harald/chainerror
1
0
Fork 0
mirror of https://github.com/haraldh/chainerror.git synced 2025-01-31 00:56:41 +01:00
Code Issues Packages Projects Releases Wiki Activity
chainerror/tutorial8.html
Harald Hoyer 4dfb67bc45 publish: Cargo.toml: 0.4.3 
generated from commit deaaf4ce9f
2019-03-04 11:46:17 +01:00

1186 lines
43 KiB
HTML
Raw Blame History

<!DOCTYPE HTML>
<html lang="en" class="sidebar-visible no-js">
<head>
<!-- Book generated using mdBook -->
<meta charset="UTF-8">
<title>Finding an Error cause - chainerror</title>
<meta content="text/html; charset=utf-8" http-equiv="Content-Type">
<meta name="description" content="A tutorial for the chainerror rust crate.">
<meta name="viewport" content="width=device-width, initial-scale=1">
<meta name="theme-color" content="#ffffff" />
<link rel="shortcut icon" href="favicon.png">
<link rel="stylesheet" href="css/variables.css">
<link rel="stylesheet" href="css/general.css">
<link rel="stylesheet" href="css/chrome.css">
<link rel="stylesheet" href="css/print.css" media="print">
<!-- Fonts -->
<link rel="stylesheet" href="FontAwesome/css/font-awesome.css">
<link href="https://fonts.googleapis.com/css?family=Open+Sans:300italic,400italic,600italic,700italic,800italic,400,300,600,700,800" rel="stylesheet" type="text/css">
<link href="https://fonts.googleapis.com/css?family=Source+Code+Pro:500" rel="stylesheet" type="text/css">
<!-- Highlight.js Stylesheets -->
<link rel="stylesheet" href="highlight.css">
<link rel="stylesheet" href="tomorrow-night.css">
<link rel="stylesheet" href="ayu-highlight.css">
<!-- Custom theme stylesheets -->
</head>
<body class="light">
<!-- Provide site root to javascript -->
<script type="text/javascript">
var path_to_root = "";
var default_theme = "light";
</script>
<!-- Work around some values being stored in localStorage wrapped in quotes -->
<script type="text/javascript">
try {
var theme = localStorage.getItem('mdbook-theme');
var sidebar = localStorage.getItem('mdbook-sidebar');
if (theme.startsWith('"') && theme.endsWith('"')) {
localStorage.setItem('mdbook-theme', theme.slice(1, theme.length - 1));
}
if (sidebar.startsWith('"') && sidebar.endsWith('"')) {
localStorage.setItem('mdbook-sidebar', sidebar.slice(1, sidebar.length - 1));
}
} catch (e) { }
</script>
<!-- Set the theme before any content is loaded, prevents flash -->
<script type="text/javascript">
var theme;
try { theme = localStorage.getItem('mdbook-theme'); } catch(e) { }
if (theme === null || theme === undefined) { theme = default_theme; }
document.body.className = theme;
document.querySelector('html').className = theme + ' js';
</script>
<!-- Hide / unhide sidebar before it is displayed -->
<script type="text/javascript">
var html = document.querySelector('html');
var sidebar = 'hidden';
if (document.body.clientWidth >= 1080) {
try { sidebar = localStorage.getItem('mdbook-sidebar'); } catch(e) { }
sidebar = sidebar || 'visible';
}
html.classList.remove('sidebar-visible');
html.classList.add("sidebar-" + sidebar);
</script>
<nav id="sidebar" class="sidebar" aria-label="Table of contents">
<ol class="chapter"><li class="affix"><a href="index.html">chainerror</a></li><li><a href="tutorial1.html"><strong aria-hidden="true">1.</strong> Simple String Errors</a></li><li><a href="tutorial2.html"><strong aria-hidden="true">2.</strong> Simple Chained String Errors</a></li><li><a href="tutorial3.html"><strong aria-hidden="true">3.</strong> Mapping Errors</a></li><li><a href="tutorial4.html"><strong aria-hidden="true">4.</strong> Saving coding chars</a></li><li><a href="tutorial5.html"><strong aria-hidden="true">5.</strong> The source() of Errors</a></li><li><a href="tutorial6.html"><strong aria-hidden="true">6.</strong> Downcast the Errors</a></li><li><a href="tutorial7.html"><strong aria-hidden="true">7.</strong> The root cause of all Errors</a></li><li><a href="tutorial8.html" class="active"><strong aria-hidden="true">8.</strong> Finding an Error cause</a></li><li><a href="tutorial9.html"><strong aria-hidden="true">9.</strong> Selective Error Handling</a></li><li><a href="tutorial10.html"><strong aria-hidden="true">10.</strong> ErrorKind to the rescue</a></li><li><a href="tutorial11.html"><strong aria-hidden="true">11.</strong> Debug for the ErrorKind</a></li><li><a href="tutorial12.html"><strong aria-hidden="true">12.</strong> Deref for the ErrorKind</a></li><li><a href="tutorial13.html"><strong aria-hidden="true">13.</strong> Writing a library</a></li><li class="affix"><a href="end.html">The End</a></li></ol>
</nav>
<div id="page-wrapper" class="page-wrapper">
<div class="page">
<div id="menu-bar" class="menu-bar">
<div id="menu-bar-sticky-container">
<div class="left-buttons">
<button id="sidebar-toggle" class="icon-button" type="button" title="Toggle Table of Contents" aria-label="Toggle Table of Contents" aria-controls="sidebar">
<i class="fa fa-bars"></i>
</button>
<button id="theme-toggle" class="icon-button" type="button" title="Change theme" aria-label="Change theme" aria-haspopup="true" aria-expanded="false" aria-controls="theme-list">
<i class="fa fa-paint-brush"></i>
</button>
<ul id="theme-list" class="theme-popup" aria-label="Themes" role="menu">
<li role="none"><button role="menuitem" class="theme" id="light">Light (default)</button></li>
<li role="none"><button role="menuitem" class="theme" id="rust">Rust</button></li>
<li role="none"><button role="menuitem" class="theme" id="coal">Coal</button></li>
<li role="none"><button role="menuitem" class="theme" id="navy">Navy</button></li>
<li role="none"><button role="menuitem" class="theme" id="ayu">Ayu</button></li>
</ul>
<button id="search-toggle" class="icon-button" type="button" title="Search. (Shortkey: s)" aria-label="Toggle Searchbar" aria-expanded="false" aria-keyshortcuts="S" aria-controls="searchbar">
<i class="fa fa-search"></i>
</button>
</div>
<h1 class="menu-title">chainerror</h1>
<div class="right-buttons">
<a href="print.html" title="Print this book" aria-label="Print this book">
<i id="print-button" class="fa fa-print"></i>
</a>
</div>
</div>
</div>
<div id="search-wrapper" class="hidden">
<form id="searchbar-outer" class="searchbar-outer">
<input type="search" name="search" id="searchbar" name="searchbar" placeholder="Search this book ..." aria-controls="searchresults-outer" aria-describedby="searchresults-header">
</form>
<div id="searchresults-outer" class="searchresults-outer hidden">
<div id="searchresults-header" class="searchresults-header"></div>
<ul id="searchresults">
</ul>
</div>
</div>
<!-- Apply ARIA attributes after the sidebar and the sidebar toggle button are added to the DOM -->
<script type="text/javascript">
document.getElementById('sidebar-toggle').setAttribute('aria-expanded', sidebar === 'visible');
document.getElementById('sidebar').setAttribute('aria-hidden', sidebar !== 'visible');
Array.from(document.querySelectorAll('#sidebar a')).forEach(function(link) {
link.setAttribute('tabIndex', sidebar === 'visible' ? 0 : -1);
});
</script>
<div id="content" class="content">
<main>
<a class="header" href="#finding-an-error-cause" id="finding-an-error-cause"><h1>Finding an Error cause</h1></a>
<p>To distinguish the errors occuring in various places, we can define named string errors with the
&quot;new type&quot; pattern.</p>
<pre><code class="language-rust ignore">derive_str_cherr!(Func2Error);
derive_str_cherr!(Func1Error);
</code></pre>
<p>Instead of <code>ChainError&lt;String&gt;</code> we now have <code>struct Func1Error(String)</code> and <code>ChainError&lt;Func1Error&gt;</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::&lt;Func2Error&gt;() {
</code></pre>
<p>as a shortcut to</p>
<pre><code class="language-rust ignore"> if let Some(f2err) = f1err.find_cause::&lt;ChainError&lt;Func2Error&gt;&gt;() {
</code></pre>
<p>hiding the <code>ChainError&lt;T&gt;</code> implementation detail.</p>
<pre><pre class="playpen"><code class="language-rust">use chainerror::*;
use std::error::Error;
use std::io;
use std::result::Result;
fn do_some_io() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
Err(io::Error::from(io::ErrorKind::NotFound))?;
Ok(())
}
derive_str_cherr!(Func2Error);
fn func2() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
let filename = &quot;foo.txt&quot;;
do_some_io().map_err(mstrerr!(Func2Error, &quot;Error reading '{}'&quot;, filename))?;
Ok(())
}
derive_str_cherr!(Func1Error);
fn func1() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
func2().map_err(mstrerr!(Func1Error, &quot;func1 error&quot;))?;
Ok(())
}
fn main() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
if let Err(e) = func1() {
if let Some(f1err) = e.downcast_chain_ref::&lt;Func1Error&gt;() {
eprintln!(&quot;Func1Error: {}&quot;, f1err);
if let Some(f2err) = f1err.find_cause::&lt;ChainError&lt;Func2Error&gt;&gt;() {
eprintln!(&quot;Func2Error: {}&quot;, f2err);
}
if let Some(f2err) = f1err.find_chain_cause::&lt;Func2Error&gt;() {
eprintln!(&quot;Debug Func2Error:\n{:?}&quot;, f2err);
}
}
}
Ok(())
}
# #[allow(dead_code)]
# mod chainerror {
# //! `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&lt;T&gt;` struct, `chainerror` comes with some useful helper macros to save a lot of typing.
# //!
# //! ## Features
# //!
# //! `no-fileline`
# //! : completely turn off storing filename and line
# //!
# //! `display-cause`
# //! : turn on printing a backtrace of the errors in `Display`
# //!
# //! `no-debug-cause`
# //! : turn off printing a backtrace of the errors in `Debug`
# //!
# //!
# //! # Tutorial
# //!
# //! Read the [Tutorial](https://haraldh.github.io/chainerror/tutorial1.html)
# //!
# //! # Examples
# //!
# //! ~~~rust
# //! use chainerror::*;
# //! use std::error::Error;
# //! use std::io;
# //! use std::result::Result;
# //!
# //! fn do_some_io() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
# //! Err(io::Error::from(io::ErrorKind::NotFound))?;
# //! Ok(())
# //! }
# //!
# //! fn func2() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
# //! let filename = &quot;foo.txt&quot;;
# //! do_some_io().map_err(mstrerr!(&quot;Error reading '{}'&quot;, filename))?;
# //! Ok(())
# //! }
# //!
# //! fn func1() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
# //! func2().map_err(mstrerr!(&quot;func1 error&quot;))?;
# //! Ok(())
# //! }
# //!
# //! fn main() {
# //! if let Err(e) = func1() {
# //! #[cfg(not(windows))]
# //! assert_eq!(
# //! format!(&quot;\n{:?}\n&quot;, e), r#&quot;
# //! src/lib.rs:20: func1 error
# //! Caused by:
# //! src/lib.rs:15: Error reading 'foo.txt'
# //! Caused by:
# //! Kind(NotFound)
# //! &quot;#
# //! );
# //! }
# //! # else {
# //! # unreachable!();
# //! # }
# //! }
# //! ~~~
# //!
# //!
# //! ~~~rust
# //! use chainerror::*;
# //! use std::error::Error;
# //! use std::io;
# //! use std::result::Result;
# //!
# //! fn do_some_io() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
# //! Err(io::Error::from(io::ErrorKind::NotFound))?;
# //! Ok(())
# //! }
# //!
# //! fn func3() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
# //! let filename = &quot;foo.txt&quot;;
# //! do_some_io().map_err(mstrerr!(&quot;Error reading '{}'&quot;, filename))?;
# //! Ok(())
# //! }
# //!
# //! derive_str_cherr!(Func2Error);
# //!
# //! fn func2() -&gt; ChainResult&lt;(), Func2Error&gt; {
# //! func3().map_err(mstrerr!(Func2Error, &quot;func2 error: calling func3&quot;))?;
# //! Ok(())
# //! }
# //!
# //! enum Func1Error {
# //! Func2,
# //! IO(String),
# //! }
# //!
# //! impl ::std::fmt::Display for Func1Error {
# //! fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
# //! match self {
# //! Func1Error::Func2 =&gt; write!(f, &quot;func1 error calling func2&quot;),
# //! Func1Error::IO(filename) =&gt; write!(f, &quot;Error reading '{}'&quot;, filename),
# //! }
# //! }
# //! }
# //!
# //! impl ::std::fmt::Debug for Func1Error {
# //! fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
# //! write!(f, &quot;{}&quot;, self)
# //! }
# //! }
# //!
# //! fn func1() -&gt; ChainResult&lt;(), Func1Error&gt; {
# //! func2().map_err(|e| cherr!(e, Func1Error::Func2))?;
# //! let filename = String::from(&quot;bar.txt&quot;);
# //! 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 =&gt; {
# //! eprintln!(&quot;Main Error Report: func1 error calling func2&quot;);
# //! true
# //! }
# //! Func1Error::IO(filename) =&gt; {
# //! eprintln!(&quot;Main Error Report: func1 error reading '{}'&quot;, filename);
# //! false
# //! }
# //! }
# //! );
# //!
# //! assert!(e.find_chain_cause::&lt;Func2Error&gt;().is_some());
# //!
# //! if let Some(e) = e.find_chain_cause::&lt;Func2Error&gt;() {
# //! eprintln!(&quot;\nError reported by Func2Error: {}&quot;, e)
# //! }
# //!
# //!
# //! assert!(e.root_cause().is_some());
# //!
# //! if let Some(e) = e.root_cause() {
# //! let ioerror = e.downcast_ref::&lt;io::Error&gt;().unwrap();
# //! eprintln!(&quot;\nThe root cause was: std::io::Error: {:#?}&quot;, ioerror);
# //! }
# //!
# //! #[cfg(not(windows))]
# //! assert_eq!(
# //! format!(&quot;\n{:?}\n&quot;, e), r#&quot;
# //! 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)
# //! &quot;#
# //! );
# //! }
# //! # else {
# //! # unreachable!();
# //! # }
# //! }
# //! ~~~
#
# use std::any::TypeId;
# use std::error::Error;
# use std::fmt::{Debug, Display, Formatter, Result};
#
# /// chains an inner error kind `T` with a causing error
# pub struct ChainError&lt;T&gt; {
# #[cfg(not(feature = &quot;no-fileline&quot;))]
# occurrence: Option&lt;(u32, &amp;'static str)&gt;,
# kind: T,
# error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
# }
#
# /// convenience type alias
# pub type ChainResult&lt;O, E&gt; = std::result::Result&lt;O, ChainError&lt;E&gt;&gt;;
#
# impl&lt;T: 'static + Display + Debug&gt; ChainError&lt;T&gt; {
# #[cfg(not(feature = &quot;no-fileline&quot;))]
# /// Use the `cherr!()` or `mstrerr!()` macro instead of calling this directly
# pub fn new(
# kind: T,
# error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
# occurrence: Option&lt;(u32, &amp;'static str)&gt;,
# ) -&gt; Self {
# Self {
# occurrence,
# kind,
# error_cause,
# }
# }
#
# #[cfg(feature = &quot;no-fileline&quot;)]
# /// Use the `cherr!()` or `mstrerr!()` macro instead of calling this directly
# pub fn new(
# kind: T,
# error_cause: Option&lt;Box&lt;dyn Error + 'static&gt;&gt;,
# _occurrence: Option&lt;(u32, &amp;'static str)&gt;,
# ) -&gt; Self {
# Self { kind, error_cause }
# }
#
# /// return the root cause of the error chain, if any exists
# pub fn root_cause(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
# self.iter().last()
# }
#
# /// 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() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
# /// Err(io::Error::from(io::ErrorKind::NotFound))?;
# /// Ok(())
# /// }
# ///
# /// derive_str_cherr!(Func2Error);
# ///
# /// fn func2() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
# /// let filename = &quot;foo.txt&quot;;
# /// do_some_io().map_err(mstrerr!(Func2Error, &quot;Error reading '{}'&quot;, filename))?;
# /// Ok(())
# /// }
# ///
# /// derive_str_cherr!(Func1Error);
# ///
# /// fn func1() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
# /// func2().map_err(mstrerr!(Func1Error, &quot;func1 error&quot;))?;
# /// Ok(())
# /// }
# ///
# /// fn main() {
# /// if let Err(e) = func1() {
# /// if let Some(f1err) = e.downcast_chain_ref::&lt;Func1Error&gt;() {
# ///
# /// assert!(f1err.find_cause::&lt;io::Error&gt;().is_some());
# ///
# /// assert!(f1err.find_chain_cause::&lt;Func2Error&gt;().is_some());
# /// }
# /// # else {
# /// # panic!();
# /// # }
# /// }
# /// # else {
# /// # unreachable!();
# /// # }
# /// }
# /// ~~~
# pub fn find_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;U&gt; {
# self.iter().filter_map(Error::downcast_ref::&lt;U&gt;).next()
# }
#
# /// Find the first error cause of type `ChainError&lt;U&gt;`, if any exists
# ///
# /// Same as `find_cause`, but hides the `ChainError&lt;U&gt;` implementation internals
# ///
# /// # Examples
# ///
# /// ~~~rust,ignore
# /// // Instead of writing
# /// err.find_cause::&lt;ChainError&lt;FooError&gt;&gt;();
# ///
# /// // leave out the ChainError&lt;FooError&gt; implementation detail
# /// err.find_chain_cause::&lt;FooError&gt;();
# /// ~~~
# pub fn find_chain_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;U&gt;&gt; {
# self.iter()
# .filter_map(Error::downcast_ref::&lt;ChainError&lt;U&gt;&gt;)
# .next()
# }
#
# /// Find the first error cause of type `ChainError&lt;U&gt;` or `U`, if any exists and return `U`
# ///
# /// Same as `find_cause` and `find_chain_cause`, but hides the `ChainError&lt;U&gt;` implementation internals
# ///
# /// # Examples
# ///
# /// ~~~rust,ignore
# /// // Instead of writing
# /// err.find_cause::&lt;ChainError&lt;FooErrorKind&gt;&gt;();
# /// // and/or
# /// err.find_chain_cause::&lt;FooErrorKind&gt;();
# /// // and/or
# /// err.find_cause::&lt;FooErrorKind&gt;();
# ///
# /// // leave out the ChainError&lt;FooErrorKind&gt; implementation detail
# /// err.find_chain_or_kind::&lt;FooErrorKind&gt;();
# /// ~~~
# pub fn find_kind_or_cause&lt;U: Error + 'static&gt;(&amp;self) -&gt; Option&lt;&amp;U&gt; {
# self.iter()
# .filter_map(|e| {
# e.downcast_ref::&lt;ChainError&lt;U&gt;&gt;()
# .map(|e| e.kind())
# .or_else(|| e.downcast_ref::&lt;U&gt;())
# })
# .next()
# }
#
# /// Return a reference to T of `ChainError&lt;T&gt;`
# ///
# /// # Examples
# ///
# /// ~~~rust
# /// # use crate::chainerror::*;
# /// # use std::error::Error;
# /// # use std::io;
# /// # use std::result::Result;
# /// #
# /// fn do_some_io() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
# /// Err(io::Error::from(io::ErrorKind::NotFound))?;
# /// Ok(())
# /// }
# ///
# /// derive_str_cherr!(Func2Error);
# ///
# /// fn func2() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
# /// let filename = &quot;foo.txt&quot;;
# /// do_some_io().map_err(mstrerr!(Func2Error, &quot;Error reading '{}'&quot;, filename))?;
# /// Ok(())
# /// }
# ///
# /// #[derive(Debug)]
# /// enum Func1ErrorKind {
# /// Func2,
# /// IO(String),
# /// }
# ///
# /// /// impl ::std::fmt::Display for Func1ErrorKind {…}
# /// # impl ::std::fmt::Display for Func1ErrorKind {
# /// # fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
# /// # match self {
# /// # Func1ErrorKind::Func2 =&gt; write!(f, &quot;func1 error calling func2&quot;),
# /// # Func1ErrorKind::IO(filename) =&gt; write!(f, &quot;Error reading '{}'&quot;, filename),
# /// # }
# /// # }
# /// # }
# ///
# /// fn func1() -&gt; ChainResult&lt;(), Func1ErrorKind&gt; {
# /// func2().map_err(|e| cherr!(e, Func1ErrorKind::Func2))?;
# /// do_some_io().map_err(|e| cherr!(e, Func1ErrorKind::IO(&quot;bar.txt&quot;.into())))?;
# /// Ok(())
# /// }
# ///
# /// fn main() {
# /// if let Err(e) = func1() {
# /// match e.kind() {
# /// Func1ErrorKind::Func2 =&gt; {},
# /// Func1ErrorKind::IO(filename) =&gt; panic!(),
# /// }
# /// }
# /// # else {
# /// # unreachable!();
# /// # }
# /// }
# /// ~~~
# pub fn kind(&amp;self) -&gt; &amp;T {
# &amp;self.kind
# }
#
# /// Returns an Iterator over all error causes/sources
# ///
# /// # Example
# ///
# ///
# pub fn iter(&amp;self) -&gt; impl Iterator&lt;Item = &amp;(dyn Error + 'static)&gt; {
# ErrorIter {
# current: Some(self),
# }
# }
# }
#
# struct ErrorIter&lt;'a&gt; {
# current: Option&lt;&amp;'a (dyn Error + 'static)&gt;,
# }
#
# impl&lt;'a&gt; Iterator for ErrorIter&lt;'a&gt; {
# type Item = &amp;'a (dyn Error + 'static);
#
# fn next(&amp;mut self) -&gt; Option&lt;Self::Item&gt; {
# let current = self.current;
# self.current = self.current.and_then(Error::source);
# current
# }
# }
#
# impl&lt;T: 'static + Display + Debug&gt; std::ops::Deref for ChainError&lt;T&gt; {
# type Target = T;
#
# fn deref(&amp;self) -&gt; &amp;Self::Target {
# &amp;self.kind
# }
# }
#
# /// Convenience trait to hide the `ChainError&lt;T&gt;` implementation internals
# pub trait ChainErrorDown {
# /// Test if of type `ChainError&lt;T&gt;`
# fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool;
# /// Downcast to a reference of `ChainError&lt;T&gt;`
# fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt;;
# /// Downcast to a mutable reference of `ChainError&lt;T&gt;`
# fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt;;
# }
#
# impl&lt;U: 'static + Display + Debug&gt; ChainErrorDown for ChainError&lt;U&gt; {
# fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
# TypeId::of::&lt;T&gt;() == TypeId::of::&lt;U&gt;()
# }
#
# fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
# if self.is_chain::&lt;T&gt;() {
# #[allow(clippy::cast_ptr_alignment)]
# unsafe {
# Some(&amp;*(self as *const dyn Error as *const &amp;ChainError&lt;T&gt;))
# }
# } else {
# None
# }
# }
#
# fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
# if self.is_chain::&lt;T&gt;() {
# #[allow(clippy::cast_ptr_alignment)]
# unsafe {
# Some(&amp;mut *(self as *mut dyn Error as *mut &amp;mut ChainError&lt;T&gt;))
# }
# } else {
# None
# }
# }
# }
#
# impl ChainErrorDown for dyn Error + 'static {
# fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
# self.is::&lt;ChainError&lt;T&gt;&gt;()
# }
#
# fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
# self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
# }
#
# fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
# self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
# }
# }
#
# impl ChainErrorDown for dyn Error + 'static + Send {
# fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
# self.is::&lt;ChainError&lt;T&gt;&gt;()
# }
#
# fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
# self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
# }
#
# fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
# self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
# }
# }
#
# impl ChainErrorDown for dyn Error + 'static + Send + Sync {
# fn is_chain&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; bool {
# self.is::&lt;ChainError&lt;T&gt;&gt;()
# }
#
# fn downcast_chain_ref&lt;T: 'static + Display + Debug&gt;(&amp;self) -&gt; Option&lt;&amp;ChainError&lt;T&gt;&gt; {
# self.downcast_ref::&lt;ChainError&lt;T&gt;&gt;()
# }
#
# fn downcast_chain_mut&lt;T: 'static + Display + Debug&gt;(&amp;mut self) -&gt; Option&lt;&amp;mut ChainError&lt;T&gt;&gt; {
# self.downcast_mut::&lt;ChainError&lt;T&gt;&gt;()
# }
# }
#
# impl&lt;T: 'static + Display + Debug&gt; Error for ChainError&lt;T&gt; {
# fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
# self.error_cause.as_ref().map(|e| e.as_ref())
# }
# }
#
# impl&lt;T: 'static + Display + Debug&gt; Error for &amp;ChainError&lt;T&gt; {
# fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
# self.error_cause.as_ref().map(|e| e.as_ref())
# }
# }
#
# impl&lt;T: 'static + Display + Debug&gt; Error for &amp;mut ChainError&lt;T&gt; {
# fn source(&amp;self) -&gt; Option&lt;&amp;(dyn Error + 'static)&gt; {
# self.error_cause.as_ref().map(|e| e.as_ref())
# }
# }
#
# impl&lt;T: 'static + Display + Debug&gt; Display for ChainError&lt;T&gt; {
# fn fmt(&amp;self, f: &amp;mut Formatter) -&gt; Result {
# write!(f, &quot;{}&quot;, self.kind)?;
#
# #[cfg(feature = &quot;display-cause&quot;)]
# {
# if let Some(e) = self.source() {
# writeln!(f, &quot;\nCaused by:&quot;)?;
# Display::fmt(&amp;e, f)?;
# }
# }
# Ok(())
# }
# }
#
# impl&lt;T: 'static + Display + Debug&gt; Debug for ChainError&lt;T&gt; {
# fn fmt(&amp;self, f: &amp;mut Formatter) -&gt; Result {
# #[cfg(not(feature = &quot;no-fileline&quot;))]
# {
# if let Some(o) = self.occurrence {
# write!(f, &quot;{}:{}: &quot;, o.1, o.0)?;
# }
# }
#
# if self.is_chain::&lt;String&gt;() {
# Display::fmt(&amp;self.kind, f)?;
# } else {
# Debug::fmt(&amp;self.kind, f)?;
# }
#
# #[cfg(not(feature = &quot;no-debug-cause&quot;))]
# {
# if let Some(e) = self.source() {
# writeln!(f, &quot;\nCaused by:&quot;)?;
# Debug::fmt(&amp;e, f)?;
# }
# }
# Ok(())
# }
# }
#
# pub trait ChainErrorFrom&lt;T&gt;: Sized {
# fn chain_error_from(_: T, line_filename: Option&lt;(u32, &amp;'static str)&gt;) -&gt; ChainError&lt;Self&gt;;
# }
#
# pub trait IntoChainError&lt;T&gt;: Sized {
# fn into_chain_error(self, line_filename: Option&lt;(u32, &amp;'static str)&gt;) -&gt; ChainError&lt;T&gt;;
# }
#
# impl&lt;T, U&gt; IntoChainError&lt;U&gt; for T
# where
# U: ChainErrorFrom&lt;T&gt;,
# {
# fn into_chain_error(self, line_filename: Option&lt;(u32, &amp;'static str)&gt;) -&gt; ChainError&lt;U&gt; {
# U::chain_error_from(self, line_filename)
# }
# }
#
# impl&lt;T, U&gt; ChainErrorFrom&lt;T&gt; for U
# where
# T: Into&lt;U&gt;,
# U: 'static + Display + Debug,
# {
# fn chain_error_from(t: T, line_filename: Option&lt;(u32, &amp;'static str)&gt;) -&gt; ChainError&lt;Self&gt; {
# let e: U = t.into();
# ChainError::&lt;_&gt;::new(e, None, line_filename)
# }
# }
#
# #[macro_export]
# macro_rules! minto_cherr {
# ( ) =&gt; {
# |e| e.into_chain_error(Some((line!(), file!())))
# };
# }
#
# #[macro_export]
# macro_rules! into_cherr {
# ( $t:expr ) =&gt; {
# $t.into_chain_error(Some((line!(), file!())))
# };
# }
#
# /// Creates a new `ChainError&lt;T&gt;`
# ///
# /// # Examples
# ///
# /// Create a new ChainError&lt;FooError&gt;, where `FooError` must implement `Display` and `Debug`.
# /// ~~~rust
# /// # use chainerror::*;
# /// #
# /// # #[derive(Debug)]
# /// enum FooError {
# /// Bar,
# /// Baz(&amp;'static str),
# /// }
# /// #
# /// # impl ::std::fmt::Display for FooError {
# /// # fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
# /// # match self {
# /// # FooError::Bar =&gt; write!(f, &quot;Bar Error&quot;),
# /// # FooError::Baz(s) =&gt; write!(f, &quot;Baz Error: '{}'&quot;, s),
# /// # }
# /// # }
# /// # }
# ///
# /// // impl ::std::fmt::Display for FooError
# ///
# /// fn do_some_stuff() -&gt; bool {
# /// false
# /// }
# ///
# /// fn func() -&gt; ChainResult&lt;(), FooError&gt; {
# /// if ! do_some_stuff() {
# /// Err(cherr!(FooError::Baz(&quot;Error&quot;)))?;
# /// }
# /// Ok(())
# /// }
# /// #
# /// # pub fn main() {
# /// # match func().unwrap_err().kind() {
# /// # FooError::Baz(s) if s == &amp;&quot;Error&quot; =&gt; {},
# /// # _ =&gt; panic!(),
# /// # }
# /// # }
# /// ~~~
# ///
# /// Additionally an error cause can be added.
# ///
# /// ~~~rust
# /// # use chainerror::*;
# /// # use std::io;
# /// # use std::error::Error;
# /// #
# /// # #[derive(Debug)]
# /// # enum FooError {
# /// # Bar,
# /// # Baz(&amp;'static str),
# /// # }
# /// #
# /// # impl ::std::fmt::Display for FooError {
# /// # fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
# /// # match self {
# /// # FooError::Bar =&gt; write!(f, &quot;Bar Error&quot;),
# /// # FooError::Baz(s) =&gt; write!(f, &quot;Baz Error: '{}'&quot;, s),
# /// # }
# /// # }
# /// # }
# /// #
# /// fn do_some_stuff() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
# /// Err(io::Error::from(io::ErrorKind::NotFound))?;
# /// Ok(())
# /// }
# ///
# /// fn func() -&gt; ChainResult&lt;(), FooError&gt; {
# /// do_some_stuff().map_err(
# /// |e| cherr!(e, FooError::Baz(&quot;Error&quot;))
# /// )?;
# /// Ok(())
# /// }
# /// #
# /// # pub fn main() {
# /// # match func().unwrap_err().kind() {
# /// # FooError::Baz(s) if s == &amp;&quot;Error&quot; =&gt; {},
# /// # _ =&gt; panic!(),
# /// # }
# /// # }
# /// ~~~
# #[macro_export]
# macro_rules! cherr {
# ( $k:expr ) =&gt; ({
# ChainError::&lt;_&gt;::new($k, None, Some((line!(), file!())))
# });
# ( None, $k:expr ) =&gt; ({
# ChainError::&lt;_&gt;::new($k, None, Some((line!(), file!())))
# });
# ( None, $fmt:expr, $($arg:tt)+ ) =&gt; ({
# cherr!(None, format!($fmt, $($arg)+ ))
# });
# ( None, $fmt:expr, $($arg:tt)+ ) =&gt; ({
# cherr!(None, format!($fmt, $($arg)+ ))
# });
# ( $e:path, $k:expr ) =&gt; ({
# ChainError::&lt;_&gt;::new($k, Some(Box::from($e)), Some((line!(), file!())))
# });
# ( $e:path, $fmt:expr, $($arg:tt)+ ) =&gt; ({
# cherr!($e, format!($fmt, $($arg)+ ))
# });
#
# }
#
# /// 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() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
# /// # Err(io::Error::from(io::ErrorKind::NotFound))?;
# /// # Ok(())
# /// # }
# /// #
# /// fn func2() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
# /// let filename = &quot;foo.txt&quot;;
# /// do_some_io().map_err(mstrerr!(&quot;Error reading '{}'&quot;, filename))?;
# /// Ok(())
# /// }
# ///
# /// fn func1() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
# /// func2().map_err(mstrerr!(&quot;func1 error&quot;))?;
# /// Ok(())
# /// }
# ///
# /// # fn main() {
# /// # if let Err(e) = func1() {
# /// # #[cfg(not(windows))]
# /// # assert_eq!(
# /// # format!(&quot;\n{:?}\n&quot;, e), r#&quot;
# /// # src/lib.rs:20: func1 error
# /// # Caused by:
# /// # src/lib.rs:15: Error reading 'foo.txt'
# /// # Caused by:
# /// # Kind(NotFound)
# /// # &quot;#
# /// # );
# /// # } else {
# /// # unreachable!();
# /// # }
# /// # }
# /// ~~~
# ///
# /// `mstrerr!()` can also be used to map a new `ChainError&lt;T&gt;`, 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() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
# /// # Err(io::Error::from(io::ErrorKind::NotFound))?;
# /// # Ok(())
# /// # }
# /// #
# /// derive_str_cherr!(Func2Error);
# ///
# /// fn func2() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
# /// let filename = &quot;foo.txt&quot;;
# /// do_some_io().map_err(mstrerr!(Func2Error, &quot;Error reading '{}'&quot;, filename))?;
# /// Ok(())
# /// }
# ///
# /// derive_str_cherr!(Func1Error);
# ///
# /// fn func1() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
# /// func2().map_err(mstrerr!(Func1Error, &quot;func1 error&quot;))?;
# /// Ok(())
# /// }
# /// #
# /// # fn main() {
# /// # if let Err(e) = func1() {
# /// # if let Some(f1err) = e.downcast_chain_ref::&lt;Func1Error&gt;() {
# /// # assert!(f1err.find_cause::&lt;ChainError&lt;Func2Error&gt;&gt;().is_some());
# /// # assert!(f1err.find_chain_cause::&lt;Func2Error&gt;().is_some());
# /// # } else {
# /// # panic!();
# /// # }
# /// # } else {
# /// # unreachable!();
# /// # }
# /// # }
# /// ~~~
# #[macro_export]
# macro_rules! mstrerr {
# ( $t:path, $msg:expr ) =&gt; ({
# |e| cherr!(e, $t ($msg.to_string()))
# });
# ( $t:path, $msg:expr, ) =&gt; ({
# |e| cherr!(e, $t ($msg.to_string()))
# });
# ( $t:path, $fmt:expr, $($arg:tt)+ ) =&gt; ({
# |e| cherr!(e, $t (format!($fmt, $($arg)+ )))
# });
# ($msg:expr) =&gt; ({
# |e| cherr!(e, $msg.to_string())
# });
# ($msg:expr, ) =&gt; ({
# |e| cherr!(e, $msg.to_string())
# });
# ($fmt:expr, $($arg:tt)+) =&gt; ({
# |e| cherr!(e, format!($fmt, $($arg)+ ))
# });
# }
#
# /// Convenience macro for `cherr!(T(format!(…)))` where `T(String)`
# ///
# /// # Examples
# ///
# /// ~~~rust
# /// # use crate::chainerror::*;
# /// # use std::error::Error;
# /// # use std::result::Result;
# /// #
# /// derive_str_cherr!(Func2Error);
# ///
# /// fn func2() -&gt; ChainResult&lt;(), Func2Error&gt; {
# /// let filename = &quot;foo.txt&quot;;
# /// Err(strerr!(Func2Error, &quot;Error reading '{}'&quot;, filename))
# /// }
# ///
# /// derive_str_cherr!(Func1Error);
# ///
# /// fn func1() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
# /// func2().map_err(mstrerr!(Func1Error, &quot;func1 error&quot;))?;
# /// Ok(())
# /// }
# /// #
# /// # fn main() {
# /// # if let Err(e) = func1() {
# /// # if let Some(f1err) = e.downcast_chain_ref::&lt;Func1Error&gt;() {
# /// # assert!(f1err.find_cause::&lt;ChainError&lt;Func2Error&gt;&gt;().is_some());
# /// # assert!(f1err.find_chain_cause::&lt;Func2Error&gt;().is_some());
# /// # } else {
# /// # panic!();
# /// # }
# /// # } else {
# /// # unreachable!();
# /// # }
# /// # }
# /// ~~~
# #[macro_export]
# macro_rules! strerr {
# ( $t:path, $msg:expr ) =&gt; ({
# cherr!($t ($msg.to_string()))
# });
# ( $t:path, $msg:expr, ) =&gt; ({
# cherr!($t ($msg.to_string()))
# });
# ( $t:path, $fmt:expr, $($arg:tt)+ ) =&gt; ({
# cherr!($t (format!($fmt, $($arg)+ )))
# });
# ($msg:expr) =&gt; ({
# cherr!($msg.to_string())
# });
# ($msg:expr, ) =&gt; ({
# cherr!($msg.to_string())
# });
# ($fmt:expr, $($arg:tt)+) =&gt; ({
# cherr!(format!($fmt, $($arg)+ ))
# });
# }
#
# /// Convenience macro to create a &quot;new type&quot; T(String) and implement Display + Debug for T
# ///
# /// # Examples
# ///
# /// ~~~rust
# /// # use crate::chainerror::*;
# /// # use std::error::Error;
# /// # use std::io;
# /// # use std::result::Result;
# /// #
# /// # fn do_some_io() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
# /// # Err(io::Error::from(io::ErrorKind::NotFound))?;
# /// # Ok(())
# /// # }
# /// #
# /// derive_str_cherr!(Func2Error);
# ///
# /// fn func2() -&gt; ChainResult&lt;(), Func2Error&gt; {
# /// let filename = &quot;foo.txt&quot;;
# /// do_some_io().map_err(mstrerr!(Func2Error, &quot;Error reading '{}'&quot;, filename))?;
# /// Ok(())
# /// }
# ///
# /// derive_str_cherr!(Func1Error);
# ///
# /// fn func1() -&gt; Result&lt;(), Box&lt;Error&gt;&gt; {
# /// func2().map_err(mstrerr!(Func1Error, &quot;func1 error&quot;))?;
# /// Ok(())
# /// }
# /// #
# /// # fn main() {
# /// # if let Err(e) = func1() {
# /// # if let Some(f1err) = e.downcast_chain_ref::&lt;Func1Error&gt;() {
# /// # assert!(f1err.find_cause::&lt;ChainError&lt;Func2Error&gt;&gt;().is_some());
# /// # assert!(f1err.find_chain_cause::&lt;Func2Error&gt;().is_some());
# /// # } else {
# /// # panic!();
# /// # }
# /// # } else {
# /// # unreachable!();
# /// # }
# /// # }
# /// ~~~
# #[macro_export]
# macro_rules! derive_str_cherr {
# ($e:ident) =&gt; {
# pub struct $e(pub String);
# impl ::std::fmt::Display for $e {
# fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
# write!(f, &quot;{}&quot;, self.0)
# }
# }
# impl ::std::fmt::Debug for $e {
# fn fmt(&amp;self, f: &amp;mut ::std::fmt::Formatter) -&gt; ::std::fmt::Result {
# write!(f, &quot;{}({})&quot;, stringify!($e), self.0)
# }
# }
# impl ::std::error::Error for $e {}
# };
# }
# }
</code></pre></pre>
</main>
<nav class="nav-wrapper" aria-label="Page navigation">
<!-- Mobile navigation buttons -->
<a rel="prev" href="tutorial7.html" class="mobile-nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
<i class="fa fa-angle-left"></i>
</a>
<a rel="next" href="tutorial9.html" class="mobile-nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
<i class="fa fa-angle-right"></i>
</a>
<div style="clear: both"></div>
</nav>
</div>
</div>
<nav class="nav-wide-wrapper" aria-label="Page navigation">
<a href="tutorial7.html" class="nav-chapters previous" title="Previous chapter" aria-label="Previous chapter" aria-keyshortcuts="Left">
<i class="fa fa-angle-left"></i>
</a>
<a href="tutorial9.html" class="nav-chapters next" title="Next chapter" aria-label="Next chapter" aria-keyshortcuts="Right">
<i class="fa fa-angle-right"></i>
</a>
</nav>
</div>
<script src="elasticlunr.min.js" type="text/javascript" charset="utf-8"></script>
<script src="mark.min.js" type="text/javascript" charset="utf-8"></script>
<script src="searcher.js" type="text/javascript" charset="utf-8"></script>
<script src="clipboard.min.js" type="text/javascript" charset="utf-8"></script>
<script src="highlight.js" type="text/javascript" charset="utf-8"></script>
<script src="book.js" type="text/javascript" charset="utf-8"></script>
<!-- Custom JS scripts -->
</body>
</html>
Reference in a new issue View git blame Copy permalink