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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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<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
binaries, you still have the error backtrace.</p>
<p>Having nested function returning errors, the output doesn't tell where the error originates from.</p>
<pre><pre class="playground"><code class="language-rust">use std::path::PathBuf;
type BoxedError = Box<dyn std::error::Error + Send + Sync>;
fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
// do stuff, return other errors
let _buf = std::fs::read_to_string(&path)?;
// do stuff, return other errors
Ok(())
}
fn process_config_file() -> Result<(), BoxedError> {
// do stuff, return other errors
let _buf = read_config_file("foo.txt".into())?;
// do stuff, return other errors
Ok(())
}
fn main() {
if let Err(e) = process_config_file() {
eprintln!("Error:\n{:?}", e);
}
}
</code></pre></pre>
<p>This gives the output:</p>
<pre><code class="language-console">Error:
Os { code: 2, kind: NotFound, message: "No such file or directory" }
</code></pre>
<p>and you have no idea where it comes from.</p>
<p>With <code>chainerror</code>, you can supply a context and get a nice error backtrace:</p>
<pre><pre class="playground"><code class="language-rust">use chainerror::prelude::v1::*;
use std::path::PathBuf;
type BoxedError = Box<dyn std::error::Error + Send + Sync>;
fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
// do stuff, return other errors
let _buf = std::fs::read_to_string(&path).context(format!("Reading file: {:?}", &path))?;
// do stuff, return other errors
Ok(())
}
fn process_config_file() -> Result<(), BoxedError> {
// do stuff, return other errors
let _buf = read_config_file("foo.txt".into()).context("read the config file")?;
// do stuff, return other errors
Ok(())
}
fn main() {
if let Err(e) = process_config_file() {
eprintln!("Error:\n{:?}", e);
}
}
</code></pre></pre>
<p>with the output:</p>
<pre><code class="language-console">Error:
examples/simple.rs:14:51: read the config file
Caused by:
examples/simple.rs:7:47: Reading file: "foo.txt"
Caused by:
Os { code: 2, kind: NotFound, message: "No such file or directory" }
</code></pre>
<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.
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><code>chainerror</code> has no dependencies!</p>
<p>Debug information is worth it!</p>
<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="#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>
<h1><a class="header" href="#simple-string-errors" id="simple-string-errors">Simple String Errors</a></h1>
<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>
<p>As you can see by running the example (by pressing the "Play" button in upper right of the code block),
this only
prints out the last <code>Error</code>.</p>
<pre><code>Error: "func1 error"
</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>
<p>You can also run the tutorial examples in the checked out
<a href="https://github.com/haraldh/chainerror">chainerror git repo</a>.</p>
<pre><code class="language-console">$ cargo run -q --example tutorial1
</code></pre>
<pre><pre class="playground"><code class="language-rust">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(())
}
fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
if let Err(_) = do_some_io() {
Err("func2 error")?;
}
Ok(())
}
fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
if let Err(_) = func2() {
Err("func1 error")?;
}
Ok(())
}
fn main() -> Result<(), Box<dyn Error + Send + Sync>> {
func1()
}
</code></pre></pre>
<h1><a class="header" href="#simple-chained-string-errors" id="simple-chained-string-errors">Simple Chained String Errors</a></h1>
<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>
<p>Press the play button in the upper right corner and see the nice debug output.</p>
<pre><pre class="playground"><code class="language-rust">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(())
}
fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
if let Err(e) = do_some_io() {
Err(e).context("func2 error")?;
}
Ok(())
}
fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
if let Err(e) = func2() {
Err(e).context("func1 error")?;
}
Ok(())
}
fn main() -> Result<(), Box<dyn Error + Send + Sync>> {
func1()
}
<span class="boring">#[allow(dead_code)]
</span><span class="boring">mod chainerror {
</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">//! Having nested function returning errors, the output doesn't tell where the error originates from.
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path)?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into())?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! }
</span><span class="boring">//! }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! This gives the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//! and you have no idea where it comes from.
</span><span class="boring">//!
</span><span class="boring">//!
</span><span class="boring">//! With `chainerror`, you can supply a context and get a nice error backtrace:
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use chainerror::prelude::v1::*;
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path).context(format!("Reading file: {:?}", &path))?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into()).context("read the config file")?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! # assert_eq!(
</span><span class="boring">//! # format!("{:?}\n", e),
</span><span class="boring">//! # "\
</span><span class="boring">//! # src/lib.rs:16:51: read the config file\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # src/lib.rs:9:47: Reading file: \"foo.txt\"\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # Os { code: 2, kind: NotFound, message: \"No such file or directory\" }\n\
</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">//! with the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! examples/simple.rs:14:51: read the config file
</span><span class="boring">//! Caused by:
</span><span class="boring">//! examples/simple.rs:7:47: Reading file: "foo.txt"
</span><span class="boring">//! Caused by:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
</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">//!
</span><span class="boring">//! `chainerror` has no dependencies!
</span><span class="boring">//!
</span><span class="boring">//! Debug information is worth it!
</span><span class="boring">//!
</span><span class="boring">//! ## Features
</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">#![deny(clippy::all)]
</span><span class="boring">#![deny(clippy::integer_arithmetic)]
</span><span class="boring">#![allow(clippy::needless_doctest_main)]
</span><span class="boring">#![deny(missing_docs)]
</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};
</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">}
</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> {
</span><span class="boring"> occurrence: Option<String>,
</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> {
</span><span class="boring"> /// Use the `context()` or `map_context()` Result methods instead of calling this directly
</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>>,
</span><span class="boring"> occurrence: Option<String>,
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</span><span class="boring"> /// derive_str_context!(Func1Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// func2().context(Func1Error("func1 error".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</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::<io::Error>().is_some());
</span><span class="boring"> ///
</span><span class="boring"> /// assert!(f1err.find_chain_cause::<Func2Error>().is_some());
</span><span class="boring"> /// }
</span><span class="boring"> /// # else {
</span><span class="boring"> /// # panic!();
</span><span class="boring"> /// # }
</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"> #[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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooError);
</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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooErrorKind);
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</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> {
</span><span class="boring"> /// func2().context(Func1ErrorKind::Func2)?;
</span><span class="boring"> /// do_some_io().context(Func1ErrorKind::IO("bar.txt".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</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!(),
</span><span class="boring"> /// }
</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"> #[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">
</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> {
</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 {
</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 {
</span><span class="boring"> if let Some(ref o) = self.occurrence {
</span><span class="boring"> write!(f, "{}: ", o)?;
</span><span class="boring"> }
</span><span class="boring">
</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"> }
</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"> }
</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"> }
</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">/// # }
</span><span class="boring">/// derive_str_context!(Func2Error);
</span><span class="boring">///
</span><span class="boring">/// fn func2() -> ChainResult<(), Func2Error> {
</span><span class="boring">/// let filename = "foo.txt";
</span><span class="boring">/// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// derive_str_context!(Func1Error);
</span><span class="boring">///
</span><span class="boring">/// fn func1() -> Result<(), Box<dyn Error>> {
</span><span class="boring">/// func2().context(Func1Error("func1 error".into()))?;
</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]
</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
</span><span class="boring">///
</span><span class="boring">/// # Examples
</span><span class="boring">///
</span><span class="boring">/// ```rust
</span><span class="boring">/// use chainerror::prelude::v1::*;
</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">///
</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))?;
</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">}
</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>
<pre><code class="language-rust ignore"> if let Err(e) = do_some_io() {
Err(e).context("func2 error")?;
}
</code></pre>
<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
again have a <code>Err(Box<Error + Send + Sync>)</code> as a result.</p>
<p>The <code>Debug</code> implementation of <code>ChainError<T></code> (which is returned by <code>context()</code>)
prints the <code>Debug</code> of <code>T</code> prefixed with the stored filename and line number.</p>
<p><code>ChainError<T></code> in our case is <code>ChainError<&str></code>.</p>
<h1><a class="header" href="#mapping-errors" id="mapping-errors">Mapping Errors</a></h1>
<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::*;
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(())
}
fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
do_some_io().context("func2 error")?;
Ok(())
}
fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
func2().context("func1 error")?;
Ok(())
}
fn main() -> Result<(), Box<dyn Error + Send + Sync>> {
if let Err(e) = func1() {
eprintln!("{:?}", e);
std::process::exit(1);
}
Ok(())
}
<span class="boring">#[allow(dead_code)]
</span><span class="boring">mod chainerror {
</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">//! Having nested function returning errors, the output doesn't tell where the error originates from.
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path)?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into())?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! }
</span><span class="boring">//! }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! This gives the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//! and you have no idea where it comes from.
</span><span class="boring">//!
</span><span class="boring">//!
</span><span class="boring">//! With `chainerror`, you can supply a context and get a nice error backtrace:
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use chainerror::prelude::v1::*;
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path).context(format!("Reading file: {:?}", &path))?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into()).context("read the config file")?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! # assert_eq!(
</span><span class="boring">//! # format!("{:?}\n", e),
</span><span class="boring">//! # "\
</span><span class="boring">//! # src/lib.rs:16:51: read the config file\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # src/lib.rs:9:47: Reading file: \"foo.txt\"\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # Os { code: 2, kind: NotFound, message: \"No such file or directory\" }\n\
</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">//! with the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! examples/simple.rs:14:51: read the config file
</span><span class="boring">//! Caused by:
</span><span class="boring">//! examples/simple.rs:7:47: Reading file: "foo.txt"
</span><span class="boring">//! Caused by:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
</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">//!
</span><span class="boring">//! `chainerror` has no dependencies!
</span><span class="boring">//!
</span><span class="boring">//! Debug information is worth it!
</span><span class="boring">//!
</span><span class="boring">//! ## Features
</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">#![deny(clippy::all)]
</span><span class="boring">#![deny(clippy::integer_arithmetic)]
</span><span class="boring">#![allow(clippy::needless_doctest_main)]
</span><span class="boring">#![deny(missing_docs)]
</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};
</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">}
</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> {
</span><span class="boring"> occurrence: Option<String>,
</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> {
</span><span class="boring"> /// Use the `context()` or `map_context()` Result methods instead of calling this directly
</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>>,
</span><span class="boring"> occurrence: Option<String>,
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</span><span class="boring"> /// derive_str_context!(Func1Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// func2().context(Func1Error("func1 error".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</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::<io::Error>().is_some());
</span><span class="boring"> ///
</span><span class="boring"> /// assert!(f1err.find_chain_cause::<Func2Error>().is_some());
</span><span class="boring"> /// }
</span><span class="boring"> /// # else {
</span><span class="boring"> /// # panic!();
</span><span class="boring"> /// # }
</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"> #[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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooError);
</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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooErrorKind);
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</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> {
</span><span class="boring"> /// func2().context(Func1ErrorKind::Func2)?;
</span><span class="boring"> /// do_some_io().context(Func1ErrorKind::IO("bar.txt".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</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!(),
</span><span class="boring"> /// }
</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"> #[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">
</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> {
</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 {
</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 {
</span><span class="boring"> if let Some(ref o) = self.occurrence {
</span><span class="boring"> write!(f, "{}: ", o)?;
</span><span class="boring"> }
</span><span class="boring">
</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"> }
</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"> }
</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"> }
</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">/// # }
</span><span class="boring">/// derive_str_context!(Func2Error);
</span><span class="boring">///
</span><span class="boring">/// fn func2() -> ChainResult<(), Func2Error> {
</span><span class="boring">/// let filename = "foo.txt";
</span><span class="boring">/// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// derive_str_context!(Func1Error);
</span><span class="boring">///
</span><span class="boring">/// fn func1() -> Result<(), Box<dyn Error>> {
</span><span class="boring">/// func2().context(Func1Error("func1 error".into()))?;
</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]
</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
</span><span class="boring">///
</span><span class="boring">/// # Examples
</span><span class="boring">///
</span><span class="boring">/// ```rust
</span><span class="boring">/// use chainerror::prelude::v1::*;
</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">///
</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))?;
</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">}
</span></code></pre></pre>
<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>
<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::*;
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(())
}
fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
let filename = "foo.txt";
do_some_io().context(format!("Error reading '{}'", filename))?;
Ok(())
}
fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
func2().context("func1 error")?;
Ok(())
}
fn main() -> Result<(), Box<dyn Error + Send + Sync>> {
if let Err(e) = func1() {
eprintln!("{:?}", e);
std::process::exit(1);
}
Ok(())
}
<span class="boring">#[allow(dead_code)]
</span><span class="boring">mod chainerror {
</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">//! Having nested function returning errors, the output doesn't tell where the error originates from.
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path)?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into())?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! }
</span><span class="boring">//! }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! This gives the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//! and you have no idea where it comes from.
</span><span class="boring">//!
</span><span class="boring">//!
</span><span class="boring">//! With `chainerror`, you can supply a context and get a nice error backtrace:
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use chainerror::prelude::v1::*;
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path).context(format!("Reading file: {:?}", &path))?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into()).context("read the config file")?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! # assert_eq!(
</span><span class="boring">//! # format!("{:?}\n", e),
</span><span class="boring">//! # "\
</span><span class="boring">//! # src/lib.rs:16:51: read the config file\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # src/lib.rs:9:47: Reading file: \"foo.txt\"\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # Os { code: 2, kind: NotFound, message: \"No such file or directory\" }\n\
</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">//! with the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! examples/simple.rs:14:51: read the config file
</span><span class="boring">//! Caused by:
</span><span class="boring">//! examples/simple.rs:7:47: Reading file: "foo.txt"
</span><span class="boring">//! Caused by:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
</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">//!
</span><span class="boring">//! `chainerror` has no dependencies!
</span><span class="boring">//!
</span><span class="boring">//! Debug information is worth it!
</span><span class="boring">//!
</span><span class="boring">//! ## Features
</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">#![deny(clippy::all)]
</span><span class="boring">#![deny(clippy::integer_arithmetic)]
</span><span class="boring">#![allow(clippy::needless_doctest_main)]
</span><span class="boring">#![deny(missing_docs)]
</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};
</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">}
</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> {
</span><span class="boring"> occurrence: Option<String>,
</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> {
</span><span class="boring"> /// Use the `context()` or `map_context()` Result methods instead of calling this directly
</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>>,
</span><span class="boring"> occurrence: Option<String>,
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</span><span class="boring"> /// derive_str_context!(Func1Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// func2().context(Func1Error("func1 error".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</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::<io::Error>().is_some());
</span><span class="boring"> ///
</span><span class="boring"> /// assert!(f1err.find_chain_cause::<Func2Error>().is_some());
</span><span class="boring"> /// }
</span><span class="boring"> /// # else {
</span><span class="boring"> /// # panic!();
</span><span class="boring"> /// # }
</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"> #[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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooError);
</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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooErrorKind);
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</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> {
</span><span class="boring"> /// func2().context(Func1ErrorKind::Func2)?;
</span><span class="boring"> /// do_some_io().context(Func1ErrorKind::IO("bar.txt".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</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!(),
</span><span class="boring"> /// }
</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"> #[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">
</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> {
</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 {
</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 {
</span><span class="boring"> if let Some(ref o) = self.occurrence {
</span><span class="boring"> write!(f, "{}: ", o)?;
</span><span class="boring"> }
</span><span class="boring">
</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"> }
</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"> }
</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"> }
</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">/// # }
</span><span class="boring">/// derive_str_context!(Func2Error);
</span><span class="boring">///
</span><span class="boring">/// fn func2() -> ChainResult<(), Func2Error> {
</span><span class="boring">/// let filename = "foo.txt";
</span><span class="boring">/// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// derive_str_context!(Func1Error);
</span><span class="boring">///
</span><span class="boring">/// fn func1() -> Result<(), Box<dyn Error>> {
</span><span class="boring">/// func2().context(Func1Error("func1 error".into()))?;
</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]
</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
</span><span class="boring">///
</span><span class="boring">/// # Examples
</span><span class="boring">///
</span><span class="boring">/// ```rust
</span><span class="boring">/// use chainerror::prelude::v1::*;
</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">///
</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))?;
</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">}
</span></code></pre></pre>
<h1><a class="header" href="#the-source-of-errors" id="the-source-of-errors">The source() of Errors</a></h1>
<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>
<pre><pre class="playground"><code class="language-rust">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(())
}
fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
let filename = "foo.txt";
do_some_io().context(format!("Error reading '{}'", filename))?;
Ok(())
}
fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
if let Err(e) = func2() {
if let Some(s) = e.source() {
eprintln!("func2 failed because of '{}'", s);
Err(e).context("func1 error")?;
}
}
Ok(())
}
fn main() -> Result<(), Box<dyn Error + Send + Sync>> {
if let Err(e) = func1() {
eprintln!("{}", e);
std::process::exit(1);
}
Ok(())
}
<span class="boring">#[allow(dead_code)]
</span><span class="boring">mod chainerror {
</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">//! Having nested function returning errors, the output doesn't tell where the error originates from.
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path)?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into())?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! }
</span><span class="boring">//! }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! This gives the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//! and you have no idea where it comes from.
</span><span class="boring">//!
</span><span class="boring">//!
</span><span class="boring">//! With `chainerror`, you can supply a context and get a nice error backtrace:
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use chainerror::prelude::v1::*;
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path).context(format!("Reading file: {:?}", &path))?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into()).context("read the config file")?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! # assert_eq!(
</span><span class="boring">//! # format!("{:?}\n", e),
</span><span class="boring">//! # "\
</span><span class="boring">//! # src/lib.rs:16:51: read the config file\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # src/lib.rs:9:47: Reading file: \"foo.txt\"\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # Os { code: 2, kind: NotFound, message: \"No such file or directory\" }\n\
</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">//! with the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! examples/simple.rs:14:51: read the config file
</span><span class="boring">//! Caused by:
</span><span class="boring">//! examples/simple.rs:7:47: Reading file: "foo.txt"
</span><span class="boring">//! Caused by:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
</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">//!
</span><span class="boring">//! `chainerror` has no dependencies!
</span><span class="boring">//!
</span><span class="boring">//! Debug information is worth it!
</span><span class="boring">//!
</span><span class="boring">//! ## Features
</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">#![deny(clippy::all)]
</span><span class="boring">#![deny(clippy::integer_arithmetic)]
</span><span class="boring">#![allow(clippy::needless_doctest_main)]
</span><span class="boring">#![deny(missing_docs)]
</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};
</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">}
</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> {
</span><span class="boring"> occurrence: Option<String>,
</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> {
</span><span class="boring"> /// Use the `context()` or `map_context()` Result methods instead of calling this directly
</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>>,
</span><span class="boring"> occurrence: Option<String>,
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</span><span class="boring"> /// derive_str_context!(Func1Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// func2().context(Func1Error("func1 error".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</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::<io::Error>().is_some());
</span><span class="boring"> ///
</span><span class="boring"> /// assert!(f1err.find_chain_cause::<Func2Error>().is_some());
</span><span class="boring"> /// }
</span><span class="boring"> /// # else {
</span><span class="boring"> /// # panic!();
</span><span class="boring"> /// # }
</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"> #[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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooError);
</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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooErrorKind);
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</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> {
</span><span class="boring"> /// func2().context(Func1ErrorKind::Func2)?;
</span><span class="boring"> /// do_some_io().context(Func1ErrorKind::IO("bar.txt".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</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!(),
</span><span class="boring"> /// }
</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"> #[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">
</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> {
</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 {
</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 {
</span><span class="boring"> if let Some(ref o) = self.occurrence {
</span><span class="boring"> write!(f, "{}: ", o)?;
</span><span class="boring"> }
</span><span class="boring">
</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"> }
</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"> }
</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"> }
</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">/// # }
</span><span class="boring">/// derive_str_context!(Func2Error);
</span><span class="boring">///
</span><span class="boring">/// fn func2() -> ChainResult<(), Func2Error> {
</span><span class="boring">/// let filename = "foo.txt";
</span><span class="boring">/// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// derive_str_context!(Func1Error);
</span><span class="boring">///
</span><span class="boring">/// fn func1() -> Result<(), Box<dyn Error>> {
</span><span class="boring">/// func2().context(Func1Error("func1 error".into()))?;
</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]
</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
</span><span class="boring">///
</span><span class="boring">/// # Examples
</span><span class="boring">///
</span><span class="boring">/// ```rust
</span><span class="boring">/// use chainerror::prelude::v1::*;
</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">///
</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))?;
</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">}
</span></code></pre></pre>
<p>Note, that because we changed the output of the error in <code>main()</code> from
<code>Debug</code> to <code>Display</code>, we don't see the error backtrace with filename and line number.</p>
<p>To enable the <code>Display</code> backtrace, you have to enable the feature <code>display-cause</code> for <code>chainerror</code>.</p>
<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
<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>
<pre><pre class="playground"><code class="language-rust">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(())
}
fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
let filename = "foo.txt";
do_some_io().context(format!("Error reading '{}'", filename))?;
Ok(())
}
fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
func2().context("func1 error")?;
Ok(())
}
fn main() -> Result<(), Box<dyn Error + Send + Sync>> {
if let Err(e) = func1() {
eprintln!("Error: {}", e);
let mut s: &(dyn Error) = e.as_ref();
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;
}
std::process::exit(1);
}
Ok(())
}
<span class="boring">#[allow(dead_code)]
</span><span class="boring">mod chainerror {
</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">//! Having nested function returning errors, the output doesn't tell where the error originates from.
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path)?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into())?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! }
</span><span class="boring">//! }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! This gives the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//! and you have no idea where it comes from.
</span><span class="boring">//!
</span><span class="boring">//!
</span><span class="boring">//! With `chainerror`, you can supply a context and get a nice error backtrace:
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use chainerror::prelude::v1::*;
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path).context(format!("Reading file: {:?}", &path))?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into()).context("read the config file")?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! # assert_eq!(
</span><span class="boring">//! # format!("{:?}\n", e),
</span><span class="boring">//! # "\
</span><span class="boring">//! # src/lib.rs:16:51: read the config file\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # src/lib.rs:9:47: Reading file: \"foo.txt\"\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # Os { code: 2, kind: NotFound, message: \"No such file or directory\" }\n\
</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">//! with the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! examples/simple.rs:14:51: read the config file
</span><span class="boring">//! Caused by:
</span><span class="boring">//! examples/simple.rs:7:47: Reading file: "foo.txt"
</span><span class="boring">//! Caused by:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
</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">//!
</span><span class="boring">//! `chainerror` has no dependencies!
</span><span class="boring">//!
</span><span class="boring">//! Debug information is worth it!
</span><span class="boring">//!
</span><span class="boring">//! ## Features
</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">#![deny(clippy::all)]
</span><span class="boring">#![deny(clippy::integer_arithmetic)]
</span><span class="boring">#![allow(clippy::needless_doctest_main)]
</span><span class="boring">#![deny(missing_docs)]
</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};
</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">}
</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> {
</span><span class="boring"> occurrence: Option<String>,
</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> {
</span><span class="boring"> /// Use the `context()` or `map_context()` Result methods instead of calling this directly
</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>>,
</span><span class="boring"> occurrence: Option<String>,
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</span><span class="boring"> /// derive_str_context!(Func1Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// func2().context(Func1Error("func1 error".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</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::<io::Error>().is_some());
</span><span class="boring"> ///
</span><span class="boring"> /// assert!(f1err.find_chain_cause::<Func2Error>().is_some());
</span><span class="boring"> /// }
</span><span class="boring"> /// # else {
</span><span class="boring"> /// # panic!();
</span><span class="boring"> /// # }
</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"> #[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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooError);
</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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooErrorKind);
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</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> {
</span><span class="boring"> /// func2().context(Func1ErrorKind::Func2)?;
</span><span class="boring"> /// do_some_io().context(Func1ErrorKind::IO("bar.txt".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</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!(),
</span><span class="boring"> /// }
</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"> #[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">
</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> {
</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 {
</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 {
</span><span class="boring"> if let Some(ref o) = self.occurrence {
</span><span class="boring"> write!(f, "{}: ", o)?;
</span><span class="boring"> }
</span><span class="boring">
</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"> }
</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"> }
</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"> }
</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">/// # }
</span><span class="boring">/// derive_str_context!(Func2Error);
</span><span class="boring">///
</span><span class="boring">/// fn func2() -> ChainResult<(), Func2Error> {
</span><span class="boring">/// let filename = "foo.txt";
</span><span class="boring">/// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// derive_str_context!(Func1Error);
</span><span class="boring">///
</span><span class="boring">/// fn func1() -> Result<(), Box<dyn Error>> {
</span><span class="boring">/// func2().context(Func1Error("func1 error".into()))?;
</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]
</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
</span><span class="boring">///
</span><span class="boring">/// # Examples
</span><span class="boring">///
</span><span class="boring">/// ```rust
</span><span class="boring">/// use chainerror::prelude::v1::*;
</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">///
</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))?;
</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">}
</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>
<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
to call <code>.find_cause::<io::Error>()</code>. </p>
<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>
<pre><pre class="playground"><code class="language-rust">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(())
}
fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
let filename = "foo.txt";
do_some_io().context(format!("Error reading '{}'", filename))?;
Ok(())
}
fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
func2().context(format!("func1 error"))?;
Ok(())
}
fn main() -> Result<(), Box<dyn Error + Send + Sync>> {
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);
}
}
std::process::exit(1);
}
Ok(())
}
<span class="boring">#[allow(dead_code)]
</span><span class="boring">mod chainerror {
</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">//! Having nested function returning errors, the output doesn't tell where the error originates from.
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path)?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into())?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! }
</span><span class="boring">//! }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! This gives the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//! and you have no idea where it comes from.
</span><span class="boring">//!
</span><span class="boring">//!
</span><span class="boring">//! With `chainerror`, you can supply a context and get a nice error backtrace:
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use chainerror::prelude::v1::*;
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path).context(format!("Reading file: {:?}", &path))?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into()).context("read the config file")?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! # assert_eq!(
</span><span class="boring">//! # format!("{:?}\n", e),
</span><span class="boring">//! # "\
</span><span class="boring">//! # src/lib.rs:16:51: read the config file\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # src/lib.rs:9:47: Reading file: \"foo.txt\"\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # Os { code: 2, kind: NotFound, message: \"No such file or directory\" }\n\
</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">//! with the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! examples/simple.rs:14:51: read the config file
</span><span class="boring">//! Caused by:
</span><span class="boring">//! examples/simple.rs:7:47: Reading file: "foo.txt"
</span><span class="boring">//! Caused by:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
</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">//!
</span><span class="boring">//! `chainerror` has no dependencies!
</span><span class="boring">//!
</span><span class="boring">//! Debug information is worth it!
</span><span class="boring">//!
</span><span class="boring">//! ## Features
</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">#![deny(clippy::all)]
</span><span class="boring">#![deny(clippy::integer_arithmetic)]
</span><span class="boring">#![allow(clippy::needless_doctest_main)]
</span><span class="boring">#![deny(missing_docs)]
</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};
</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">}
</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> {
</span><span class="boring"> occurrence: Option<String>,
</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> {
</span><span class="boring"> /// Use the `context()` or `map_context()` Result methods instead of calling this directly
</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>>,
</span><span class="boring"> occurrence: Option<String>,
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</span><span class="boring"> /// derive_str_context!(Func1Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// func2().context(Func1Error("func1 error".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</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::<io::Error>().is_some());
</span><span class="boring"> ///
</span><span class="boring"> /// assert!(f1err.find_chain_cause::<Func2Error>().is_some());
</span><span class="boring"> /// }
</span><span class="boring"> /// # else {
</span><span class="boring"> /// # panic!();
</span><span class="boring"> /// # }
</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"> #[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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooError);
</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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooErrorKind);
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</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> {
</span><span class="boring"> /// func2().context(Func1ErrorKind::Func2)?;
</span><span class="boring"> /// do_some_io().context(Func1ErrorKind::IO("bar.txt".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</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!(),
</span><span class="boring"> /// }
</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"> #[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">
</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> {
</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 {
</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 {
</span><span class="boring"> if let Some(ref o) = self.occurrence {
</span><span class="boring"> write!(f, "{}: ", o)?;
</span><span class="boring"> }
</span><span class="boring">
</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"> }
</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"> }
</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"> }
</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">/// # }
</span><span class="boring">/// derive_str_context!(Func2Error);
</span><span class="boring">///
</span><span class="boring">/// fn func2() -> ChainResult<(), Func2Error> {
</span><span class="boring">/// let filename = "foo.txt";
</span><span class="boring">/// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// derive_str_context!(Func1Error);
</span><span class="boring">///
</span><span class="boring">/// fn func1() -> Result<(), Box<dyn Error>> {
</span><span class="boring">/// func2().context(Func1Error("func1 error".into()))?;
</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]
</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
</span><span class="boring">///
</span><span class="boring">/// # Examples
</span><span class="boring">///
</span><span class="boring">/// ```rust
</span><span class="boring">/// use chainerror::prelude::v1::*;
</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">///
</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))?;
</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">}
</span></code></pre></pre>
<h1><a class="header" href="#finding-an-error-cause" id="finding-an-error-cause">Finding an Error cause</a></h1>
<p>To distinguish the errors occuring in various places, we can define named string errors with the
"new type" pattern.</p>
<pre><code class="language-rust ignore">derive_str_context!(Func2Error);
derive_str_context!(Func1Error);
</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>
<pre><pre class="playground"><code class="language-rust">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(())
}
derive_str_context!(Func2Error);
fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
let filename = "foo.txt";
do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
Ok(())
}
derive_str_context!(Func1Error);
fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
func2().context(Func1Error(format!("func1 error")))?;
Ok(())
}
fn main() -> Result<(), Box<dyn Error + Send + Sync>> {
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);
}
}
std::process::exit(1);
}
Ok(())
}
<span class="boring">#[allow(dead_code)]
</span><span class="boring">mod chainerror {
</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">//! Having nested function returning errors, the output doesn't tell where the error originates from.
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path)?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into())?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! }
</span><span class="boring">//! }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! This gives the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//! and you have no idea where it comes from.
</span><span class="boring">//!
</span><span class="boring">//!
</span><span class="boring">//! With `chainerror`, you can supply a context and get a nice error backtrace:
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use chainerror::prelude::v1::*;
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path).context(format!("Reading file: {:?}", &path))?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into()).context("read the config file")?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! # assert_eq!(
</span><span class="boring">//! # format!("{:?}\n", e),
</span><span class="boring">//! # "\
</span><span class="boring">//! # src/lib.rs:16:51: read the config file\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # src/lib.rs:9:47: Reading file: \"foo.txt\"\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # Os { code: 2, kind: NotFound, message: \"No such file or directory\" }\n\
</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">//! with the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! examples/simple.rs:14:51: read the config file
</span><span class="boring">//! Caused by:
</span><span class="boring">//! examples/simple.rs:7:47: Reading file: "foo.txt"
</span><span class="boring">//! Caused by:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
</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">//!
</span><span class="boring">//! `chainerror` has no dependencies!
</span><span class="boring">//!
</span><span class="boring">//! Debug information is worth it!
</span><span class="boring">//!
</span><span class="boring">//! ## Features
</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">#![deny(clippy::all)]
</span><span class="boring">#![deny(clippy::integer_arithmetic)]
</span><span class="boring">#![allow(clippy::needless_doctest_main)]
</span><span class="boring">#![deny(missing_docs)]
</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};
</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">}
</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> {
</span><span class="boring"> occurrence: Option<String>,
</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> {
</span><span class="boring"> /// Use the `context()` or `map_context()` Result methods instead of calling this directly
</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>>,
</span><span class="boring"> occurrence: Option<String>,
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</span><span class="boring"> /// derive_str_context!(Func1Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// func2().context(Func1Error("func1 error".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</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::<io::Error>().is_some());
</span><span class="boring"> ///
</span><span class="boring"> /// assert!(f1err.find_chain_cause::<Func2Error>().is_some());
</span><span class="boring"> /// }
</span><span class="boring"> /// # else {
</span><span class="boring"> /// # panic!();
</span><span class="boring"> /// # }
</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"> #[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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooError);
</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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooErrorKind);
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</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> {
</span><span class="boring"> /// func2().context(Func1ErrorKind::Func2)?;
</span><span class="boring"> /// do_some_io().context(Func1ErrorKind::IO("bar.txt".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</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!(),
</span><span class="boring"> /// }
</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"> #[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">
</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> {
</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 {
</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 {
</span><span class="boring"> if let Some(ref o) = self.occurrence {
</span><span class="boring"> write!(f, "{}: ", o)?;
</span><span class="boring"> }
</span><span class="boring">
</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"> }
</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"> }
</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"> }
</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">/// # }
</span><span class="boring">/// derive_str_context!(Func2Error);
</span><span class="boring">///
</span><span class="boring">/// fn func2() -> ChainResult<(), Func2Error> {
</span><span class="boring">/// let filename = "foo.txt";
</span><span class="boring">/// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// derive_str_context!(Func1Error);
</span><span class="boring">///
</span><span class="boring">/// fn func1() -> Result<(), Box<dyn Error>> {
</span><span class="boring">/// func2().context(Func1Error("func1 error".into()))?;
</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]
</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
</span><span class="boring">///
</span><span class="boring">/// # Examples
</span><span class="boring">///
</span><span class="boring">/// ```rust
</span><span class="boring">/// use chainerror::prelude::v1::*;
</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">///
</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))?;
</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">}
</span></code></pre></pre>
<h1><a class="header" href="#selective-error-handling" id="selective-error-handling">Selective Error Handling</a></h1>
<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>
<pre><code class="language-rust ignore">fn main() -> Result<(), Box<Error + Send + Sync>> {
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>
<pre><pre class="playground"><code class="language-rust">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(())
}
derive_str_context!(Func2Error);
fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
let filename = "foo.txt";
do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
Ok(())
}
derive_str_context!(Func1ErrorFunc2);
derive_str_context!(Func1ErrorIO);
fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
func2().context(Func1ErrorFunc2(format!("func1 error calling func2")))?;
let filename = "bar.txt";
do_some_io().context(Func1ErrorIO(format!("Error reading '{}'", filename)))?;
Ok(())
}
fn main() -> Result<(), Box<dyn Error + Send + Sync>> {
if let Err(e) = func1() {
if let Some(s) = e.downcast_ref::<ChainError<Func1ErrorIO>>() {
eprintln!("Func1ErrorIO:\n{:?}", s);
}
if let Some(s) = e.downcast_chain_ref::<Func1ErrorFunc2>() {
eprintln!("Func1ErrorFunc2:\n{:?}", s);
}
std::process::exit(1);
}
Ok(())
}
<span class="boring">#[allow(dead_code)]
</span><span class="boring">mod chainerror {
</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">//! Having nested function returning errors, the output doesn't tell where the error originates from.
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path)?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into())?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! }
</span><span class="boring">//! }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! This gives the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//! and you have no idea where it comes from.
</span><span class="boring">//!
</span><span class="boring">//!
</span><span class="boring">//! With `chainerror`, you can supply a context and get a nice error backtrace:
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use chainerror::prelude::v1::*;
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path).context(format!("Reading file: {:?}", &path))?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into()).context("read the config file")?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! # assert_eq!(
</span><span class="boring">//! # format!("{:?}\n", e),
</span><span class="boring">//! # "\
</span><span class="boring">//! # src/lib.rs:16:51: read the config file\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # src/lib.rs:9:47: Reading file: \"foo.txt\"\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # Os { code: 2, kind: NotFound, message: \"No such file or directory\" }\n\
</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">//! with the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! examples/simple.rs:14:51: read the config file
</span><span class="boring">//! Caused by:
</span><span class="boring">//! examples/simple.rs:7:47: Reading file: "foo.txt"
</span><span class="boring">//! Caused by:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
</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">//!
</span><span class="boring">//! `chainerror` has no dependencies!
</span><span class="boring">//!
</span><span class="boring">//! Debug information is worth it!
</span><span class="boring">//!
</span><span class="boring">//! ## Features
</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">#![deny(clippy::all)]
</span><span class="boring">#![deny(clippy::integer_arithmetic)]
</span><span class="boring">#![allow(clippy::needless_doctest_main)]
</span><span class="boring">#![deny(missing_docs)]
</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};
</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">}
</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> {
</span><span class="boring"> occurrence: Option<String>,
</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> {
</span><span class="boring"> /// Use the `context()` or `map_context()` Result methods instead of calling this directly
</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>>,
</span><span class="boring"> occurrence: Option<String>,
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</span><span class="boring"> /// derive_str_context!(Func1Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// func2().context(Func1Error("func1 error".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</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::<io::Error>().is_some());
</span><span class="boring"> ///
</span><span class="boring"> /// assert!(f1err.find_chain_cause::<Func2Error>().is_some());
</span><span class="boring"> /// }
</span><span class="boring"> /// # else {
</span><span class="boring"> /// # panic!();
</span><span class="boring"> /// # }
</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"> #[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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooError);
</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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooErrorKind);
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</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> {
</span><span class="boring"> /// func2().context(Func1ErrorKind::Func2)?;
</span><span class="boring"> /// do_some_io().context(Func1ErrorKind::IO("bar.txt".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</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!(),
</span><span class="boring"> /// }
</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"> #[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">
</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> {
</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 {
</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 {
</span><span class="boring"> if let Some(ref o) = self.occurrence {
</span><span class="boring"> write!(f, "{}: ", o)?;
</span><span class="boring"> }
</span><span class="boring">
</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"> }
</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"> }
</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"> }
</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">/// # }
</span><span class="boring">/// derive_str_context!(Func2Error);
</span><span class="boring">///
</span><span class="boring">/// fn func2() -> ChainResult<(), Func2Error> {
</span><span class="boring">/// let filename = "foo.txt";
</span><span class="boring">/// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// derive_str_context!(Func1Error);
</span><span class="boring">///
</span><span class="boring">/// fn func1() -> Result<(), Box<dyn Error>> {
</span><span class="boring">/// func2().context(Func1Error("func1 error".into()))?;
</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]
</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
</span><span class="boring">///
</span><span class="boring">/// # Examples
</span><span class="boring">///
</span><span class="boring">/// ```rust
</span><span class="boring">/// use chainerror::prelude::v1::*;
</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">///
</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))?;
</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">}
</span></code></pre></pre>
<h1><a class="header" href="#errorkind-to-the-rescue" id="errorkind-to-the-rescue">ErrorKind to the rescue</a></h1>
<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>
<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
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>
<p>Also a nice <code>match</code> on <code>ChainError<T>.kind()</code> is now possible, which returns <code>&T</code>, meaning
<code>&Func1ErrorKind</code> here.</p>
<pre><pre class="playground"><code class="language-rust">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(())
}
derive_str_context!(Func2Error);
fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
let filename = "foo.txt";
do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
Ok(())
}
#[derive(Debug)]
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::error::Error for Func1ErrorKind {}
fn func1() -> ChainResult<(), Func1ErrorKind> {
func2().context(Func1ErrorKind::Func2)?;
let filename = String::from("bar.txt");
do_some_io().context(Func1ErrorKind::IO(filename))?;
Ok(())
}
fn main() -> Result<(), Box<dyn Error + Send + Sync>> {
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);
std::process::exit(1);
}
Ok(())
}
<span class="boring">#[allow(dead_code)]
</span><span class="boring">mod chainerror {
</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">//! Having nested function returning errors, the output doesn't tell where the error originates from.
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path)?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into())?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! }
</span><span class="boring">//! }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! This gives the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//! and you have no idea where it comes from.
</span><span class="boring">//!
</span><span class="boring">//!
</span><span class="boring">//! With `chainerror`, you can supply a context and get a nice error backtrace:
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use chainerror::prelude::v1::*;
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path).context(format!("Reading file: {:?}", &path))?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into()).context("read the config file")?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! # assert_eq!(
</span><span class="boring">//! # format!("{:?}\n", e),
</span><span class="boring">//! # "\
</span><span class="boring">//! # src/lib.rs:16:51: read the config file\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # src/lib.rs:9:47: Reading file: \"foo.txt\"\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # Os { code: 2, kind: NotFound, message: \"No such file or directory\" }\n\
</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">//! with the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! examples/simple.rs:14:51: read the config file
</span><span class="boring">//! Caused by:
</span><span class="boring">//! examples/simple.rs:7:47: Reading file: "foo.txt"
</span><span class="boring">//! Caused by:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
</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">//!
</span><span class="boring">//! `chainerror` has no dependencies!
</span><span class="boring">//!
</span><span class="boring">//! Debug information is worth it!
</span><span class="boring">//!
</span><span class="boring">//! ## Features
</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">#![deny(clippy::all)]
</span><span class="boring">#![deny(clippy::integer_arithmetic)]
</span><span class="boring">#![allow(clippy::needless_doctest_main)]
</span><span class="boring">#![deny(missing_docs)]
</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};
</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">}
</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> {
</span><span class="boring"> occurrence: Option<String>,
</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> {
</span><span class="boring"> /// Use the `context()` or `map_context()` Result methods instead of calling this directly
</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>>,
</span><span class="boring"> occurrence: Option<String>,
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</span><span class="boring"> /// derive_str_context!(Func1Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// func2().context(Func1Error("func1 error".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</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::<io::Error>().is_some());
</span><span class="boring"> ///
</span><span class="boring"> /// assert!(f1err.find_chain_cause::<Func2Error>().is_some());
</span><span class="boring"> /// }
</span><span class="boring"> /// # else {
</span><span class="boring"> /// # panic!();
</span><span class="boring"> /// # }
</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"> #[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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooError);
</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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooErrorKind);
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</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> {
</span><span class="boring"> /// func2().context(Func1ErrorKind::Func2)?;
</span><span class="boring"> /// do_some_io().context(Func1ErrorKind::IO("bar.txt".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</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!(),
</span><span class="boring"> /// }
</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"> #[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">
</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> {
</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 {
</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 {
</span><span class="boring"> if let Some(ref o) = self.occurrence {
</span><span class="boring"> write!(f, "{}: ", o)?;
</span><span class="boring"> }
</span><span class="boring">
</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"> }
</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"> }
</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"> }
</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">/// # }
</span><span class="boring">/// derive_str_context!(Func2Error);
</span><span class="boring">///
</span><span class="boring">/// fn func2() -> ChainResult<(), Func2Error> {
</span><span class="boring">/// let filename = "foo.txt";
</span><span class="boring">/// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// derive_str_context!(Func1Error);
</span><span class="boring">///
</span><span class="boring">/// fn func1() -> Result<(), Box<dyn Error>> {
</span><span class="boring">/// func2().context(Func1Error("func1 error".into()))?;
</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]
</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
</span><span class="boring">///
</span><span class="boring">/// # Examples
</span><span class="boring">///
</span><span class="boring">/// ```rust
</span><span class="boring">/// use chainerror::prelude::v1::*;
</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">///
</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))?;
</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">}
</span></code></pre></pre>
<h1><a class="header" href="#debug-for-the-errorkind" id="debug-for-the-errorkind">Debug for the ErrorKind</a></h1>
<p>One small improvement is to fix the debug output of
<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>
<pre><pre class="playground"><code class="language-rust">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(())
}
derive_str_context!(Func2Error);
fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
let filename = "foo.txt";
do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
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> {
func2().context(Func1ErrorKind::Func2)?;
let filename = String::from("bar.txt");
do_some_io().context(Func1ErrorKind::IO(filename))?;
Ok(())
}
fn main() -> Result<(), Box<dyn Error + Send + Sync>> {
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);
std::process::exit(1);
}
Ok(())
}
<span class="boring">#[allow(dead_code)]
</span><span class="boring">mod chainerror {
</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">//! Having nested function returning errors, the output doesn't tell where the error originates from.
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path)?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into())?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! }
</span><span class="boring">//! }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! This gives the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//! and you have no idea where it comes from.
</span><span class="boring">//!
</span><span class="boring">//!
</span><span class="boring">//! With `chainerror`, you can supply a context and get a nice error backtrace:
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use chainerror::prelude::v1::*;
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path).context(format!("Reading file: {:?}", &path))?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into()).context("read the config file")?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! # assert_eq!(
</span><span class="boring">//! # format!("{:?}\n", e),
</span><span class="boring">//! # "\
</span><span class="boring">//! # src/lib.rs:16:51: read the config file\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # src/lib.rs:9:47: Reading file: \"foo.txt\"\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # Os { code: 2, kind: NotFound, message: \"No such file or directory\" }\n\
</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">//! with the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! examples/simple.rs:14:51: read the config file
</span><span class="boring">//! Caused by:
</span><span class="boring">//! examples/simple.rs:7:47: Reading file: "foo.txt"
</span><span class="boring">//! Caused by:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
</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">//!
</span><span class="boring">//! `chainerror` has no dependencies!
</span><span class="boring">//!
</span><span class="boring">//! Debug information is worth it!
</span><span class="boring">//!
</span><span class="boring">//! ## Features
</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">#![deny(clippy::all)]
</span><span class="boring">#![deny(clippy::integer_arithmetic)]
</span><span class="boring">#![allow(clippy::needless_doctest_main)]
</span><span class="boring">#![deny(missing_docs)]
</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};
</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">}
</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> {
</span><span class="boring"> occurrence: Option<String>,
</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> {
</span><span class="boring"> /// Use the `context()` or `map_context()` Result methods instead of calling this directly
</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>>,
</span><span class="boring"> occurrence: Option<String>,
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</span><span class="boring"> /// derive_str_context!(Func1Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// func2().context(Func1Error("func1 error".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</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::<io::Error>().is_some());
</span><span class="boring"> ///
</span><span class="boring"> /// assert!(f1err.find_chain_cause::<Func2Error>().is_some());
</span><span class="boring"> /// }
</span><span class="boring"> /// # else {
</span><span class="boring"> /// # panic!();
</span><span class="boring"> /// # }
</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"> #[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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooError);
</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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooErrorKind);
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</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> {
</span><span class="boring"> /// func2().context(Func1ErrorKind::Func2)?;
</span><span class="boring"> /// do_some_io().context(Func1ErrorKind::IO("bar.txt".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</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!(),
</span><span class="boring"> /// }
</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"> #[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">
</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> {
</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 {
</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 {
</span><span class="boring"> if let Some(ref o) = self.occurrence {
</span><span class="boring"> write!(f, "{}: ", o)?;
</span><span class="boring"> }
</span><span class="boring">
</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"> }
</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"> }
</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"> }
</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">/// # }
</span><span class="boring">/// derive_str_context!(Func2Error);
</span><span class="boring">///
</span><span class="boring">/// fn func2() -> ChainResult<(), Func2Error> {
</span><span class="boring">/// let filename = "foo.txt";
</span><span class="boring">/// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// derive_str_context!(Func1Error);
</span><span class="boring">///
</span><span class="boring">/// fn func1() -> Result<(), Box<dyn Error>> {
</span><span class="boring">/// func2().context(Func1Error("func1 error".into()))?;
</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]
</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
</span><span class="boring">///
</span><span class="boring">/// # Examples
</span><span class="boring">///
</span><span class="boring">/// ```rust
</span><span class="boring">/// use chainerror::prelude::v1::*;
</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">///
</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))?;
</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">}
</span></code></pre></pre>
<h1><a class="header" href="#deref-for-the-errorkind" id="deref-for-the-errorkind">Deref for the ErrorKind</a></h1>
<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>
<pre><pre class="playground"><code class="language-rust">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(())
}
derive_str_context!(Func2Error);
fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
let filename = "foo.txt";
do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
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> {
func2().context(Func1ErrorKind::Func2)?;
let filename = String::from("bar.txt");
do_some_io().context(Func1ErrorKind::IO(filename))?;
Ok(())
}
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)
}
}
}
fn main() -> Result<(), Box<dyn Error + Send + Sync>> {
if let Err(e) = func1() {
match *e {
Func1ErrorKind::Func2 => eprintln!("Main Error Report: func1 error calling func2"),
Func1ErrorKind::IO(ref filename) => {
eprintln!("Main Error Report: func1 error reading '{}'", filename)
}
}
handle_func1errorkind(&e);
if let Some(e) = e.find_chain_cause::<Func2Error>() {
eprintln!("\nError reported by Func2Error: {}", e)
}
eprintln!("\nDebug Error:\n{:?}", e);
std::process::exit(1);
}
Ok(())
}
<span class="boring">#[allow(dead_code)]
</span><span class="boring">mod chainerror {
</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">//! Having nested function returning errors, the output doesn't tell where the error originates from.
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path)?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into())?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! }
</span><span class="boring">//! }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! This gives the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//! and you have no idea where it comes from.
</span><span class="boring">//!
</span><span class="boring">//!
</span><span class="boring">//! With `chainerror`, you can supply a context and get a nice error backtrace:
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use chainerror::prelude::v1::*;
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path).context(format!("Reading file: {:?}", &path))?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into()).context("read the config file")?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! # assert_eq!(
</span><span class="boring">//! # format!("{:?}\n", e),
</span><span class="boring">//! # "\
</span><span class="boring">//! # src/lib.rs:16:51: read the config file\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # src/lib.rs:9:47: Reading file: \"foo.txt\"\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # Os { code: 2, kind: NotFound, message: \"No such file or directory\" }\n\
</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">//! with the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! examples/simple.rs:14:51: read the config file
</span><span class="boring">//! Caused by:
</span><span class="boring">//! examples/simple.rs:7:47: Reading file: "foo.txt"
</span><span class="boring">//! Caused by:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
</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">//!
</span><span class="boring">//! `chainerror` has no dependencies!
</span><span class="boring">//!
</span><span class="boring">//! Debug information is worth it!
</span><span class="boring">//!
</span><span class="boring">//! ## Features
</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">#![deny(clippy::all)]
</span><span class="boring">#![deny(clippy::integer_arithmetic)]
</span><span class="boring">#![allow(clippy::needless_doctest_main)]
</span><span class="boring">#![deny(missing_docs)]
</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};
</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">}
</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> {
</span><span class="boring"> occurrence: Option<String>,
</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> {
</span><span class="boring"> /// Use the `context()` or `map_context()` Result methods instead of calling this directly
</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>>,
</span><span class="boring"> occurrence: Option<String>,
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</span><span class="boring"> /// derive_str_context!(Func1Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// func2().context(Func1Error("func1 error".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</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::<io::Error>().is_some());
</span><span class="boring"> ///
</span><span class="boring"> /// assert!(f1err.find_chain_cause::<Func2Error>().is_some());
</span><span class="boring"> /// }
</span><span class="boring"> /// # else {
</span><span class="boring"> /// # panic!();
</span><span class="boring"> /// # }
</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"> #[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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooError);
</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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooErrorKind);
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</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> {
</span><span class="boring"> /// func2().context(Func1ErrorKind::Func2)?;
</span><span class="boring"> /// do_some_io().context(Func1ErrorKind::IO("bar.txt".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</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!(),
</span><span class="boring"> /// }
</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"> #[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">
</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> {
</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 {
</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 {
</span><span class="boring"> if let Some(ref o) = self.occurrence {
</span><span class="boring"> write!(f, "{}: ", o)?;
</span><span class="boring"> }
</span><span class="boring">
</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"> }
</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"> }
</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"> }
</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">/// # }
</span><span class="boring">/// derive_str_context!(Func2Error);
</span><span class="boring">///
</span><span class="boring">/// fn func2() -> ChainResult<(), Func2Error> {
</span><span class="boring">/// let filename = "foo.txt";
</span><span class="boring">/// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// derive_str_context!(Func1Error);
</span><span class="boring">///
</span><span class="boring">/// fn func1() -> Result<(), Box<dyn Error>> {
</span><span class="boring">/// func2().context(Func1Error("func1 error".into()))?;
</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]
</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
</span><span class="boring">///
</span><span class="boring">/// # Examples
</span><span class="boring">///
</span><span class="boring">/// ```rust
</span><span class="boring">/// use chainerror::prelude::v1::*;
</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">///
</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))?;
</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">}
</span></code></pre></pre>
<h1><a class="header" href="#writing-a-library" id="writing-a-library">Writing a library</a></h1>
<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>
<pre><pre class="playground"><code class="language-rust"><span class="boring">#[allow(dead_code)]
</span><span class="boring">#[macro_use]
</span><span class="boring">pub mod chainerror {
</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">//! Having nested function returning errors, the output doesn't tell where the error originates from.
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path)?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into())?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! }
</span><span class="boring">//! }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! This gives the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//! and you have no idea where it comes from.
</span><span class="boring">//!
</span><span class="boring">//!
</span><span class="boring">//! With `chainerror`, you can supply a context and get a nice error backtrace:
</span><span class="boring">//!
</span><span class="boring">//! ```rust
</span><span class="boring">//! use chainerror::prelude::v1::*;
</span><span class="boring">//! use std::path::PathBuf;
</span><span class="boring">//!
</span><span class="boring">//! type BoxedError = Box<dyn std::error::Error + Send + Sync>;
</span><span class="boring">//! fn read_config_file(path: PathBuf) -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = std::fs::read_to_string(&path).context(format!("Reading file: {:?}", &path))?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn process_config_file() -> Result<(), BoxedError> {
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! let _buf = read_config_file("foo.txt".into()).context("read the config file")?;
</span><span class="boring">//! // do stuff, return other errors
</span><span class="boring">//! Ok(())
</span><span class="boring">//! }
</span><span class="boring">//!
</span><span class="boring">//! fn main() {
</span><span class="boring">//! if let Err(e) = process_config_file() {
</span><span class="boring">//! eprintln!("Error:\n{:?}", e);
</span><span class="boring">//! # assert_eq!(
</span><span class="boring">//! # format!("{:?}\n", e),
</span><span class="boring">//! # "\
</span><span class="boring">//! # src/lib.rs:16:51: read the config file\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # src/lib.rs:9:47: Reading file: \"foo.txt\"\n\
</span><span class="boring">//! # Caused by:\n\
</span><span class="boring">//! # Os { code: 2, kind: NotFound, message: \"No such file or directory\" }\n\
</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">//! with the output:
</span><span class="boring">//! ```console
</span><span class="boring">//! Error:
</span><span class="boring">//! examples/simple.rs:14:51: read the config file
</span><span class="boring">//! Caused by:
</span><span class="boring">//! examples/simple.rs:7:47: Reading file: "foo.txt"
</span><span class="boring">//! Caused by:
</span><span class="boring">//! Os { code: 2, kind: NotFound, message: "No such file or directory" }
</span><span class="boring">//! ```
</span><span class="boring">//!
</span><span class="boring">//! `chainerror` uses `.source()` of `std::error::Error` along with `#[track_caller]` and `Location` to provide a nice debug error backtrace.
</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">//!
</span><span class="boring">//! `chainerror` has no dependencies!
</span><span class="boring">//!
</span><span class="boring">//! Debug information is worth it!
</span><span class="boring">//!
</span><span class="boring">//! ## Features
</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">#![deny(clippy::all)]
</span><span class="boring">#![deny(clippy::integer_arithmetic)]
</span><span class="boring">#![allow(clippy::needless_doctest_main)]
</span><span class="boring">#![deny(missing_docs)]
</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};
</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">}
</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> {
</span><span class="boring"> occurrence: Option<String>,
</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> {
</span><span class="boring"> /// Use the `context()` or `map_context()` Result methods instead of calling this directly
</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>>,
</span><span class="boring"> occurrence: Option<String>,
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</span><span class="boring"> /// derive_str_context!(Func1Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func1() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// func2().context(Func1Error("func1 error".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</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::<io::Error>().is_some());
</span><span class="boring"> ///
</span><span class="boring"> /// assert!(f1err.find_chain_cause::<Func2Error>().is_some());
</span><span class="boring"> /// }
</span><span class="boring"> /// # else {
</span><span class="boring"> /// # panic!();
</span><span class="boring"> /// # }
</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"> #[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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooError);
</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
</span><span class="boring"> /// # use chainerror::prelude::v1::*;
</span><span class="boring"> /// # derive_str_context!(FooErrorKind);
</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
</span><span class="boring"> /// use chainerror::prelude::v1::*;
</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"> ///
</span><span class="boring"> /// derive_str_context!(Func2Error);
</span><span class="boring"> ///
</span><span class="boring"> /// fn func2() -> Result<(), Box<dyn Error + Send + Sync>> {
</span><span class="boring"> /// let filename = "foo.txt";
</span><span class="boring"> /// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</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> {
</span><span class="boring"> /// func2().context(Func1ErrorKind::Func2)?;
</span><span class="boring"> /// do_some_io().context(Func1ErrorKind::IO("bar.txt".into()))?;
</span><span class="boring"> /// Ok(())
</span><span class="boring"> /// }
</span><span class="boring"> ///
</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!(),
</span><span class="boring"> /// }
</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"> #[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">
</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> {
</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 {
</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 {
</span><span class="boring"> if let Some(ref o) = self.occurrence {
</span><span class="boring"> write!(f, "{}: ", o)?;
</span><span class="boring"> }
</span><span class="boring">
</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"> }
</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"> }
</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"> }
</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">/// # }
</span><span class="boring">/// derive_str_context!(Func2Error);
</span><span class="boring">///
</span><span class="boring">/// fn func2() -> ChainResult<(), Func2Error> {
</span><span class="boring">/// let filename = "foo.txt";
</span><span class="boring">/// do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
</span><span class="boring">/// Ok(())
</span><span class="boring">/// }
</span><span class="boring">///
</span><span class="boring">/// derive_str_context!(Func1Error);
</span><span class="boring">///
</span><span class="boring">/// fn func1() -> Result<(), Box<dyn Error>> {
</span><span class="boring">/// func2().context(Func1Error("func1 error".into()))?;
</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]
</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
</span><span class="boring">///
</span><span class="boring">/// # Examples
</span><span class="boring">///
</span><span class="boring">/// ```rust
</span><span class="boring">/// use chainerror::prelude::v1::*;
</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">///
</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))?;
</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">}
</span>pub mod mycrate {
use crate::chainerror::*; // omit the `crate::` part
use std::io;
fn do_some_io() -> std::result::Result<(), Box<dyn std::error::Error + Send + Sync>> {
Err(io::Error::from(io::ErrorKind::NotFound))?;
Ok(())
}
derive_str_context!(Func2Error);
fn func2() -> std::result::Result<(), Box<dyn std::error::Error + Send + Sync>> {
let filename = "foo.txt";
do_some_io().context(Func2Error(format!("Error reading '{}'", filename)))?;
Ok(())
}
#[derive(Debug, Clone)]
pub enum ErrorKind {
Func2,
IO(String),
}
derive_err_kind!(Error, ErrorKind);
pub type Result<T> = std::result::Result<T, Error>;
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),
}
}
}
pub fn func1() -> Result<()> {
func2().context(ErrorKind::Func2)?;
let filename = String::from("bar.txt");
do_some_io().context(ErrorKind::IO(filename))?;
Ok(())
}
}
fn main() -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
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!();
let mut s: &dyn Error = &e;
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);
std::process::exit(1);
}
Ok(())
}
</code></pre></pre>
<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>
<pre><pre class="playground"><code class="language-rust">pub mod mycrate {
use std::error::Error as StdError;
use self::func2mod::{do_some_io, func2};
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),
}
}
}
macro_rules! mcontext {
( $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";
do_some_io().map_err(mcontext!(ErrorKind::IO(format!(
"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),
}
}
}
macro_rules! mcontext {
( $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<()> {
func2().map_err(mcontext!(ErrorKind::Func2))?;
let filename = String::from("bar.txt");
do_some_io().map_err(mcontext!(ErrorKind::IO(filename)))?;
Ok(())
}
}
fn main() -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
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!();
let mut s: &dyn Error = &e;
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);
std::process::exit(1);
}
Ok(())
}
</code></pre></pre>
<h1><a class="header" href="#the-end" id="the-end">The End</a></h1>
<p>That's it for now…</p>
<p>Happy error handling!</p>
<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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