swiftlint

SwiftLint is the industry-standard linter and formatter for Swift code that enforces style guidelines and best practices based on the community-driven Swift Style Guide. It serves as an essential tool for maintaining high-quality, consistent Swift codebases.

Key Features:

Comprehensive Rule Set: Over 200 built-in rules covering code style, performance, best practices, and potential bug detection
SourceKit Integration: Leverages Apple's SourceKit for accurate AST-based analysis and precise error detection
Automatic Fixing: Intelligent auto-correction for many rule violations, saving manual effort
Highly Configurable: Extensive configuration options with support for enabling/disabling rules and custom severity levels
Custom Rules: Support for project-specific custom rules using regular expressions and AST patterns
Xcode Integration: Seamless integration with Xcode projects through build phases and scheme actions
Performance Optimized: Fast analysis even for large Swift projects with incremental linting support
Multiple Output Formats: Supports various report formats including JSON, HTML, and checkstyle for tool integration

swiftlint documentation

Version in MegaLinter: 0.61.0
Visit Official Web Site
Docker image: ghcr.io/realm/swiftlint:SWIFT_SWIFTLINT_VERSION
- arguments: -v {{WORKSPACE}}:/tmp/lint:rw -w /tmp/lint
See How to configure swiftlint rules
See How to disable swiftlint rules in files
See Index of problems detected by swiftlint

Configuration in MegaLinter

Enable swiftlint by adding SWIFT_SWIFTLINT in ENABLE_LINTERS variable
Disable swiftlint by adding SWIFT_SWIFTLINT in DISABLE_LINTERS variable

Enable autofixes by adding SWIFT_SWIFTLINT in APPLY_FIXES variable

Variable	Description	Default value
SWIFT_SWIFTLINT_DOCKER_IMAGE_VERSION	Docker image version	`SWIFT_SWIFTLINT_VERSION`
SWIFT_SWIFTLINT_ARGUMENTS	User custom arguments to add in linter CLI call Ex: `-s --foo "bar"`
SWIFT_SWIFTLINT_COMMAND_REMOVE_ARGUMENTS	User custom arguments to remove from command line before calling the linter Ex: `-s --foo "bar"`
SWIFT_SWIFTLINT_CLI_LINT_MODE	Override default CLI lint mode ⚠️ As default value is project, overriding might not work - `file`: Calls the linter for each file - `list_of_files`: Call the linter with the list of files as argument - `project`: Call the linter from the root of the project	`project`
SWIFT_SWIFTLINT_FILE_EXTENSIONS	Allowed file extensions. `"*"` matches any extension, `""` matches empty extension. Empty list excludes all files Ex: `[".py", ""]`	`[".swift"]`
SWIFT_SWIFTLINT_FILE_NAMES_REGEX	File name regex filters. Regular expression list for filtering files by their base names using regex full match. Empty list includes all files Ex: `["Dockerfile(-.+)?", "Jenkinsfile"]`	Include every file
SWIFT_SWIFTLINT_PRE_COMMANDS	List of bash commands to run before the linter	None
SWIFT_SWIFTLINT_POST_COMMANDS	List of bash commands to run after the linter	None
SWIFT_SWIFTLINT_UNSECURED_ENV_VARIABLES	List of env variables explicitly not filtered before calling SWIFT_SWIFTLINT and its pre/post commands	None
SWIFT_SWIFTLINT_CONFIG_FILE	swiftlint configuration file name Use `LINTER_DEFAULT` to let the linter find it	`.swiftlint.yml`
SWIFT_SWIFTLINT_RULES_PATH	Path where to find linter configuration file	Workspace folder, then MegaLinter default rules
SWIFT_SWIFTLINT_DISABLE_ERRORS	Run linter but consider errors as warnings	`false`
SWIFT_SWIFTLINT_DISABLE_ERRORS_IF_LESS_THAN	Maximum number of errors allowed	`0`
SWIFT_SWIFTLINT_CLI_EXECUTABLE	Override CLI executable	`['swiftlint']`

IDE Integration

Use swiftlint in your favorite IDE to catch errors before MegaLinter !

	IDE	Extension Name	Install
	IDEA	swiftlint
	xcode	Configure manually	Visit Web Site

MegaLinter Flavors

This linter is available in the following flavors

Flavor	Description	Embedded linters
all	Default MegaLinter Flavor	126
cupcake	MegaLinter for the most commonly used languages	87
swift	Optimized for SWIFT based projects	50

Behind the scenes

How are identified applicable files

Activated only if one of these files is found: .swiftlint.yml
File extensions: .swift

How the linting is performed

swiftlint is called once on the whole project directory (project CLI lint mode)

filtering can not be done using MegaLinter configuration variables,it must be done using swiftlint configuration or ignore file (if existing)
VALIDATE_ALL_CODEBASE: false doesn't make swiftlint analyze only updated files

Example calls

docker run -v /tmp/lint:/tmp/lint:rw ghcr.io/realm/swiftlint:latest swiftlint --strict

docker run -v /tmp/lint:/tmp/lint:rw ghcr.io/realm/swiftlint:latest swiftlint --fix --strict

Help content

OVERVIEW: Print lint warnings and errors

USAGE: swiftlint lint [<options>] [<paths> ...]

ARGUMENTS:
  <paths>                 List of paths to the files or directories to lint.

OPTIONS:
  --config <config>       The path to one or more SwiftLint configuration
                          files, evaluated as a parent-child hierarchy.
  --fix, --autocorrect    Correct violations whenever possible.
  --format                Should reformat the Swift files using the same
                          mechanism used by Xcode (via SourceKit).
                          Only applied with `--fix`/`--autocorrect`.
  --use-alternative-excluding
                          Use an alternative algorithm to exclude paths for
                          `excluded`, which may be faster in some cases.
  --use-script-input-files
                          Read SCRIPT_INPUT_FILE* environment variables as
                          files.
  --use-script-input-file-lists
                          Read SCRIPT_INPUT_FILE_LIST* environment variables as
                          file lists.
  --strict                Upgrades warnings to serious violations (errors).
  --lenient               Downgrades serious violations to warnings, warning
                          threshold is disabled.
  --force-exclude         Exclude files in config `excluded` even if their
                          paths are explicitly specified.
  --benchmark             Save benchmarks to `benchmark_files.txt` and
                          `benchmark_rules.txt`.
  --reporter <reporter>   The reporter used to log errors and warnings.
  --baseline <baseline>   The path to a baseline file, which will be used to
                          filter out detected violations.
  --write-baseline <write-baseline>
                          The path to save detected violations to as a new
                          baseline.
  --working-directory <working-directory>
                          The working directory to use when running SwiftLint.
  --output <output>       The file where violations should be saved. Prints to
                          stdout by default.
  --progress              Show a live-updating progress bar instead of each
                          file being processed.
  --check-for-updates     Check whether a later version of SwiftLint is
                          available after processing all files.
  --only-rule <only-rule> Run only the specified rule, ignoring `only_rules`,
                          `opt_in_rules` and `disabled_rules`.
                          Can be specified repeatedly to run multiple rules.
  --use-stdin             Lint standard input.
  --quiet                 Don't print status logs like 'Linting <file>' & 'Done
                          linting'.
  --silence-deprecation-warnings
                          Don't print deprecation warnings.
  --cache-path <cache-path>
                          The directory of the cache used when linting.
  --no-cache              Ignore cache when linting.
  --enable-all-rules      Run all rules, even opt-in and disabled ones,
                          ignoring `only_rules`.
  --version               Show the version.
  -h, --help              Show help information.

Installation on mega-linter Docker image

Dockerfile commands :

# renovate: datasource=docker depName=ghcr.io/realm/swiftlint
ENV SWIFT_SWIFTLINT_VERSION=0.61.0