mirror of
https://github.com/haraldh/chainerror.git
synced 2025-01-30 16:46:42 +01:00
lots of documentation
This commit is contained in:
parent
5145b950b5
commit
8ad6eaceac
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@ -1,9 +1,9 @@
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[package]
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name = "chainerror"
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version = "0.1.0"
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version = "0.1.1"
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authors = ["Harald Hoyer <harald@redhat.com>"]
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edition = "2018"
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license = "MIT"
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license = "MIT OR Apache-2.0"
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documentation = "https://docs.rs/chainerror"
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homepage = "https://haraldh.github.io/chainerror/"
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repository = "https://github.com/haraldh/chainerror"
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112
README.md
112
README.md
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@ -12,4 +12,114 @@ Along with the `ChainError<T>` struct, `chainerror` comes with some useful helpe
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Debug information is worth it!
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For an introduction read the [Tutorial](https://haraldh.github.io/chainerror/)
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Now continue reading the
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[Tutorial](https://haraldh.github.io/chainerror/tutorial1.html)
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## Example:
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Output:
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~~~
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$ cargo run -q --example example
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Main Error Report: func1 error calling func2
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Error reported by Func2Error: func2 error: calling func3
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The root cause was: std::io::Error: Kind(
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NotFound
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)
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Debug Error:
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examples/example.rs:45: func1 error calling func2
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Caused by:
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examples/example.rs:20: Func2Error(func2 error: calling func3)
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Caused by:
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examples/example.rs:13: Error reading 'foo.txt'
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Caused by:
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Kind(NotFound)
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~~~
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~~~rust,ignore
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use chainerror::*;
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use std::error::Error;
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use std::io;
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use std::result::Result;
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fn do_some_io() -> Result<(), Box<Error>> {
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Err(io::Error::from(io::ErrorKind::NotFound))?;
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Ok(())
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}
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fn func3() -> Result<(), Box<Error>> {
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let filename = "foo.txt";
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do_some_io().map_err(mstrerr!("Error reading '{}'", filename))?;
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Ok(())
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}
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derive_str_cherr!(Func2Error);
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fn func2() -> ChainResult<(), Func2Error> {
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func3().map_err(mstrerr!(Func2Error, "func2 error: calling func3"))?;
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Ok(())
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}
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enum Func1Error {
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Func2,
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IO(String),
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}
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impl ::std::fmt::Display for Func1Error {
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fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
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match self {
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Func1Error::Func2 => write!(f, "func1 error calling func2"),
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Func1Error::IO(filename) => write!(f, "Error reading '{}'", filename),
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}
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}
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}
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impl ::std::fmt::Debug for Func1Error {
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fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
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write!(f, "{}", self)
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}
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}
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fn func1() -> ChainResult<(), Func1Error> {
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func2().map_err(|e| cherr!(e, Func1Error::Func2))?;
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let filename = String::from("bar.txt");
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do_some_io().map_err(|e| cherr!(e, Func1Error::IO(filename)))?;
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Ok(())
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}
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fn main() {
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if let Err(e) = func1() {
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match e.kind() {
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Func1Error::Func2 => eprintln!("Main Error Report: func1 error calling func2"),
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Func1Error::IO(filename) => {
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eprintln!("Main Error Report: func1 error reading '{}'", filename)
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}
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}
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if let Some(e) = e.find_chain_cause::<Func2Error>() {
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eprintln!("\nError reported by Func2Error: {}", e)
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}
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if let Some(e) = e.root_cause() {
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let ioerror = e.downcast_ref::<io::Error>().unwrap();
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eprintln!("\nThe root cause was: std::io::Error: {:#?}", ioerror);
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}
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eprintln!("\nDebug Error:\n{:?}", e);
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}
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}
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~~~
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## Features
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`no-fileline`
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: completely turn off storing filename and line
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`display-cause`
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: turn on printing a backtrace of the errors in `Display`
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`no-debug-cause`
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: turn off printing a backtrace of the errors in `Debug`
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@ -3,11 +3,8 @@ authors = ["Harald Hoyer"]
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multilingual = false
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src = "booksrc"
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title = "chainerror"
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[output.html.playpen]
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editable = true
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description = "A tutorial for the chainerror rust crate."
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[build]
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build-dir = "book"
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create-missing = false
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1
booksrc/README.md
Symbolic link
1
booksrc/README.md
Symbolic link
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@ -0,0 +1 @@
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../README.md
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@ -1,13 +1,17 @@
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# Summary
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- [Chapter 1](./tutorial1.md)
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- [Chapter 2](./tutorial2.md)
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- [Chapter 3](./tutorial3.md)
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- [Chapter 4](./tutorial4.md)
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- [Chapter 5](./tutorial5.md)
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- [Chapter 6](./tutorial6.md)
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- [Chapter 7](./tutorial7.md)
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- [Chapter 8](./tutorial8.md)
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- [Chapter 9](./tutorial9.md)
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- [Chapter 10](./tutorial10.md)
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- [Chapter 11](./tutorial11.md)
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[chainerror](README.md)
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- [Simple String Errors](tutorial1.md)
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- [Simple Chained String Errors](tutorial2.md)
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- [Mapping Errors](tutorial3.md)
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- [Saving coding chars](tutorial4.md)
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- [The source() of Errors](tutorial5.md)
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- [Downcast the Errors](tutorial6.md)
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- [The root cause of all Errors](tutorial7.md)
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- [Finding an Error cause](tutorial8.md)
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- [Selective Error Handling](tutorial9.md)
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- [ErrorKind to the rescue](tutorial10.md)
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- [Debug for the ErrorKind](tutorial11.md)
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[The End](end.md)
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5
booksrc/end.md
Normal file
5
booksrc/end.md
Normal file
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# The End
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That's it for now…
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Happy error handling!
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# Simple String Errors
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The most simplest of doing error handling in rust is by returning `String` as a `Box<Error>`.
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An easy way of doing error handling in rust is by returning `String` as a `Box<std::error::Error>`.
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As you can see by running the example (the "Play" button in upper right of the code block), this only
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If the rust `main` function returns an `Err()`, this `Err()` will be displayed with `std::fmt::Debug`.
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As you can see by running the example (by pressing the "Play" button in upper right of the code block),
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this only
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prints out the last `Error`.
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If the rust `main` function returns an Err(), this Err() will be displayed with `std::fmt::Debug`.
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~~~
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Error: StringError("func1 error")
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~~~
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The next chapters of this tutorial show how `chainerror` adds more information
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and improves inspecting the sources of an error.
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You can also run the tutorial examples in the checked out
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[chainerror git repo](https://github.com/haraldh/chainerror).
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~~~
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$ cargo run -q --example tutorial1
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~~~
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~~~rust
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{{#include ../examples/tutorial1.rs:2:}}
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{{#include ../examples/tutorial1.rs}}
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~~~
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# ErrorKind to the rescue
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[TBD]
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To cope with different kind of errors, we introduce the kind of an error `Func1ErrorKind` with an enum.
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Because we derive `Debug` and implement `Display` our `Func1ErrorKind` enum, this enum can be used as
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a `std::error::Error`.
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Not using `String` errors anymore, the `cherr!()` macro seen in the beginning of
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the tutorial has to be used again.
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Only returning `Func1ErrorKind` in `func1()` now let us get rid of `Result<(), Box<Error>>` and we can
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use `ChainResult<(), Func1ErrorKind>`.
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In `main` we can now directly use the methods of `ChainError<T>` without downcasting the error first.
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Also a nice `match` on `ChainError<T>.kind()` is now possible, which returns `&T`, meaning
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`&Func1ErrorKind` here.
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~~~rust
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use crate::chainerror::*;
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# Debug for the ErrorKind
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[TBD]
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One small improvement at the end of the tutorial is to fix the debug output of
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`Func1ErrorKind`. As you probably noticed, the output doesn't say much of the enum.
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~~~
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Debug Error:
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src/main.rs:35: Func2
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[…]
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~~~
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As a lazy shortcut, we implement `Debug` by calling `Display` and end up with
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~~~
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Debug Error:
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src/main.rs:40: func1 error calling func2
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[…}
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~~~
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which gives us a lot more detail.
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~~~rust
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use crate::chainerror::*;
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# Simple Chained String Errors
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Now with the help of the `chainerror` crate, we can have a nicer output.
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With relatively small changes and the help of the `cherr!` macro of the `chainerror` crate
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the `String` errors are now chained together.
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Press the play button in the upper right corner and see the nice debug output.
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### What did we do here?
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~~~rust,ignore
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{{#include ../examples/tutorial2.rs:11:13}}
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{{#include ../examples/tutorial2.rs:13:15}}
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~~~
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The macro `cherr!(cause, newerror)` stores `cause` as the source/cause of `newerror` and returns
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`newerror`, along with the filename (`file!()`) and line number (`line!()`).
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The macro `cherr!(olderror, newerror)` stores `olderror` as the source/cause of `newerror`
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along with the filename (`file!()`) and line number (`line!()`)
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and returns `newerror`.
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`Err(e)?` then returns the error `e` applying `e.into()`, so that we
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`Err()?` then returns the inner error applying `.into()`, so that we
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again have a `Err(Box<Error>)` as a result.
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The `Debug` implementation of `ChainError<T>` (which is returned by `cherr!()`)
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prints the `Debug` of `T` prefixed with the stored filename and line number.
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`ChainError<T>` is in our case `ChainError<String>`.
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`ChainError<T>` in our case is `ChainError<String>`.
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@ -12,8 +12,8 @@ use crate::chainerror::*;
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# }
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~~~
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Note, that we changed the output of the error in `main()` from `Debug` to `Display`, so we don't see
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the error backtrace with filename and line number.
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Note, that because we changed the output of the error in `main()` from
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`Debug` to `Display`, we don't see the error backtrace with filename and line number.
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To enable the `Display` backtrace, you have to enable the feature `display-cause` for `chainerror`.
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@ -1,6 +1,14 @@
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# Downcast the Errors
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[TBD]
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`std::error::Error` comes with some helper methods to get to the original object of the
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`&(dyn Error + 'static)` returned by `.source()`.
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~~~rust,ignore
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pub fn downcast_ref<T: Error + 'static>(&self) -> Option<&T>
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pub fn downcast_mut<T: Error + 'static>(&mut self) -> Option<&mut T>
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~~~
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This is how it looks like, when using those:
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~~~rust
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use crate::chainerror::*;
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|
|
|
@ -1,6 +1,30 @@
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# The root cause of all Errors
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[TBD]
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`chainerror` also has some helper methods:
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~~~rust,ignore
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fn is_chain<T: 'static + Display + Debug>(&self) -> bool
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fn downcast_chain_ref<T: 'static + Display + Debug>(&self) -> Option<&ChainError<T>>
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fn downcast_chain_mut<T: 'static + Display + Debug>(&mut self) -> Option<&mut ChainError<T>>
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fn root_cause(&self) -> Option<&(dyn Error + 'static)>
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fn find_cause<U: Error + 'static>(&self) -> Option<&U>
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fn find_chain_cause<U: Error + 'static>(&self) -> Option<&ChainError<U>>
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fn kind<'a>(&'a self) -> &'a T
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~~~
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Using `downcast_chain_ref::<String>()` gives a `ChainError<String>`, which can be used
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to call `.find_cause::<io::Error>()`.
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~~~rust,ignore
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if let Some(s) = e.downcast_chain_ref::<String>() {
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if let Some(ioerror) = s.find_cause::<io::Error>() {
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~~~
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or to use `.root_cause()`, which of course can be of any type implementing `std::error::Error`.
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|
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~~~rust,ignore
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if let Some(e) = s.root_cause() {
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~~~
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~~~rust
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use crate::chainerror::*;
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|
|
|
@ -1,6 +1,26 @@
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# Finding an Error cause
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[TBD]
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To distinguish the errors occuring in various places, we can define named string errors with the
|
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"new type" pattern.
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~~~rust,ignore
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derive_str_cherr!(Func2Error);
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derive_str_cherr!(Func1Error);
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~~~
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|
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Instead of `ChainError<String>` we now have `struct Func1Error(String)` and `ChainError<Func1Error>`.
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In the `main` function you can see, how we can match the different errors.
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|
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Also see:
|
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~~~rust,ignore
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if let Some(f2err) = f1err.find_chain_cause::<Func2Error>() {
|
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~~~
|
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as a shortcut to
|
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~~~rust,ignore
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if let Some(f2err) = f1err.find_cause::<ChainError<Func2Error>>() {
|
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~~~
|
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hiding the `ChainError<T>` implementation detail.
|
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|
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~~~rust
|
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use crate::chainerror::*;
|
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|
|
|
@ -1,6 +1,28 @@
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# Selective Error Handling
|
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|
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[TBD]
|
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What about functions returning different Error types?
|
||||
|
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In this example `func1()` can return either `Func1ErrorFunc2` or `Func1ErrorIO`.
|
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|
||||
We might want to `match` on `func1()` with something like:
|
||||
|
||||
~~~rust,ignore
|
||||
fn main() -> Result<(), Box<Error>> {
|
||||
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(())
|
||||
}
|
||||
~~~
|
||||
|
||||
but this is not valid rust code, so we end up doing it the hard way.
|
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In the next chapter, we will see, how to solve this more elegantly.
|
||||
|
||||
~~~rust
|
||||
use crate::chainerror::*;
|
||||
|
|
71
examples/example.rs
Normal file
71
examples/example.rs
Normal file
|
@ -0,0 +1,71 @@
|
|||
use chainerror::*;
|
||||
use std::error::Error;
|
||||
use std::io;
|
||||
use std::result::Result;
|
||||
|
||||
fn do_some_io() -> Result<(), Box<Error>> {
|
||||
Err(io::Error::from(io::ErrorKind::NotFound))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
fn func3() -> Result<(), Box<Error>> {
|
||||
let filename = "foo.txt";
|
||||
do_some_io().map_err(mstrerr!("Error reading '{}'", filename))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
derive_str_cherr!(Func2Error);
|
||||
|
||||
fn func2() -> ChainResult<(), Func2Error> {
|
||||
func3().map_err(mstrerr!(Func2Error, "func2 error: calling func3"))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
enum Func1Error {
|
||||
Func2,
|
||||
IO(String),
|
||||
}
|
||||
|
||||
impl ::std::fmt::Display for Func1Error {
|
||||
fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
|
||||
match self {
|
||||
Func1Error::Func2 => write!(f, "func1 error calling func2"),
|
||||
Func1Error::IO(filename) => write!(f, "Error reading '{}'", filename),
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
impl ::std::fmt::Debug for Func1Error {
|
||||
fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
|
||||
write!(f, "{}", self)
|
||||
}
|
||||
}
|
||||
|
||||
fn func1() -> ChainResult<(), Func1Error> {
|
||||
func2().map_err(|e| cherr!(e, Func1Error::Func2))?;
|
||||
let filename = String::from("bar.txt");
|
||||
do_some_io().map_err(|e| cherr!(e, Func1Error::IO(filename)))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
fn main() {
|
||||
if let Err(e) = func1() {
|
||||
match e.kind() {
|
||||
Func1Error::Func2 => eprintln!("Main Error Report: func1 error calling func2"),
|
||||
Func1Error::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)
|
||||
}
|
||||
|
||||
if let Some(e) = e.root_cause() {
|
||||
let ioerror = e.downcast_ref::<io::Error>().unwrap();
|
||||
eprintln!("\nThe root cause was: std::io::Error: {:#?}", ioerror);
|
||||
}
|
||||
|
||||
eprintln!("\nDebug Error:\n{:?}", e);
|
||||
}
|
||||
}
|
|
@ -1,9 +1,9 @@
|
|||
|
||||
use std::error::Error;
|
||||
use std::io;
|
||||
use std::result::Result;
|
||||
|
||||
fn do_some_io() -> Result<(), Box<Error>> {
|
||||
Err("do_some_io error")?;
|
||||
Err(io::Error::from(io::ErrorKind::NotFound))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
|
|
|
@ -17,38 +17,38 @@ fn func2() -> Result<(), Box<Error>> {
|
|||
}
|
||||
|
||||
#[derive(Debug)]
|
||||
enum Func1Error {
|
||||
enum Func1ErrorKind {
|
||||
Func2,
|
||||
IO(String),
|
||||
}
|
||||
|
||||
impl ::std::fmt::Display for Func1Error {
|
||||
impl ::std::fmt::Display for Func1ErrorKind {
|
||||
fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
|
||||
match self {
|
||||
Func1Error::Func2 => write!(f, "func1 error calling func2"),
|
||||
Func1Error::IO(filename) => write!(f, "Error reading '{}'", filename),
|
||||
Func1ErrorKind::Func2 => write!(f, "func1 error calling func2"),
|
||||
Func1ErrorKind::IO(filename) => write!(f, "Error reading '{}'", filename),
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
fn func1() -> ChainResult<(), Func1Error> {
|
||||
func2().map_err(|e| cherr!(e, Func1Error::Func2))?;
|
||||
fn func1() -> ChainResult<(), Func1ErrorKind> {
|
||||
func2().map_err(|e| cherr!(e, Func1ErrorKind::Func2))?;
|
||||
let filename = String::from("bar.txt");
|
||||
do_some_io().map_err(|e| cherr!(e, Func1Error::IO(filename)))?;
|
||||
do_some_io().map_err(|e| cherr!(e, Func1ErrorKind::IO(filename)))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
fn main() -> Result<(), Box<Error>> {
|
||||
if let Err(e) = func1() {
|
||||
match e.kind() {
|
||||
Func1Error::Func2 => eprintln!("Main Error Report: func1 error calling func2"),
|
||||
Func1Error::IO(filename) => {
|
||||
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!("Error reported by Func2Error: {}", e)
|
||||
eprintln!("\nError reported by Func2Error: {}", e)
|
||||
}
|
||||
|
||||
eprintln!("\nDebug Error:\n{:?}", e);
|
||||
|
|
|
@ -16,44 +16,44 @@ fn func2() -> Result<(), Box<Error>> {
|
|||
Ok(())
|
||||
}
|
||||
|
||||
enum Func1Error {
|
||||
enum Func1ErrorKind {
|
||||
Func2,
|
||||
IO(String),
|
||||
}
|
||||
|
||||
impl ::std::fmt::Display for Func1Error {
|
||||
impl ::std::fmt::Display for Func1ErrorKind {
|
||||
fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
|
||||
match self {
|
||||
Func1Error::Func2 => write!(f, "func1 error calling func2"),
|
||||
Func1Error::IO(filename) => write!(f, "Error reading '{}'", filename),
|
||||
Func1ErrorKind::Func2 => write!(f, "func1 error calling func2"),
|
||||
Func1ErrorKind::IO(filename) => write!(f, "Error reading '{}'", filename),
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
impl ::std::fmt::Debug for Func1Error {
|
||||
impl ::std::fmt::Debug for Func1ErrorKind {
|
||||
fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
|
||||
write!(f, "{}", self)
|
||||
}
|
||||
}
|
||||
|
||||
fn func1() -> ChainResult<(), Func1Error> {
|
||||
func2().map_err(|e| cherr!(e, Func1Error::Func2))?;
|
||||
fn func1() -> ChainResult<(), Func1ErrorKind> {
|
||||
func2().map_err(|e| cherr!(e, Func1ErrorKind::Func2))?;
|
||||
let filename = String::from("bar.txt");
|
||||
do_some_io().map_err(|e| cherr!(e, Func1Error::IO(filename)))?;
|
||||
do_some_io().map_err(|e| cherr!(e, Func1ErrorKind::IO(filename)))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
fn main() -> Result<(), Box<Error>> {
|
||||
if let Err(e) = func1() {
|
||||
match e.kind() {
|
||||
Func1Error::Func2 => eprintln!("Main Error Report: func1 error calling func2"),
|
||||
Func1Error::IO(filename) => {
|
||||
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!("Error reported by Func2Error: {}", e)
|
||||
eprintln!("\nError reported by Func2Error: {}", e)
|
||||
}
|
||||
|
||||
eprintln!("\nDebug Error:\n{:?}", e);
|
||||
|
|
|
@ -1,9 +1,11 @@
|
|||
use chainerror::*;
|
||||
|
||||
use std::error::Error;
|
||||
use std::io;
|
||||
use std::result::Result;
|
||||
|
||||
fn do_some_io() -> Result<(), Box<Error>> {
|
||||
Err("do_some_io error")?;
|
||||
Err(io::Error::from(io::ErrorKind::NotFound))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
|
|
|
@ -1,9 +1,11 @@
|
|||
use chainerror::*;
|
||||
|
||||
use std::error::Error;
|
||||
use std::io;
|
||||
use std::result::Result;
|
||||
|
||||
fn do_some_io() -> Result<(), Box<Error>> {
|
||||
Err("do_some_io error")?;
|
||||
Err(io::Error::from(io::ErrorKind::NotFound))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
|
|
|
@ -1,9 +1,10 @@
|
|||
use chainerror::*;
|
||||
use std::error::Error;
|
||||
use std::io;
|
||||
use std::result::Result;
|
||||
|
||||
fn do_some_io() -> Result<(), Box<Error>> {
|
||||
Err("do_some_io error")?;
|
||||
Err(io::Error::from(io::ErrorKind::NotFound))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
|
|
|
@ -32,7 +32,7 @@ fn main() -> Result<(), Box<Error>> {
|
|||
eprintln!("Func1ErrorIO:\n{:?}", s);
|
||||
}
|
||||
|
||||
if let Some(s) = try_cherr_ref!(e, Func1ErrorFunc2) {
|
||||
if let Some(s) = e.downcast_chain_ref::<Func1ErrorFunc2>() {
|
||||
eprintln!("Func1ErrorFunc2:\n{:?}", s);
|
||||
}
|
||||
}
|
||||
|
|
537
src/lib.rs
537
src/lib.rs
|
@ -1,7 +1,164 @@
|
|||
/*!
|
||||
|
||||
`chainerror` provides an error backtrace without doing a real backtrace, so even after you `strip` your
|
||||
binaries, you still have the error backtrace.
|
||||
|
||||
`chainerror` has no dependencies!
|
||||
|
||||
`chainerror` uses `.source()` of `std::error::Error` along with `line()!` and `file()!` to provide a nice debug error backtrace.
|
||||
It encapsulates all types, which have `Display + Debug` and can store the error cause internally.
|
||||
|
||||
Along with the `ChainError<T>` struct, `chainerror` comes with some useful helper macros to save a lot of typing.
|
||||
|
||||
# Examples
|
||||
|
||||
~~~rust
|
||||
use chainerror::*;
|
||||
use std::error::Error;
|
||||
use std::io;
|
||||
use std::result::Result;
|
||||
|
||||
fn do_some_io() -> Result<(), Box<Error>> {
|
||||
Err(io::Error::from(io::ErrorKind::NotFound))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
fn func2() -> Result<(), Box<Error>> {
|
||||
let filename = "foo.txt";
|
||||
do_some_io().map_err(mstrerr!("Error reading '{}'", filename))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
fn func1() -> Result<(), Box<Error>> {
|
||||
func2().map_err(mstrerr!("func1 error"))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
fn main() {
|
||||
if let Err(e) = func1() {
|
||||
assert_eq!(
|
||||
format!("\n{:?}\n", e), r#"
|
||||
src/lib.rs:20: func1 error
|
||||
Caused by:
|
||||
src/lib.rs:15: Error reading 'foo.txt'
|
||||
Caused by:
|
||||
Kind(NotFound)
|
||||
"#
|
||||
);
|
||||
}
|
||||
# else {
|
||||
# unreachable!();
|
||||
# }
|
||||
}
|
||||
~~~
|
||||
|
||||
|
||||
~~~rust
|
||||
use chainerror::*;
|
||||
use std::error::Error;
|
||||
use std::io;
|
||||
use std::result::Result;
|
||||
|
||||
fn do_some_io() -> Result<(), Box<Error>> {
|
||||
Err(io::Error::from(io::ErrorKind::NotFound))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
fn func3() -> Result<(), Box<Error>> {
|
||||
let filename = "foo.txt";
|
||||
do_some_io().map_err(mstrerr!("Error reading '{}'", filename))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
derive_str_cherr!(Func2Error);
|
||||
|
||||
fn func2() -> ChainResult<(), Func2Error> {
|
||||
func3().map_err(mstrerr!(Func2Error, "func2 error: calling func3"))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
enum Func1Error {
|
||||
Func2,
|
||||
IO(String),
|
||||
}
|
||||
|
||||
impl ::std::fmt::Display for Func1Error {
|
||||
fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
|
||||
match self {
|
||||
Func1Error::Func2 => write!(f, "func1 error calling func2"),
|
||||
Func1Error::IO(filename) => write!(f, "Error reading '{}'", filename),
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
impl ::std::fmt::Debug for Func1Error {
|
||||
fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
|
||||
write!(f, "{}", self)
|
||||
}
|
||||
}
|
||||
|
||||
fn func1() -> ChainResult<(), Func1Error> {
|
||||
func2().map_err(|e| cherr!(e, Func1Error::Func2))?;
|
||||
let filename = String::from("bar.txt");
|
||||
do_some_io().map_err(|e| cherr!(e, Func1Error::IO(filename)))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
fn main() {
|
||||
if let Err(e) = func1() {
|
||||
assert!(
|
||||
match e.kind() {
|
||||
Func1Error::Func2 => {
|
||||
eprintln!("Main Error Report: func1 error calling func2");
|
||||
true
|
||||
}
|
||||
Func1Error::IO(filename) => {
|
||||
eprintln!("Main Error Report: func1 error reading '{}'", filename);
|
||||
false
|
||||
}
|
||||
}
|
||||
);
|
||||
|
||||
assert!(e.find_chain_cause::<Func2Error>().is_some());
|
||||
|
||||
if let Some(e) = e.find_chain_cause::<Func2Error>() {
|
||||
eprintln!("\nError reported by Func2Error: {}", e)
|
||||
}
|
||||
|
||||
|
||||
assert!(e.root_cause().is_some());
|
||||
|
||||
if let Some(e) = e.root_cause() {
|
||||
let ioerror = e.downcast_ref::<io::Error>().unwrap();
|
||||
eprintln!("\nThe root cause was: std::io::Error: {:#?}", ioerror);
|
||||
}
|
||||
|
||||
assert_eq!(
|
||||
format!("\n{:?}\n", e), r#"
|
||||
src/lib.rs:47: func1 error calling func2
|
||||
Caused by:
|
||||
src/lib.rs:22: Func2Error(func2 error: calling func3)
|
||||
Caused by:
|
||||
src/lib.rs:15: Error reading 'foo.txt'
|
||||
Caused by:
|
||||
Kind(NotFound)
|
||||
"#
|
||||
);
|
||||
}
|
||||
# else {
|
||||
# unreachable!();
|
||||
# }
|
||||
}
|
||||
~~~
|
||||
|
||||
!*/
|
||||
|
||||
use std::any::TypeId;
|
||||
use std::error::Error;
|
||||
use std::fmt::{Debug, Display, Formatter, Result};
|
||||
use std::result::Result as StdResult;
|
||||
|
||||
/** chains an inner error kind `T` with a causing error
|
||||
**/
|
||||
pub struct ChainError<T> {
|
||||
#[cfg(not(feature = "no-fileline"))]
|
||||
occurrence: Option<(u32, &'static str)>,
|
||||
|
@ -9,10 +166,12 @@ pub struct ChainError<T> {
|
|||
error_cause: Option<Box<dyn Error + 'static>>,
|
||||
}
|
||||
|
||||
pub type ChainResult<O, E> = StdResult<O, ChainError<E>>;
|
||||
/// convenience type alias
|
||||
pub type ChainResult<O, E> = std::result::Result<O, ChainError<E>>;
|
||||
|
||||
impl<T: 'static + Display + Debug> ChainError<T> {
|
||||
#[cfg(not(feature = "no-fileline"))]
|
||||
/// Use the `cherr!()` or `mstrerr!()` macro instead of calling this directly
|
||||
pub fn new(
|
||||
kind: T,
|
||||
error_cause: Option<Box<dyn Error + 'static>>,
|
||||
|
@ -26,6 +185,7 @@ impl<T: 'static + Display + Debug> ChainError<T> {
|
|||
}
|
||||
|
||||
#[cfg(feature = "no-fileline")]
|
||||
/// Use the `cherr!()` or `mstrerr!()` macro instead of calling this directly
|
||||
pub fn new(
|
||||
kind: T,
|
||||
error_cause: Option<Box<dyn Error + 'static>>,
|
||||
|
@ -34,6 +194,7 @@ impl<T: 'static + Display + Debug> ChainError<T> {
|
|||
Self { kind, error_cause }
|
||||
}
|
||||
|
||||
/// return the root cause of the error chain, if any exists
|
||||
pub fn root_cause(&self) -> Option<&(dyn Error + 'static)> {
|
||||
let mut cause = self as &(dyn Error + 'static);
|
||||
while let Some(c) = cause.source() {
|
||||
|
@ -42,6 +203,54 @@ impl<T: 'static + Display + Debug> ChainError<T> {
|
|||
Some(cause)
|
||||
}
|
||||
|
||||
/** find the first error cause of type U, if any exists
|
||||
|
||||
# Examples
|
||||
|
||||
~~~rust
|
||||
# use crate::chainerror::*;
|
||||
# use std::error::Error;
|
||||
# use std::io;
|
||||
# use std::result::Result;
|
||||
#
|
||||
fn do_some_io() -> Result<(), Box<Error>> {
|
||||
Err(io::Error::from(io::ErrorKind::NotFound))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
derive_str_cherr!(Func2Error);
|
||||
|
||||
fn func2() -> Result<(), Box<Error>> {
|
||||
let filename = "foo.txt";
|
||||
do_some_io().map_err(mstrerr!(Func2Error, "Error reading '{}'", filename))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
derive_str_cherr!(Func1Error);
|
||||
|
||||
fn func1() -> Result<(), Box<Error>> {
|
||||
func2().map_err(mstrerr!(Func1Error, "func1 error"))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
fn main() {
|
||||
if let Err(e) = func1() {
|
||||
if let Some(f1err) = e.downcast_chain_ref::<Func1Error>() {
|
||||
|
||||
assert!(f1err.find_cause::<io::Error>().is_some());
|
||||
|
||||
assert!(f1err.find_chain_cause::<Func2Error>().is_some());
|
||||
}
|
||||
# else {
|
||||
# panic!();
|
||||
# }
|
||||
}
|
||||
# else {
|
||||
# unreachable!();
|
||||
# }
|
||||
}
|
||||
~~~
|
||||
**/
|
||||
pub fn find_cause<U: Error + 'static>(&self) -> Option<&U> {
|
||||
let mut cause = self as &(dyn Error + 'static);
|
||||
loop {
|
||||
|
@ -56,6 +265,21 @@ impl<T: 'static + Display + Debug> ChainError<T> {
|
|||
}
|
||||
}
|
||||
|
||||
/** find the first error cause of type ChainError<U>, if any exists
|
||||
|
||||
Same as `find_cause`, but hides the `ChainError<U>` implementation internals
|
||||
|
||||
# Examples
|
||||
|
||||
~~~rust,ignore
|
||||
/// Instead of writing
|
||||
err.find_cause::<ChainError<FooError>>();
|
||||
|
||||
/// leave out the ChainError<T> implementation detail
|
||||
err.find_chain_cause::<FooError>();
|
||||
~~~
|
||||
|
||||
**/
|
||||
pub fn find_chain_cause<U: Error + 'static>(&self) -> Option<&ChainError<U>> {
|
||||
let mut cause = self as &(dyn Error + 'static);
|
||||
loop {
|
||||
|
@ -70,19 +294,84 @@ impl<T: 'static + Display + Debug> ChainError<T> {
|
|||
}
|
||||
}
|
||||
|
||||
/** return a reference to T of `ChainError<T>`
|
||||
|
||||
# Examples
|
||||
|
||||
~~~rust
|
||||
# use crate::chainerror::*;
|
||||
# use std::error::Error;
|
||||
# use std::io;
|
||||
# use std::result::Result;
|
||||
#
|
||||
fn do_some_io() -> Result<(), Box<Error>> {
|
||||
Err(io::Error::from(io::ErrorKind::NotFound))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
derive_str_cherr!(Func2Error);
|
||||
|
||||
fn func2() -> Result<(), Box<Error>> {
|
||||
let filename = "foo.txt";
|
||||
do_some_io().map_err(mstrerr!(Func2Error, "Error reading '{}'", filename))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
#[derive(Debug)]
|
||||
enum Func1ErrorKind {
|
||||
Func2,
|
||||
IO(String),
|
||||
}
|
||||
|
||||
// impl ::std::fmt::Display for Func1ErrorKind {…}
|
||||
# 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),
|
||||
# }
|
||||
# }
|
||||
# }
|
||||
|
||||
fn func1() -> ChainResult<(), Func1ErrorKind> {
|
||||
func2().map_err(|e| cherr!(e, Func1ErrorKind::Func2))?;
|
||||
do_some_io().map_err(|e| cherr!(e, Func1ErrorKind::IO("bar.txt".into())))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
fn main() {
|
||||
if let Err(e) = func1() {
|
||||
match e.kind() {
|
||||
Func1ErrorKind::Func2 => {},
|
||||
Func1ErrorKind::IO(filename) => panic!(),
|
||||
}
|
||||
}
|
||||
# else {
|
||||
# unreachable!();
|
||||
# }
|
||||
}
|
||||
~~~
|
||||
|
||||
**/
|
||||
pub fn kind<'a>(&'a self) -> &'a T {
|
||||
&self.kind
|
||||
}
|
||||
}
|
||||
|
||||
/** convenience trait to hide the `ChainError<T>` implementation internals
|
||||
**/
|
||||
pub trait ChainErrorDown {
|
||||
/** test if of type `ChainError<T>`
|
||||
**/
|
||||
fn is_chain<T: 'static + Display + Debug>(&self) -> bool;
|
||||
/** downcast to a reference of `ChainError<T>`
|
||||
**/
|
||||
fn downcast_chain_ref<T: 'static + Display + Debug>(&self) -> Option<&ChainError<T>>;
|
||||
/** downcast to a mutable reference of `ChainError<T>`
|
||||
**/
|
||||
fn downcast_chain_mut<T: 'static + Display + Debug>(&mut self) -> Option<&mut ChainError<T>>;
|
||||
}
|
||||
|
||||
use std::any::TypeId;
|
||||
|
||||
impl<U: 'static + Display + Debug> ChainErrorDown for ChainError<U> {
|
||||
fn is_chain<T: 'static + Display + Debug>(&self) -> bool {
|
||||
TypeId::of::<T>() == TypeId::of::<U>()
|
||||
|
@ -201,7 +490,11 @@ impl<T: 'static + Display + Debug> Debug for ChainError<T> {
|
|||
}
|
||||
}
|
||||
|
||||
if self.is_chain::<String>() {
|
||||
Display::fmt(&self.kind, f)?;
|
||||
} else {
|
||||
Debug::fmt(&self.kind, f)?;
|
||||
}
|
||||
|
||||
#[cfg(not(feature = "no-debug-cause"))]
|
||||
{
|
||||
|
@ -214,6 +507,93 @@ impl<T: 'static + Display + Debug> Debug for ChainError<T> {
|
|||
}
|
||||
}
|
||||
|
||||
/** creates a new `ChainError<T>`
|
||||
|
||||
# Examples
|
||||
|
||||
Create a new ChainError<FooError>, where `FooError` must implement `Display` and `Debug`.
|
||||
~~~rust
|
||||
# use chainerror::*;
|
||||
#
|
||||
# #[derive(Debug)]
|
||||
enum FooError {
|
||||
Bar,
|
||||
Baz(&'static str),
|
||||
}
|
||||
#
|
||||
# impl ::std::fmt::Display for FooError {
|
||||
# fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
|
||||
# match self {
|
||||
# FooError::Bar => write!(f, "Bar Error"),
|
||||
# FooError::Baz(s) => write!(f, "Baz Error: '{}'", s),
|
||||
# }
|
||||
# }
|
||||
# }
|
||||
|
||||
// impl ::std::fmt::Display for FooError
|
||||
|
||||
fn do_some_stuff() -> bool {
|
||||
false
|
||||
}
|
||||
|
||||
fn func() -> ChainResult<(), FooError> {
|
||||
if ! do_some_stuff() {
|
||||
Err(cherr!(FooError::Baz("Error")))?;
|
||||
}
|
||||
Ok(())
|
||||
}
|
||||
#
|
||||
# pub fn main() {
|
||||
# match func().unwrap_err().kind() {
|
||||
# FooError::Baz(s) if s == &"Error" => {},
|
||||
# _ => panic!(),
|
||||
# }
|
||||
# }
|
||||
~~~
|
||||
|
||||
Additionally an error cause can be added.
|
||||
|
||||
~~~rust
|
||||
# use chainerror::*;
|
||||
# use std::io;
|
||||
# use std::error::Error;
|
||||
#
|
||||
# #[derive(Debug)]
|
||||
# enum FooError {
|
||||
# Bar,
|
||||
# Baz(&'static str),
|
||||
# }
|
||||
#
|
||||
# impl ::std::fmt::Display for FooError {
|
||||
# fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
|
||||
# match self {
|
||||
# FooError::Bar => write!(f, "Bar Error"),
|
||||
# FooError::Baz(s) => write!(f, "Baz Error: '{}'", s),
|
||||
# }
|
||||
# }
|
||||
# }
|
||||
#
|
||||
fn do_some_stuff() -> Result<(), Box<Error>> {
|
||||
Err(io::Error::from(io::ErrorKind::NotFound))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
fn func() -> ChainResult<(), FooError> {
|
||||
do_some_stuff().map_err(
|
||||
|e| cherr!(e, FooError::Baz("Error"))
|
||||
)?;
|
||||
Ok(())
|
||||
}
|
||||
#
|
||||
# pub fn main() {
|
||||
# match func().unwrap_err().kind() {
|
||||
# FooError::Baz(s) if s == &"Error" => {},
|
||||
# _ => panic!(),
|
||||
# }
|
||||
# }
|
||||
~~~
|
||||
|
||||
**/
|
||||
#[macro_export]
|
||||
macro_rules! cherr {
|
||||
( $k:expr ) => {
|
||||
|
@ -224,6 +604,92 @@ macro_rules! cherr {
|
|||
};
|
||||
}
|
||||
|
||||
/** convenience macro for |e| cherr!(e, format!(…))
|
||||
|
||||
# Examples
|
||||
|
||||
~~~rust
|
||||
# use crate::chainerror::*;
|
||||
# use std::error::Error;
|
||||
# use std::io;
|
||||
# use std::result::Result;
|
||||
#
|
||||
# fn do_some_io() -> Result<(), Box<Error>> {
|
||||
# Err(io::Error::from(io::ErrorKind::NotFound))?;
|
||||
# Ok(())
|
||||
# }
|
||||
#
|
||||
fn func2() -> Result<(), Box<Error>> {
|
||||
let filename = "foo.txt";
|
||||
do_some_io().map_err(mstrerr!("Error reading '{}'", filename))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
fn func1() -> Result<(), Box<Error>> {
|
||||
func2().map_err(mstrerr!("func1 error"))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
# fn main() {
|
||||
# if let Err(e) = func1() {
|
||||
# assert_eq!(
|
||||
# format!("\n{:?}\n", e), r#"
|
||||
# src/lib.rs:20: func1 error
|
||||
# Caused by:
|
||||
# src/lib.rs:15: Error reading 'foo.txt'
|
||||
# Caused by:
|
||||
# Kind(NotFound)
|
||||
# "#
|
||||
# );
|
||||
# } else {
|
||||
# unreachable!();
|
||||
# }
|
||||
# }
|
||||
~~~
|
||||
|
||||
`mstrerr!()` can also be used to map a new `ChainError<T>`, where T was defined with
|
||||
`derive_str_cherr!(T)`
|
||||
|
||||
~~~rust
|
||||
# use crate::chainerror::*;
|
||||
# use std::error::Error;
|
||||
# use std::io;
|
||||
# use std::result::Result;
|
||||
#
|
||||
# fn do_some_io() -> Result<(), Box<Error>> {
|
||||
# Err(io::Error::from(io::ErrorKind::NotFound))?;
|
||||
# Ok(())
|
||||
# }
|
||||
#
|
||||
derive_str_cherr!(Func2Error);
|
||||
|
||||
fn func2() -> Result<(), Box<Error>> {
|
||||
let filename = "foo.txt";
|
||||
do_some_io().map_err(mstrerr!(Func2Error, "Error reading '{}'", filename))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
derive_str_cherr!(Func1Error);
|
||||
|
||||
fn func1() -> Result<(), Box<Error>> {
|
||||
func2().map_err(mstrerr!(Func1Error, "func1 error"))?;
|
||||
Ok(())
|
||||
}
|
||||
#
|
||||
# fn main() {
|
||||
# if let Err(e) = func1() {
|
||||
# if let Some(f1err) = e.downcast_chain_ref::<Func1Error>() {
|
||||
# assert!(f1err.find_cause::<ChainError<Func2Error>>().is_some());
|
||||
# assert!(f1err.find_chain_cause::<Func2Error>().is_some());
|
||||
# } else {
|
||||
# panic!();
|
||||
# }
|
||||
# } else {
|
||||
# unreachable!();
|
||||
# }
|
||||
# }
|
||||
~~~
|
||||
**/
|
||||
#[macro_export]
|
||||
macro_rules! mstrerr {
|
||||
( $t:ident, $v:expr $(, $more:expr)* ) => {
|
||||
|
@ -237,6 +703,49 @@ macro_rules! mstrerr {
|
|||
};
|
||||
}
|
||||
|
||||
/** convenience macro to create a "new type" T(String) and implement Display + Debug for T
|
||||
|
||||
~~~rust
|
||||
# use crate::chainerror::*;
|
||||
# use std::error::Error;
|
||||
# use std::io;
|
||||
# use std::result::Result;
|
||||
#
|
||||
# fn do_some_io() -> Result<(), Box<Error>> {
|
||||
# Err(io::Error::from(io::ErrorKind::NotFound))?;
|
||||
# Ok(())
|
||||
# }
|
||||
#
|
||||
derive_str_cherr!(Func2Error);
|
||||
|
||||
fn func2() -> ChainResult<(), Func2Error> {
|
||||
let filename = "foo.txt";
|
||||
do_some_io().map_err(mstrerr!(Func2Error, "Error reading '{}'", filename))?;
|
||||
Ok(())
|
||||
}
|
||||
|
||||
derive_str_cherr!(Func1Error);
|
||||
|
||||
fn func1() -> Result<(), Box<Error>> {
|
||||
func2().map_err(mstrerr!(Func1Error, "func1 error"))?;
|
||||
Ok(())
|
||||
}
|
||||
#
|
||||
# fn main() {
|
||||
# if let Err(e) = func1() {
|
||||
# if let Some(f1err) = e.downcast_chain_ref::<Func1Error>() {
|
||||
# assert!(f1err.find_cause::<ChainError<Func2Error>>().is_some());
|
||||
# assert!(f1err.find_chain_cause::<Func2Error>().is_some());
|
||||
# } else {
|
||||
# panic!();
|
||||
# }
|
||||
# } else {
|
||||
# unreachable!();
|
||||
# }
|
||||
# }
|
||||
~~~
|
||||
|
||||
**/
|
||||
#[macro_export]
|
||||
macro_rules! derive_str_cherr {
|
||||
($e:ident) => {
|
||||
|
@ -254,23 +763,3 @@ macro_rules! derive_str_cherr {
|
|||
impl ::std::error::Error for $e {}
|
||||
};
|
||||
}
|
||||
|
||||
#[macro_export]
|
||||
macro_rules! try_cherr_ref {
|
||||
( $e:expr, $t:ident ) => {
|
||||
$e.downcast_ref::<ChainError<$t>>()
|
||||
};
|
||||
( $e:expr, $t:path ) => {
|
||||
$e.downcast_ref::<ChainError<$t>>()
|
||||
};
|
||||
}
|
||||
|
||||
#[macro_export]
|
||||
macro_rules! try_cherr_mut {
|
||||
( $e:expr, $t:ident ) => {
|
||||
$e.downcast_mut::<ChainError<$t>>()
|
||||
};
|
||||
( $e:expr, $t:path ) => {
|
||||
$e.downcast_mut::<ChainError<$t>>()
|
||||
};
|
||||
}
|
||||
|
|
Loading…
Reference in a new issue