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<ol class="chapter"><li class="expanded affix "><a href="index.html" class="active">chainerror</a></li><li class="expanded "><a href="tutorial1.html"><strong aria-hidden="true">1.</strong> Simple String Errors</a></li><li class="expanded "><a href="tutorial2.html"><strong aria-hidden="true">2.</strong> Simple Chained String Errors</a></li><li class="expanded "><a href="tutorial3.html"><strong aria-hidden="true">3.</strong> Mapping Errors</a></li><li class="expanded "><a href="tutorial4.html"><strong aria-hidden="true">4.</strong> Saving coding chars</a></li><li class="expanded "><a href="tutorial5.html"><strong aria-hidden="true">5.</strong> The source() of Errors</a></li><li class="expanded "><a href="tutorial6.html"><strong aria-hidden="true">6.</strong> Downcast the Errors</a></li><li class="expanded "><a href="tutorial7.html"><strong aria-hidden="true">7.</strong> The root cause of all Errors</a></li><li class="expanded "><a href="tutorial8.html"><strong aria-hidden="true">8.</strong> Finding an Error cause</a></li><li class="expanded "><a href="tutorial9.html"><strong aria-hidden="true">9.</strong> Selective Error Handling</a></li><li class="expanded "><a href="tutorial10.html"><strong aria-hidden="true">10.</strong> ErrorKind to the rescue</a></li><li class="expanded "><a href="tutorial11.html"><strong aria-hidden="true">11.</strong> Debug for the ErrorKind</a></li><li class="expanded "><a href="tutorial12.html"><strong aria-hidden="true">12.</strong> Deref for the ErrorKind</a></li><li class="expanded "><a href="tutorial13.html"><strong aria-hidden="true">13.</strong> Writing a library</a></li><li class="expanded "><a href="tutorial14.html"><strong aria-hidden="true">14.</strong> Going back to std</a></li><li class="expanded affix "><a href="end.html">The End</a></li></ol>
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<ol class="chapter"><li class="chapter-item expanded affix "><a href="index.html" class="active">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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<h1 class="menu-title">chainerror</h1>
<h1 class="menu-title">chainerror</h1>
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<div id="content" class="content">
<main>
<h1><a class="header" href="#chainerror" id="chainerror">chainerror</a></h1>
<p><a href="https://travis-ci.org/haraldh/chainerror"><img src="https://travis-ci.org/haraldh/chainerror.svg?branch=master" alt="Build Status" /></a>
<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></p>
<p><code>chainerror</code> provides an error backtrace like <code>failure</code> without doing a real backtrace, so even after you <code>strip</code> your
<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>
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<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>
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<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><code>chainerror</code> has no dependencies!</p>
<p><code>chainerror</code> uses <code>.source()</code> of <code>std::error::Error</code> along with <code>line()!</code> and <code>file()!</code> to provide a nice debug error backtrace.
<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&lt;T&gt;</code> struct, <code>chainerror</code> comes with some useful helper macros to save a lot of typing.</p>
<p>Debug information is worth it!</p>
<p>Now continue reading the
<a href="https://haraldh.github.io/chainerror/tutorial1.html">Tutorial</a></p>
<h2><a class="header" href="#example" id="example">Example:</a></h2>
<p>Output:</p>
<pre><code>$ cargo run -q --example example
Main Error Report: func1 error calling func2
Error reported by Func2Error: func2 error: calling func3
The root cause was: std::io::Error: Kind(
NotFound
)
Debug Error:
examples/example.rs:45: func1 error calling func2
<h3><a class="header" href="#features" id="features">Features</a></h3>
<p><code>display-cause</code>
: turn on printing a backtrace of the errors in <code>Display</code></p>
<h2><a class="header" href="#tutorial" id="tutorial">Tutorial</a></h2>
<p>Read the <a href="https://haraldh.github.io/chainerror/tutorial1.html">Tutorial</a></p>
<h2><a class="header" href="#examples" id="examples">Examples</a></h2>
<p>examples/example.rs:</p>
<pre><pre class="playground"><code class="language-rust">// […]
fn main() {
if let Err(e) = func1() {
eprintln!(&quot;\nDebug Error {{:?}}:\n{:?}&quot;, e);
eprintln!(&quot;\nAlternative Debug Error {{:#?}}:\n{:#?}\n&quot;, e);
// […]
}
}
</code></pre></pre>
<pre><code class="language-console">$ cargo run -q --example example
Debug Error {:?}:
examples/example.rs:46:13: func1 error calling func2
Caused by:
examples/example.rs:20: Func2Error(func2 error: calling func3)
examples/example.rs:21:13: Func2Error(func2 error: calling func3)
Caused by:
examples/example.rs:13: Error reading 'foo.txt'
examples/example.rs:14:18: Error reading 'foo.txt'
Caused by:
Kind(NotFound)
Alternative Debug Error {:#?}:
ChainError&lt;example::Func1Error&gt; {
occurrence: Some(
&quot;examples/example.rs:46:13&quot;,
),
kind: func1 error calling func2,
source: Some(
ChainError&lt;example::Func2Error&gt; {
occurrence: Some(
&quot;examples/example.rs:21:13&quot;,
),
kind: Func2Error(func2 error: calling func3),
source: Some(
ChainError&lt;alloc::string::String&gt; {
occurrence: Some(
&quot;examples/example.rs:14:18&quot;,
),
kind: &quot;Error reading \'foo.txt\'&quot;,
source: Some(
Kind(
NotFound,
),
),
},
),
},
),
}
</code></pre>
<pre><code class="language-rust ignore">use chainerror::*;
<pre><pre class="playground"><code class="language-rust">
<span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>use chainerror::prelude::v1::*;
use std::error::Error;
use std::io;
use std::result::Result;
fn do_some_io() -&gt; Result&lt;(), Box&lt;Error + Send + Sync&gt;&gt; {
fn do_some_io() -&gt; Result&lt;(), Box&lt;dyn Error + Send + Sync&gt;&gt; {
Err(io::Error::from(io::ErrorKind::NotFound))?;
Ok(())
}
fn func3() -&gt; Result&lt;(), Box&lt;Error + Send + Sync&gt;&gt; {
fn func2() -&gt; Result&lt;(), Box&lt;dyn Error + Send + Sync&gt;&gt; {
let filename = &quot;foo.txt&quot;;
do_some_io().map_err(mstrerr!(&quot;Error reading '{}'&quot;, filename))?;
do_some_io().context(format!(&quot;Error reading '{}'&quot;, filename))?;
Ok(())
}
derive_str_cherr!(Func2Error);
fn func1() -&gt; Result&lt;(), Box&lt;dyn Error + Send + Sync&gt;&gt; {
func2().context(&quot;func1 error&quot;)?;
Ok(())
}
if let Err(e) = func1() {
#[cfg(not(windows))]
assert_eq!(
format!(&quot;\n{:?}\n&quot;, e),
r#&quot;
src/lib.rs:21:13: func1 error
Caused by:
src/lib.rs:16:18: Error reading 'foo.txt'
Caused by:
Kind(NotFound)
&quot;#
);
}
<span class="boring">}
</span></code></pre></pre>
<pre><pre class="playground"><code class="language-rust">
<span class="boring">#![allow(unused)]
</span><span class="boring">fn main() {
</span>use chainerror::prelude::v1::*;
use std::error::Error;
use std::io;
use std::result::Result;
fn do_some_io() -&gt; Result&lt;(), Box&lt;dyn Error + Send + Sync&gt;&gt; {
Err(io::Error::from(io::ErrorKind::NotFound))?;
Ok(())
}
fn func3() -&gt; Result&lt;(), Box&lt;dyn Error + Send + Sync&gt;&gt; {
let filename = &quot;foo.txt&quot;;
do_some_io().context(format!(&quot;Error reading '{}'&quot;, filename))?;
Ok(())
}
derive_str_context!(Func2Error);
fn func2() -&gt; ChainResult&lt;(), Func2Error&gt; {
func3().map_err(mstrerr!(Func2Error, &quot;func2 error: calling func3&quot;))?;
func3().context(Func2Error(&quot;func2 error: calling func3&quot;.into()))?;
Ok(())
}
@ -225,42 +315,65 @@ impl ::std::fmt::Debug for Func1Error {
}
fn func1() -&gt; ChainResult&lt;(), Func1Error&gt; {
func2().map_err(|e| cherr!(e, Func1Error::Func2))?;
func2().context(Func1Error::Func2)?;
let filename = String::from(&quot;bar.txt&quot;);
do_some_io().map_err(|e| cherr!(e, Func1Error::IO(filename)))?;
do_some_io().context(Func1Error::IO(filename))?;
Ok(())
}
fn main() {
if let Err(e) = func1() {
match e.kind() {
Func1Error::Func2 =&gt; eprintln!(&quot;Main Error Report: func1 error calling func2&quot;),
Func1Error::IO(filename) =&gt; {
eprintln!(&quot;Main Error Report: func1 error reading '{}'&quot;, filename)
}
if let Err(e) = func1() {
assert!(match e.kind() {
Func1Error::Func2 =&gt; {
eprintln!(&quot;Main Error Report: func1 error calling func2&quot;);
true
}
if let Some(e) = e.find_chain_cause::&lt;Func2Error&gt;() {
eprintln!(&quot;\nError reported by Func2Error: {}&quot;, e)
Func1Error::IO(filename) =&gt; {
eprintln!(&quot;Main Error Report: func1 error reading '{}'&quot;, filename);
false
}
});
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);
}
assert!(e.find_chain_cause::&lt;Func2Error&gt;().is_some());
eprintln!(&quot;\nDebug Error:\n{:?}&quot;, e);
if let Some(e) = e.find_chain_cause::&lt;Func2Error&gt;() {
eprintln!(&quot;\nError reported by Func2Error: {}&quot;, e)
}
}
</code></pre>
<h2><a class="header" href="#features" id="features">Features</a></h2>
<p><code>no-fileline</code>
: completely turn off storing filename and line</p>
<p><code>display-cause</code>
: turn on printing a backtrace of the errors in <code>Display</code></p>
<p><code>no-debug-cause</code>
: turn off printing a backtrace of the errors in <code>Debug</code></p>
assert!(e.root_cause().is_some());
if let Some(e) = e.root_cause() {
let io_error = e.downcast_ref::&lt;io::Error&gt;().unwrap();
eprintln!(&quot;\nThe root cause was: std::io::Error: {:#?}&quot;, io_error);
}
#[cfg(not(windows))]
assert_eq!(
format!(&quot;\n{:?}\n&quot;, e),
r#&quot;
src/lib.rs:48:13: func1 error calling func2
Caused by:
src/lib.rs:23:13: Func2Error(func2 error: calling func3)
Caused by:
src/lib.rs:16:18: Error reading 'foo.txt'
Caused by:
Kind(NotFound)
&quot;#
);
}
<span class="boring">}
</span></code></pre></pre>
<h2><a class="header" href="#license" id="license">License</a></h2>
<p>Licensed under either of</p>
<ul>
<li>Apache License, Version 2.0, (<a href="LICENSE-APACHE">LICENSE-APACHE</a> or https://www.apache.org/licenses/LICENSE-2.0)</li>
<li>MIT license (<a href="LICENSE-MIT">LICENSE-MIT</a> or https://opensource.org/licenses/MIT)</li>
</ul>
<p>at your option.</p>
<h3><a class="header" href="#contribution" id="contribution">Contribution</a></h3>
<p>Unless you explicitly state otherwise, any contribution intentionally
submitted for inclusion in the work by you, as defined in the Apache-2.0
license, shall be dual licensed as above, without any additional terms or
conditions.</p>
</main>
@ -283,7 +396,7 @@ fn main() {
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