())
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> ChainResult< (), Func2Error> {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// # if let Err(e) = func1() {
< / span > < span class = "boring" > /// # if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// # assert!(f1err.find_cause::< ChainError< Func2Error> > ().is_some());
< / span > < span class = "boring" > /// # assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
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< / span > < span class = "boring" > macro_rules! derive_str_context {
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< / span > < span class = "boring" > ($e:ident) => {
< / span > < span class = "boring" > #[derive(Clone)]
< / span > < span class = "boring" > pub struct $e(pub String);
< / span > < span class = "boring" > impl ::std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}" , self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}({})" , stringify!($e), self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::error::Error for $e {}
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Derive an Error for an ErrorKind, which wraps a `ChainError` and implements a `kind()` method
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// It basically hides `ChainError` to the outside and only exposes the `kind()`
< / span > < span class = "boring" > /// method.
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Error::kind() returns the ErrorKind
< / span > < span class = "boring" > /// Error::source() returns the parent error
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io(_f: & str) -> std::result::Result< (), io::Error> {
< / span > < span class = "boring" > /// return Err(io::Error::from(io::ErrorKind::NotFound));
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug, Clone)]
< / span > < span class = "boring" > /// pub enum ErrorKind {
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// FatalError(String),
< / span > < span class = "boring" > /// Unknown,
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// derive_err_kind!(Error, ErrorKind);
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl std::fmt::Display for ErrorKind {
< / span > < span class = "boring" > /// fn fmt(& self, f: & mut ::std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > /// match self {
< / span > < span class = "boring" > /// ErrorKind::FatalError(e) => write!(f, " fatal error {}" , e),
< / span > < span class = "boring" > /// ErrorKind::Unknown => write!(f, " unknown error" ),
< / span > < span class = "boring" > /// ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl ErrorKind {
< / span > < span class = "boring" > /// fn from_io_error(e: & io::Error, f: String) -> Self {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// io::ErrorKind::BrokenPipe => panic!(" Should not happen" ),
< / span > < span class = "boring" > /// io::ErrorKind::ConnectionReset => {
< / span > < span class = "boring" > /// ErrorKind::FatalError(format!(" While reading `{}`: {}" , f, e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// _ => ErrorKind::IO(f),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl From< & io::Error> for ErrorKind {
< / span > < span class = "boring" > /// fn from(e: & io::Error) -> Self {
< / span > < span class = "boring" > /// ErrorKind::IO(format!(" {}" , e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// pub fn func1() -> std::result::Result< (), Error> {
< / span > < span class = "boring" > /// let filename = " bar.txt" ;
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from_io_error(e, filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::IO(filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from(e))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
< / span > < span class = "boring" > macro_rules! derive_err_kind {
< / span > < span class = "boring" > ($e:ident, $k:ident) => {
< / span > < span class = "boring" > pub struct $e($crate::ChainError< $k> );
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl $e {
< / span > < span class = "boring" > pub fn kind(& self) -> & $k {
< / span > < span class = "boring" > self.0.kind()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< $k> for $e {
< / span > < span class = "boring" > fn from(e: $k) -> Self {
< / span > < span class = "boring" > $e($crate::ChainError::new(e, None, None))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< ChainError< $k> > for $e {
< / span > < span class = "boring" > fn from(e: $crate::ChainError< $k> ) -> Self {
< / span > < span class = "boring" > $e(e)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< & $e> for $k
< / span > < span class = "boring" > where
< / span > < span class = "boring" > $k: Clone,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > fn from(e: & $e) -> Self {
< / span > < span class = "boring" > e.kind().clone()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::error::Error for $e {
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn std::error::Error + 'static)> {
< / span > < span class = "boring" > self.0.source()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Display::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Debug::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < / code > < / pre > < / pre >
< h1 > < a class = "header" href = "#deref-for-the-errorkind" id = "deref-for-the-errorkind" > Deref for the ErrorKind< / a > < / h1 >
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< p > Because ChainError< T > implements Deref to & T, we can also match on < code > *e< / code > instead of < code > e.kind()< / code >
or call a function with < code > & e< / code > < / p >
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< pre > < pre class = "playground" > < code class = "language-rust" > use chainerror::prelude::v1::*;
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use std::error::Error;
use std::io;
use std::result::Result;
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fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
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Err(io::Error::from(io::ErrorKind::NotFound))?;
Ok(())
}
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derive_str_context!(Func2Error);
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fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
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let filename = " foo.txt" ;
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do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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Ok(())
}
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enum Func1ErrorKind {
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Func2,
IO(String),
}
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impl ::std::fmt::Display for Func1ErrorKind {
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fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
match self {
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Func1ErrorKind::Func2 => write!(f, " func1 error calling func2" ),
Func1ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
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}
}
}
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impl ::std::fmt::Debug for Func1ErrorKind {
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fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
write!(f, " {}" , self)
}
}
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impl ::std::error::Error for Func1ErrorKind {}
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fn func1() -> ChainResult< (), Func1ErrorKind> {
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func2().context(Func1ErrorKind::Func2)?;
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let filename = String::from(" bar.txt" );
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do_some_io().context(Func1ErrorKind::IO(filename))?;
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Ok(())
}
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fn handle_func1errorkind(e: & Func1ErrorKind) {
match e {
Func1ErrorKind::Func2 => eprintln!(" Main Error Report: func1 error calling func2" ),
Func1ErrorKind::IO(ref filename) => {
eprintln!(" Main Error Report: func1 error reading '{}'" , filename)
}
}
}
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fn main() -> Result< (), Box< dyn Error + Send + Sync> > {
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if let Err(e) = func1() {
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match *e {
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Func1ErrorKind::Func2 => eprintln!(" Main Error Report: func1 error calling func2" ),
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Func1ErrorKind::IO(ref filename) => {
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eprintln!(" Main Error Report: func1 error reading '{}'" , filename)
}
}
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handle_func1errorkind(& e);
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if let Some(e) = e.find_chain_cause::< Func2Error> () {
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eprintln!(" \nError reported by Func2Error: {}" , e)
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}
eprintln!(" \nDebug Error:\n{:?}" , e);
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std::process::exit(1);
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}
Ok(())
}
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< span class = "boring" > #[allow(dead_code)]
< / span > < span class = "boring" > mod chainerror {
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< / span > < span class = "boring" > //! `chainerror` provides an error backtrace without doing a real backtrace, so even after you `strip` your
< / span > < span class = "boring" > //! binaries, you still have the error backtrace.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `chainerror` has no dependencies!
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
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< / span > < span class = "boring" > //! It encapsulates all types, which have `Display + Debug` and can store the error cause internally.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Along with the `ChainError< T> ` struct, `chainerror` comes with some useful helper macros to save a lot of typing.
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! Debug information is worth it!
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ## Features
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `display-cause`
< / span > < span class = "boring" > //! : turn on printing a backtrace of the errors in `Display`
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Tutorial
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Read the [Tutorial](https://haraldh.github.io/chainerror/tutorial1.html)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Examples
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! examples/example.rs:
< / span > < span class = "boring" > //! ```rust,ignore
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! fn main() {
< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! eprintln!(" \nDebug Error {{:?}}:\n{:?}" , e);
< / span > < span class = "boring" > //! eprintln!(" \nAlternative Debug Error {{:#?}}:\n{:#?}\n" , e);
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```console
< / span > < span class = "boring" > //! $ cargo run -q --example example
< / span > < span class = "boring" > //! Debug Error {:?}:
< / span > < span class = "boring" > //! examples/example.rs:46:13: func1 error calling func2
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:21:13: Func2Error(func2 error: calling func3)
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:14:18: Error reading 'foo.txt'
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Alternative Debug Error {:#?}:
< / span > < span class = "boring" > //! ChainError< example::Func1Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:46:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: func1 error calling func2,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< example::Func2Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:21:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: Func2Error(func2 error: calling func3),
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< alloc::string::String> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:14:18" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: " Error reading \'foo.txt\'" ,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! Kind(
< / span > < span class = "boring" > //! NotFound,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > //! func2().context(" func1 error" )?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:21:13: func1 error
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func3() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! derive_str_context!(Func2Error);
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> ChainResult< (), Func2Error> {
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< / span > < span class = "boring" > //! func3().context(Func2Error(" func2 error: calling func3" .into()))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! enum Func1Error {
< / span > < span class = "boring" > //! Func2,
< / span > < span class = "boring" > //! IO(String),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Display for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! match self {
< / span > < span class = "boring" > //! Func1Error::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > //! Func1Error::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Debug for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! write!(f, " {}" , self)
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> ChainResult< (), Func1Error> {
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< / span > < span class = "boring" > //! func2().context(Func1Error::Func2)?;
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< / span > < span class = "boring" > //! let filename = String::from(" bar.txt" );
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< / span > < span class = "boring" > //! do_some_io().context(Func1Error::IO(filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! assert!(match e.kind() {
< / span > < span class = "boring" > //! Func1Error::Func2 => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error calling func2" );
< / span > < span class = "boring" > //! true
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! Func1Error::IO(filename) => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error reading '{}'" , filename);
< / span > < span class = "boring" > //! false
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< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! });
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! assert!(e.find_chain_cause::< Func2Error> ().is_some());
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Some(e) = e.find_chain_cause::< Func2Error> () {
< / span > < span class = "boring" > //! eprintln!(" \nError reported by Func2Error: {}" , e)
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! assert!(e.root_cause().is_some());
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! if let Some(e) = e.root_cause() {
< / span > < span class = "boring" > //! let io_error = e.downcast_ref::< io::Error> ().unwrap();
< / span > < span class = "boring" > //! eprintln!(" \nThe root cause was: std::io::Error: {:#?}" , io_error);
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:48:13: func1 error calling func2
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:23:13: Func2Error(func2 error: calling func3)
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" >
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< / span > < span class = "boring" > #![deny(clippy::all)]
< / span > < span class = "boring" > #![deny(clippy::integer_arithmetic)]
< / span > < span class = "boring" > #![deny(missing_docs)]
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< / span > < span class = "boring" >
< / span > < span class = "boring" > use std::any::TypeId;
< / span > < span class = "boring" > use std::error::Error;
< / span > < span class = "boring" > use std::fmt::{Debug, Display, Formatter, Result};
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< / span > < span class = "boring" > use std::panic::Location;
< / span > < span class = "boring" >
< / span > < span class = "boring" > pub mod prelude {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub mod v1 {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub use super::super::ChainErrorDown as _;
< / span > < span class = "boring" > pub use super::super::ResultTrait as _;
< / span > < span class = "boring" > pub use super::super::{ChainError, ChainResult};
< / span > < span class = "boring" > pub use crate::{derive_err_kind, derive_str_context};
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > /// chains an inner error kind `T` with a causing error
< / span > < span class = "boring" > pub struct ChainError< T> {
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// convenience type alias
< / span > < span class = "boring" > pub type ChainResult< O, E> = std::result::Result< O, ChainError< E> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> ChainError< T> {
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< / span > < span class = "boring" > /// Use the `context()` or `map_context()` Result methods instead of calling this directly
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< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn new(
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > ) -> Self {
< / span > < span class = "boring" > Self {
< / span > < span class = "boring" > occurrence,
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > error_cause,
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// return the root cause of the error chain, if any exists
< / span > < span class = "boring" > pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.iter().last()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type U, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// assert!(f1err.find_cause::< io::Error> ().is_some());
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< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter().filter_map(Error::downcast_ref::< U> ).next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> `, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooError);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooError> > ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooError> implementation detail
< / span > < span class = "boring" > /// err.find_chain_cause::< FooError> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(Error::downcast_ref::< ChainError< U> > )
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> ` or `U`, if any exists and return `U`
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause` and `find_chain_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooErrorKind);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooErrorKind> > ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_chain_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_cause::< FooErrorKind> ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooErrorKind> implementation detail
< / span > < span class = "boring" > /// err.find_kind_or_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_kind_or_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(|e| {
< / span > < span class = "boring" > e.downcast_ref::< ChainError< U> > ()
< / span > < span class = "boring" > .map(|e| e.kind())
< / span > < span class = "boring" > .or_else(|| e.downcast_ref::< U> ())
< / span > < span class = "boring" > })
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Return a reference to T of `ChainError< T> `
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug)]
< / span > < span class = "boring" > /// enum Func1ErrorKind {
< / span > < span class = "boring" > /// Func2,
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// /// impl ::std::fmt::Display for Func1ErrorKind {…}
< / span > < span class = "boring" > /// # impl ::std::fmt::Display for Func1ErrorKind {
< / span > < span class = "boring" > /// # fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > /// # match self {
< / span > < span class = "boring" > /// # Func1ErrorKind::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > /// # Func1ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> ChainResult< (), Func1ErrorKind> {
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< / span > < span class = "boring" > /// func2().context(Func1ErrorKind::Func2)?;
< / span > < span class = "boring" > /// do_some_io().context(Func1ErrorKind::IO(" bar.txt" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// Func1ErrorKind::Func2 => {}
< / span > < span class = "boring" > /// Func1ErrorKind::IO(filename) => panic!(),
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn kind(& self) -> & T {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Returns an Iterator over all error causes/sources
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Example
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn iter(& self) -> impl Iterator< Item = & (dyn Error + 'static)> {
< / span > < span class = "boring" > ErrorIter {
< / span > < span class = "boring" > current: Some(self),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > /// Convenience methods for `Result< > ` to turn the error into a decorated ChainError
< / span > < span class = "boring" > pub trait ResultTrait< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > {
< / span > < span class = "boring" > /// Decorate the error with a `kind` of type `T` and the source `Location`
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Decorate the `error` with a `kind` of type `T` produced with a `FnOnce(& error)` and the source `Location`
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > ResultTrait< O, E>
< / span > < span class = "boring" > for std::result::Result< O, E>
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > )),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => {
< / span > < span class = "boring" > let kind = op(& error_cause);
< / span > < span class = "boring" > Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// An iterator over all error causes/sources
< / span > < span class = "boring" > pub struct ErrorIter< 'a> {
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< / span > < span class = "boring" > current: Option< & 'a (dyn Error + 'static)> ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< 'a> Iterator for ErrorIter< 'a> {
< / span > < span class = "boring" > type Item = & 'a (dyn Error + 'static);
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn next(& mut self) -> Option< Self::Item> {
< / span > < span class = "boring" > let current = self.current;
< / span > < span class = "boring" > self.current = self.current.and_then(Error::source);
< / span > < span class = "boring" > current
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> std::ops::Deref for ChainError< T> {
< / span > < span class = "boring" > type Target = T;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn deref(& self) -> & Self::Target {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience trait to hide the `ChainError< T> ` implementation internals
< / span > < span class = "boring" > pub trait ChainErrorDown {
< / span > < span class = "boring" > /// Test if of type `ChainError< T> `
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
< / span > < span class = "boring" > /// Downcast to a reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to a mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to T of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> ;
< / span > < span class = "boring" > /// Downcast to T mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< U: 'static + Display + Debug> ChainErrorDown for ChainError< U> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > TypeId::of::< T> () == TypeId::of::< U> ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& *(self as *const dyn Error as *const & ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& (*(self as *const dyn Error as *const & ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut (*(self as *mut dyn Error as *mut & mut ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send + Sync {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Display for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
< / span > < span class = "boring" > write!(f, " {}" , self.kind)?;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[cfg(feature = " display-cause" )]
< / span > < span class = "boring" > {
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Display::fmt(& e, f)?;
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > Ok(())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Debug for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
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< / span > < span class = "boring" > if f.alternate() {
< / span > < span class = "boring" > let mut f = f.debug_struct(& format!(" ChainError< {}> " , std::any::type_name::< T> ()));
< / span > < span class = "boring" >
< / span > < span class = "boring" > let f = f
< / span > < span class = "boring" > .field(" occurrence" , & self.occurrence)
< / span > < span class = "boring" > .field(" kind" , & self.kind)
< / span > < span class = "boring" > .field(" source" , & self.source());
< / span > < span class = "boring" >
< / span > < span class = "boring" > f.finish()
< / span > < span class = "boring" > } else {
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< / span > < span class = "boring" > if let Some(ref o) = self.occurrence {
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< / span > < span class = "boring" > write!(f, " {}: " , o)?;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > if TypeId::of::< String> () == TypeId::of::< T> ()
< / span > < span class = "boring" > || TypeId::of::< & str> () == TypeId::of::< T> ()
< / span > < span class = "boring" > {
< / span > < span class = "boring" > Display::fmt(& self.kind, f)?;
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > Debug::fmt(& self.kind, f)?;
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Debug::fmt(& e, f)?;
< / span > < span class = "boring" > }
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< / span > < span class = "boring" > Ok(())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `ChainErrorFrom< T> ` is similar to `From< T> `
< / span > < span class = "boring" > pub trait ChainErrorFrom< T> : Sized {
< / span > < span class = "boring" > /// similar to From< T> ::from()
< / span > < span class = "boring" > fn chain_error_from(from: T, line_filename: Option< String> ) -> ChainError< Self> ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `IntoChainError< T> ` is similar to `Into< T> `
< / span > < span class = "boring" > pub trait IntoChainError< T> : Sized {
< / span > < span class = "boring" > /// similar to Into< T> ::into()
< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< T> ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> IntoChainError< U> for T
< / span > < span class = "boring" > where
< / span > < span class = "boring" > U: ChainErrorFrom< T> ,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< U> {
< / span > < span class = "boring" > U::chain_error_from(self, line_filename)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> ChainErrorFrom< T> for U
< / span > < span class = "boring" > where
< / span > < span class = "boring" > T: Into< U> ,
< / span > < span class = "boring" > U: 'static + Display + Debug,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn chain_error_from(t: T, line_filename: Option< String> ) -> ChainError< Self> {
< / span > < span class = "boring" > let e: U = t.into();
< / span > < span class = "boring" > ChainError::new(e, None, line_filename)
< / span > < span class = "boring" > }
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience macro to create a " new type" T(String) and implement Display + Debug for T
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
< / span > < span class = "boring" > /// # use crate::chainerror::*;
< / span > < span class = "boring" > /// # use std::error::Error;
< / span > < span class = "boring" > /// # use std::io;
< / span > < span class = "boring" > /// # use std::result::Result;
< / span > < span class = "boring" > /// # fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// # Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// # Ok(())
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> ChainResult< (), Func2Error> {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// # if let Err(e) = func1() {
< / span > < span class = "boring" > /// # if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// # assert!(f1err.find_cause::< ChainError< Func2Error> > ().is_some());
< / span > < span class = "boring" > /// # assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
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< / span > < span class = "boring" > macro_rules! derive_str_context {
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< / span > < span class = "boring" > ($e:ident) => {
< / span > < span class = "boring" > #[derive(Clone)]
< / span > < span class = "boring" > pub struct $e(pub String);
< / span > < span class = "boring" > impl ::std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}" , self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}({})" , stringify!($e), self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::error::Error for $e {}
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Derive an Error for an ErrorKind, which wraps a `ChainError` and implements a `kind()` method
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// It basically hides `ChainError` to the outside and only exposes the `kind()`
< / span > < span class = "boring" > /// method.
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Error::kind() returns the ErrorKind
< / span > < span class = "boring" > /// Error::source() returns the parent error
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io(_f: & str) -> std::result::Result< (), io::Error> {
< / span > < span class = "boring" > /// return Err(io::Error::from(io::ErrorKind::NotFound));
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug, Clone)]
< / span > < span class = "boring" > /// pub enum ErrorKind {
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// FatalError(String),
< / span > < span class = "boring" > /// Unknown,
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// derive_err_kind!(Error, ErrorKind);
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl std::fmt::Display for ErrorKind {
< / span > < span class = "boring" > /// fn fmt(& self, f: & mut ::std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > /// match self {
< / span > < span class = "boring" > /// ErrorKind::FatalError(e) => write!(f, " fatal error {}" , e),
< / span > < span class = "boring" > /// ErrorKind::Unknown => write!(f, " unknown error" ),
< / span > < span class = "boring" > /// ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl ErrorKind {
< / span > < span class = "boring" > /// fn from_io_error(e: & io::Error, f: String) -> Self {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// io::ErrorKind::BrokenPipe => panic!(" Should not happen" ),
< / span > < span class = "boring" > /// io::ErrorKind::ConnectionReset => {
< / span > < span class = "boring" > /// ErrorKind::FatalError(format!(" While reading `{}`: {}" , f, e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// _ => ErrorKind::IO(f),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl From< & io::Error> for ErrorKind {
< / span > < span class = "boring" > /// fn from(e: & io::Error) -> Self {
< / span > < span class = "boring" > /// ErrorKind::IO(format!(" {}" , e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// pub fn func1() -> std::result::Result< (), Error> {
< / span > < span class = "boring" > /// let filename = " bar.txt" ;
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from_io_error(e, filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::IO(filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from(e))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
< / span > < span class = "boring" > macro_rules! derive_err_kind {
< / span > < span class = "boring" > ($e:ident, $k:ident) => {
< / span > < span class = "boring" > pub struct $e($crate::ChainError< $k> );
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl $e {
< / span > < span class = "boring" > pub fn kind(& self) -> & $k {
< / span > < span class = "boring" > self.0.kind()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< $k> for $e {
< / span > < span class = "boring" > fn from(e: $k) -> Self {
< / span > < span class = "boring" > $e($crate::ChainError::new(e, None, None))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< ChainError< $k> > for $e {
< / span > < span class = "boring" > fn from(e: $crate::ChainError< $k> ) -> Self {
< / span > < span class = "boring" > $e(e)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< & $e> for $k
< / span > < span class = "boring" > where
< / span > < span class = "boring" > $k: Clone,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > fn from(e: & $e) -> Self {
< / span > < span class = "boring" > e.kind().clone()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::error::Error for $e {
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn std::error::Error + 'static)> {
< / span > < span class = "boring" > self.0.source()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Display::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Debug::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < / code > < / pre > < / pre >
< h1 > < a class = "header" href = "#writing-a-library" id = "writing-a-library" > Writing a library< / a > < / h1 >
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< p > I would advise to only expose an < code > mycrate::ErrorKind< / code > and type alias < code > mycrate::Error< / code > to < code > ChainError< mycrate::ErrorKind> < / code >
so you can tell your library users to use the < code > .kind()< / code > method as < code > std::io::Error< / code > does.< / p >
< p > If you later decide to make your own < code > Error< / code > implementation, your library users don't
have to change much or anything.< / p >
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< pre > < pre class = "playground" > < code class = "language-rust" > < span class = "boring" > #[allow(dead_code)]
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< / span > < span class = "boring" > #[macro_use]
< / span > < span class = "boring" > pub mod chainerror {
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< / span > < span class = "boring" > //! `chainerror` provides an error backtrace without doing a real backtrace, so even after you `strip` your
< / span > < span class = "boring" > //! binaries, you still have the error backtrace.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `chainerror` has no dependencies!
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
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< / span > < span class = "boring" > //! It encapsulates all types, which have `Display + Debug` and can store the error cause internally.
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Along with the `ChainError< T> ` struct, `chainerror` comes with some useful helper macros to save a lot of typing.
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! Debug information is worth it!
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ## Features
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! `display-cause`
< / span > < span class = "boring" > //! : turn on printing a backtrace of the errors in `Display`
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Tutorial
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Read the [Tutorial](https://haraldh.github.io/chainerror/tutorial1.html)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! # Examples
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! examples/example.rs:
< / span > < span class = "boring" > //! ```rust,ignore
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! fn main() {
< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! eprintln!(" \nDebug Error {{:?}}:\n{:?}" , e);
< / span > < span class = "boring" > //! eprintln!(" \nAlternative Debug Error {{:#?}}:\n{:#?}\n" , e);
< / span > < span class = "boring" > //! // […]
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```console
< / span > < span class = "boring" > //! $ cargo run -q --example example
< / span > < span class = "boring" > //! Debug Error {:?}:
< / span > < span class = "boring" > //! examples/example.rs:46:13: func1 error calling func2
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:21:13: Func2Error(func2 error: calling func3)
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! examples/example.rs:14:18: Error reading 'foo.txt'
< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! Alternative Debug Error {:#?}:
< / span > < span class = "boring" > //! ChainError< example::Func1Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:46:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: func1 error calling func2,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< example::Func2Error> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:21:13" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: Func2Error(func2 error: calling func3),
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! ChainError< alloc::string::String> {
< / span > < span class = "boring" > //! occurrence: Some(
< / span > < span class = "boring" > //! " examples/example.rs:14:18" ,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! kind: " Error reading \'foo.txt\'" ,
< / span > < span class = "boring" > //! source: Some(
< / span > < span class = "boring" > //! Kind(
< / span > < span class = "boring" > //! NotFound,
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! },
< / span > < span class = "boring" > //! ),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > //! func2().context(" func1 error" )?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:21:13: func1 error
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! ```rust
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< / span > < span class = "boring" > //! use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > //! use std::error::Error;
< / span > < span class = "boring" > //! use std::io;
< / span > < span class = "boring" > //! use std::result::Result;
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func3() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > //! let filename = " foo.txt" ;
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< / span > < span class = "boring" > //! do_some_io().context(format!(" Error reading '{}'" , filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! derive_str_context!(Func2Error);
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< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func2() -> ChainResult< (), Func2Error> {
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< / span > < span class = "boring" > //! func3().context(Func2Error(" func2 error: calling func3" .into()))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! enum Func1Error {
< / span > < span class = "boring" > //! Func2,
< / span > < span class = "boring" > //! IO(String),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Display for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! match self {
< / span > < span class = "boring" > //! Func1Error::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > //! Func1Error::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! impl ::std::fmt::Debug for Func1Error {
< / span > < span class = "boring" > //! fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > //! write!(f, " {}" , self)
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! fn func1() -> ChainResult< (), Func1Error> {
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< / span > < span class = "boring" > //! func2().context(Func1Error::Func2)?;
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< / span > < span class = "boring" > //! let filename = String::from(" bar.txt" );
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< / span > < span class = "boring" > //! do_some_io().context(Func1Error::IO(filename))?;
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< / span > < span class = "boring" > //! Ok(())
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Err(e) = func1() {
< / span > < span class = "boring" > //! assert!(match e.kind() {
< / span > < span class = "boring" > //! Func1Error::Func2 => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error calling func2" );
< / span > < span class = "boring" > //! true
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< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! Func1Error::IO(filename) => {
< / span > < span class = "boring" > //! eprintln!(" Main Error Report: func1 error reading '{}'" , filename);
< / span > < span class = "boring" > //! false
< / span > < span class = "boring" > //! }
< / span > < span class = "boring" > //! });
< / span > < span class = "boring" > //!
< / span > < span class = "boring" > //! assert!(e.find_chain_cause::< Func2Error> ().is_some());
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Some(e) = e.find_chain_cause::< Func2Error> () {
< / span > < span class = "boring" > //! eprintln!(" \nError reported by Func2Error: {}" , e)
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! assert!(e.root_cause().is_some());
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! if let Some(e) = e.root_cause() {
< / span > < span class = "boring" > //! let io_error = e.downcast_ref::< io::Error> ().unwrap();
< / span > < span class = "boring" > //! eprintln!(" \nThe root cause was: std::io::Error: {:#?}" , io_error);
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //!
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< / span > < span class = "boring" > //! #[cfg(not(windows))]
< / span > < span class = "boring" > //! assert_eq!(
< / span > < span class = "boring" > //! format!(" \n{:?}\n" , e),
< / span > < span class = "boring" > //! r#"
< / span > < span class = "boring" > //! src/lib.rs:48:13: func1 error calling func2
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:23:13: Func2Error(func2 error: calling func3)
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< / span > < span class = "boring" > //! Caused by:
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< / span > < span class = "boring" > //! src/lib.rs:16:18: Error reading 'foo.txt'
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< / span > < span class = "boring" > //! Caused by:
< / span > < span class = "boring" > //! Kind(NotFound)
< / span > < span class = "boring" > //! " #
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< / span > < span class = "boring" > //! );
< / span > < span class = "boring" > //! }
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< / span > < span class = "boring" > //! # else {
< / span > < span class = "boring" > //! # unreachable!();
< / span > < span class = "boring" > //! # }
< / span > < span class = "boring" > //! ```
< / span > < span class = "boring" >
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< / span > < span class = "boring" > #![deny(clippy::all)]
< / span > < span class = "boring" > #![deny(clippy::integer_arithmetic)]
< / span > < span class = "boring" > #![deny(missing_docs)]
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< / span > < span class = "boring" >
< / span > < span class = "boring" > use std::any::TypeId;
< / span > < span class = "boring" > use std::error::Error;
< / span > < span class = "boring" > use std::fmt::{Debug, Display, Formatter, Result};
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< / span > < span class = "boring" > use std::panic::Location;
< / span > < span class = "boring" >
< / span > < span class = "boring" > pub mod prelude {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub mod v1 {
< / span > < span class = "boring" > //! convenience prelude
< / span > < span class = "boring" > pub use super::super::ChainErrorDown as _;
< / span > < span class = "boring" > pub use super::super::ResultTrait as _;
< / span > < span class = "boring" > pub use super::super::{ChainError, ChainResult};
< / span > < span class = "boring" > pub use crate::{derive_err_kind, derive_str_context};
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > /// chains an inner error kind `T` with a causing error
< / span > < span class = "boring" > pub struct ChainError< T> {
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// convenience type alias
< / span > < span class = "boring" > pub type ChainResult< O, E> = std::result::Result< O, ChainError< E> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> ChainError< T> {
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< / span > < span class = "boring" > /// Use the `context()` or `map_context()` Result methods instead of calling this directly
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< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn new(
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > error_cause: Option< Box< dyn Error + 'static + Send + Sync> > ,
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< / span > < span class = "boring" > occurrence: Option< String> ,
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< / span > < span class = "boring" > ) -> Self {
< / span > < span class = "boring" > Self {
< / span > < span class = "boring" > occurrence,
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > error_cause,
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// return the root cause of the error chain, if any exists
< / span > < span class = "boring" > pub fn root_cause(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.iter().last()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type U, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error + Send + Sync> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// assert!(f1err.find_cause::< io::Error> ().is_some());
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< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter().filter_map(Error::downcast_ref::< U> ).next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> `, if any exists
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooError);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooError> > ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooError> implementation detail
< / span > < span class = "boring" > /// err.find_chain_cause::< FooError> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_chain_cause< U: Error + 'static> (& self) -> Option< & ChainError< U> > {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(Error::downcast_ref::< ChainError< U> > )
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Find the first error cause of type `ChainError< U> ` or `U`, if any exists and return `U`
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Same as `find_cause` and `find_chain_cause`, but hides the `ChainError< U> ` implementation internals
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// # use chainerror::prelude::v1::*;
< / span > < span class = "boring" > /// # derive_str_context!(FooErrorKind);
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< / span > < span class = "boring" > /// # let err = ChainError::new(String::new(), None, None);
< / span > < span class = "boring" > /// // Instead of writing
< / span > < span class = "boring" > /// err.find_cause::< ChainError< FooErrorKind> > ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_chain_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// // and/or
< / span > < span class = "boring" > /// err.find_cause::< FooErrorKind> ();
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// // leave out the ChainError< FooErrorKind> implementation detail
< / span > < span class = "boring" > /// err.find_kind_or_cause::< FooErrorKind> ();
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn find_kind_or_cause< U: Error + 'static> (& self) -> Option< & U> {
< / span > < span class = "boring" > self.iter()
< / span > < span class = "boring" > .filter_map(|e| {
< / span > < span class = "boring" > e.downcast_ref::< ChainError< U> > ()
< / span > < span class = "boring" > .map(|e| e.kind())
< / span > < span class = "boring" > .or_else(|| e.downcast_ref::< U> ())
< / span > < span class = "boring" > })
< / span > < span class = "boring" > .next()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Return a reference to T of `ChainError< T> `
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::error::Error;
< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug)]
< / span > < span class = "boring" > /// enum Func1ErrorKind {
< / span > < span class = "boring" > /// Func2,
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// /// impl ::std::fmt::Display for Func1ErrorKind {…}
< / span > < span class = "boring" > /// # impl ::std::fmt::Display for Func1ErrorKind {
< / span > < span class = "boring" > /// # fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > /// # match self {
< / span > < span class = "boring" > /// # Func1ErrorKind::Func2 => write!(f, " func1 error calling func2" ),
< / span > < span class = "boring" > /// # Func1ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> ChainResult< (), Func1ErrorKind> {
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< / span > < span class = "boring" > /// func2().context(Func1ErrorKind::Func2)?;
< / span > < span class = "boring" > /// do_some_io().context(Func1ErrorKind::IO(" bar.txt" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// if let Err(e) = func1() {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// Func1ErrorKind::Func2 => {}
< / span > < span class = "boring" > /// Func1ErrorKind::IO(filename) => panic!(),
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// }
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< / span > < span class = "boring" > /// # else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn kind(& self) -> & T {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Returns an Iterator over all error causes/sources
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Example
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > pub fn iter(& self) -> impl Iterator< Item = & (dyn Error + 'static)> {
< / span > < span class = "boring" > ErrorIter {
< / span > < span class = "boring" > current: Some(self),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > /// Convenience methods for `Result< > ` to turn the error into a decorated ChainError
< / span > < span class = "boring" > pub trait ResultTrait< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > {
< / span > < span class = "boring" > /// Decorate the error with a `kind` of type `T` and the source `Location`
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Decorate the `error` with a `kind` of type `T` produced with a `FnOnce(& error)` and the source `Location`
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< O, E: Into< Box< dyn Error + 'static + Send + Sync> > > ResultTrait< O, E>
< / span > < span class = "boring" > for std::result::Result< O, E>
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn context< T: 'static + Display + Debug> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > kind: T,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > )),
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[track_caller]
< / span > < span class = "boring" > fn map_context< T: 'static + Display + Debug, F: FnOnce(& E) -> T> (
< / span > < span class = "boring" > self,
< / span > < span class = "boring" > op: F,
< / span > < span class = "boring" > ) -> std::result::Result< O, ChainError< T> > {
< / span > < span class = "boring" > match self {
< / span > < span class = "boring" > Ok(t) => Ok(t),
< / span > < span class = "boring" > Err(error_cause) => {
< / span > < span class = "boring" > let kind = op(& error_cause);
< / span > < span class = "boring" > Err(ChainError::new(
< / span > < span class = "boring" > kind,
< / span > < span class = "boring" > Some(error_cause.into()),
< / span > < span class = "boring" > Some(Location::caller().to_string()),
< / span > < span class = "boring" > ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// An iterator over all error causes/sources
< / span > < span class = "boring" > pub struct ErrorIter< 'a> {
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< / span > < span class = "boring" > current: Option< & 'a (dyn Error + 'static)> ,
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< 'a> Iterator for ErrorIter< 'a> {
< / span > < span class = "boring" > type Item = & 'a (dyn Error + 'static);
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn next(& mut self) -> Option< Self::Item> {
< / span > < span class = "boring" > let current = self.current;
< / span > < span class = "boring" > self.current = self.current.and_then(Error::source);
< / span > < span class = "boring" > current
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> std::ops::Deref for ChainError< T> {
< / span > < span class = "boring" > type Target = T;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn deref(& self) -> & Self::Target {
< / span > < span class = "boring" > & self.kind
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience trait to hide the `ChainError< T> ` implementation internals
< / span > < span class = "boring" > pub trait ChainErrorDown {
< / span > < span class = "boring" > /// Test if of type `ChainError< T> `
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool;
< / span > < span class = "boring" > /// Downcast to a reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to a mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > ;
< / span > < span class = "boring" > /// Downcast to T of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> ;
< / span > < span class = "boring" > /// Downcast to T mutable reference of `ChainError< T> `
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> ;
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< U: 'static + Display + Debug> ChainErrorDown for ChainError< U> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > TypeId::of::< T> () == TypeId::of::< U> ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& *(self as *const dyn Error as *const & ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut *(self as *mut dyn Error as *mut & mut ChainError< T> ))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& (*(self as *const dyn Error as *const & ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is_chain::< T> () {
< / span > < span class = "boring" > #[allow(clippy::cast_ptr_alignment)]
< / span > < span class = "boring" > unsafe {
< / span > < span class = "boring" > #[allow(trivial_casts)]
< / span > < span class = "boring" > Some(& mut (*(self as *mut dyn Error as *mut & mut ChainError< T> )).kind)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > None
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl ChainErrorDown for dyn Error + 'static + Send + Sync {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn is_chain< T: 'static + Display + Debug> (& self) -> bool {
< / span > < span class = "boring" > self.is::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_ref< T: 'static + Display + Debug> (& self) -> Option< & ChainError< T> > {
< / span > < span class = "boring" > self.downcast_ref::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_chain_mut< T: 'static + Display + Debug> (& mut self) -> Option< & mut ChainError< T> > {
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_ref< T: 'static + Error> (& self) -> Option< & T> {
< / span > < span class = "boring" > self.downcast_ref::< T> ()
< / span > < span class = "boring" > .or_else(|| self.downcast_ref::< ChainError< T> > ().map(|e| e.kind()))
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn downcast_inner_mut< T: 'static + Error> (& mut self) -> Option< & mut T> {
< / span > < span class = "boring" > if self.is::< T> () {
< / span > < span class = "boring" > return self.downcast_mut::< T> ();
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > self.downcast_mut::< ChainError< T> > ()
< / span > < span class = "boring" > .and_then(|e| e.downcast_inner_mut::< T> ())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Error for & mut ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn Error + 'static)> {
< / span > < span class = "boring" > self.error_cause
< / span > < span class = "boring" > .as_ref()
< / span > < span class = "boring" > .map(|e| e.as_ref() as & (dyn Error + 'static))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Display for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
< / span > < span class = "boring" > write!(f, " {}" , self.kind)?;
< / span > < span class = "boring" >
< / span > < span class = "boring" > #[cfg(feature = " display-cause" )]
< / span > < span class = "boring" > {
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Display::fmt(& e, f)?;
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > Ok(())
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T: 'static + Display + Debug> Debug for ChainError< T> {
< / span > < span class = "boring" > #[inline]
< / span > < span class = "boring" > fn fmt(& self, f: & mut Formatter< '_> ) -> Result {
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< / span > < span class = "boring" > if f.alternate() {
< / span > < span class = "boring" > let mut f = f.debug_struct(& format!(" ChainError< {}> " , std::any::type_name::< T> ()));
< / span > < span class = "boring" >
< / span > < span class = "boring" > let f = f
< / span > < span class = "boring" > .field(" occurrence" , & self.occurrence)
< / span > < span class = "boring" > .field(" kind" , & self.kind)
< / span > < span class = "boring" > .field(" source" , & self.source());
< / span > < span class = "boring" >
< / span > < span class = "boring" > f.finish()
< / span > < span class = "boring" > } else {
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< / span > < span class = "boring" > if let Some(ref o) = self.occurrence {
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< / span > < span class = "boring" > write!(f, " {}: " , o)?;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
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< / span > < span class = "boring" > if TypeId::of::< String> () == TypeId::of::< T> ()
< / span > < span class = "boring" > || TypeId::of::< & str> () == TypeId::of::< T> ()
< / span > < span class = "boring" > {
< / span > < span class = "boring" > Display::fmt(& self.kind, f)?;
< / span > < span class = "boring" > } else {
< / span > < span class = "boring" > Debug::fmt(& self.kind, f)?;
< / span > < span class = "boring" > }
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< / span > < span class = "boring" >
< / span > < span class = "boring" > if let Some(e) = self.source() {
< / span > < span class = "boring" > writeln!(f, " \nCaused by:" )?;
< / span > < span class = "boring" > Debug::fmt(& e, f)?;
< / span > < span class = "boring" > }
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< / span > < span class = "boring" > Ok(())
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< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `ChainErrorFrom< T> ` is similar to `From< T> `
< / span > < span class = "boring" > pub trait ChainErrorFrom< T> : Sized {
< / span > < span class = "boring" > /// similar to From< T> ::from()
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< / span > < span class = "boring" > fn chain_error_from(from: T, line_filename: Option< String> ) -> ChainError< Self> ;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// `IntoChainError< T> ` is similar to `Into< T> `
< / span > < span class = "boring" > pub trait IntoChainError< T> : Sized {
< / span > < span class = "boring" > /// similar to Into< T> ::into()
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< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< T> ;
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< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> IntoChainError< U> for T
< / span > < span class = "boring" > where
< / span > < span class = "boring" > U: ChainErrorFrom< T> ,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
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< / span > < span class = "boring" > fn into_chain_error(self, line_filename: Option< String> ) -> ChainError< U> {
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< / span > < span class = "boring" > U::chain_error_from(self, line_filename)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl< T, U> ChainErrorFrom< T> for U
< / span > < span class = "boring" > where
< / span > < span class = "boring" > T: Into< U> ,
< / span > < span class = "boring" > U: 'static + Display + Debug,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > #[inline]
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< / span > < span class = "boring" > fn chain_error_from(t: T, line_filename: Option< String> ) -> ChainError< Self> {
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< / span > < span class = "boring" > let e: U = t.into();
< / span > < span class = "boring" > ChainError::new(e, None, line_filename)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Convenience macro to create a " new type" T(String) and implement Display + Debug for T
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
< / span > < span class = "boring" > /// # use crate::chainerror::*;
< / span > < span class = "boring" > /// # use std::error::Error;
< / span > < span class = "boring" > /// # use std::io;
< / span > < span class = "boring" > /// # use std::result::Result;
< / span > < span class = "boring" > /// # fn do_some_io() -> Result< (), Box< dyn Error + Send + Sync> > {
< / span > < span class = "boring" > /// # Err(io::Error::from(io::ErrorKind::NotFound))?;
< / span > < span class = "boring" > /// # Ok(())
< / span > < span class = "boring" > /// # }
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< / span > < span class = "boring" > /// derive_str_context!(Func2Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func2() -> ChainResult< (), Func2Error> {
< / span > < span class = "boring" > /// let filename = " foo.txt" ;
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< / span > < span class = "boring" > /// do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// derive_str_context!(Func1Error);
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< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn func1() -> Result< (), Box< dyn Error> > {
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< / span > < span class = "boring" > /// func2().context(Func1Error(" func1 error" .into()))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// # if let Err(e) = func1() {
< / span > < span class = "boring" > /// # if let Some(f1err) = e.downcast_chain_ref::< Func1Error> () {
< / span > < span class = "boring" > /// # assert!(f1err.find_cause::< ChainError< Func2Error> > ().is_some());
< / span > < span class = "boring" > /// # assert!(f1err.find_chain_cause::< Func2Error> ().is_some());
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # panic!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// # } else {
< / span > < span class = "boring" > /// # unreachable!();
< / span > < span class = "boring" > /// # }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
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< / span > < span class = "boring" > macro_rules! derive_str_context {
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< / span > < span class = "boring" > ($e:ident) => {
< / span > < span class = "boring" > #[derive(Clone)]
< / span > < span class = "boring" > pub struct $e(pub String);
< / span > < span class = "boring" > impl ::std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}" , self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut ::std::fmt::Formatter) -> ::std::fmt::Result {
< / span > < span class = "boring" > write!(f, " {}({})" , stringify!($e), self.0)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > impl ::std::error::Error for $e {}
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > /// Derive an Error for an ErrorKind, which wraps a `ChainError` and implements a `kind()` method
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// It basically hides `ChainError` to the outside and only exposes the `kind()`
< / span > < span class = "boring" > /// method.
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// Error::kind() returns the ErrorKind
< / span > < span class = "boring" > /// Error::source() returns the parent error
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// # Examples
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// ```rust
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< / span > < span class = "boring" > /// use chainerror::prelude::v1::*;
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< / span > < span class = "boring" > /// use std::io;
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// fn do_some_io(_f: & str) -> std::result::Result< (), io::Error> {
< / span > < span class = "boring" > /// return Err(io::Error::from(io::ErrorKind::NotFound));
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// #[derive(Debug, Clone)]
< / span > < span class = "boring" > /// pub enum ErrorKind {
< / span > < span class = "boring" > /// IO(String),
< / span > < span class = "boring" > /// FatalError(String),
< / span > < span class = "boring" > /// Unknown,
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// derive_err_kind!(Error, ErrorKind);
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl std::fmt::Display for ErrorKind {
< / span > < span class = "boring" > /// fn fmt(& self, f: & mut ::std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > /// match self {
< / span > < span class = "boring" > /// ErrorKind::FatalError(e) => write!(f, " fatal error {}" , e),
< / span > < span class = "boring" > /// ErrorKind::Unknown => write!(f, " unknown error" ),
< / span > < span class = "boring" > /// ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl ErrorKind {
< / span > < span class = "boring" > /// fn from_io_error(e: & io::Error, f: String) -> Self {
< / span > < span class = "boring" > /// match e.kind() {
< / span > < span class = "boring" > /// io::ErrorKind::BrokenPipe => panic!(" Should not happen" ),
< / span > < span class = "boring" > /// io::ErrorKind::ConnectionReset => {
< / span > < span class = "boring" > /// ErrorKind::FatalError(format!(" While reading `{}`: {}" , f, e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// _ => ErrorKind::IO(f),
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// impl From< & io::Error> for ErrorKind {
< / span > < span class = "boring" > /// fn from(e: & io::Error) -> Self {
< / span > < span class = "boring" > /// ErrorKind::IO(format!(" {}" , e))
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > ///
< / span > < span class = "boring" > /// pub fn func1() -> std::result::Result< (), Error> {
< / span > < span class = "boring" > /// let filename = " bar.txt" ;
< / span > < span class = "boring" > ///
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< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from_io_error(e, filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::IO(filename.into()))?;
< / span > < span class = "boring" > /// do_some_io(filename).map_context(|e| ErrorKind::from(e))?;
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< / span > < span class = "boring" > /// Ok(())
< / span > < span class = "boring" > /// }
< / span > < span class = "boring" > /// ```
< / span > < span class = "boring" > #[macro_export]
< / span > < span class = "boring" > macro_rules! derive_err_kind {
< / span > < span class = "boring" > ($e:ident, $k:ident) => {
< / span > < span class = "boring" > pub struct $e($crate::ChainError< $k> );
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl $e {
< / span > < span class = "boring" > pub fn kind(& self) -> & $k {
< / span > < span class = "boring" > self.0.kind()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< $k> for $e {
< / span > < span class = "boring" > fn from(e: $k) -> Self {
< / span > < span class = "boring" > $e($crate::ChainError::new(e, None, None))
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< ChainError< $k> > for $e {
< / span > < span class = "boring" > fn from(e: $crate::ChainError< $k> ) -> Self {
< / span > < span class = "boring" > $e(e)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl From< & $e> for $k
< / span > < span class = "boring" > where
< / span > < span class = "boring" > $k: Clone,
< / span > < span class = "boring" > {
< / span > < span class = "boring" > fn from(e: & $e) -> Self {
< / span > < span class = "boring" > e.kind().clone()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::error::Error for $e {
< / span > < span class = "boring" > fn source(& self) -> Option< & (dyn std::error::Error + 'static)> {
< / span > < span class = "boring" > self.0.source()
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Display for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Display::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" >
< / span > < span class = "boring" > impl std::fmt::Debug for $e {
< / span > < span class = "boring" > fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
< / span > < span class = "boring" > std::fmt::Debug::fmt(& self.0, f)
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
< / span > < span class = "boring" > };
< / span > < span class = "boring" > }
< / span > < span class = "boring" > }
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< / span > pub mod mycrate {
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use crate::chainerror::*; // omit the `crate::` part
use std::io;
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fn do_some_io() -> std::result::Result< (), Box< dyn std::error::Error + Send + Sync> > {
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Err(io::Error::from(io::ErrorKind::NotFound))?;
Ok(())
}
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derive_str_context!(Func2Error);
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fn func2() -> std::result::Result< (), Box< dyn std::error::Error + Send + Sync> > {
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let filename = " foo.txt" ;
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do_some_io().context(Func2Error(format!(" Error reading '{}'" , filename)))?;
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Ok(())
}
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#[derive(Debug, Clone)]
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pub enum ErrorKind {
Func2,
IO(String),
}
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derive_err_kind!(Error, ErrorKind);
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pub type Result< T> = std::result::Result< T, Error> ;
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impl std::fmt::Display for ErrorKind {
fn fmt(& self, f: & mut ::std::fmt::Formatter) -> std::fmt::Result {
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match self {
ErrorKind::Func2 => write!(f, " func1 error calling func2" ),
ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
}
}
}
pub fn func1() -> Result< ()> {
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func2().context(ErrorKind::Func2)?;
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let filename = String::from(" bar.txt" );
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do_some_io().context(ErrorKind::IO(filename))?;
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Ok(())
}
}
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fn main() -> Result< (), Box< dyn std::error::Error + Send + Sync> > {
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use mycrate::func1;
use mycrate::ErrorKind;
use std::error::Error;
use std::io;
if let Err(e) = func1() {
match e.kind() {
ErrorKind::Func2 => eprintln!(" Main Error Report: func1 error calling func2" ),
ErrorKind::IO(ref filename) => {
eprintln!(" Main Error Report: func1 error reading '{}'" , filename)
}
}
eprintln!();
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let mut s: & dyn Error = & e;
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while let Some(c) = s.source() {
if let Some(ioerror) = c.downcast_ref::< io::Error> () {
eprintln!(" caused by: std::io::Error: {}" , ioerror);
match ioerror.kind() {
io::ErrorKind::NotFound => eprintln!(" of kind: std::io::ErrorKind::NotFound" ),
_ => {}
}
} else {
eprintln!(" caused by: {}" , c);
}
s = c;
}
eprintln!(" \nDebug Error:\n{:?}" , e);
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std::process::exit(1);
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}
Ok(())
}
< / code > < / pre > < / pre >
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< h1 > < a class = "header" href = "#going-back-to-std" id = "going-back-to-std" > Going back to std< / a > < / h1 >
< p > Not using < code > chainerror< / code > and going full < code > std< / code > would look like this:< / p >
< p > Btw, the code size is bigger than using < code > chainerror< / code > :-)< / p >
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< pre > < pre class = "playground" > < code class = "language-rust" > pub mod mycrate {
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use std::error::Error as StdError;
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use self::func2mod::{do_some_io, func2};
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pub mod func2mod {
use std::error::Error as StdError;
use std::io;
pub enum ErrorKind {
IO(String),
}
impl std::fmt::Display for ErrorKind {
fn fmt(& self, f: & mut ::std::fmt::Formatter) -> std::fmt::Result {
match self {
ErrorKind::IO(s) => std::fmt::Display::fmt(s, f),
}
}
}
impl std::fmt::Debug for ErrorKind {
fn fmt(& self, f: & mut ::std::fmt::Formatter) -> std::fmt::Result {
match self {
ErrorKind::IO(s) => std::fmt::Display::fmt(s, f),
}
}
}
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macro_rules! mcontext {
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( $k:expr ) => {{
|e| {
Error(
$k,
Some(Box::from(e)),
Some(concat!(file!(), " :" , line!(), " : " )),
)
}
}};
}
pub struct Error(
ErrorKind,
Option< Box< dyn std::error::Error + 'static> > ,
Option< & 'static str> ,
);
impl Error {
pub fn kind(& self) -> & ErrorKind {
& self.0
}
}
impl From< ErrorKind> for Error {
fn from(e: ErrorKind) -> Self {
Error(e, None, None)
}
}
impl std::error::Error for Error {
fn source(& self) -> Option< & (dyn std::error::Error + 'static)> {
self.1.as_ref().map(|e| e.as_ref())
}
}
impl std::fmt::Display for Error {
fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
std::fmt::Display::fmt(& self.0, f)
}
}
impl std::fmt::Debug for Error {
fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
if let Some(ref o) = self.2 {
std::fmt::Display::fmt(o, f)?;
}
std::fmt::Debug::fmt(& self.0, f)?;
if let Some(e) = self.source() {
std::fmt::Display::fmt(" \nCaused by:\n" , f)?;
std::fmt::Debug::fmt(& e, f)?;
}
Ok(())
}
}
pub fn do_some_io() -> std::result::Result< (), Box< dyn std::error::Error> > {
Err(io::Error::from(io::ErrorKind::NotFound))?;
Ok(())
}
pub fn func2() -> std::result::Result< (), Error> {
let filename = " foo.txt" ;
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do_some_io().map_err(mcontext!(ErrorKind::IO(format!(
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" Error reading '{}'" ,
filename
))))?;
Ok(())
}
}
#[derive(Debug)]
pub enum ErrorKind {
Func2,
IO(String),
}
impl std::fmt::Display for ErrorKind {
fn fmt(& self, f: & mut ::std::fmt::Formatter) -> std::fmt::Result {
match self {
ErrorKind::Func2 => write!(f, " func1 error calling func2" ),
ErrorKind::IO(filename) => write!(f, " Error reading '{}'" , filename),
}
}
}
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macro_rules! mcontext {
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( $k:expr ) => {{
|e| {
Error(
$k,
Some(Box::from(e)),
Some(concat!(file!(), " :" , line!(), " : " )),
)
}
}};
}
pub struct Error(
ErrorKind,
Option< Box< dyn std::error::Error + 'static> > ,
Option< & 'static str> ,
);
impl Error {
pub fn kind(& self) -> & ErrorKind {
& self.0
}
}
impl From< ErrorKind> for Error {
fn from(e: ErrorKind) -> Self {
Error(e, None, None)
}
}
impl std::error::Error for Error {
fn source(& self) -> Option< & (dyn std::error::Error + 'static)> {
self.1.as_ref().map(|e| e.as_ref())
}
}
impl std::fmt::Display for Error {
fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
std::fmt::Display::fmt(& self.0, f)
}
}
impl std::fmt::Debug for Error {
fn fmt(& self, f: & mut std::fmt::Formatter) -> std::fmt::Result {
if let Some(ref o) = self.2 {
std::fmt::Display::fmt(o, f)?;
}
std::fmt::Debug::fmt(& self.0, f)?;
if let Some(e) = self.source() {
std::fmt::Display::fmt(" \nCaused by:\n" , f)?;
std::fmt::Debug::fmt(& e, f)?;
}
Ok(())
}
}
pub type Result< T> = std::result::Result< T, Error> ;
pub fn func1() -> Result< ()> {
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func2().map_err(mcontext!(ErrorKind::Func2))?;
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let filename = String::from(" bar.txt" );
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do_some_io().map_err(mcontext!(ErrorKind::IO(filename)))?;
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Ok(())
}
}
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fn main() -> Result< (), Box< dyn std::error::Error + Send + Sync> > {
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use mycrate::func1;
use mycrate::ErrorKind;
use std::error::Error;
use std::io;
if let Err(e) = func1() {
match e.kind() {
ErrorKind::Func2 => eprintln!(" Main Error Report: func1 error calling func2" ),
ErrorKind::IO(ref filename) => {
eprintln!(" Main Error Report: func1 error reading '{}'" , filename)
}
}
eprintln!();
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let mut s: & dyn Error = & e;
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while let Some(c) = s.source() {
if let Some(ioerror) = c.downcast_ref::< io::Error> () {
eprintln!(" caused by: std::io::Error: {}" , ioerror);
match ioerror.kind() {
io::ErrorKind::NotFound => eprintln!(" of kind: std::io::ErrorKind::NotFound" ),
_ => {}
}
} else {
eprintln!(" caused by: {}" , c);
}
s = c;
}
eprintln!(" \nDebug Error:\n{:?}" , e);
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std::process::exit(1);
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}
Ok(())
}
< / code > < / pre > < / pre >
< h1 > < a class = "header" href = "#the-end" id = "the-end" > The End< / a > < / h1 >
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< p > That's it for now…< / p >
< p > Happy error handling!< / p >
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< p > To report issues, submit pull request or for the source code, examples and the book source, visit
the < a href = "https://github.com/haraldh/chainerror" > Git Repo< / a > .< / p >
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< / main >
< nav class = "nav-wrapper" aria-label = "Page navigation" >
<!-- Mobile navigation buttons -->
< div style = "clear: both" > < / div >
< / nav >
< / div >
< / div >
< nav class = "nav-wide-wrapper" aria-label = "Page navigation" >
< / nav >
< / div >
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< script type = "text/javascript" >
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window.playground_copyable = true;
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< / script >
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< script src = "elasticlunr.min.js" type = "text/javascript" charset = "utf-8" > < / script >
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window.setTimeout(window.print, 100);
});
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