A tool to enforce Swift style and conventions, loosely based on the now archived 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.
SwiftLint hooks into Clang and SourceKit to use the AST representation 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].
Using Homebrew:
brew install swiftlint
Using CocoaPods:
Simply add the following line to your Podfile:
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:
$ mint install realm/SwiftLint
You can also install SwiftLint by downloading SwiftLint.pkg
from the
latest GitHub release and
running it.
You can also build and install from source by cloning this project and running
make install
(Xcode 13.3 or later).
Put this in your WORKSPACE
:
WORKSPACE
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 = "d34bf123e6380a7527ee78c5f6ec7ede5e00e8c39a9c3b394f590374f566c57d",
url = "https://github.com/realm/SwiftLint/releases/download/0.49.0-rc.2/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
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:
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:
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
export PATH="$PATH:/opt/homebrew/bin"
if which swiftlint > /dev/null; then
swiftlint
else
echo "warning: SwiftLint not installed, download from https://github.com/realm/SwiftLint"
fi
or you can create a symbolic link in /usr/local/bin
pointing to the actual binary:
ln -s /opt/homebrew/bin/swiftlint /usr/local/bin/swiftlint
You might want to move your SwiftLint phase directly before the 'Compile Sources' step to detect errors quickly before compiling. However, SwiftLint is designed to run on valid Swift code that cleanly completes the compiler's parsing stage. So running SwiftLint before 'Compile Sources' might yield some incorrect results.
If you wish to fix violations as well, your script could run
swiftlint --fix && swiftlint
instead of just swiftlint
. This will mean
that all correctable violations are fixed while ensuring warnings show up in
your project for remaining violations.
If you've installed SwiftLint via CocoaPods the script should look like this:
"${PODS_ROOT}/SwiftLint/swiftlint"
To integrate SwiftLint with AppCode, install
this plugin and configure
SwiftLint's installed path in the plugin's preferences.
The fix
action is available via ⌥⏎
.
To integrate SwiftLint with Atom, install the
linter-swiftlint
package from
APM.
To integrate SwiftLint with vscode, install the
vscode-swiftlint
extension from the marketplace.
You can use the official swiftlint fastlane 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)
)
swiftlint
is also available as a Docker image 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 run swiftlint
inside of the docker like:
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:
$ 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.
$ 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 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 <subcommand>' 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
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.
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:
$ 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.
SwiftLint can be run as a pre-commit hook.
Once installed, add this to the
.pre-commit-config.yaml
in the root of your repository:
repos:
- repo: https://github.com/realm/SwiftLint
rev: 0.44.0
hooks:
- id: swiftlint
Adjust rev
to the SwiftLint version of your choice.
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 Source/SwiftLintFramework/Rules directory to see their implementation.
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
)
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
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:
// 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:
// 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.
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 alongsidedisabled_rules
oropt_in_rules
.analyzer_rules
: This is an entirely separate list of rules that are only run by theanalyze
command. All analyzer rules are opt-in, so this is the only configurable rule list, there are no equivalents fordisabled_rules
only_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
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.
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:
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
.
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.
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
- Cleaning DerivedData (incremental builds won't work with analyze)
- Running
xcodebuild -workspace {WORKSPACE}.xcworkspace -scheme {SCHEME} > xcodebuild.log
- Running
swiftlint analyze --compiler-log-path xcodebuild.log
Analyzer rules tend to be considerably slower than lint rules.
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
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:
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.
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 https://
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:
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).
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
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.
SwiftLint is maintained and funded by Realm Inc. The names and logos for Realm are trademarks of Realm Inc.
We ❤️ open source software! See our other open source projects, read our blog, or say hi on twitter (@realm).
Our thanks to MacStadium for providing a Mac Mini to run our performance tests.