SwiftLint

A tool to enforce Swift style and conventions, loosely based on the now archivedGitHub Swift Style Guide. SwiftLint enforces the style guide rules that are generally accepted by the Swift community. These rules are well described in popular style guides like Kodeco's Swift Style Guide.

SwiftLint hooks intoClangand SourceKitto use the ASTrepresentation of your source files for more accurate results.

This project adheres to the Contributor Covenant Code of Conduct. By participating, you are expected to uphold this code. Please report unacceptable behavior to[email protected].

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Video Introduction

To get a high-level overview of SwiftLint, we encourage you to watch this presentation recorded January 9th, 2017 by JP Simard (transcript provided):

Installation

Swift Package Manager

SwiftLint can be used as acommand plugin or abuild tool plugin.

Add

.package(url:"https://github /SimplyDanny/SwiftLintPlugins",from:"<version>")

to yourPackage.swiftfile to consume the latest release of SwiftLint automatically or pin the dependency to a specific version:

.package(url:"https://github /SimplyDanny/SwiftLintPlugins",exact:"<version>")

Therein, replace<version>with the desired minimum or exact version.

Note

Consuming the plugins directly from the SwiftLint repository comes with several drawbacks. To avoid them and reduce the overhead imposed, it's highly recommended to consume the plugins from the dedicated SwiftLintPlugins repository, even though plugins from the SwiftLint repository are also absolutely functional. If the plugins from SwiftLint are preferred, just use the URL https://github /realm/SwiftLintin the package declarations above.

However,SwiftLintPlugins facilitates plugin adoption massively. It lists some of the reasons that drive the plugins as provided by SwiftLint itself very troublesome. Since the plugin code and the releases are kept in sync, there is no difference in functionality between the two, but you spare yourself a lot of time and trouble using the dedicated plugins repository.

This document assumes you're relying on SwiftLintPlugins.

Xcode Package Dependency

Use the following link to add SwiftLint as a Package Dependency to an Xcode project:

https://github /SimplyDanny/SwiftLintPlugins

Homebrew

brew install swiftlint

CocoaPods

Add the following to yourPodfile:

pod'SwiftLint'

This will download the SwiftLint binaries and dependencies inPods/during your nextpod installexecution and will allow you to invoke it via ${PODS_ROOT}/SwiftLint/swiftlintin your Script Build Phases.

Installing via Cocoapods also enables pinning to a specific version of SwiftLint rather than simply the latest (which is the case with Homebrew).

Note that this will add the SwiftLint binaries, its dependencies' binaries, and the Swift binary library distribution to thePods/directory, so checking in this directory to SCM such as Git is discouraged.

Mint

mint install realm/SwiftLint

Bazel

Put this in yourMODULE.bazel:

bazel_dep(name="swiftlint",version="0.52.4",repo_name="SwiftLint")

Or put this in yourWORKSPACE:

WORKSPACE

load("@bazel_tools//tools/build_defs/repo:http.bzl","http_archive")

http_archive(
name="build_bazel_rules_apple",
sha256="390841dd5f8a85fc25776684f4793d56e21b098dfd7243cd145b9831e6ef8be6",
url="https://github /bazelbuild/rules_apple/releases/download/2.4.1/rules_apple.2.4.1.tar.gz",
)

load(
"@build_bazel_rules_apple//apple:repositories.bzl",
"apple_rules_dependencies",
)

apple_rules_dependencies()

load(
"@build_bazel_rules_swift//swift:repositories.bzl",
"swift_rules_dependencies",
)

swift_rules_dependencies()

load(
"@build_bazel_rules_swift//swift:extras.bzl",
"swift_rules_extra_dependencies",
)

swift_rules_extra_dependencies()

http_archive(
name="SwiftLint",
sha256="c6ea58b9c72082cdc1ada4a2d48273ecc355896ed72204cedcc586b6ccb8aca6",
url="https://github /realm/SwiftLint/releases/download/0.52.4/bazel.tar.gz",
)

load("@SwiftLint//bazel:repos.bzl","swiftlint_repos")

swiftlint_repos()

load("@SwiftLint//bazel:deps.bzl","swiftlint_deps")

swiftlint_deps()

Then you can run SwiftLint in the current directory with this command:

bazel run -c opt @SwiftLint//:swiftlint

Pre-Built Package

DownloadSwiftLint.pkgfrom the latest GitHub releaseand run it.

From Source

Make sure the build toolBazeland a recentSwift toolchainare installed and all tools are discoverable in yourPATH.

To build SwiftLint, clone this repository and runmake install.

Setup

Important

While it may seem intuitive to run SwiftLint before compiling Swift source files to exit a build early when there are lint violations, it is important to understand that SwiftLint is designed to analyze valid source code that is compilable. Non-compiling code can very easily lead to unexpected and confusing results, especially when executing with--fix/--autocorrect command line arguments.

Build Tool Plugins

SwiftLint can be used as a build tool plugin for both Swift Package projects andXcode projects.

The build tool plugin determines the SwiftLint working directory by locating the topmost config file within the package/project directory. If a config file is not found therein, the package/project directory is used as the working directory.

The plugin throws an error when it is unable to resolve the SwiftLint working directory. For example, this will occur in Xcode projects where the target's Swift files are not located within the project directory.

To maximize compatibility with the plugin, avoid project structures that require the use of the--configoption.

Swift Package Projects

Note

Requires installing viaSwift Package Manager.

Build tool plugins run when building each target. When a project has multiple targets, the plugin must be added to the desired targets individually.

To do this, add the plugin to the target(s) to be linted as follows:

.target(
...
plugins:[.plugin(name:"SwiftLintBuildToolPlugin",package:"SwiftLintPlugins")]
),

Swift Package Command Plugin

Note

Requires installing viaSwift Package Manager.

The command plugin enables running SwiftLint from the command line as follows:

swift package plugin swiftlint

Xcode Projects

Note

Requires installing viaXcode Package Dependency.

Build tool plugins run as a build phase of each target. When a project has multiple targets, the plugin must be added to the desired targets individually.

To do this, add theSwiftLintBuildToolPluginto theRun Build Tool Plug-ins phase of theBuild Phasesfor the target(s) to be linted.

Tip

When using the plugin for the first time, be sure to trust and enable it when prompted. If a macros build warning exists, select it to trust and enable the macros as well.

For unattended use (e.g. on CI), package plugin and macro validations can be disabled with either of the following:

• Usingxcodebuildoptions:

  -skipPackagePluginValidation
  -skipMacroValidation

• Setting Xcode defaults:

  defaults write com.apple.dt.Xcode IDESkipPackagePluginFingerprintValidatation -bool YES
  defaults write com.apple.dt.Xcode IDESkipMacroFingerprintValidation -bool YES

Important

The unattended use options bypass Xcode's validation dialogs and implicitly trust all plugins and macros, which has security implications.

Unexpected Xcode Project Structures

Project structures where SwiftLint's configuration file is located outside of the package/project directory are not directly supported by the build tool plugin. This is because it isn't possible to pass arguments to build tool plugins (e.g., passing the config file path).

If your project structure doesn't work directly with the build tool plugin, please consider one of the following options:

• To use a config file located outside the package/project directory, a config file may be added to that directory specifying a parent config path to the other config file, e.g.,parent_config: path/to/.swiftlint.yml.
• You can also consider the use of a Run Script Build Phasein place of the build tool plugin.

Xcode Run Script Build Phase

Note

Based upon the installation method used, the shell command syntax in the Run Script Build Phase may be different or additional configuration could be required. Refer to theinstallationinstructions for more information.

If the build tool plugin does not work for your project setup or when additional custom setup is required, SwiftLint can be added as a Run Script Build Phase. This is useful when a project setup relies on the--config SwiftLint option; or to lint all targets together in a singleswiftlint invocation. File inclusions and exclusions can be configured in the .swiftlint.ymlconfiguration.

To do this, add a custom script to aRun Scriptphase of theBuild Phases of the primary app target, after theCompile Sourcesphase. Use the following script implementation:

ifcommand-v swiftlint>/dev/null2>&1
then
swiftlint
else
echo"warning:`swiftlint`command not found - See https://github /realm/SwiftLint#installation for installation instructions."
fi

If you're using the SwiftLintPlugin in a Swift package, you may refer to theswiftlintexecutable in the following way:

SWIFT_PACKAGE_DIR="${BUILD_DIR%Build/*}SourcePackages/artifacts"
SWIFTLINT_CMD=$(ls"$SWIFT_PACKAGE_DIR"/swiftlintplugins/SwiftLintBinary/SwiftLintBinary.artifactbundle/swiftlint-*/bin/swiftlint|head -n 1)

iftest-f"$SWIFTLINT_CMD"2>&1
then
"$SWIFTLINT_CMD"
else
echo"warning:`swiftlint`command not found - See https://github /realm/SwiftLint#installation for installation instructions."
fi

Note

TheSWIFTLINT_CMDpath uses the default Xcode configuration and has been tested on Xcode 15/16. In case of another configuration (e.g. a custom Swift package path), please adapt the values accordingly.

Tip

UncheckBased on dependency analysisto runswiftlinton all incremental builds, suppressing the unspecified outputs warning.

Consideration for Xcode 15.0

Xcode 15 made a significant change by setting the default value of the ENABLE_USER_SCRIPT_SANDBOXINGbuild setting fromNOtoYES. As a result, SwiftLint encounters an error related to missing file permissions, which typically manifests as error: Sandbox: swiftlint(19427) deny(1) file-read-data.

To resolve this issue, it is necessary to manually set the ENABLE_USER_SCRIPT_SANDBOXINGsetting toNOfor the specific target that SwiftLint is being configured for.

Consideration for Apple Silicon

If you installed SwiftLint via Homebrew on Apple Silicon, you might experience this warning:

warning: SwiftLint not installed, download from https://github /realm/SwiftLint

That is because Homebrew on Apple Silicon installs the binaries into the /opt/homebrew/binfolder by default. To instruct Xcode where to find SwiftLint, you can either add/opt/homebrew/binto thePATHenvironment variable in your build phase:

if[["$(uname -m)"==arm64 ]]
then
exportPATH="/opt/homebrew/bin:$PATH"
fi

ifcommand-v swiftlint>/dev/null2>&1
then
swiftlint
else
echo"warning:`swiftlint`command not found - See https://github /realm/SwiftLint#installation for installation instructions."
fi

or you can create a symbolic link in/usr/local/binpointing to the actual binary:

ln -s /opt/homebrew/bin/swiftlint /usr/local/bin/swiftlint

Additional Considerations

If you wish to fix violations as well, your script could run swiftlint --fix && swiftlintinstead of justswiftlint.This will mean that all correctable violations are fixed while ensuring warnings show up in your project for remaining violations.

If you've installed SwiftLint via CocoaPods the script should look like this:

"${PODS_ROOT}/SwiftLint/swiftlint"

Visual Studio Code

To integrate SwiftLint withVisual Studio Code,install the vscode-swiftlint extension from the marketplace.

Fastlane

You can use the official swiftlintfastlane action to run SwiftLint as part of your fastlane process.

swiftlint(
mode::lint,# SwiftLint mode::lint (default) or:autocorrect
executable:"Pods/SwiftLint/swiftlint",# The SwiftLint binary path (optional). Important if you've installed it via CocoaPods
path:"/path/to/lint",# Specify path to lint (optional)
output_file:"swiftlint.result.json",# The path of the output file (optional)
reporter:"json",# The custom reporter to use (optional)
config_file:".swiftlint-ci.yml",# The path of the configuration file (optional)
files:[# List of files to process (optional)
"AppDelegate.swift",
"path/to/project/Model.swift"
],
ignore_exit_status:true,# Allow fastlane to continue even if SwiftLint returns a non-zero exit status (Default: false)
quiet:true,# Don't print status logs like 'Linting ' & 'Done linting' (Default: false)
strict:true# Fail on warnings? (Default: false)
)

Docker

SwiftLint is also available as aDockerimage using Ubuntu.So just the first time you need to pull the docker image using the next command:

docker pull ghcr.io/realm/swiftlint:latest

Then following times, you just runswiftlintinside of the docker like:

docker run -it -v`pwd`:`pwd`-w`pwd`ghcr.io/realm/swiftlint:latest

This will executeswiftlintin the folder where you are right now (pwd), showing an output like:

$ docker run -it -v`pwd`:`pwd`-w`pwd`ghcr.io/realm/swiftlint:latest
Linting Swift filesincurrent working directory
Linting'RuleDocumentation.swift'(1/490)
...
Linting'YamlSwiftLintTests.swift'(490/490)
Done linting!Found 0 violations, 0 seriousin490 files.

Here you have more documentation about the usage of Docker Images.

Command Line Usage

$swiftlint help
OVERVIEW: A tool to enforce Swift style and conventions.

USAGE: swiftlint <subcommand>

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 selected group of rules
lint (default) Print lint warnings and errors
baseline Operations on existing baselines
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 <subcommand>' for detailed help.

Runswiftlintin the directory containing the Swift files to lint. Directories will be searched recursively.

To specify a list of files when usinglintoranalyze (like the list of files modified by Xcode specified by the ExtraBuildPhaseXcode plugin, or modified files in the working tree based ongit ls-files -m), you can do so by passing the option--use-script-input-filesand setting the following instance variables:SCRIPT_INPUT_FILE_COUNT andSCRIPT_INPUT_FILE_0,SCRIPT_INPUT_FILE_1,..., SCRIPT_INPUT_FILE_{SCRIPT_INPUT_FILE_COUNT - 1}.

These are same environment variables set for input files to custom Xcode script phases.

Working With Multiple Swift Versions

SwiftLint hooks into SourceKit so it continues working even as Swift evolves!

This also keeps SwiftLint lean, as it doesn't need to ship with a full Swift compiler, it just communicates with the official one you already have installed on your machine.

You should always run SwiftLint with the same toolchain you use to compile your code.

You may want to override SwiftLint's default Swift toolchain if you have multiple toolchains or Xcodes installed.

Here's the order in which SwiftLint determines which Swift toolchain to use:

• $XCODE_DEFAULT_TOOLCHAIN_OVERRIDE
• $TOOLCHAIN_DIRor$TOOLCHAINS
• xcrun -find swift
• /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain
• /Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain
• ~/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain
• ~/Applications/Xcode-beta.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain

sourcekitd.frameworkis expected to be found in theusr/lib/subdirectory of the value passed in the paths above.

You may also set theTOOLCHAINSenvironment variable to the reverse-DNS notation that identifies a Swift toolchain version:

TOOLCHAINS=com.apple.dt.toolchain.Swift_2_3 swiftlint --fix

On Linux, SourceKit is expected to be located in /usr/lib/libsourcekitdInProc.soor specified by theLINUX_SOURCEKIT_LIB_PATH environment variable.

Gitpre-commitHook

SwiftLint can be run as apre-commithook. Onceinstalled,add this to the .pre-commit-config.yamlin the root of your repository:

repos:
-repo:https://github /realm/SwiftLint
rev:0.50.3
hooks:
-id:swiftlint

Adjustrevto the SwiftLint version of your choice.pre-commit autoupdate can be used to update to the current version.

SwiftLint can be configured usingentryto apply fixes and fail on errors:

-repo:https://github /realm/SwiftLint
rev:0.50.3
hooks:
-id:swiftlint
entry:swiftlint --fix --strict

Rules

Over 200 rules are included in SwiftLint and the Swift community (that's you!) continues to contribute more over time. Pull requests are encouraged.

You can find an updated list of rules and more information about them here.

You can also check the Source/SwiftLintBuiltInRules/Rules directory to see their implementation.

Opt-In Rules

opt_in_rulesare disabled by default (i.e., you have to explicitly enable them in your configuration file).

Guidelines on when to mark a rule as opt-in:

• A rule that can have many false positives (e.g.empty_count)
• A rule that is too slow
• A rule that is not general consensus or is only useful in some cases (e.g.force_unwrapping)

Disable rules in code

Rules can be disabled with a comment inside a source file with the following format:

// swiftlint:disable <rule1> [<rule2> <rule3>...]

The rules will be disabled until the end of the file or until the linter sees a matching enable comment:

// swiftlint:enable <rule1> [<rule2> <rule3>...]

For example:

// swiftlint:disable colon
letnoWarning:String=""// No warning about colons immediately after variable names!
// swiftlint:enable colon
lethasWarning:String=""// Warning generated about colons immediately after variable names

Including theallkeyword will disable all rules until the linter sees a matching enable comment:

// swiftlint:disable all // swiftlint:enable all

For example:

// swiftlint:disable all
letnoWarning:String=""// No warning about colons immediately after variable names!
leti=""// Also no warning about short identifier names
// swiftlint:enable all
lethasWarning:String=""// Warning generated about colons immediately after variable names
lety=""// Warning generated about short identifier names

It's also possible to modify adisableorenablecommand by appending :previous,:thisor:nextfor only applying the command to the previous, this (current) or next line respectively.

For example:

// swiftlint:disable:next force_cast
letnoWarning=NSNumber()as!Int
lethasWarning=NSNumber()as!Int
letnoWarning2=NSNumber()as!Int// swiftlint:disable:this force_cast
letnoWarning3=NSNumber()as!Int
// swiftlint:disable:previous force_cast

Runswiftlint rulesto print a list of all available rules and their identifiers.

Configuration

Configure SwiftLint by adding a.swiftlint.ymlfile from the directory you'll run SwiftLint from. The following parameters can be configured:

Rule inclusion:

• disabled_rules:Disable rules from the default enabled set.
• opt_in_rules:Enable rules that are not part of the default set. The specialallidentifier will enable all opt in linter rules, except the ones listed indisabled_rules.
• only_rules:Only the rules specified in this list will be enabled. Cannot be specified alongsidedisabled_rulesoropt_in_rules.
• analyzer_rules:This is an entirely separate list of rules that are only run by theanalyzecommand. All analyzer rules are opt-in, so this is the only configurable rule list, there are no equivalents fordisabled_rules andonly_rules.The specialallidentifier can also be used here to enable all analyzer rules, except the ones listed indisabled_rules.

#By default, SwiftLint uses a set of sensible default rules you can adjust:
disabled_rules:#rule identifiers turned on by default to exclude from running
-colon
-comma
-control_statement
opt_in_rules:#some rules are turned off by default, so you need to opt-in
-empty_count#find all the available rules by running: `swiftlint rules`

#Alternatively, specify all rules explicitly by uncommenting this option:
#only_rules: # delete `disabled_rules` & `opt_in_rules` if using this
#- empty_parameters
#- vertical_whitespace

analyzer_rules:#rules run by `swiftlint analyze`
-explicit_self

#Case-sensitive paths to include during linting. Directory paths supplied on the
#command line will be ignored.
included:
-Sources
excluded:#case-sensitive paths to ignore during linting. Takes precedence over `included`
-Carthage
-Pods
-Sources/ExcludedFolder
-Sources/ExcludedFile.swift
-Sources/*/ExcludedFile.swift#exclude files with a wildcard

#If true, SwiftLint will not fail if no lintable files are found.
allow_zero_lintable_files:false

#If true, SwiftLint will treat all warnings as errors.
strict:false

#The path to a baseline file, which will be used to filter out detected violations.
baseline:Baseline.json

#The path to save detected violations to as a new baseline.
write_baseline:Baseline.json

#If true, SwiftLint will check for updates after linting or analyzing.
check_for_updates:true

#configurable rules can be customized from this configuration file
#binary rules can set their severity level
force_cast:warning#implicitly
force_try:
severity:warning#explicitly
#rules that have both warning and error levels, can set just the warning level
#implicitly
line_length:110
#they can set both implicitly with an array
type_body_length:
-300#warning
-400#error
#or they can set both explicitly
file_length:
warning:500
error:1200
#naming rules can set warnings/errors for min_length and max_length
#additionally they can set excluded names
type_name:
min_length:4#only warning
max_length:#warning and error
warning:40
error:50
excluded:iPhone#excluded via string
allowed_symbols:[ "_" ]#these are allowed in type names
identifier_name:
min_length:#only min_length
error:4#only error
excluded:#excluded via string array
-id
-URL
-GlobalAPIKey
reporter:"xcode"#reporter type (xcode, json, csv, checkstyle, codeclimate, junit, html, emoji, sonarqube, markdown, github-actions-logging, summary)

You can also use environment variables in your configuration file, by using${SOME_VARIABLE}in a string.

Defining Custom Rules

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:

1. Swift Custom Rules

These rules are written the same way as the Swift-based rules that ship with SwiftLint so they're fast, accurate, can leverage SwiftSyntax, can be unit tested, and more.

Using these requires building SwiftLint with Bazel as described in this videoor its associated code in github /jpsim/swiftlint-bazel-example.

2. Regex Custom Rules

You can define custom regex-based rules in your configuration file using the following syntax:

custom_rules:
pirates_beat_ninjas:#rule identifier
included:
-".*\\.swift"#regex that defines paths to include during linting. optional.
excluded:
-".*Test\\.swift"#regex that defines paths to exclude during linting. optional
name:"Pirates Beat Ninjas"#rule name. optional.
regex:"([nN]inja)"#matching pattern
capture_group:0#number of regex capture group to highlight the rule violation at. optional.
match_kinds:#SyntaxKinds to match. optional.
-comment
-identifier
message:"Pirates are better than ninjas."#violation message. optional.
severity:error#violation severity. optional.
no_hiding_in_strings:
regex:"([nN]inja)"
match_kinds:string

This is what the output would look like:

It is important to note that the regular expression pattern is used with the flagssandmenabled, that is. matches newlines and^/$ match the start and end of lines, respectively. If you do not want to have.match newlines, for example, the regex can be prepended by(?-s).

You can filter the matches by providing one or morematch_kinds,which will reject matches that include syntax kinds that are not present in this list. Here are all the possible syntax kinds:

• argument
• attribute.builtin
• attribute.id
• buildconfig.id
• buildconfig.keyword
• comment
• comment.mark
• comment.url
• doccomment
• doccomment.field
• identifier
• keyword
• number
• objectliteral
• parameter
• placeholder
• string
• string_interpolation_anchor
• typeidentifier

All syntax kinds used in a snippet of Swift code can be extracted asking SourceKitten.For example, sourcekitten syntax --text "struct S {}"delivers

• source.lang.swift.syntaxtype.keywordfor thestructkeyword and
• source.lang.swift.syntaxtype.identifierfor its nameS

which match tokeywordandidentifierin the above list.

If using custom rules in combination withonly_rules,you must include the literal stringcustom_rulesin theonly_ruleslist:

only_rules:
-custom_rules

custom_rules:
no_hiding_in_strings:
regex:"([nN]inja)"
match_kinds:string

Unlike Swift custom rules, you can use official SwiftLint builds (e.g. from Homebrew) to run regex custom rules.

Auto-correct

SwiftLint can automatically correct certain violations. Files on disk are overwritten with a corrected version.

Please make sure to have backups of these files before running swiftlint --fix,otherwise important data may be lost.

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.

Analyze

Theswiftlint analyzecommand can lint Swift files using the full type-checked AST. The compiler log path containing the cleanswiftcbuild command invocation (incremental builds will fail) must be passed toanalyze via the--compiler-log-pathflag. e.g.--compiler-log-path /path/to/xcodebuild.log

This can be obtained by

1. Cleaning DerivedData (incremental builds won't work with analyze)
2. Runningxcodebuild -workspace {WORKSPACE}.xcworkspace -scheme {SCHEME} > xcodebuild.log
3. Runningswiftlint analyze --compiler-log-path xcodebuild.log

Analyzer rules tend to be considerably slower than lint rules.

Using Multiple Configuration Files

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.

There are quite a lot of use cases where using multiple configuration files could be helpful:

For instance, one could use a team-wide shared SwiftLint configuration while allowing overrides in each project via a child configuration file.

Team-Wide Configuration:

disabled_rules:
-force_cast

Project-Specific Configuration:

opt_in_rules:
-force_cast

Child/Parent Configs (Locally)

You can specify achild_configand/or aparent_configreference 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.

A child config is treated as a refinement and thus has a higher priority, while a parent config is considered a base with lower priority in case of conflicts.

Here's an example, assuming you have the following file structure:

ProjectRoot
|_.swiftlint.yml
|_.swiftlint_refinement.yml
|_ Base
|_.swiftlint_base.yml

To include both the refinement and the base file, your.swiftlint.ymlshould look like this:

child_config:.swiftlint_refinement.yml
parent_config:Base/.swiftlint_base.yml

When merging parent and child configs,includedandexcludedconfigurations are processed carefully to account for differences in the directory location of the containing configuration files.

Child/Parent Configs (Remote)

Just as you can provide localchild_config/parent_configreferences, 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 withhttp://orhttps://.

The referenced remote configuration files may even recursively reference other remote configuration files, but aren't allowed to include local references.

Using a remote reference, your.swiftlint.ymlcould look like this:

parent_config:https://myteamserver /our-base-swiftlint-config.yml

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.

If needed, the timeouts for the remote configuration fetching can be specified manually via the configuration file(s) using the remote_timeout/remote_timeout_if_cachedspecifiers. These values default to 2 seconds or 1 second, respectively.

Command Line

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.

A simple example including just two configuration files looks like this:

swiftlint --config.swiftlint.yml --config.swiftlint_child.yml

Nested Configurations

In addition to a main configuration (the.swiftlint.ymlfile in the root folder), you can put other configuration files named.swiftlint.ymlinto 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't another configuration file. In other words: Nested configurations don't work recursively – there's a maximum number of one nested configuration per file that may be applied in addition to the main configuration.

.swiftlint.ymlfiles 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 likechild_config: Folder/.swiftlint.yml). Also,parent_config/child_configspecifications of nested configurations are getting ignored because there's no sense to that.

If one (or more) SwiftLint file(s) are explicitly specified via the--config parameter, that configuration will be treated as an override, no matter whether there exist other.swiftlint.ymlfiles somewhere within the directory. So if you want to use nested configurations, you can't use the--config parameter.

License

MIT licensed.

About

SwiftLint is maintained and funded by Realm Inc. The names and logos for Realm are trademarks of Realm Inc.

We ❤️ open source software! Seeour other open source projects, readour blog,or say hi on twitter (@realm).

Our thanks to MacStadium for providing a Mac Mini to run our performance tests.