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<!DOCTYPE html><html lang="en"><head><meta charset="utf-8"><meta name="viewport" content="width=device-width, initial-scale=1.0"><meta name="generator" content="rustdoc"><meta name="description" content="Install the provided error hook for constructing EyreHandlers when converting Errors to Reports"><title>set_hook in eyre - Rust</title><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceSerif4-Regular-46f98efaafac5295.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><link rel="preload" as="font" type="font/woff2" crossorigin href="../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2"><link rel="stylesheet" href="../static.files/normalize-76eba96aa4d2e634.css"><link rel="stylesheet" href="../static.files/rustdoc-ac92e1bbe349e143.css"><meta name="rustdoc-vars" data-root-path="../" data-static-root-path="../static.files/" data-current-crate="eyre" data-themes="" data-resource-suffix="" data-rustdoc-version="1.76.0 (07dca489a 2024-02-04)" data-channel="1.76.0" data-search-js="search-2b6ce74ff89ae146.js" data-settings-js="settings-4313503d2e1961c2.js" ><script src="../static.files/storage-f2adc0d6ca4d09fb.js"></script><script defer src="sidebar-items.js"></script><script defer src="../static.files/main-305769736d49e732.js"></script><noscript><link rel="stylesheet" href="../static.files/noscript-feafe1bb7466e4bd.css"></noscript><link rel="alternate icon" type="image/png" href="../static.files/favicon-16x16-8b506e7a72182f1c.png"><link rel="alternate icon" type="image/png" href="../static.files/favicon-32x32-422f7d1d52889060.png"><link rel="icon" type="image/svg+xml" href="../static.files/favicon-2c020d218678b618.svg"></head><body class="rustdoc fn"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><nav class="mobile-topbar"><button class="sidebar-menu-toggle">☰</button></nav><nav class="sidebar"><div class="sidebar-crate"><h2><a href="../eyre/index.html">eyre</a><span class="version">0.6.12</span></h2></div><div class="sidebar-elems"></div></nav><div class="sidebar-resizer"></div>
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<main><div class="width-limiter"><nav class="sub"><form class="search-form"><span></span><div id="sidebar-button" tabindex="-1"><a href="../eyre/all.html" title="show sidebar"></a></div><input class="search-input" name="search" aria-label="Run search in the documentation" autocomplete="off" spellcheck="false" placeholder="Click or press ‘S’ to search, ‘?’ for more options…" type="search"><div id="help-button" tabindex="-1"><a href="../help.html" title="help">?</a></div><div id="settings-menu" tabindex="-1"><a href="../settings.html" title="settings"><img width="22" height="22" alt="Change settings" src="../static.files/wheel-7b819b6101059cd0.svg"></a></div></form></nav><section id="main-content" class="content"><div class="main-heading"><h1>Function <a href="index.html">eyre</a>::<wbr><a class="fn" href="#">set_hook</a><button id="copy-path" title="Copy item path to clipboard"><img src="../static.files/clipboard-7571035ce49a181d.svg" width="19" height="18" alt="Copy item path"></button></h1><span class="out-of-band"><a class="src" href="../src/eyre/lib.rs.html#583-585">source</a> · <button id="toggle-all-docs" title="collapse all docs">[<span>−</span>]</button></span></div><pre class="rust item-decl"><code>pub fn set_hook(
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hook: <a class="struct" href="https://doc.rust-lang.org/1.76.0/alloc/boxed/struct.Box.html" title="struct alloc::boxed::Box">Box</a><dyn <a class="trait" href="https://doc.rust-lang.org/1.76.0/core/ops/function/trait.Fn.html" title="trait core::ops::function::Fn">Fn</a>(&(dyn <a class="trait" href="https://doc.rust-lang.org/1.76.0/core/error/trait.Error.html" title="trait core::error::Error">StdError</a> + 'static)) -> <a class="struct" href="https://doc.rust-lang.org/1.76.0/alloc/boxed/struct.Box.html" title="struct alloc::boxed::Box">Box</a><dyn <a class="trait" href="trait.EyreHandler.html" title="trait eyre::EyreHandler">EyreHandler</a>> + <a class="trait" href="https://doc.rust-lang.org/1.76.0/core/marker/trait.Sync.html" title="trait core::marker::Sync">Sync</a> + <a class="trait" href="https://doc.rust-lang.org/1.76.0/core/marker/trait.Send.html" title="trait core::marker::Send">Send</a> + 'static>
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) -> <a class="type" href="type.Result.html" title="type eyre::Result">Result</a><<a class="primitive" href="https://doc.rust-lang.org/1.76.0/std/primitive.unit.html">()</a>, <a class="struct" href="struct.InstallError.html" title="struct eyre::InstallError">InstallError</a>></code></pre><details class="toggle top-doc" open><summary class="hideme"><span>Expand description</span></summary><div class="docblock"><p>Install the provided error hook for constructing EyreHandlers when converting
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Errors to Reports</p>
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<h2 id="details"><a href="#details">Details</a></h2>
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<p>To customize the format and content of error reports from <code>eyre</code> you must
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first define a new <code>EyreHandler</code> type to capture and store the extra context
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and to define the format of how to display the chain of errors and this
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stored context. Once this type has been defined you must also define a global
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hook used to construct these handlers whenever <code>Report</code>s are constructed.</p>
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<h2 id="examples"><a href="#examples">Examples</a></h2>
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<div class="example-wrap should_panic"><a href="#" class="tooltip" title="This example panics">ⓘ</a><pre class="rust rust-example-rendered"><code><span class="kw">use </span>backtrace::Backtrace;
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<span class="kw">use </span>eyre::EyreHandler;
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<span class="kw">use </span>std::error::Error;
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<span class="kw">use </span>std::{fmt, iter};
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<span class="kw">fn </span>main() -> eyre::Result<()> {
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<span class="comment">// Install our custom eyre report hook for constructing our custom Handlers
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</span>install().unwrap();
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<span class="comment">// construct a report with, hopefully, our custom handler!
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</span><span class="kw">let </span><span class="kw-2">mut </span>report = <span class="macro">eyre::eyre!</span>(<span class="string">"hello from custom error town!"</span>);
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<span class="comment">// manually set the custom msg for this report after it has been constructed
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</span><span class="kw">if let </span><span class="prelude-val">Some</span>(handler) = report.handler_mut().downcast_mut::<Handler>() {
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handler.custom_msg = <span class="prelude-val">Some</span>(<span class="string">"you're the best users, you know that right???"</span>);
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}
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<span class="comment">// print that shit!!
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</span><span class="prelude-val">Err</span>(report)
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}
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<span class="comment">// define a handler that captures backtraces unless told not to
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</span><span class="kw">fn </span>install() -> <span class="prelude-ty">Result</span><(), <span class="kw">impl </span>Error> {
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<span class="kw">let </span>capture_backtrace = std::env::var(<span class="string">"RUST_BACKWARDS_TRACE"</span>)
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.map(|val| val != <span class="string">"0"</span>)
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.unwrap_or(<span class="bool-val">true</span>);
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<span class="kw">let </span>hook = Hook { capture_backtrace };
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eyre::set_hook(Box::new(<span class="kw">move </span>|e| Box::new(hook.make_handler(e))))
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}
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<span class="kw">struct </span>Hook {
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capture_backtrace: bool,
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}
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<span class="kw">impl </span>Hook {
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<span class="kw">fn </span>make_handler(<span class="kw-2">&</span><span class="self">self</span>, _error: <span class="kw-2">&</span>(<span class="kw">dyn </span>Error + <span class="lifetime">'static</span>)) -> Handler {
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<span class="kw">let </span>backtrace = <span class="kw">if </span><span class="self">self</span>.capture_backtrace {
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<span class="prelude-val">Some</span>(Backtrace::new())
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} <span class="kw">else </span>{
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<span class="prelude-val">None
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</span>};
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Handler {
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backtrace,
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custom_msg: <span class="prelude-val">None</span>,
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}
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}
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}
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<span class="kw">struct </span>Handler {
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<span class="comment">// custom configured backtrace capture
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</span>backtrace: <span class="prelude-ty">Option</span><Backtrace>,
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<span class="comment">// customizable message payload associated with reports
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</span>custom_msg: <span class="prelude-ty">Option</span><<span class="kw-2">&</span><span class="lifetime">'static </span>str>,
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}
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<span class="kw">impl </span>EyreHandler <span class="kw">for </span>Handler {
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<span class="kw">fn </span>debug(<span class="kw-2">&</span><span class="self">self</span>, error: <span class="kw-2">&</span>(<span class="kw">dyn </span>Error + <span class="lifetime">'static</span>), f: <span class="kw-2">&mut </span>fmt::Formatter<<span class="lifetime">'_</span>>) -> fmt::Result {
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<span class="kw">if </span>f.alternate() {
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<span class="kw">return </span>fmt::Debug::fmt(error, f);
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}
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<span class="kw">let </span>errors = iter::successors(<span class="prelude-val">Some</span>(error), |error| (<span class="kw-2">*</span>error).source());
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<span class="kw">for </span>(ind, error) <span class="kw">in </span>errors.enumerate() {
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<span class="macro">write!</span>(f, <span class="string">"\n{:>4}: {}"</span>, ind, error)<span class="question-mark">?</span>;
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}
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<span class="kw">if let </span><span class="prelude-val">Some</span>(backtrace) = <span class="self">self</span>.backtrace.as_ref() {
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<span class="macro">writeln!</span>(f, <span class="string">"\n\nBacktrace:\n{:?}"</span>, backtrace)<span class="question-mark">?</span>;
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}
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<span class="kw">if let </span><span class="prelude-val">Some</span>(msg) = <span class="self">self</span>.custom_msg.as_ref() {
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<span class="macro">writeln!</span>(f, <span class="string">"\n\n{}"</span>, msg)<span class="question-mark">?</span>;
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}
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<span class="prelude-val">Ok</span>(())
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}
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}</code></pre></div>
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</div></details></section></div></main></body></html> |