# SwiftLint A tool to enforce Swift style and conventions, loosely based on the now archived [GitHub Swift Style Guide](https://github.com/github/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 [Ray Wenderlich's Swift Style Guide](https://github.com/raywenderlich/swift-style-guide). SwiftLint hooks into [Clang](http://clang.llvm.org) and [SourceKit](http://www.jpsim.com/uncovering-sourcekit) to use the [AST](http://clang.llvm.org/docs/IntroductionToTheClangAST.html) representation of your source files for more accurate results. [![Build Status](https://dev.azure.com/jpsim/SwiftLint/_apis/build/status/realm.SwiftLint?branchName=master)](https://dev.azure.com/jpsim/SwiftLint/_build/latest?definitionId=4?branchName=master) [![codecov.io](https://codecov.io/github/realm/SwiftLint/coverage.svg?branch=master)](https://codecov.io/github/realm/SwiftLint?branch=master) ![](assets/screenshot.png) This project adheres to the [Contributor Covenant Code of Conduct](https://realm.io/conduct). By participating, you are expected to uphold this code. Please report unacceptable behavior to [info@realm.io](mailto:info@realm.io). > Language Switch: [中文](https://github.com/realm/SwiftLint/blob/master/README_CN.md), [한국어](https://github.com/realm/SwiftLint/blob/master/README_KR.md). ## Installation ### Using [Homebrew](http://brew.sh/): ``` brew install swiftlint ``` ### Using [CocoaPods](https://cocoapods.org): Simply add the following line to your Podfile: ```ruby pod 'SwiftLint' ``` This will download the SwiftLint binaries and dependencies in `Pods/` during your next `pod install` execution and will allow you to invoke it via `${PODS_ROOT}/SwiftLint/swiftlint` in your Script Build Phases. 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). Note that this will add the SwiftLint binaries, its dependencies' binaries, and the Swift binary library distribution to the `Pods/` directory, so checking in this directory to SCM such as git is discouraged. ### Using [Mint](https://github.com/yonaskolb/mint): ``` $ mint install realm/SwiftLint ``` ### Using a pre-built package: You can also install SwiftLint by downloading `SwiftLint.pkg` from the [latest GitHub release](https://github.com/realm/SwiftLint/releases/latest) and running it. ### Installing from source: You can also build and install from source by cloning this project and running `make install` (Xcode 13.3 or later). ### Using Bazel Put this in your `WORKSPACE`:
WORKSPACE ```python load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive") http_archive( name = "build_bazel_rules_apple", sha256 = "36072d4f3614d309d6a703da0dfe48684ec4c65a89611aeb9590b45af7a3e592", url = "https://github.com/bazelbuild/rules_apple/releases/download/1.0.1/rules_apple.1.0.1.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 = "e954f4483f7f4cf523896693ee3505585f6beb0f791e362b42d9bdbb615f051a", url = "https://github.com/realm/SwiftLint/releases/download/0.49.0-rc.1/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: ```console bazel run -c opt @SwiftLint//:swiftlint ``` ## Usage ### Presentation 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: [![Presentation](assets/presentation.svg)](https://academy.realm.io/posts/slug-jp-simard-swiftlint/) ### Xcode Integrate SwiftLint into your Xcode project to get warnings and errors displayed in the issue navigator. 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 "New Run Script Phase". Insert the following as the script: ![](assets/runscript.png) If you installed SwiftLint via Homebrew on Apple Silicon, you might experience this warning: > warning: SwiftLint not installed, download from https://github.com/realm/SwiftLint That is because Homebrew on Apple Silicon installs the binaries into the `/opt/homebrew/bin` folder by default. To instruct Xcode where to find SwiftLint, you can either add `/opt/homebrew/bin` to the `PATH` environment variable in your build phase ```bash export PATH="$PATH:/opt/homebrew/bin" if which swiftlint > /dev/null; then swiftlint else echo "warning: SwiftLint not installed, download from https://github.com/realm/SwiftLint" fi ``` or you can create a symbolic link in `/usr/local/bin` pointing to the actual binary: ```bash ln -s /opt/homebrew/bin/swiftlint /usr/local/bin/swiftlint ``` You might want to move your SwiftLint phase directly before the 'Compile Sources' step to detect errors quickly before compiling. However, SwiftLint is designed to run on valid Swift code that cleanly completes the compiler's parsing stage. So running SwiftLint before 'Compile Sources' might yield some incorrect results. If you wish to fix violations as well, your script could run `swiftlint --fix && swiftlint` instead of just `swiftlint`. This will mean that all correctable violations are fixed while ensuring warnings show up in your project for remaining violations. If you've installed SwiftLint via CocoaPods the script should look like this: ```bash "${PODS_ROOT}/SwiftLint/swiftlint" ``` ### AppCode To integrate SwiftLint with AppCode, install [this plugin](https://plugins.jetbrains.com/plugin/9175) and configure SwiftLint's installed path in the plugin's preferences. The `fix` action is available via `⌥⏎`. ### Atom To integrate SwiftLint with [Atom](https://atom.io/), install the [`linter-swiftlint`](https://atom.io/packages/linter-swiftlint) package from APM. ### Visual Studio Code To integrate SwiftLint with [vscode](https://code.visualstudio.com), install the [`vscode-swiftlint`](https://marketplace.visualstudio.com/items?itemName=vknabel.vscode-swiftlint) extension from the marketplace. ### fastlane You can use the [official swiftlint fastlane action](https://docs.fastlane.tools/actions/swiftlint) to run SwiftLint as part of your fastlane process. ```ruby 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 a [Docker](https://www.docker.com/) image using `Ubuntu`. So just the first time you need to pull the docker image using the next command: ```bash docker pull ghcr.io/realm/swiftlint:latest ``` Then following times, you just run `swiftlint` inside of the docker like: ```bash docker run -it -v `pwd`:`pwd` -w `pwd` ghcr.io/realm/swiftlint:latest ``` This will execute `swiftlint` in the folder where you are right now (`pwd`), showing an output like: ```bash $ docker run -it -v `pwd`:`pwd` -w `pwd` ghcr.io/realm/swiftlint:latest Linting Swift files in current working directory Linting 'RuleDocumentation.swift' (1/490) ... Linting 'YamlSwiftLintTests.swift' (490/490) Done linting! Found 0 violations, 0 serious in 490 files. ``` Here you have more documentation about the usage of [Docker Images](https://docs.docker.com/). ### Command Line ``` $ swiftlint help OVERVIEW: A tool to enforce Swift style and conventions. USAGE: swiftlint 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 rules Display the list of rules and their identifiers version Display the current version of SwiftLint See 'swiftlint help ' for detailed help. ``` Run `swiftlint` in the directory containing the Swift files to lint. Directories will be searched recursively. To specify a list of files when using `lint` or `analyze` (like the list of files modified by Xcode specified by the [`ExtraBuildPhase`](https://github.com/norio-nomura/ExtraBuildPhase) Xcode plugin, or modified files in the working tree based on `git ls-files -m`), you can do so by passing the option `--use-script-input-files` and setting the following instance variables: `SCRIPT_INPUT_FILE_COUNT` and `SCRIPT_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](http://indiestack.com/2014/12/speeding-up-custom-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_DIR` or `$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.framework` is expected to be found in the `usr/lib/` subdirectory of the value passed in the paths above. You may also set the `TOOLCHAINS` environment variable to the reverse-DNS notation that identifies a Swift toolchain version: ```shell $ TOOLCHAINS=com.apple.dt.toolchain.Swift_2_3 swiftlint --fix ``` On Linux, SourceKit is expected to be located in `/usr/lib/libsourcekitdInProc.so` or specified by the `LINUX_SOURCEKIT_LIB_PATH` environment variable. ### pre-commit SwiftLint can be run as a [pre-commit](https://pre-commit.com/) hook. Once [installed](https://pre-commit.com/#install), add this to the `.pre-commit-config.yaml` in the root of your repository: ```yaml repos: - repo: https://github.com/realm/SwiftLint rev: 0.44.0 hooks: - id: swiftlint ``` Adjust `rev` to the SwiftLint version of your choice. ## Rules Over 200 rules are included in SwiftLint and the Swift community (that's you!) continues to contribute more over time. [Pull requests](CONTRIBUTING.md) are encouraged. You can find an updated list of rules and more information about them [here](https://realm.github.io/SwiftLint/rule-directory.html). You can also check [Source/SwiftLintFramework/Rules](https://github.com/realm/SwiftLint/tree/master/Source/SwiftLintFramework/Rules) directory to see their implementation. ### Opt-In Rules `opt_in_rules` are 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 [ ...]` The rules will be disabled until the end of the file or until the linter sees a matching enable comment: `// swiftlint:enable [ ...]` For example: ```swift // swiftlint:disable colon let noWarning :String = "" // No warning about colons immediately after variable names! // swiftlint:enable colon let hasWarning :String = "" // Warning generated about colons immediately after variable names ``` Including the `all` keyword will disable all rules until the linter sees a matching enable comment: `// swiftlint:disable all` `// swiftlint:enable all` For example: ```swift // swiftlint:disable all let noWarning :String = "" // No warning about colons immediately after variable names! let i = "" // Also no warning about short identifier names // swiftlint:enable all let hasWarning :String = "" // Warning generated about colons immediately after variable names let y = "" // Warning generated about short identifier names ``` It's also possible to modify a `disable` or `enable` command by appending `:previous`, `:this` or `:next` for only applying the command to the previous, this (current) or next line respectively. For example: ```swift // swiftlint:disable:next force_cast let noWarning = NSNumber() as! Int let hasWarning = NSNumber() as! Int let noWarning2 = NSNumber() as! Int // swiftlint:disable:this force_cast let noWarning3 = NSNumber() as! Int // swiftlint:disable:previous force_cast ``` Run `swiftlint rules` to print a list of all available rules and their identifiers. ### Configuration Configure SwiftLint by adding a `.swiftlint.yml` file 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. * `only_rules`: Only the rules specified in this list will be enabled. Cannot be specified alongside `disabled_rules` or `opt_in_rules`. * `analyzer_rules`: This is an entirely separate list of rules that are only run by the `analyze` command. All analyzer rules are opt-in, so this is the only configurable rule list, there are no equivalents for `disabled_rules` `only_rules`. ```yaml # 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 included: # paths to include during linting. `--path` is ignored if present. - Source excluded: # paths to ignore during linting. Takes precedence over `included`. - Carthage - Pods - Source/ExcludedFolder - Source/ExcludedFile.swift - Source/*/ExcludedFile.swift # Exclude files with a wildcard analyzer_rules: # Rules run by `swiftlint analyze` - explicit_self # 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) ``` You can also use environment variables in your configuration file, by using `${SOME_VARIABLE}` in a string. #### Defining Custom Rules You can define custom regex-based rules in your configuration file using the following syntax: ```yaml 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: ![](assets/custom-rule.png) You can filter the matches by providing one or more `match_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 If using custom rules in combination with `only_rules`, make sure to add `custom_rules` as an item under `only_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 The `swiftlint analyze` command can lint Swift files using the full type-checked AST. The compiler log path containing the clean `swiftc` build command invocation (incremental builds will fail) must be passed to `analyze` via the `--compiler-log-path` flag. 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. Running `xcodebuild -workspace {WORKSPACE}.xcworkspace -scheme {SCHEME} > xcodebuild.log` 3. Running `swiftlint 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: ```yaml disabled_rules: - force_cast ``` Project-Specific Configuration: ```yaml opt_in_rules: - force_cast ``` ### Child / Parent Configs (Locally) You can specify a `child_config` and / or a `parent_config` 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. **A child config is treated as a refinement and therefore 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.yml` should look like this: ```yaml child_config: .swiftlint_refinement.yml parent_config: Base/.swiftlint_base.yml ``` When merging parent and child configs, `included` and `excluded` configurations 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 local `child_config` / `parent_config` 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 `http://` or `https://`. 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.yml` could look like this: ```yaml parent_config: https://myteamserver.com/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_cached` specifiers. These values default to 2 / 1 second(s). ### 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.yml` file in the root folder), you can put other configuration files named `.swiftlint.yml` 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'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.yml` 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 `child_config: Folder/.swiftlint.yml`). Also, `parent_config` / `child_config` specifications 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.yml` files somewhere within the directory. **So if you want to use nested configurations, you can't use the `--config` parameter.** ## License [MIT licensed.](LICENSE) ## About SwiftLint is maintained and funded by Realm Inc. The names and logos for Realm are trademarks of Realm Inc. We :heart: open source software! See [our other open source projects](https://github.com/realm), read [our blog](https://realm.io/news), or say hi on twitter ([@realm](https://twitter.com/realm)). Our thanks to MacStadium for providing a Mac Mini to run our performance tests.