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<div class="section-content top-matter">
<h1 id='swiftlint' class='heading'>SwiftLint</h1>
<p>A tool to enforce Swift style and conventions, loosely based on the now archived <a href="https://github.com/github/swift-style-guide">GitHub Swift Style Guide</a>. SwiftLint enforces the style guide rules that are generally accepted by the Swift community. These rules are well described in popular style guides like <a href="https://github.com/kodecocodes/swift-style-guide">Kodeco&rsquo;s Swift Style Guide</a>.</p>
<p>SwiftLint hooks into <a href="http://clang.llvm.org">Clang</a> and
<a href="http://www.jpsim.com/uncovering-sourcekit">SourceKit</a> to use the
<a href="http://clang.llvm.org/docs/IntroductionToTheClangAST.html">AST</a> representation
of your source files for more accurate results.</p>
<p><a href="https://dev.azure.com/jpsim/SwiftLint/_build/latest?definitionId=4?branchName=main"><img src="https://dev.azure.com/jpsim/SwiftLint/_apis/build/status/realm.SwiftLint?branchName=main" alt="Build Status"></a>
<a href="https://codecov.io/github/realm/SwiftLint?branch=main"><img src="https://codecov.io/github/realm/SwiftLint/coverage.svg?branch=main" alt="codecov.io"></a></p>
<p><img src="assets/screenshot.png" alt=""></p>
<p>This project adheres to the <a href="https://realm.io/conduct">Contributor Covenant Code of Conduct</a>.
By participating, you are expected to uphold this code. Please report
unacceptable behavior to <a href="mailto:info@realm.io">info@realm.io</a>.</p>
<blockquote>
<p>Language Switch: <a href="https://github.com/realm/SwiftLint/blob/main/README_CN.md">中文</a>, <a href="https://github.com/realm/SwiftLint/blob/main/README_KR.md">한국어</a>.</p>
</blockquote>
<h2 id='installation' class='heading'>Installation</h2>
<h3 id='using-a-href-http-brew-sh-homebrew-a' class='heading'>Using <a href="http://brew.sh/">Homebrew</a>:</h3>
<pre class="highlight plaintext"><code>brew install swiftlint
</code></pre>
<h3 id='using-a-href-https-cocoapods-org-cocoapods-a' class='heading'>Using <a href="https://cocoapods.org">CocoaPods</a>:</h3>
<p>Simply add the following line to your Podfile:</p>
<pre class="highlight ruby"><code><span class="n">pod</span> <span class="s1">'SwiftLint'</span>
</code></pre>
<p>This will download the SwiftLint binaries and dependencies in <code>Pods/</code> during your next
<code>pod install</code> execution and will allow you to invoke it via <code>${PODS_ROOT}/SwiftLint/swiftlint</code>
in your Script Build Phases.</p>
<p>This is the recommended way to install a specific version of SwiftLint since it supports
installing a pinned version rather than simply the latest (which is the case with Homebrew).</p>
<p>Note that this will add the SwiftLint binaries, its dependencies&rsquo; binaries, and the Swift binary
library distribution to the <code>Pods/</code> directory, so checking in this directory to SCM such as
git is discouraged.</p>
<h3 id='using-a-href-https-github-com-yonaskolb-mint-mint-a' class='heading'>Using <a href="https://github.com/yonaskolb/mint">Mint</a>:</h3>
<pre class="highlight plaintext"><code>$ mint install realm/SwiftLint
</code></pre>
<h3 id='using-a-pre-built-package' class='heading'>Using a pre-built package:</h3>
<p>You can also install SwiftLint by downloading <code>SwiftLint.pkg</code> from the
<a href="https://github.com/realm/SwiftLint/releases/latest">latest GitHub release</a> and
running it.</p>
<h3 id='installing-from-source' class='heading'>Installing from source:</h3>
<p>You can also build and install from source by cloning this project and running
<code>make install</code> (Xcode 13.3 or later).</p>
<h3 id='using-bazel' class='heading'>Using Bazel</h3>
<p>Put this in your <code>MODULE.bazel</code>:</p>
<pre class="highlight plaintext"><code>bazel_dep(name = "swiftlint", version = "0.50.4", repo_name = "SwiftLint")
</code></pre>
<p>Or put this in your <code>WORKSPACE</code>:</p>
<details>
<summary>WORKSPACE</summary>
&ldquo;`bzl
load(&rdquo;@bazel_tools//tools/build_defs/repo:http.bzl&quot;, &ldquo;http_archive&rdquo;)
http_archive(
name = &ldquo;build_bazel_rules_apple&rdquo;,
sha256 = &ldquo;f94e6dddf74739ef5cb30f000e13a2a613f6ebfa5e63588305a71fce8a8a9911&rdquo;,
url = &ldquo;https://github.com/bazelbuild/rules_apple/releases/download/1.1.3/rules_apple.1.1.3.tar.gz&rdquo;,
)
load(
&ldquo;@build_bazel_rules_apple//apple:repositories.bzl&rdquo;,
&ldquo;apple_rules_dependencies&rdquo;,
)
apple_rules_dependencies()
load(
&ldquo;@build_bazel_rules_swift//swift:repositories.bzl&rdquo;,
&ldquo;swift_rules_dependencies&rdquo;,
)
swift_rules_dependencies()
load(
&ldquo;@build_bazel_rules_swift//swift:extras.bzl&rdquo;,
&ldquo;swift_rules_extra_dependencies&rdquo;,
)
swift_rules_extra_dependencies()
http_archive(
name = &ldquo;SwiftLint&rdquo;,
sha256 = &ldquo;7c454ff4abeeecdd9513f6293238a6d9f803b587eb93de147f9aa1be0d8337c4&rdquo;,
url = &ldquo;https://github.com/realm/SwiftLint/releases/download/0.49.1/bazel.tar.gz&rdquo;,
)
load(&ldquo;@SwiftLint//bazel:repos.bzl&rdquo;, &ldquo;swiftlint_repos&rdquo;)
swiftlint_repos()
load(&ldquo;@SwiftLint//bazel:deps.bzl&rdquo;, &ldquo;swiftlint_deps&rdquo;)
swiftlint_deps()
&ldquo;`
</details>
<p>Then you can run SwiftLint in the current directory with this command:</p>
<pre class="highlight console"><code><span class="go">bazel run -c opt @SwiftLint//:swiftlint
</span></code></pre>
<h2 id='usage' class='heading'>Usage</h2>
<h3 id='presentation' class='heading'>Presentation</h3>
<p>To get a high-level overview of recommended ways to integrate SwiftLint into your project,
we encourage you to watch this presentation or read the transcript:</p>
<p><a href="https://youtu.be/9Z1nTMTejqU"><img src="assets/presentation.svg" alt="Presentation"></a></p>
<h3 id='xcode' class='heading'>Xcode</h3>
<p>Integrate SwiftLint into your Xcode project to get warnings and errors displayed
in the issue navigator.</p>
<p>To do this select the project in the file navigator, then select the primary app
target, and go to Build Phases. Click the + and select &quot;New Run Script Phase&rdquo;.
Insert the following as the script:</p>
<p><img src="assets/runscript.png" alt=""></p>
<p>If you installed SwiftLint via Homebrew on Apple Silicon, you might experience this warning:</p>
<div class="aside aside-warning">
<p class="aside-title">Warning</p>
<p>SwiftLint not installed, download from <a href="https://github.com/realm/SwiftLint">https://github.com/realm/SwiftLint</a></p>
</div>
<p>That is because Homebrew on Apple Silicon installs the binaries into the <code>/opt/homebrew/bin</code>
folder by default. To instruct Xcode where to find SwiftLint, you can either add
<code>/opt/homebrew/bin</code> to the <code>PATH</code> environment variable in your build phase</p>
<pre class="highlight shell"><code><span class="k">if</span> <span class="o">[[</span> <span class="s2">"</span><span class="si">$(</span><span class="nb">uname</span> <span class="nt">-m</span><span class="si">)</span><span class="s2">"</span> <span class="o">==</span> arm64 <span class="o">]]</span><span class="p">;</span> <span class="k">then
</span><span class="nb">export </span><span class="nv">PATH</span><span class="o">=</span><span class="s2">"/opt/homebrew/bin:</span><span class="nv">$PATH</span><span class="s2">"</span>
<span class="k">fi
if </span>which swiftlint <span class="o">&gt;</span> /dev/null<span class="p">;</span> <span class="k">then
</span>swiftlint
<span class="k">else
</span><span class="nb">echo</span> <span class="s2">"warning: SwiftLint not installed, download from https://github.com/realm/SwiftLint"</span>
<span class="k">fi</span>
</code></pre>
<p>or you can create a symbolic link in <code>/usr/local/bin</code> pointing to the actual binary:</p>
<pre class="highlight shell"><code><span class="nb">ln</span> <span class="nt">-s</span> /opt/homebrew/bin/swiftlint /usr/local/bin/swiftlint
</code></pre>
<p>You might want to move your SwiftLint phase directly before the &lsquo;Compile Sources&rsquo;
step to detect errors quickly before compiling. However, SwiftLint is designed
to run on valid Swift code that cleanly completes the compiler&rsquo;s parsing stage.
So running SwiftLint before &lsquo;Compile Sources&rsquo; might yield some incorrect
results.</p>
<p>If you wish to fix violations as well, your script could run
<code>swiftlint --fix &amp;&amp; swiftlint</code> instead of just <code>swiftlint</code>. This will mean
that all correctable violations are fixed while ensuring warnings show up in
your project for remaining violations.</p>
<p>If you&rsquo;ve installed SwiftLint via CocoaPods the script should look like this:</p>
<pre class="highlight shell"><code><span class="s2">"</span><span class="k">${</span><span class="nv">PODS_ROOT</span><span class="k">}</span><span class="s2">/SwiftLint/swiftlint"</span>
</code></pre>
<h3 id='plug-in-support' class='heading'>Plug-in Support</h3>
<p>SwiftLint can be used as a build tool plug-in for both Xcode projects as well as
Swift packages.</p>
<blockquote>
<p>Due to limitations with Swift Package Manager Plug-ins this is only
recommended for projects that have a SwiftLint configuration in their root directory as
there is currently no way to pass any additional options to the SwiftLint executable.</p>
</blockquote>
<h4 id='xcode' class='heading'>Xcode</h4>
<p>You can integrate SwiftLint as an Xcode Build Tool Plug-in if you&rsquo;re working
with a project in Xcode.</p>
<p>Add SwiftLint as a package dependency to your project without linking any of the
products.</p>
<p>Select the target you want to add linting to and open the <code>Build Phases</code> inspector.
Open <code>Run Build Tool Plug-ins</code> and select the <code>+</code> button.
Select <code>SwiftLintPlugin</code> from the list and add it to the project.</p>
<p><img src="assets/select-swiftlint-plugin.png" alt=""></p>
<p>For unattended use (e.g. on CI), you can disable the package validation dialog by</p>
<ul>
<li>individually passing <code>-skipPackagePluginValidation</code> to <code>xcodebuild</code> or</li>
<li>globally setting <code>defaults write com.apple.dt.Xcode IDESkipPackagePluginFingerprintValidatation -bool YES</code>
for that user.</li>
</ul>
<p><em>Note: This implicitly trusts all Xcode package plugins and bypasses Xcode&rsquo;s package validation
dialogs, which has security implications.</em></p>
<h4 id='swift-package' class='heading'>Swift Package</h4>
<p>You can integrate SwiftLint as a Swift Package Manager Plug-in if you&rsquo;re working with
a Swift Package with a <code>Package.swift</code> manifest.</p>
<p>Add SwiftLint as a package dependency to your <code>Package.swift</code> file.<br>
Add SwiftLint to a target using the <code>plugins</code> parameter.</p>
<pre class="highlight swift"><code><span class="o">.</span><span class="nf">target</span><span class="p">(</span>
<span class="o">...</span>
<span class="nv">plugins</span><span class="p">:</span> <span class="p">[</span><span class="o">.</span><span class="nf">plugin</span><span class="p">(</span><span class="nv">name</span><span class="p">:</span> <span class="s">"SwiftLintPlugin"</span><span class="p">,</span> <span class="nv">package</span><span class="p">:</span> <span class="s">"SwiftLint"</span><span class="p">)]</span>
<span class="p">),</span>
</code></pre>
<h3 id='visual-studio-code' class='heading'>Visual Studio Code</h3>
<p>To integrate SwiftLint with <a href="https://code.visualstudio.com">vscode</a>, install the
<a href="https://marketplace.visualstudio.com/items?itemName=vknabel.vscode-swiftlint"><code>vscode-swiftlint</code></a> extension from the marketplace.</p>
<h3 id='fastlane' class='heading'>fastlane</h3>
<p>You can use the <a href="https://docs.fastlane.tools/actions/swiftlint">official swiftlint fastlane action</a> to run SwiftLint as part of your fastlane process.</p>
<pre class="highlight ruby"><code><span class="n">swiftlint</span><span class="p">(</span>
<span class="ss">mode: :lint</span><span class="p">,</span> <span class="c1"># SwiftLint mode: :lint (default) or :autocorrect</span>
<span class="ss">executable: </span><span class="s2">"Pods/SwiftLint/swiftlint"</span><span class="p">,</span> <span class="c1"># The SwiftLint binary path (optional). Important if you've installed it via CocoaPods</span>
<span class="ss">path: </span><span class="s2">"/path/to/lint"</span><span class="p">,</span> <span class="c1"># Specify path to lint (optional)</span>
<span class="ss">output_file: </span><span class="s2">"swiftlint.result.json"</span><span class="p">,</span> <span class="c1"># The path of the output file (optional)</span>
<span class="ss">reporter: </span><span class="s2">"json"</span><span class="p">,</span> <span class="c1"># The custom reporter to use (optional)</span>
<span class="ss">config_file: </span><span class="s2">".swiftlint-ci.yml"</span><span class="p">,</span> <span class="c1"># The path of the configuration file (optional)</span>
<span class="ss">files: </span><span class="p">[</span> <span class="c1"># List of files to process (optional)</span>
<span class="s2">"AppDelegate.swift"</span><span class="p">,</span>
<span class="s2">"path/to/project/Model.swift"</span>
<span class="p">],</span>
<span class="ss">ignore_exit_status: </span><span class="kp">true</span><span class="p">,</span> <span class="c1"># Allow fastlane to continue even if SwiftLint returns a non-zero exit status (Default: false)</span>
<span class="ss">quiet: </span><span class="kp">true</span><span class="p">,</span> <span class="c1"># Don't print status logs like 'Linting ' &amp; 'Done linting' (Default: false)</span>
<span class="ss">strict: </span><span class="kp">true</span> <span class="c1"># Fail on warnings? (Default: false)</span>
<span class="p">)</span>
</code></pre>
<h3 id='docker' class='heading'>Docker</h3>
<p><code>swiftlint</code> is also available as a <a href="https://www.docker.com/">Docker</a> image using <code>Ubuntu</code>.
So just the first time you need to pull the docker image using the next command:</p>
<pre class="highlight shell"><code>docker pull ghcr.io/realm/swiftlint:latest
</code></pre>
<p>Then following times, you just run <code>swiftlint</code> inside of the docker like:</p>
<pre class="highlight shell"><code>docker run <span class="nt">-it</span> <span class="nt">-v</span> <span class="sb">`</span><span class="nb">pwd</span><span class="sb">`</span>:<span class="sb">`</span><span class="nb">pwd</span><span class="sb">`</span> <span class="nt">-w</span> <span class="sb">`</span><span class="nb">pwd</span><span class="sb">`</span> ghcr.io/realm/swiftlint:latest
</code></pre>
<p>This will execute <code>swiftlint</code> in the folder where you are right now (<code>pwd</code>), showing an output like:</p>
<pre class="highlight shell"><code><span class="nv">$ </span>docker run <span class="nt">-it</span> <span class="nt">-v</span> <span class="sb">`</span><span class="nb">pwd</span><span class="sb">`</span>:<span class="sb">`</span><span class="nb">pwd</span><span class="sb">`</span> <span class="nt">-w</span> <span class="sb">`</span><span class="nb">pwd</span><span class="sb">`</span> ghcr.io/realm/swiftlint:latest
Linting Swift files <span class="k">in </span>current working directory
Linting <span class="s1">'RuleDocumentation.swift'</span> <span class="o">(</span>1/490<span class="o">)</span>
...
Linting <span class="s1">'YamlSwiftLintTests.swift'</span> <span class="o">(</span>490/490<span class="o">)</span>
Done linting! Found 0 violations, 0 serious <span class="k">in </span>490 files.
</code></pre>
<p>Here you have more documentation about the usage of <a href="https://docs.docker.com/">Docker Images</a>.</p>
<h3 id='command-line' class='heading'>Command Line</h3>
<pre class="highlight plaintext"><code>$ swiftlint help
OVERVIEW: A tool to enforce Swift style and conventions.
USAGE: swiftlint &lt;subcommand&gt;
OPTIONS:
--version Show the version.
-h, --help Show help information.
SUBCOMMANDS:
analyze Run analysis rules
docs Open SwiftLint documentation website in the default web browser
generate-docs Generates markdown documentation for all rules
lint (default) Print lint warnings and errors
reporters Display the list of reporters and their identifiers
rules Display the list of rules and their identifiers
version Display the current version of SwiftLint
See 'swiftlint help &lt;subcommand&gt;' for detailed help.
</code></pre>
<p>Run <code>swiftlint</code> in the directory containing the Swift files to lint. Directories
will be searched recursively.</p>
<p>To specify a list of files when using <code>lint</code> or <code>analyze</code>
(like the list of files modified by Xcode specified by the
<a href="https://github.com/norio-nomura/ExtraBuildPhase"><code>ExtraBuildPhase</code></a> Xcode
plugin, or modified files in the working tree based on <code>git ls-files -m</code>), you
can do so by passing the option <code>--use-script-input-files</code> and setting the
following instance variables: <code>SCRIPT_INPUT_FILE_COUNT</code> and
<code>SCRIPT_INPUT_FILE_0</code>, <code>SCRIPT_INPUT_FILE_1</code>&hellip;<code>SCRIPT_INPUT_FILE_{SCRIPT_INPUT_FILE_COUNT - 1}</code>.</p>
<p>These are same environment variables set for input files to
<a href="http://indiestack.com/2014/12/speeding-up-custom-script-phases/">custom Xcode script phases</a>.</p>
<h3 id='working-with-multiple-swift-versions' class='heading'>Working With Multiple Swift Versions</h3>
<p>SwiftLint hooks into SourceKit so it continues working even as Swift evolves!</p>
<p>This also keeps SwiftLint lean, as it doesn&rsquo;t need to ship with a full Swift
compiler, it just communicates with the official one you already have installed
on your machine.</p>
<p>You should always run SwiftLint with the same toolchain you use to compile your
code.</p>
<p>You may want to override SwiftLint&rsquo;s default Swift toolchain if you have
multiple toolchains or Xcodes installed.</p>
<p>Here&rsquo;s the order in which SwiftLint determines which Swift toolchain to use:</p>
<ul>
<li><code>$XCODE_DEFAULT_TOOLCHAIN_OVERRIDE</code></li>
<li><code>$TOOLCHAIN_DIR</code> or <code>$TOOLCHAINS</code></li>
<li><code>xcrun -find swift</code></li>
<li><code>/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain</code></li>
<li><code>/Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain</code></li>
<li><code>~/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain</code></li>
<li><code>~/Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain</code></li>
</ul>
<p><code>sourcekitd.framework</code> is expected to be found in the <code>usr/lib/</code> subdirectory of
the value passed in the paths above.</p>
<p>You may also set the <code>TOOLCHAINS</code> environment variable to the reverse-DNS
notation that identifies a Swift toolchain version:</p>
<pre class="highlight shell"><code><span class="nv">$ TOOLCHAINS</span><span class="o">=</span>com.apple.dt.toolchain.Swift_2_3 swiftlint <span class="nt">--fix</span>
</code></pre>
<p>On Linux, SourceKit is expected to be located in
<code>/usr/lib/libsourcekitdInProc.so</code> or specified by the <code>LINUX_SOURCEKIT_LIB_PATH</code>
environment variable.</p>
<h3 id='pre-commit' class='heading'>pre-commit</h3>
<p>SwiftLint can be run as a <a href="https://pre-commit.com/">pre-commit</a> hook.
Once <a href="https://pre-commit.com/#install">installed</a>, add this to the
<code>.pre-commit-config.yaml</code> in the root of your repository:</p>
<pre class="highlight yaml"><code><span class="na">repos</span><span class="pi">:</span>
<span class="pi">-</span> <span class="na">repo</span><span class="pi">:</span> <span class="s">https://github.com/realm/SwiftLint</span>
<span class="na">rev</span><span class="pi">:</span> <span class="s">0.50.3</span>
<span class="na">hooks</span><span class="pi">:</span>
<span class="pi">-</span> <span class="na">id</span><span class="pi">:</span> <span class="s">swiftlint</span>
</code></pre>
<p>Adjust <code>rev</code> to the SwiftLint version of your choice. <code>pre-commit autoupdate</code> can be used to update to the current version.</p>
<p>SwiftLint can be configured using <code>entry</code> to apply fixes and fail on errors:</p>
<pre class="highlight yaml"><code><span class="pi">-</span> <span class="na">repo</span><span class="pi">:</span> <span class="s">https://github.com/realm/SwiftLint</span>
<span class="na">rev</span><span class="pi">:</span> <span class="s">0.50.3</span>
<span class="na">hooks</span><span class="pi">:</span>
<span class="pi">-</span> <span class="na">id</span><span class="pi">:</span> <span class="s">swiftlint</span>
<span class="na">entry</span><span class="pi">:</span> <span class="s">swiftlint --fix --strict</span>
</code></pre>
<h2 id='rules' class='heading'>Rules</h2>
<p>Over 200 rules are included in SwiftLint and the Swift community (that&rsquo;s you!)
continues to contribute more over time.
<a href="CONTRIBUTING.md">Pull requests</a> are encouraged.</p>
<p>You can find an updated list of rules and more information about them
<a href="https://realm.github.io/SwiftLint/rule-directory.html">here</a>.</p>
<p>You can also check <a href="https://github.com/realm/SwiftLint/tree/main/Source/SwiftLintBuiltInRules/Rules">Source/SwiftLintBuiltInRules/Rules</a>
directory to see their implementation.</p>
<h3 id='opt-in-rules' class='heading'>Opt-In Rules</h3>
<p><code>opt_in_rules</code> are disabled by default (i.e., you have to explicitly enable them
in your configuration file).</p>
<p>Guidelines on when to mark a rule as opt-in:</p>
<ul>
<li>A rule that can have many false positives (e.g. <code><a href="empty_count.html">empty_count</a></code>)</li>
<li>A rule that is too slow</li>
<li>A rule that is not general consensus or is only useful in some cases
(e.g. <code><a href="force_unwrapping.html">force_unwrapping</a></code>)</li>
</ul>
<h3 id='disable-rules-in-code' class='heading'>Disable rules in code</h3>
<p>Rules can be disabled with a comment inside a source file with the following
format:</p>
<p><code>// swiftlint:disable &lt;rule1&gt; [&lt;rule2&gt; &lt;rule3&gt;...]</code></p>
<p>The rules will be disabled until the end of the file or until the linter sees a
matching enable comment:</p>
<p><code>// swiftlint:enable &lt;rule1&gt; [&lt;rule2&gt; &lt;rule3&gt;...]</code></p>
<p>For example:</p>
<pre class="highlight swift"><code><span class="c1">// swiftlint:disable colon</span>
<span class="k">let</span> <span class="nv">noWarning</span> <span class="p">:</span><span class="kt">String</span> <span class="o">=</span> <span class="s">""</span> <span class="c1">// No warning about colons immediately after variable names!</span>
<span class="c1">// swiftlint:enable colon</span>
<span class="k">let</span> <span class="nv">hasWarning</span> <span class="p">:</span><span class="kt">String</span> <span class="o">=</span> <span class="s">""</span> <span class="c1">// Warning generated about colons immediately after variable names</span>
</code></pre>
<p>Including the <code>all</code> keyword will disable all rules until the linter sees a matching enable comment:</p>
<p><code>// swiftlint:disable all</code>
<code>// swiftlint:enable all</code></p>
<p>For example:</p>
<pre class="highlight swift"><code><span class="c1">// swiftlint:disable all</span>
<span class="k">let</span> <span class="nv">noWarning</span> <span class="p">:</span><span class="kt">String</span> <span class="o">=</span> <span class="s">""</span> <span class="c1">// No warning about colons immediately after variable names!</span>
<span class="k">let</span> <span class="nv">i</span> <span class="o">=</span> <span class="s">""</span> <span class="c1">// Also no warning about short identifier names</span>
<span class="c1">// swiftlint:enable all</span>
<span class="k">let</span> <span class="nv">hasWarning</span> <span class="p">:</span><span class="kt">String</span> <span class="o">=</span> <span class="s">""</span> <span class="c1">// Warning generated about colons immediately after variable names</span>
<span class="k">let</span> <span class="nv">y</span> <span class="o">=</span> <span class="s">""</span> <span class="c1">// Warning generated about short identifier names</span>
</code></pre>
<p>It&rsquo;s also possible to modify a <code>disable</code> or <code>enable</code> command by appending
<code>:previous</code>, <code>:this</code> or <code>:next</code> for only applying the command to the previous,
this (current) or next line respectively.</p>
<p>For example:</p>
<pre class="highlight swift"><code><span class="c1">// swiftlint:disable:next force_cast</span>
<span class="k">let</span> <span class="nv">noWarning</span> <span class="o">=</span> <span class="kt">NSNumber</span><span class="p">()</span> <span class="k">as!</span> <span class="kt">Int</span>
<span class="k">let</span> <span class="nv">hasWarning</span> <span class="o">=</span> <span class="kt">NSNumber</span><span class="p">()</span> <span class="k">as!</span> <span class="kt">Int</span>
<span class="k">let</span> <span class="nv">noWarning2</span> <span class="o">=</span> <span class="kt">NSNumber</span><span class="p">()</span> <span class="k">as!</span> <span class="kt">Int</span> <span class="c1">// swiftlint:disable:this force_cast</span>
<span class="k">let</span> <span class="nv">noWarning3</span> <span class="o">=</span> <span class="kt">NSNumber</span><span class="p">()</span> <span class="k">as!</span> <span class="kt">Int</span>
<span class="c1">// swiftlint:disable:previous force_cast</span>
</code></pre>
<p>Run <code>swiftlint rules</code> to print a list of all available rules and their
identifiers.</p>
<h3 id='configuration' class='heading'>Configuration</h3>
<p>Configure SwiftLint by adding a <code>.swiftlint.yml</code> file from the directory you&rsquo;ll
run SwiftLint from. The following parameters can be configured:</p>
<p>Rule inclusion:</p>
<ul>
<li><code>disabled_rules</code>: Disable rules from the default enabled set.</li>
<li><code>opt_in_rules</code>: Enable rules that are not part of the default set. The
special <code>all</code> identifier will enable all opt in linter rules, except the ones
listed in <code>disabled_rules</code>.</li>
<li><code>only_rules</code>: Only the rules specified in this list will be enabled.
Cannot be specified alongside <code>disabled_rules</code> or <code>opt_in_rules</code>.</li>
<li><code>analyzer_rules</code>: This is an entirely separate list of rules that are only
run by the <code>analyze</code> command. All analyzer rules are opt-in, so this is the
only configurable rule list, there are no equivalents for <code>disabled_rules</code>
<code>only_rules</code>.</li>
</ul>
<pre class="highlight yaml"><code><span class="c1"># By default, SwiftLint uses a set of sensible default rules you can adjust:</span>
<span class="na">disabled_rules</span><span class="pi">:</span> <span class="c1"># rule identifiers turned on by default to exclude from running</span>
<span class="pi">-</span> <span class="s">colon</span>
<span class="pi">-</span> <span class="s">comma</span>
<span class="pi">-</span> <span class="s">control_statement</span>
<span class="na">opt_in_rules</span><span class="pi">:</span> <span class="c1"># some rules are turned off by default, so you need to opt-in</span>
<span class="pi">-</span> <span class="s">empty_count</span> <span class="c1"># Find all the available rules by running: `swiftlint rules`</span>
<span class="c1"># Alternatively, specify all rules explicitly by uncommenting this option:</span>
<span class="c1"># only_rules: # delete `disabled_rules` &amp; `opt_in_rules` if using this</span>
<span class="c1"># - empty_parameters</span>
<span class="c1"># - vertical_whitespace</span>
<span class="na">analyzer_rules</span><span class="pi">:</span> <span class="c1"># Rules run by `swiftlint analyze`</span>
<span class="pi">-</span> <span class="s">explicit_self</span>
<span class="na">included</span><span class="pi">:</span> <span class="c1"># paths to include during linting. `--path` is ignored if present.</span>
<span class="pi">-</span> <span class="s">Source</span>
<span class="na">excluded</span><span class="pi">:</span> <span class="c1"># paths to ignore during linting. Takes precedence over `included`.</span>
<span class="pi">-</span> <span class="s">Carthage</span>
<span class="pi">-</span> <span class="s">Pods</span>
<span class="pi">-</span> <span class="s">Source/ExcludedFolder</span>
<span class="pi">-</span> <span class="s">Source/ExcludedFile.swift</span>
<span class="pi">-</span> <span class="s">Source/*/ExcludedFile.swift</span> <span class="c1"># Exclude files with a wildcard</span>
<span class="c1"># If true, SwiftLint will not fail if no lintable files are found.</span>
<span class="na">allow_zero_lintable_files</span><span class="pi">:</span> <span class="no">false</span>
<span class="c1"># configurable rules can be customized from this configuration file</span>
<span class="c1"># binary rules can set their severity level</span>
<span class="na">force_cast</span><span class="pi">:</span> <span class="s">warning</span> <span class="c1"># implicitly</span>
<span class="na">force_try</span><span class="pi">:</span>
<span class="na">severity</span><span class="pi">:</span> <span class="s">warning</span> <span class="c1"># explicitly</span>
<span class="c1"># rules that have both warning and error levels, can set just the warning level</span>
<span class="c1"># implicitly</span>
<span class="na">line_length</span><span class="pi">:</span> <span class="m">110</span>
<span class="c1"># they can set both implicitly with an array</span>
<span class="na">type_body_length</span><span class="pi">:</span>
<span class="pi">-</span> <span class="m">300</span> <span class="c1"># warning</span>
<span class="pi">-</span> <span class="m">400</span> <span class="c1"># error</span>
<span class="c1"># or they can set both explicitly</span>
<span class="na">file_length</span><span class="pi">:</span>
<span class="na">warning</span><span class="pi">:</span> <span class="m">500</span>
<span class="na">error</span><span class="pi">:</span> <span class="m">1200</span>
<span class="c1"># naming rules can set warnings/errors for min_length and max_length</span>
<span class="c1"># additionally they can set excluded names</span>
<span class="na">type_name</span><span class="pi">:</span>
<span class="na">min_length</span><span class="pi">:</span> <span class="m">4</span> <span class="c1"># only warning</span>
<span class="na">max_length</span><span class="pi">:</span> <span class="c1"># warning and error</span>
<span class="na">warning</span><span class="pi">:</span> <span class="m">40</span>
<span class="na">error</span><span class="pi">:</span> <span class="m">50</span>
<span class="na">excluded</span><span class="pi">:</span> <span class="s">iPhone</span> <span class="c1"># excluded via string</span>
<span class="na">allowed_symbols</span><span class="pi">:</span> <span class="pi">[</span><span class="s2">"</span><span class="s">_"</span><span class="pi">]</span> <span class="c1"># these are allowed in type names</span>
<span class="na">identifier_name</span><span class="pi">:</span>
<span class="na">min_length</span><span class="pi">:</span> <span class="c1"># only min_length</span>
<span class="na">error</span><span class="pi">:</span> <span class="m">4</span> <span class="c1"># only error</span>
<span class="na">excluded</span><span class="pi">:</span> <span class="c1"># excluded via string array</span>
<span class="pi">-</span> <span class="s">id</span>
<span class="pi">-</span> <span class="s">URL</span>
<span class="pi">-</span> <span class="s">GlobalAPIKey</span>
<span class="na">reporter</span><span class="pi">:</span> <span class="s2">"</span><span class="s">xcode"</span> <span class="c1"># reporter type (xcode, json, csv, checkstyle, codeclimate, junit, html, emoji, sonarqube, markdown, github-actions-logging, summary)</span>
</code></pre>
<p>You can also use environment variables in your configuration file,
by using <code>${SOME_VARIABLE}</code> in a string.</p>
<h3 id='defining-custom-rules' class='heading'>Defining Custom Rules</h3>
<p>In addition to the rules that the main SwiftLint project ships with, SwiftLint
can also run two types of custom rules that you can define yourself in your own
projects:</p>
<h4 id='1-swift-custom-rules' class='heading'>1. Swift Custom Rules</h4>
<p>These rules are written the same way as the Swift-based rules that ship with
SwiftLint so they&rsquo;re fast, accurate, can leverage SwiftSyntax, can be unit
tested, and more.</p>
<p>Using these requires building SwiftLint with Bazel as described in
<a href="https://vimeo.com/820572803">this video</a> or its associated code in
<a href="https://github.com/jpsim/swiftlint-bazel-example">github.com/jpsim/swiftlint-bazel-example</a>.</p>
<h4 id='2-regex-custom-rules' class='heading'>2. Regex Custom Rules</h4>
<p>You can define custom regex-based rules in your configuration file using the
following syntax:</p>
<pre class="highlight yaml"><code><span class="na">custom_rules</span><span class="pi">:</span>
<span class="na">pirates_beat_ninjas</span><span class="pi">:</span> <span class="c1"># rule identifier</span>
<span class="na">included</span><span class="pi">:</span>
<span class="pi">-</span> <span class="s2">"</span><span class="s">.*</span><span class="se">\\</span><span class="s">.swift"</span> <span class="c1"># regex that defines paths to include during linting. optional.</span>
<span class="na">excluded</span><span class="pi">:</span>
<span class="pi">-</span> <span class="s2">"</span><span class="s">.*Test</span><span class="se">\\</span><span class="s">.swift"</span> <span class="c1"># regex that defines paths to exclude during linting. optional</span>
<span class="na">name</span><span class="pi">:</span> <span class="s2">"</span><span class="s">Pirates</span><span class="nv"> </span><span class="s">Beat</span><span class="nv"> </span><span class="s">Ninjas"</span> <span class="c1"># rule name. optional.</span>
<span class="na">regex</span><span class="pi">:</span> <span class="s2">"</span><span class="s">([nN]inja)"</span> <span class="c1"># matching pattern</span>
<span class="na">capture_group</span><span class="pi">:</span> <span class="m">0</span> <span class="c1"># number of regex capture group to highlight the rule violation at. optional.</span>
<span class="na">match_kinds</span><span class="pi">:</span> <span class="c1"># SyntaxKinds to match. optional.</span>
<span class="pi">-</span> <span class="s">comment</span>
<span class="pi">-</span> <span class="s">identifier</span>
<span class="na">message</span><span class="pi">:</span> <span class="s2">"</span><span class="s">Pirates</span><span class="nv"> </span><span class="s">are</span><span class="nv"> </span><span class="s">better</span><span class="nv"> </span><span class="s">than</span><span class="nv"> </span><span class="s">ninjas."</span> <span class="c1"># violation message. optional.</span>
<span class="na">severity</span><span class="pi">:</span> <span class="s">error</span> <span class="c1"># violation severity. optional.</span>
<span class="na">no_hiding_in_strings</span><span class="pi">:</span>
<span class="na">regex</span><span class="pi">:</span> <span class="s2">"</span><span class="s">([nN]inja)"</span>
<span class="na">match_kinds</span><span class="pi">:</span> <span class="s">string</span>
</code></pre>
<p>This is what the output would look like:</p>
<p><img src="assets/custom-rule.png" alt=""></p>
<p>You can filter the matches by providing one or more <code>match_kinds</code>, which will
reject matches that include syntax kinds that are not present in this list. Here
are all the possible syntax kinds:</p>
<ul>
<li><code>argument</code></li>
<li><code>attribute.builtin</code></li>
<li><code>attribute.id</code></li>
<li><code>buildconfig.id</code></li>
<li><code>buildconfig.keyword</code></li>
<li><code>comment</code></li>
<li><code>comment.mark</code></li>
<li><code>comment.url</code></li>
<li><code>doccomment</code></li>
<li><code>doccomment.field</code></li>
<li><code>identifier</code></li>
<li><code>keyword</code></li>
<li><code>number</code></li>
<li><code>objectliteral</code></li>
<li><code>parameter</code></li>
<li><code>placeholder</code></li>
<li><code>string</code></li>
<li><code>string_interpolation_anchor</code></li>
<li><code>typeidentifier</code></li>
</ul>
<p>All syntax kinds used in a snippet of Swift code can be extracted asking
<a href="https://github.com/jpsim/SourceKitten">SourceKitten</a>. For example,
<code>sourcekitten syntax --text &quot;struct S {}&quot;</code> delivers</p>
<ul>
<li><code>source.lang.swift.syntaxtype.keyword</code> for the <code>struct</code> keyword and</li>
<li><code>source.lang.swift.syntaxtype.identifier</code> for its name <code>S</code></li>
</ul>
<p>which match to <code>keyword</code> and <code>identifier</code> in the above list.</p>
<p>If using custom rules in combination with <code>only_rules</code>, make sure to add
<code><a href="custom_rules.html">custom_rules</a></code> as an item under <code>only_rules</code>.</p>
<p>Unlike Swift custom rules, you can use official SwiftLint builds
(e.g. from Homebrew) to run regex custom rules.</p>
<h3 id='auto-correct' class='heading'>Auto-correct</h3>
<p>SwiftLint can automatically correct certain violations. Files on disk are
overwritten with a corrected version.</p>
<p>Please make sure to have backups of these files before running
<code>swiftlint --fix</code>, otherwise important data may be lost.</p>
<p>Standard linting is disabled while correcting because of the high likelihood of
violations (or their offsets) being incorrect after modifying a file while
applying corrections.</p>
<h3 id='analyze' class='heading'>Analyze</h3>
<p>The <code>swiftlint analyze</code> command can lint Swift files using the
full type-checked AST. The compiler log path containing the clean <code>swiftc</code> build
command invocation (incremental builds will fail) must be passed to <code>analyze</code>
via the <code>--compiler-log-path</code> flag.
e.g. <code>--compiler-log-path /path/to/xcodebuild.log</code></p>
<p>This can be obtained by </p>
<ol>
<li>Cleaning DerivedData (incremental builds won&rsquo;t work with analyze)</li>
<li>Running <code>xcodebuild -workspace {WORKSPACE}.xcworkspace -scheme {SCHEME} &gt; xcodebuild.log</code></li>
<li>Running <code>swiftlint analyze --compiler-log-path xcodebuild.log</code></li>
</ol>
<p>Analyzer rules tend to be considerably slower than lint rules.</p>
<h2 id='using-multiple-configuration-files' class='heading'>Using Multiple Configuration Files</h2>
<p>SwiftLint offers a variety of ways to include multiple configuration files.
Multiple configuration files get merged into one single configuration that is then applied
just as a single configuration file would get applied.</p>
<p>There are quite a lot of use cases where using multiple configuration files could be helpful:</p>
<p>For instance, one could use a team-wide shared SwiftLint configuration while allowing overrides
in each project via a child configuration file.</p>
<p>Team-Wide Configuration:</p>
<pre class="highlight yaml"><code><span class="na">disabled_rules</span><span class="pi">:</span>
<span class="pi">-</span> <span class="s">force_cast</span>
</code></pre>
<p>Project-Specific Configuration:</p>
<pre class="highlight yaml"><code><span class="na">opt_in_rules</span><span class="pi">:</span>
<span class="pi">-</span> <span class="s">force_cast</span>
</code></pre>
<h3 id='child-parent-configs-locally' class='heading'>Child / Parent Configs (Locally)</h3>
<p>You can specify a <code>child_config</code> and / or a <code>parent_config</code> reference within a configuration file.
These references should be local paths relative to the folder of the configuration file they are specified in.
This even works recursively, as long as there are no cycles and no ambiguities.</p>
<p><strong>A child config is treated as a refinement and therefore has a higher priority</strong>,
while a parent config is considered a base with lower priority in case of conflicts.</p>
<p>Here&rsquo;s an example, assuming you have the following file structure:</p>
<pre class="highlight plaintext"><code>ProjectRoot
|_ .swiftlint.yml
|_ .swiftlint_refinement.yml
|_ Base
|_ .swiftlint_base.yml
</code></pre>
<p>To include both the refinement and the base file, your <code>.swiftlint.yml</code> should look like this:</p>
<pre class="highlight yaml"><code><span class="na">child_config</span><span class="pi">:</span> <span class="s">.swiftlint_refinement.yml</span>
<span class="na">parent_config</span><span class="pi">:</span> <span class="s">Base/.swiftlint_base.yml</span>
</code></pre>
<p>When merging parent and child configs, <code>included</code> and <code>excluded</code> configurations
are processed carefully to account for differences in the directory location
of the containing configuration files.</p>
<h3 id='child-parent-configs-remote' class='heading'>Child / Parent Configs (Remote)</h3>
<p>Just as you can provide local <code>child_config</code> / <code>parent_config</code> references, instead of
referencing local paths, you can just put urls that lead to configuration files.
In order for SwiftLint to detect these remote references, they must start with <code>http://</code> or <code>https://</code>.</p>
<p>The referenced remote configuration files may even recursively reference other
remote configuration files, but aren&rsquo;t allowed to include local references.</p>
<p>Using a remote reference, your <code>.swiftlint.yml</code> could look like this:</p>
<pre class="highlight yaml"><code><span class="na">parent_config</span><span class="pi">:</span> <span class="s">https://myteamserver.com/our-base-swiftlint-config.yml</span>
</code></pre>
<p>Every time you run SwiftLint and have an Internet connection, SwiftLint tries to get a new version of
every remote configuration that is referenced. If this request times out, a cached version is
used if available. If there is no cached version available, SwiftLint fails but no worries, a cached version
should be there once SwiftLint has run successfully at least once.</p>
<p>If needed, the timeouts for the remote configuration fetching can be specified manually via the
configuration file(s) using the <code>remote_timeout</code> / <code>remote_timeout_if_cached</code> specifiers.
These values default to 2 / 1 second(s).</p>
<h3 id='command-line' class='heading'>Command Line</h3>
<p>Instead of just providing one configuration file when running SwiftLint via the command line,
you can also pass a hierarchy, where the first configuration is treated as a parent,
while the last one is treated as the highest-priority child.</p>
<p>A simple example including just two configuration files looks like this:</p>
<p><code>swiftlint --config .swiftlint.yml --config .swiftlint_child.yml</code></p>
<h3 id='nested-configurations' class='heading'>Nested Configurations</h3>
<p>In addition to a main configuration (the <code>.swiftlint.yml</code> file in the root folder),
you can put other configuration files named <code>.swiftlint.yml</code> into the directory structure
that then get merged as a child config, but only with an effect for those files
that are within the same directory as the config or in a deeper directory where
there isn&rsquo;t another configuration file. In other words: Nested configurations don&rsquo;t work
recursively there&rsquo;s a maximum number of one nested configuration per file
that may be applied in addition to the main configuration.</p>
<p><code>.swiftlint.yml</code> files are only considered as a nested configuration if they have not been
used to build the main configuration already (e. g. by having been referenced via something
like <code>child_config: Folder/.swiftlint.yml</code>). Also, <code>parent_config</code> / <code>child_config</code>
specifications of nested configurations are getting ignored because there&rsquo;s no sense to that.</p>
<p>If one (or more) SwiftLint file(s) are explicitly specified via the <code>--config</code> parameter,
that configuration will be treated as an override, no matter whether there exist
other <code>.swiftlint.yml</code> files somewhere within the directory. <strong>So if you want to use
nested configurations, you can&rsquo;t use the <code>--config</code> parameter.</strong></p>
<h2 id='license' class='heading'>License</h2>
<p><a href="LICENSE">MIT licensed.</a></p>
<h2 id='about' class='heading'>About</h2>
<p><img src="assets/realm.png" width="184" /></p>
<p>SwiftLint is maintained and funded by Realm Inc. The names and logos for
Realm are trademarks of Realm Inc.</p>
<p>We :heart: open source software!
See <a href="https://github.com/realm">our other open source projects</a>,
read <a href="https://realm.io/news">our blog</a>, or say hi on twitter
(<a href="https://twitter.com/realm">@realm</a>).</p>
<p><img src="assets/macstadium.png" width="184" /></p>
<p>Our thanks to MacStadium for providing a Mac Mini to run our performance
tests.</p>
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