<!DOCTYPE html><htmllang="en"><head><metacharset="utf-8"><metaname="viewport"content="width=device-width, initial-scale=1.0"><metaname="generator"content="rustdoc"><metaname="description"content="A writer intended to support `libtest`’s output capturing for use in unit tests."><title>TestWriter in tracing_subscriber::fmt - Rust</title><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../static.files/SourceSerif4-Regular-46f98efaafac5295.ttf.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../static.files/FiraSans-Regular-018c141bf0843ffd.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../static.files/FiraSans-Medium-8f9a781e4970d388.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../static.files/SourceCodePro-Regular-562dcc5011b6de7d.ttf.woff2"><linkrel="preload"as="font"type="font/woff2"crossoriginhref="../../static.files/SourceCodePro-Semibold-d899c5a5c4aeb14a.ttf.woff2"><linkrel="stylesheet"href="../../static.files/normalize-76eba96aa4d2e634.css"><linkrel="stylesheet"href="../../static.files/rustdoc-5bc39a1768837dd0.css"><metaname="rustdoc-vars"data-root-path="../../"data-static-root-path="../../static.files/"data-current-crate="tracing_subscriber"data-themes=""data-resource-suffix=""data-rustdoc-version="1.77.2 (25ef9e3d8 2024-04-09)"data-channel="1.77.2"data-search-js="search-dd67cee4cfa65049.js"data-settings-js="settings-4313503d2e1961c2.js"><scriptsrc="../../static.files/storage-4c98445ec4002617.js"></script><scriptdefersrc="sidebar-items.js"></script><scriptdefersrc="../../static.files/main-48f368f3872407c8.js"></script><noscript><linkrel="stylesheet"href="../../static.files/noscript-04d5337699b92874.css"></noscript><linkrel="alternate icon"type="image/png"href="../../static.files/favicon-16x16-8b506e7a72182f1c.png"><linkrel="alternate icon"type="image/png"href="../../static.files/favicon-32x32-422f7d1d52889060.png"><linkrel="icon"type="image/svg+xml"href="../../static.files/favicon-2c020d218678b618.svg"></head><bodyclass="rustdoc struct"><!--[if lte IE 11]><div class="warning">This old browser is unsupported and will most likely display funky things.</div><![endif]--><navclass="mobile-topbar"><buttonclass="sidebar-menu-toggle"title="show sidebar"></button><aclass="logo-container"href="../../tracing_subscriber/index.html"><imgsrc="https://raw.githubusercontent.com/tokio-rs/tracing/master/assets/logo-type.png"alt=""></a></nav><navclass="sidebar"><divclass="sidebar-crate"><aclass="logo-container"href="../../tracing_subscriber/index.html"><imgsrc="https://raw.githubusercontent.com/tokio-rs/tracing/master/assets/logo-type.png"alt="logo"></a><h2><ahref="../../tracing_subscriber/index.html">tracing_subscriber</a><spanclass="version">0.3.18</span></h2></div><h2class="location"><ahref="#">TestWriter</a></h2><divclass="sidebar-elems"><section><h3><ahref="#implementations">Methods</a></h3><ulclass="block method"><li><ahref="#method.new">new</a></li></ul><h3><ahref="#trait-implementations">Trait Implementations</a></h3><ulclass="block trait-implementation"><li><ahref="#impl-Debug-for-TestWriter">Debug</a></li><li><ahref="#impl-Default-for-TestWriter">Default</a></li><li><ahref="#impl-MakeWriter%3C'a%3E-for-TestWriter">MakeWriter<'a></a></li><li><ahref="#impl-Write-for-TestWriter">Write</a></li></ul><h3><ahref="#synthetic-implementations">Auto Trait Implementations</a></h3><ulclass="block synthetic-implementation"><li><ahref="#impl-RefUnwindSafe-for-TestWriter">RefUnwindSafe</a></li><li><ahref="#impl-Send-for-TestWriter">Send</a></li><li><ahref="#impl-Sync-for-TestWriter">Sync</a></li><li><ahref="#impl-Unpin-for-TestWriter">Unpin</a></li><li><ahref="#impl-UnwindSafe-for-TestWriter">UnwindSafe</a></li></ul><h3><ahref="#blanket-implementations">Blanket Implementations</a></h3><ulclass="block blanket-implementation"><li><ahref="#impl-Any-for-T">Any</a></li><li><ahref="#impl-Borrow%3CT%3E-for-T">Borrow<T></a></li><li><ahref="#
<main><divclass="width-limiter"><navclass="sub"><formclass="search-form"><span></span><divid="sidebar-button"tabindex="-1"><ahref="../../tracing_subscriber/all.html"title="show sidebar"></a></div><inputclass="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"><divid="help-button"tabindex="-1"><ahref="../../help.html"title="help">?</a></div><divid="settings-menu"tabindex="-1"><ahref="../../settings.html"title="settings"><imgwidth="22"height="22"alt="Change settings"src="../../static.files/wheel-7b819b6101059cd0.svg"></a></div></form></nav><sectionid="main-content"class="content"><divclass="main-heading"><h1>Struct <ahref="../index.html">tracing_subscriber</a>::<wbr><ahref="index.html">fmt</a>::<wbr><aclass="struct"href="#">TestWriter</a><buttonid="copy-path"title="Copy item path to clipboard"><imgsrc="../../static.files/clipboard-7571035ce49a181d.svg"width="19"height="18"alt="Copy item path"></button></h1><spanclass="out-of-band"><aclass="src"href="../../src/tracing_subscriber/fmt/writer.rs.html#511-513">source</a> · <buttonid="toggle-all-docs"title="collapse all docs">[<span>−</span>]</button></span></div><preclass="rust item-decl"><code>pub struct TestWriter { <spanclass="comment">/* private fields */</span> }</code></pre><detailsclass="toggle top-doc"open><summaryclass="hideme"><span>Expand description</span></summary><divclass="docblock"><p>A writer intended to support <ahref="https://doc.rust-lang.org/book/ch11-02-running-tests.html#showing-function-output"><code>libtest</code>’s output capturing</a> for use in unit tests.</p>
<p><code>TestWriter</code> is used by <ahref="struct.Subscriber.html"title="struct tracing_subscriber::fmt::Subscriber"><code>fmt::Subscriber</code></a> or <ahref="struct.Layer.html"title="struct tracing_subscriber::fmt::Layer"><code>fmt::Layer</code></a> to enable capturing support.</p>
<p><code>cargo test</code> can only capture output from the standard library’s <ahref="https://doc.rust-lang.org/1.77.2/std/macro.print.html"title="macro std::print"><code>print!</code></a> macro. See
<ahref="https://doc.rust-lang.org/book/ch11-02-running-tests.html#showing-function-output"><code>libtest</code>’s output capturing</a> for more details about output capturing.</p>
<p>Writing to <ahref="https://doc.rust-lang.org/1.77.2/std/io/stdio/fn.stdout.html"title="fn std::io::stdio::stdout"><code>io::stdout</code></a> and <ahref="https://doc.rust-lang.org/1.77.2/std/io/stdio/fn.stderr.html"title="fn std::io::stdio::stderr"><code>io::stderr</code></a> produces the same results as using
<ahref="https://doc.rust-lang.org/cargo/commands/cargo-test.html"><code>libtest</code>’s <code>--nocapture</code> option</a> which may make the results look unreadable.</p>
</div></details><h2id="implementations"class="section-header">Implementations<ahref="#implementations"class="anchor">§</a></h2><divid="implementations-list"><detailsclass="toggle implementors-toggle"open><summary><sectionid="impl-TestWriter"class="impl"><aclass="src rightside"href="../../src/tracing_subscriber/fmt/writer.rs.html#703-708">source</a><ahref="#impl-TestWriter"class="anchor">§</a><h3class="code-header">impl <aclass="struct"href="struct.TestWriter.html"title="struct tracing_subscriber::fmt::TestWriter">TestWriter</a></h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.new"class="method"><aclass="src rightside"href="../../src/tracing_subscriber/fmt/writer.rs.html#705-707">source</a><h4class="code-header">pub fn <ahref="#method.new"class="fn">new</a>() -> Self</h4></section></summary><divclass="docblock"><p>Returns a new <code>TestWriter</code> with the default configuration.</p>
</div></details></div></details></div><h2id="trait-implementations"class="section-header">Trait Implementations<ahref="#trait-implementations"class="anchor">§</a></h2><divid="trait-implementations-list"><detailsclass="toggle implementors-toggle"open><summary><sectionid="impl-Debug-for-TestWriter"class="impl"><aclass="src rightside"href="../../src/tracing_subscriber/fmt/writer.rs.html#510">source</a><ahref="#impl-Debug-for-TestWriter"class="anchor">§</a><h3class="code-header">impl <aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/fmt/trait.Debug.html"title="trait core::fmt::Debug">Debug</a> for <aclass="struct"href="struct.TestWriter.html"title="struct tracing_subscriber::fmt::TestWriter">TestWriter</a></h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.fmt"class="method trait-impl"><aclass="src rightside"href="../../src/tracing_subscriber/fmt/writer.rs.html#510">source</a><ahref="#method.fmt"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.77.2/core/fmt/trait.Debug.html#tymethod.fmt"class="fn">fmt</a>(&self, f: &mut <aclass="struct"href="https://doc.rust-lang.org/1.77.2/core/fmt/struct.Formatter.html"title="struct core::fmt::Formatter">Formatter</a><'_>) -><aclass="type"href="https://doc.rust-lang.org/1.77.2/core/fmt/type.Result.html"title="type core::fmt::Result">Result</a></h4></section></summary><divclass='docblock'>Formats the value using the given formatter. <ahref="https://doc.rust-lang.org/1.77.2/core/fmt/trait.Debug.html#tymethod.fmt">Read more</a></div></details></div></details><detailsclass="toggle implementors-toggle"open><summary><sectionid="impl-Default-for-TestWriter"class="impl"><aclass="src rightside"href="../../src/tracing_subscriber/fmt/writer.rs.html#510">source</a><ahref="#impl-Default-for-TestWriter"class="anchor">§</a><h3class="code-header">impl <aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/default/trait.Default.html"title="trait core::default::Default">Default</a> for <aclass="struct"href="struct.TestWriter.html"title="struct tracing_subscriber::fmt::TestWriter">TestWriter</a></h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.default"class="method trait-impl"><aclass="src rightside"href="../../src/tracing_subscriber/fmt/writer.rs.html#510">source</a><ahref="#method.default"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.77.2/core/default/trait.Default.html#tymethod.default"class="fn">default</a>() -><aclass="struct"href="struct.TestWriter.html"title="struct tracing_subscriber::fmt::TestWriter">TestWriter</a><ahref="#"class="tooltip"data-notable-ty="TestWriter">ⓘ</a></h4></section></summary><divclass='docblock'>Returns the “default value” for a type. <ahref="https://doc.rust-lang.org/1.77.2/core/default/trait.Default.html#tymethod.default">Read more</a></div></details></div></details><detailsclass="toggle implementors-toggle"open><summary><sectionid="impl-MakeWriter%3C'a%3E-for-TestWriter"class="impl"><aclass="src rightside"href="../../src/tracing_subscriber/fmt/writer.rs.html#722-728">source</a><ahref="#impl-MakeWriter%3C'a%3E-for-TestWriter"class="anchor">§</a><h3class="code-header">impl<'a><aclass="trait"href="trait.MakeWriter.html"title="trait tracing_subscriber::fmt::MakeWriter">MakeWriter</a><'a> for <aclass="struct"href="struct.TestWriter.html"title="struct tracing_subscriber::fmt::TestWriter">TestWriter</a></h3></section></summary><divclass="impl-items"><detailsclass="toggle"open><summary><sectionid="associatedtype.Writer"class="associatedtype trait-impl"><ahref="#associatedtype.Writer"class="anchor">§</a><h4class="code-header">type <ahref="trait.MakeWriter.html#associatedtype.Writer"class="associatedtype">Writer</a> = <aclass="struct"href="struct.TestWriter.html"title="struct tracing_subscriber::fmt::TestWriter">TestWriter</
by the provided <ahref="../../tracing_core/metadata/struct.Metadata.html"title="struct tracing_core::metadata::Metadata"><code>Metadata</code></a>. <ahref="trait.MakeWriter.html#method.make_writer_for">Read more</a></div></details></div></details><detailsclass="toggle implementors-toggle"open><summary><sectionid="impl-Write-for-TestWriter"class="impl"><aclass="src rightside"href="../../src/tracing_subscriber/fmt/writer.rs.html#710-720">source</a><ahref="#impl-Write-for-TestWriter"class="anchor">§</a><h3class="code-header">impl <aclass="trait"href="https://doc.rust-lang.org/1.77.2/std/io/trait.Write.html"title="trait std::io::Write">Write</a> for <aclass="struct"href="struct.TestWriter.html"title="struct tracing_subscriber::fmt::TestWriter">TestWriter</a></h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.write"class="method trait-impl"><aclass="src rightside"href="../../src/tracing_subscriber/fmt/writer.rs.html#711-715">source</a><ahref="#method.write"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.77.2/std/io/trait.Write.html#tymethod.write"class="fn">write</a>(&mut self, buf: &[<aclass="primitive"href="https://doc.rust-lang.org/1.77.2/std/primitive.u8.html">u8</a>]) -><aclass="type"href="https://doc.rust-lang.org/1.77.2/std/io/error/type.Result.html"title="type std::io::error::Result">Result</a><<aclass="primitive"href="https://doc.rust-lang.org/1.77.2/std/primitive.usize.html">usize</a>></h4></section></summary><divclass='docblock'>Write a buffer into this writer, returning how many bytes were written. <ahref="https://doc.rust-lang.org/1.77.2/std/io/trait.Write.html#tymethod.write">Read more</a></div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.flush"class="method trait-impl"><aclass="src rightside"href="../../src/tracing_subscriber/fmt/writer.rs.html#717-719">source</a><ahref="#method.flush"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.77.2/std/io/trait.Write.html#tymethod.flush"class="fn">flush</a>(&mut self) -><aclass="type"href="https://doc.rust-lang.org/1.77.2/std/io/error/type.Result.html"title="type std::io::error::Result">Result</a><<aclass="primitive"href="https://doc.rust-lang.org/1.77.2/std/primitive.unit.html">()</a>></h4></section></summary><divclass='docblock'>Flush this output stream, ensuring that all intermediately buffered
contents reach their destination. <ahref="https://doc.rust-lang.org/1.77.2/std/io/trait.Write.html#tymethod.flush">Read more</a></div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.write_vectored"class="method trait-impl"><spanclass="rightside"><spanclass="since"title="Stable since Rust version 1.36.0">1.36.0</span> · <aclass="src"href="https://doc.rust-lang.org/1.77.2/src/std/io/mod.rs.html#1627">source</a></span><ahref="#method.write_vectored"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.77.2/std/io/trait.Write.html#method.write_vectored"class="fn">write_vectored</a>(&mut self, bufs: &[<aclass="struct"href="https://doc.rust-lang.org/1.77.2/std/io/struct.IoSlice.html"title="struct std::io::IoSlice">IoSlice</a><'_>]) -><aclass="enum"href="https://doc.rust-lang.org/1.77.2/core/result/enum.Result.html"title="enum core::result::Result">Result</a><<aclass="primitive"href="https://doc.rust-lang.org/1.77.2/std/primitive.usize.html">usize</a>, <aclass="struct"href="https://doc.rust-lang.org/1.77.2/std/io/error/struct.Error.html"title="struct std::io::error::Error">Error</a>></h4></section></summary><divclass='docblock'>Like <ahref="https://doc.rust-lang.org/1.77.2/std/io/trait.Write.html#tymethod.write"title="method std::io::Write::write"><code>write</code></a>, except that it writes from a slice of buffers. <ahref="https://doc.rust-lang.org/1.77.2/std/io/trait.Write.html#method.write_vectored">Read more</a></div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.is_write_vectored"class="method trait-impl"><aclass="src rightside"href="https://doc.rust-lang.org/1.77.2/src/std/io/mod.rs.html#1642">source</a><ahref="#method.is_write_vectored"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.77.2/std/io/trait.Write.html#method.is_write_vectored"class="fn">is_write_vectored</a>(&self) -><aclass="primitive"href="https://doc.rust-lang.org/1.77.2/std/primitive.bool.html">bool</a></h4></section></summary><spanclass="item-info"><divclass="stab unstable"><spanclass="emoji">🔬</span><span>This is a nightly-only experimental API. (<code>can_vector</code> <ahref="https://github.com/tokio-rs/tracing/issues/69941">#69941</a>)</span></div></span><divclass='docblock'>Determines if this <code>Write</code>r has an efficient <ahref="https://doc.rust-lang.org/1.77.2/std/io/trait.Write.html#method.write_vectored"title="method std::io::Write::write_vectored"><code>write_vectored</code></a>
implementation. <ahref="https://doc.rust-lang.org/1.77.2/std/io/trait.Write.html#method.is_write_vectored">Read more</a></div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.write_all"class="method trait-impl"><spanclass="rightside"><spanclass="since"title="Stable since Rust version 1.0.0">1.0.0</span> · <aclass="src"href="https://doc.rust-lang.org/1.77.2/src/std/io/mod.rs.html#1704">source</a></span><ahref="#method.write_all"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.77.2/std/io/trait.Write.html#method.write_all"class="fn">write_all</a>(&mut self, buf: &[<aclass="primitive"href="https://doc.rust-lang.org/1.77.2/std/primitive.u8.html">u8</a>]) -><aclass="enum"href="https://doc.rust-lang.org/1.77.2/core/result/enum.Result.html"title="enum core::result::Result">Result</a><<aclass="primitive"href="https://doc.rust-lang.org/1.77.2/std/primitive.unit.html">()</a>, <aclass="struct"href="https://doc.rust-lang.org/1.77.2/std/io/error/struct.Error.html"title="struct std::io::error::Error">Error</a>></h4></section></summary><divclass='docblock'>Attempts to write an entire buffer into this writer. <ahref="https://doc.rust-lang.org/1.77.2/std/io/trait.Write.html#method.write_all">Read more</a></div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.write_all_vectored"class="method trait-impl"><aclass="src rightside"href="https://doc.rust-lang.org/1.77.2/src/std/io/mod.rs.html#1769">source</a><ahref="#method.write_all_vectored"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.77.2/std/io/trait.Write.html#method.write_all_vectored"class="fn">write_all_vectored</a>(&mut self, bufs: &mut [<aclass="struct"href="https://doc.rust-lang.org/1.77.2/std/io/struct.IoSlice.html"title="struct std::io::IoSlice">IoSlice</a><'_>]) -><aclass="enum"href="https://doc.rust-lang.org/1.77.2/core/result/enum.Result.html"title="enum core::result::Result">Result</a><<aclass="primitive"href="https://doc.rust-lang.org/1.77.2/std/primitive.unit.html">()</a>, <aclass="struct"href="https://doc.rust-lang.org/1.77.2/std/io/error/struct.Error.html"title="struct std::io::error::Error">Error</a>></h4></section></summary><spanclass="item-info"><divclass="stab unstable"><spanclass="emoji">🔬</span><span>This is a nightly-only experimental API. (<code>write_all_vectored</code> <ahref="https://github.com/tokio-rs/tracing/issues/70436">#70436</a>)</span></div></span><divclass='docblock'>Attempts to write multiple buffers into this writer. <ahref="https://doc.rust-lang.org/1.77.2/std/io/trait.Write.html#method.write_all_vectored">Read more</a></div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.write_fmt"class="method trait-impl"><spanclass="rightside"><spanclass="since"title="Stable since Rust version 1.0.0">1.0.0</span> · <aclass="src"href="https://doc.rust-lang.org/1.77.2/src/std/io/mod.rs.html#1825">source</a></span><ahref="#method.write_fmt"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.77.2/std/io/trait.Write.html#method.write_fmt"class="fn">write_fmt</a>(&mut self, fmt: <aclass="struct"href="https://doc.rust-lang.org/1.77.2/core/fmt/struct.Arguments.html"title="struct core::fmt::Arguments">Arguments</a><'_>) -><aclass="enum"href="https://doc.rust-lang.org/1.77.2/core/result/enum.Result.html"title="enum core::result::Result">Result</a><<aclass="primitive"href="https://doc.rust-lang.org/1.77.2/std/primitive.unit.html">()</a>, <aclass="struct"href="https://doc.rust-lang.org/1.77.2/std/io/error/struct.Error.html"title="struct std::io::error::Error">Error</a>></h4></section></summary><divclass='docblock'>Writes a formatted string into this writer, returning any error
encountered. <ahref="https://doc.rust-lang.org/1.77.2/std/io/trait.Write.html#method.write_fmt">Read more</a></div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.by_ref"class="method trait-impl"><spanclass="rightside"><spanclass="since"title="Stable since Rust version 1.0.0">1.0.0</span> · <aclass="src"href="https://doc.rust-lang.org/1.77.2/src/std/io/mod.rs.html#1881-1883">source</a></span><ahref="#method.by_ref"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.77.2/std/io/trait.Write.html#method.by_ref"class="fn">by_ref</a>(&mut self) -><aclass="primitive"href="https://doc.rust-lang.org/1.77.2/std/primitive.reference.html">&mut Self</a><divclass="where">where
Self: <aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/marker/trait.Sized.html"title="trait core::marker::Sized">Sized</a>,</div></h4></section></summary><divclass='docblock'>Creates a “by reference” adapter for this instance of <code>Write</code>. <ahref="https://doc.rust-lang.org/1.77.2/std/io/trait.Write.html#method.by_ref">Read more</a></div></details></div></details></div><h2id="synthetic-implementations"class="section-header">Auto Trait Implementations<ahref="#synthetic-implementations"class="anchor">§</a></h2><divid="synthetic-implementations-list"><sectionid="impl-RefUnwindSafe-for-TestWriter"class="impl"><ahref="#impl-RefUnwindSafe-for-TestWriter"class="anchor">§</a><h3class="code-header">impl <aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/panic/unwind_safe/trait.RefUnwindSafe.html"title="trait core::panic::unwind_safe::RefUnwindSafe">RefUnwindSafe</a> for <aclass="struct"href="struct.TestWriter.html"title="struct tracing_subscriber::fmt::TestWriter">TestWriter</a></h3></section><sectionid="impl-Send-for-TestWriter"class="impl"><ahref="#impl-Send-for-TestWriter"class="anchor">§</a><h3class="code-header">impl <aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/marker/trait.Send.html"title="trait core::marker::Send">Send</a> for <aclass="struct"href="struct.TestWriter.html"title="struct tracing_subscriber::fmt::TestWriter">TestWriter</a></h3></section><sectionid="impl-Sync-for-TestWriter"class="impl"><ahref="#impl-Sync-for-TestWriter"class="anchor">§</a><h3class="code-header">impl <aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/marker/trait.Sync.html"title="trait core::marker::Sync">Sync</a> for <aclass="struct"href="struct.TestWriter.html"title="struct tracing_subscriber::fmt::TestWriter">TestWriter</a></h3></section><sectionid="impl-Unpin-for-TestWriter"class="impl"><ahref="#impl-Unpin-for-TestWriter"class="anchor">§</a><h3class="code-header">impl <aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/marker/trait.Unpin.html"title="trait core::marker::Unpin">Unpin</a> for <aclass="struct"href="struct.TestWriter.html"title="struct tracing_subscriber::fmt::TestWriter">TestWriter</a></h3></section><sectionid="impl-UnwindSafe-for-TestWriter"class="impl"><ahref="#impl-UnwindSafe-for-TestWriter"class="anchor">§</a><h3class="code-header">impl <aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/panic/unwind_safe/trait.UnwindSafe.html"title="trait core::panic::unwind_safe::UnwindSafe">UnwindSafe</a> for <aclass="struct"href="struct.TestWriter.html"title="struct tracing_subscriber::fmt::TestWriter">TestWriter</a></h3></section></div><h2id="blanket-implementations"class="section-header">Blanket Implementations<ahref="#blanket-implementations"class="anchor">§</a></h2><divid="blanket-implementations-list"><detailsclass="toggle implementors-toggle"><summary><sectionid="impl-Any-for-T"class="impl"><aclass="src rightside"href="https://doc.rust-lang.org/1.77.2/src/core/any.rs.html#140">source</a><ahref="#impl-Any-for-T"class="anchor">§</a><h3class="code-header">impl<T><aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/any/trait.Any.html"title="trait core::any::Any">Any</a> for T<divclass="where">where
T: 'static + ?<aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/marker/trait.Sized.html"title="trait core::marker::Sized">Sized</a>,</div></h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.type_id"class="method trait-impl"><aclass="src rightside"href="https://doc.rust-lang.org/1.77.2/src/core/any.rs.html#141">source</a><ahref="#method.type_id"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.77.2/core/any/trait.Any.html#tymethod.type_id"class="fn">type_id</a>(&self) -><aclass="struct"href="https://doc.rust-lang.org/1.77.2/core/any/struct.TypeId.html"title="struct core::any::TypeId">TypeId</a></h4></section></summary><divclass='docblock'>Gets the <code>TypeId</code> of <code>self</code>. <ahref="https://doc.rust-lang.org/1.77.2/core/any/trait.Any.html#tymethod.type_id">Read more</a></div></details></div></details><detailsclass="toggle implementors-toggle"><summary><sectionid="impl-Borrow%3CT%3E-for-T"class="impl"><aclass="src rightside"href="https://doc.rust-lang.org/1.77.2/src/core/borrow.rs.html#208">source</a><ahref="#impl-Borrow%3CT%3E-for-T"class="anchor">§</a><h3class="code-header">impl<T><aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/borrow/trait.Borrow.html"title="trait core::borrow::Borrow">Borrow</a><T> for T<divclass="where">where
T: ?<aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/marker/trait.Sized.html"title="trait core::marker::Sized">Sized</a>,</div></h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.borrow"class="method trait-impl"><aclass="src rightside"href="https://doc.rust-lang.org/1.77.2/src/core/borrow.rs.html#210">source</a><ahref="#method.borrow"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.77.2/core/borrow/trait.Borrow.html#tymethod.borrow"class="fn">borrow</a>(&self) -><aclass="primitive"href="https://doc.rust-lang.org/1.77.2/std/primitive.reference.html">&T</a></h4></section></summary><divclass='docblock'>Immutably borrows from an owned value. <ahref="https://doc.rust-lang.org/1.77.2/core/borrow/trait.Borrow.html#tymethod.borrow">Read more</a></div></details></div></details><detailsclass="toggle implementors-toggle"><summary><sectionid="impl-BorrowMut%3CT%3E-for-T"class="impl"><aclass="src rightside"href="https://doc.rust-lang.org/1.77.2/src/core/borrow.rs.html#216">source</a><ahref="#impl-BorrowMut%3CT%3E-for-T"class="anchor">§</a><h3class="code-header">impl<T><aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/borrow/trait.BorrowMut.html"title="trait core::borrow::BorrowMut">BorrowMut</a><T> for T<divclass="where">where
T: ?<aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/marker/trait.Sized.html"title="trait core::marker::Sized">Sized</a>,</div></h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.borrow_mut"class="method trait-impl"><aclass="src rightside"href="https://doc.rust-lang.org/1.77.2/src/core/borrow.rs.html#217">source</a><ahref="#method.borrow_mut"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.77.2/core/borrow/trait.BorrowMut.html#tymethod.borrow_mut"class="fn">borrow_mut</a>(&mut self) -><aclass="primitive"href="https://doc.rust-lang.org/1.77.2/std/primitive.reference.html">&mut T</a></h4></section></summary><divclass='docblock'>Mutably borrows from an owned value. <ahref="https://doc.rust-lang.org/1.77.2/core/borrow/trait.BorrowMut.html#tymethod.borrow_mut">Read more</a></div></details></div></details><detailsclass="toggle implementors-toggle"><summary><sectionid="impl-From%3CT%3E-for-T"class="impl"><aclass="src rightside"href="https://doc.rust-lang.org/1.77.2/src/core/convert/mod.rs.html#764">source</a><ahref="#impl-From%3CT%3E-for-T"class="anchor">§</a><h3class="code-header">impl<T><aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/convert/trait.From.html"title="trait core::convert::From">From</a><T> for T</h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.from"class="method trait-impl"><aclass="src rightside"href="https://doc.rust-lang.org/1.77.2/src/core/convert/mod.rs.html#767">source</a><ahref="#method.from"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.77.2/core/convert/trait.From.html#tymethod.from"class="fn">from</a>(t: T) -> T</h4></section></summary><divclass="docblock"><p>Returns the argument unchanged.</p>
</div></details></div></details><detailsclass="toggle implementors-toggle"><summary><sectionid="impl-Instrument-for-T"class="impl"><aclass="src rightside"href="../../src/tracing/instrument.rs.html#325">source</a><ahref="#impl-Instrument-for-T"class="anchor">§</a><h3class="code-header">impl<T><aclass="trait"href="../../tracing/instrument/trait.Instrument.html"title="trait tracing::instrument::Instrument">Instrument</a> for T</h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.instrument"class="method trait-impl"><aclass="src rightside"href="../../src/tracing/instrument.rs.html#86">source</a><ahref="#method.instrument"class="anchor">§</a><h4class="code-header">fn <ahref="../../tracing/instrument/trait.Instrument.html#method.instrument"class="fn">instrument</a>(self, span: <aclass="struct"href="../../tracing/span/struct.Span.html"title="struct tracing::span::Span">Span</a>) -><aclass="struct"href="../../tracing/instrument/struct.Instrumented.html"title="struct tracing::instrument::Instrumented">Instrumented</a><Self></h4></section></summary><divclass='docblock'>Instruments this type with the provided <ahref="../../tracing/span/struct.Span.html"title="struct tracing::span::Span"><code>Span</code></a>, returning an
<code>Instrumented</code> wrapper. <ahref="../../tracing/instrument/trait.Instrument.html#method.instrument">Read more</a></div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.in_current_span"class="method trait-impl"><aclass="src rightside"href="../../src/tracing/instrument.rs.html#128">source</a><ahref="#method.in_current_span"class="anchor">§</a><h4class="code-header">fn <ahref="../../tracing/instrument/trait.Instrument.html#method.in_current_span"class="fn">in_current_span</a>(self) -><aclass="struct"href="../../tracing/instrument/struct.Instrumented.html"title="struct tracing::instrument::Instrumented">Instrumented</a><Self></h4></section></summary><divclass='docblock'>Instruments this type with the <ahref="../../tracing/span/struct.Span.html#method.current"title="associated function tracing::span::Span::current">current</a><ahref="../../tracing/span/struct.Span.html"title="struct tracing::span::Span"><code>Span</code></a>, returning an
<code><ahref="https://doc.rust-lang.org/1.77.2/core/convert/trait.From.html"title="trait core::convert::From">From</a><T> for U</code> chooses to do.</p>
Self: <aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/marker/trait.Sized.html"title="trait core::marker::Sized">Sized</a>,</div></h4></section></summary><divclass='docblock'>Wraps <code>self</code> and returns a <ahref="trait.MakeWriter.html"title="trait tracing_subscriber::fmt::MakeWriter"><code>MakeWriter</code></a> that will only write output
for events at or below the provided verbosity <ahref="../../tracing_core/metadata/struct.Level.html"title="struct tracing_core::metadata::Level"><code>Level</code></a>. For instance,
<code>Level::TRACE</code> is considered to be _more verbose<code>than</code>Level::INFO`. <ahref="writer/trait.MakeWriterExt.html#method.with_max_level">Read more</a></div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.with_min_level"class="method trait-impl"><aclass="src rightside"href="../../src/tracing_subscriber/fmt/writer.rs.html#318-323">source</a><ahref="#method.with_min_level"class="anchor">§</a><h4class="code-header">fn <ahref="writer/trait.MakeWriterExt.html#method.with_min_level"class="fn">with_min_level</a>(self, level: <aclass="struct"href="../../tracing_core/metadata/struct.Level.html"title="struct tracing_core::metadata::Level">Level</a>) -><aclass="struct"href="writer/struct.WithMinLevel.html"title="struct tracing_subscriber::fmt::writer::WithMinLevel">WithMinLevel</a><Self><divclass="where">where
Self: <aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/marker/trait.Sized.html"title="trait core::marker::Sized">Sized</a>,</div></h4></section></summary><divclass='docblock'>Wraps <code>self</code> and returns a <ahref="trait.MakeWriter.html"title="trait tracing_subscriber::fmt::MakeWriter"><code>MakeWriter</code></a> that will only write output
F: <aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/ops/function/trait.Fn.html"title="trait core::ops::function::Fn">Fn</a>(&<aclass="struct"href="../../tracing_core/metadata/struct.Metadata.html"title="struct tracing_core::metadata::Metadata">Metadata</a><'_>) -><aclass="primitive"href="https://doc.rust-lang.org/1.77.2/std/primitive.bool.html">bool</a>,</div></h4></section></summary><divclass='docblock'>Wraps <code>self</code> with a predicate that takes a span or event’s <ahref="../../tracing_core/metadata/struct.Metadata.html"title="struct tracing_core::metadata::Metadata"><code>Metadata</code></a>
and returns a <code>bool</code>. The returned <ahref="trait.MakeWriter.html"title="trait tracing_subscriber::fmt::MakeWriter"><code>MakeWriter</code></a>’s
<ahref="trait.MakeWriter.html#method.make_writer_for"title="method tracing_subscriber::fmt::MakeWriter::make_writer_for"><code>MakeWriter::make_writer_for</code></a> method will check the predicate to
determine if a writer should be produced for a given span or event. <ahref="writer/trait.MakeWriterExt.html#method.with_filter">Read more</a></div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.and"class="method trait-impl"><aclass="src rightside"href="../../src/tracing_subscriber/fmt/writer.rs.html#452-458">source</a><ahref="#method.and"class="anchor">§</a><h4class="code-header">fn <ahref="writer/trait.MakeWriterExt.html#method.and"class="fn">and</a><B>(self, other: B) -><aclass="struct"href="writer/struct.Tee.html"title="struct tracing_subscriber::fmt::writer::Tee">Tee</a><Self, B><ahref="#"class="tooltip"data-notable-ty="Tee<Self, B>">ⓘ</a><divclass="where">where
B: <aclass="trait"href="trait.MakeWriter.html"title="trait tracing_subscriber::fmt::MakeWriter">MakeWriter</a><'a> + <aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/marker/trait.Sized.html"title="trait core::marker::Sized">Sized</a>,</div></h4></section></summary><divclass='docblock'>Combines <code>self</code> with another type implementing <ahref="trait.MakeWriter.html"title="trait tracing_subscriber::fmt::MakeWriter"><code>MakeWriter</code></a>, returning
a new <ahref="trait.MakeWriter.html"title="trait tracing_subscriber::fmt::MakeWriter"><code>MakeWriter</code></a> that produces <ahref="https://doc.rust-lang.org/1.77.2/std/io/trait.Write.html"title="trait std::io::Write">writers</a> that write to <em>both</em>
W: <aclass="trait"href="https://doc.rust-lang.org/1.77.2/std/io/trait.Write.html"title="trait std::io::Write">Write</a>,</div></h4></section></summary><divclass='docblock'>Combines <code>self</code> with another type implementing <ahref="trait.MakeWriter.html"title="trait tracing_subscriber::fmt::MakeWriter"><code>MakeWriter</code></a>, returning
a new <ahref="trait.MakeWriter.html"title="trait tracing_subscriber::fmt::MakeWriter"><code>MakeWriter</code></a> that calls <code>other</code>’s <ahref="trait.MakeWriter.html#tymethod.make_writer"title="method tracing_subscriber::fmt::MakeWriter::make_writer"><code>make_writer</code></a> if <code>self</code>’s
<code>make_writer</code> returns <ahref="writer/enum.EitherWriter.html#method.none"title="associated function tracing_subscriber::fmt::writer::EitherWriter::none"><code>OptionalWriter::none</code></a>. <ahref="writer/trait.MakeWriterExt.html#method.or_else">Read more</a></div></details></div></details><detailsclass="toggle implementors-toggle"><summary><sectionid="impl-TryFrom%3CU%3E-for-T"class="impl"><aclass="src rightside"href="https://doc.rust-lang.org/1.77.2/src/core/convert/mod.rs.html#804-806">source</a><ahref="#impl-TryFrom%3CU%3E-for-T"class="anchor">§</a><h3class="code-header">impl<T, U><aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/convert/trait.TryFrom.html"title="trait core::convert::TryFrom">TryFrom</a><U> for T<divclass="where">where
U: <aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/convert/trait.Into.html"title="trait core::convert::Into">Into</a><T>,</div></h3></section></summary><divclass="impl-items"><detailsclass="toggle"open><summary><sectionid="associatedtype.Error-1"class="associatedtype trait-impl"><ahref="#associatedtype.Error-1"class="anchor">§</a><h4class="code-header">type <ahref="https://doc.rust-lang.org/1.77.2/core/convert/trait.TryFrom.html#associatedtype.Error"class="associatedtype">Error</a> = <aclass="enum"href="https://doc.rust-lang.org/1.77.2/core/convert/enum.Infallible.html"title="enum core::convert::Infallible">Infallible</a></h4></section></summary><divclass='docblock'>The type returned in the event of a conversion error.</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.try_from"class="method trait-impl"><aclass="src rightside"href="https://doc.rust-lang.org/1.77.2/src/core/convert/mod.rs.html#811">source</a><ahref="#method.try_from"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.77.2/core/convert/trait.TryFrom.html#tymethod.try_from"class="fn">try_from</a>(value: U) -><aclass="enum"href="https://doc.rust-lang.org/1.77.2/core/result/enum.Result.html"title="enum core::result::Result">Result</a><T, <T as <aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/convert/trait.TryFrom.html"title="trait core::convert::TryFrom">TryFrom</a><U>>::<aclass="associatedtype"href="https://doc.rust-lang.org/1.77.2/core/convert/trait.TryFrom.html#associatedtype.Error"title="type core::convert::TryFrom::Error">Error</a>></h4></section></summary><divclass='docblock'>Performs the conversion.</div></details></div></details><detailsclass="toggle implementors-toggle"><summary><sectionid="impl-TryInto%3CU%3E-for-T"class="impl"><aclass="src rightside"href="https://doc.rust-lang.org/1.77.2/src/core/convert/mod.rs.html#789-791">source</a><ahref="#impl-TryInto%3CU%3E-for-T"class="anchor">§</a><h3class="code-header">impl<T, U><aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/convert/trait.TryInto.html"title="trait core::convert::TryInto">TryInto</a><U> for T<divclass="where">where
U: <aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/convert/trait.TryFrom.html"title="trait core::convert::TryFrom">TryFrom</a><T>,</div></h3></section></summary><divclass="impl-items"><detailsclass="toggle"open><summary><sectionid="associatedtype.Error"class="associatedtype trait-impl"><ahref="#associatedtype.Error"class="anchor">§</a><h4class="code-header">type <ahref="https://doc.rust-lang.org/1.77.2/core/convert/trait.TryInto.html#associatedtype.Error"class="associatedtype">Error</a> = <U as <aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/convert/trait.TryFrom.html"title="trait core::convert::TryFrom">TryFrom</a><T>>::<aclass="associatedtype"href="https://doc.rust-lang.org/1.77.2/core/convert/trait.TryFrom.html#associatedtype.Error"title="type core::convert::TryFrom::Error">Error</a></h4></section></summary><divclass='docblock'>The type returned in the event of a conversion error.</div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.try_into"class="method trait-impl"><aclass="src rightside"href="https://doc.rust-lang.org/1.77.2/src/core/convert/mod.rs.html#796">source</a><ahref="#method.try_into"class="anchor">§</a><h4class="code-header">fn <ahref="https://doc.rust-lang.org/1.77.2/core/convert/trait.TryInto.html#tymethod.try_into"class="fn">try_into</a>(self) -><aclass="enum"href="https://doc.rust-lang.org/1.77.2/core/result/enum.Result.html"title="enum core::result::Result">Result</a><U, <U as <aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/convert/trait.TryFrom.html"title="trait core::convert::TryFrom">TryFrom</a><T>>::<aclass="associatedtype"href="https://doc.rust-lang.org/1.77.2/core/convert/trait.TryFrom.html#associatedtype.Error"title="type core::convert::TryFrom::Error">Error</a>></h4></section></summary><divclass='docblock'>Performs the conversion.</div></details></div></details><detailsclass="toggle implementors-toggle"><summary><sectionid="impl-WithSubscriber-for-T"class="impl"><aclass="src rightside"href="../../src/tracing/instrument.rs.html#393">source</a><ahref="#impl-WithSubscriber-for-T"class="anchor">§</a><h3class="code-header">impl<T><aclass="trait"href="../../tracing/instrument/trait.WithSubscriber.html"title="trait tracing::instrument::WithSubscriber">WithSubscriber</a> for T</h3></section></summary><divclass="impl-items"><detailsclass="toggle method-toggle"open><summary><sectionid="method.with_subscriber"class="method trait-impl"><aclass="src rightside"href="../../src/tracing/instrument.rs.html#176-178">source</a><ahref="#method.with_subscriber"class="anchor">§</a><h4class="code-header">fn <ahref="../../tracing/instrument/trait.WithSubscriber.html#method.with_subscriber"class="fn">with_subscriber</a><S>(self, subscriber: S) -><aclass="struct"href="../../tracing/instrument/struct.WithDispatch.html"title="struct tracing::instrument::WithDispatch">WithDispatch</a><Self><divclass="where">where
S: <aclass="trait"href="https://doc.rust-lang.org/1.77.2/core/convert/trait.Into.html"title="trait core::convert::Into">Into</a><<aclass="struct"href="../../tracing_core/dispatcher/struct.Dispatch.html"title="struct tracing_core::dispatcher::Dispatch">Dispatch</a>>,</div></h4></section></summary><divclass='docblock'>Attaches the provided <ahref="../../tracing_core/subscriber/trait.Subscriber.html"title="trait tracing_core::subscriber::Subscriber"><code>Subscriber</code></a> to this type, returning a
<ahref="../../tracing/instrument/struct.WithDispatch.html"title="struct tracing::instrument::WithDispatch"><code>WithDispatch</code></a> wrapper. <ahref="../../tracing/instrument/trait.WithSubscriber.html#method.with_subscriber">Read more</a></div></details><detailsclass="toggle method-toggle"open><summary><sectionid="method.with_current_subscriber"class="method trait-impl"><aclass="src rightside"href="../../src/tracing/instrument.rs.html#228">source</a><ahref="#method.with_current_subscriber"class="anchor">§</a><h4class="code-header">fn <ahref="../../tracing/instrument/trait.WithSubscriber.html#method.with_current_subscriber"class="fn">with_current_subscriber</a>(self) -><aclass="struct"href="../../tracing/instrument/struct.WithDispatch.html"title="struct tracing::instrument::WithDispatch">WithDispatch</a><Self></h4></section></summary><divclass='docblock'>Attaches the current <ahref="../../tracing/dispatcher/index.html#setting-the-default-subscriber"title="mod tracing::dispatcher">default</a><ahref="../../tracing_core/subscriber/trait.Subscriber.html"title="trait tracing_core::subscriber::Subscriber"><code>Subscriber</code></a> to this type, returning a
