SwiftLint
A tool to enforce Swift style and conventions, loosely based on GitHub'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 info@realm.io.
Installation
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 run realm/SwiftLint
Using a pre-built package:
You can also install SwiftLint by downloading SwiftLint.pkg
from the
latest GitHub release and
running it.
Compiling from source:
You can also build from source by cloning this project and running
git submodule update --init --recursive; make install
(Xcode 9.0 or later).
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:
Xcode
Integrate SwiftLint into an Xcode scheme to get warnings and errors displayed in the IDE. Just add a new "Run Script Phase" with:
if which swiftlint >/dev/null; then
swiftlint
else
echo "warning: SwiftLint not installed, download from https://github.com/realm/SwiftLint"
fi
Alternatively, if you've installed SwiftLint via CocoaPods the script should look like this:
"${PODS_ROOT}/SwiftLint/swiftlint"
Format on Save Xcode Plugin
To run swiftlint autocorrect
on save in Xcode, install the
SwiftLintXcode plugin from Alcatraz.
⚠️This plugin will not work with Xcode 8 or later without disabling SIP. This is not recommended.
AppCode
To integrate SwiftLint with AppCode, install
this plugin and configure
SwiftLint's installed path in the plugin's preferences.
The autocorrect
action is available via ⌥⏎
.
Atom
To integrate SwiftLint with Atom, install the
linter-swiftlint
package from
APM.
fastlane
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)
)
Command Line
$ swiftlint help
Available commands:
autocorrect Automatically correct warnings and errors
help Display general or command-specific help
lint Print lint warnings and errors for the Swift files in the current directory (default command)
rules Display the list of rules and their identifiers
version Display the current version of SwiftLint
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 autocorrect
(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}
.
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
$TOOLCHAIN_DIR
or$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 autocorrect
On Linux, SourceKit is expected to be located in
/usr/lib/libsourcekitdInProc.so
or specified by the LINUX_SOURCEKIT_LIB_PATH
environment variable.
Swift Version Support
Here's a reference of which SwiftLint version to use for a given Swift version.
| Swift version | Last supported SwiftLint release | | ------------- | -------------------------------- | | Swift 1.x | SwiftLint 0.1.2 | | Swift 2.x | SwiftLint 0.18.1 | | Swift 3.x | Latest | | Swift 4.x | Latest |
Rules
Over 75 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 in Rules.md.
You can also check 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 <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.
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 not from the default set.whitelist_rules
: Acts as a whitelist, only the rules specified in this list will be enabled. Can not be specified alongsidedisabled_rules
oropt_in_rules
.
disabled_rules: # rule identifiers to exclude from running
- colon
- comma
- control_statement
opt_in_rules: # some rules are only opt-in
- empty_count
# Find all the available rules by running:
# swiftlint rules
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
# 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
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, junit, html, emoji)
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:
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: "([n,N]inja)" # matching pattern
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: "([n,N]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 alongside a whitelist, make sure to add custom_rules
as an item under whitelist_rules
.
Nested Configurations
SwiftLint supports nesting configuration files for more granular control over the linting process.
- Include additional
.swiftlint.yml
files where necessary in your directory structure. - Each file will be linted using the configuration file that is in its directory or at the deepest level of its parent directories. Otherwise the root configuration will be used.
excluded
andincluded
are ignored for nested configurations.
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 autocorrect
, 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.
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, read our blog, or say hi on twitter (@realm).
Github
link |
Stars: 9206 |
Help us keep the lights on
Used By
Total: 14
Releases
0.25.1 - Apr 8, 2018
This is the last release to support building with Swift 3.2 and Swift 3.3. The next release will require Swift 4.0 or higher to build.
Breaking
- None.
Enhancements
-
Add
LowerACLThanParent
rule.
Keith Smiley #2136 -
Add
UIOffsetMake
tolegacy_constructor
rule.
Nealon Young #2126 -
Add a new
excluded
config parameter to theexplicit_type_interface
rule to exempt certain types of variables from the rule.
Rounak Jain #2028 -
Add
empty_string
opt-in rule to validate against comparing strings to""
instead of using.isEmpty
.
Davide Sibilio -
Add
untyped_error_in_catch
opt-in rule to warn against declaring errors without an explicit type in catch statements instead of using the impliciterror
variable.
Daniel Metzing #2045 -
Add
all
keyword for use in disable / enable statement:// swiftlint:disable all
. It allows disabling SwiftLint entirely, in-code, for a particular section.
fredpi #2071 -
Adds
--force-exclude
option tolint
andautocorrect
commands, which will force SwiftLint to exclude files specified in the configexcluded
even if they are explicitly specified with--path
.
Ash Furrow #2051 -
Adds
discouraged_optional_collection
opt-in rule to encourage the use of empty collections instead of optional collections.
Ornithologist Coder #1885 -
Add 4.1.0, 4.1.1 and 4.2.0 to Swift version detection.
Norio Nomura #2143 -
Support building with Swift 4.1.
Norio Nomura #2038
Bug Fixes
-
Fixes an issue with the
yoda_condition
rule where the severity would always display as a warning, and the reason would display as the severity type.
Twig -
Fix TODOs lint message to state that TODOs should be resolved instead of avoided.
Adonis Peralta #150 -
Fix some cases where
colon
rule wouldn't autocorrect dictionary literals.
Marcelo Fabri #2050 -
Fix linux crash on sources with surrogate pair emojis as variable names.
Cyril Lashkevich -
Make
legacy_constructor
rule more reliable, especially for autocorrecting.
Marcelo Fabri #2098 -
Fix
colon
rule autocorrect when preprocessor macros are present.
Marcelo Fabri #2099 -
Fix crash when saving cache if there're entries referring to the same path but with different capitalization.
Marcelo Fabri #2032 -
Fix several rules (
empty_enum_arguments
,explicit_init
empty_parentheses_with_trailing_closure
,joined_default_parameter
,redundant_optional_initialization
,redundant_void_return
andunused_closure_parameter
) rules autocorrection inside functions or other declarations.
Marcelo Fabri -
Fix
redundant_void_return
rule autocorrect when preprocessor macros are present.
John Szumski #2115 -
Fix issue where the autocorrect done message used the plural form of "files" even if only 1 file changed.
John Szumski -
Fix false positives in
attributes
rule when using Swift 4.1.
Marcelo Fabri #2125 #2141
0.25.0 - Feb 12, 2018
Breaking
- None.
Enhancements
- Adds
discouraged_optional_boolean
opt-in rule to discourage the use of optional booleans.
Ornithologist Coder #2011
Bug Fixes
-
Fix some cases where
colon
rule wouldn't be autocorrected.
Manabu Nakazawa -
Fix false positives in
explicit_acl
rule when declaring functions and properties in protocols or implementingdeinit
.
Marcelo Fabri #2014 -
Fix false negatives in
unneeded_parentheses_in_closure_argument
rule when using_
as one of the closure arguments.
Marcelo Fabri #2017 -
Fix several rules that use attributes when linting with a Swift 4.1 toolchain.
Marcelo Fabri #2019 -
Don't trigger violations in
let_var_whitespace
rule when using local variables when linting with a Swift 4.1 toolchain.
Marcelo Fabri #2021 -
Improve
type_name
rule violations to be positioned on the type name.
Marcelo Fabri #2021 -
Use SourceKit to validate
associatedtype
andtypealias
intype_name
rule when linting with Swift 4.1.
Marcelo Fabri #2021 -
Fix some cases where violations would still be triggered when using the
ignores_function_declarations
configuration ofline_length
rule.
Manabu Nakazawa -
Fix false positive in
empty_enum_arguments
rule when using closures.
Marcelo Fabri #2041 -
Fix false positives in
force_unwrapping
rule when declaring functions that return implicitly unwrapped collections (for example[Int]!
or[AnyHashable: Any]!
).
Marcelo Fabri #2042 -
Fix directories with a
.swift
suffix being treated as files.
Jamie Edge #1948
0.24.2 - Jan 10, 2018
Breaking
- None.
Enhancements
- None.
Bug Fixes
0.24.1: Dented Tumbler
Breaking
- None.
Enhancements
-
Invalidate cache when Swift patch version changes.
Norio Nomura -
Add
private_action
opt-in rule which warns against public @IBAction methods.
Ornithologist Coder #1931 -
Add
yoda_condition
opt-in rule which warns when Yoda conditions are used. That is, when the constant portion of the expression is on the left side of a conditional statement.
Daniel Metzing #1924 -
Indentation can now be specified via a configuration file.
Noah McCann RubenSandwich #319 -
Add
required_enum_case
opt-in rule which allows enums that conform to protocols to require one or more cases. Useful for result enums.
Donald Ritter -
Add
discouraged_object_literal
opt-in rule which encourages initializers over object literals.
Ornithologist Coder #1987 -
Adds
prefixed_toplevel_constant
opt-in rule which encourages top-level constants to be prefixed byk
.
Ornithologist Coder #1907 -
Added
explicit_acl
opt-in rule to enforce explicit access control levels.
Josep Rodriguez #1822
Bug Fixes
-
Fix false positives in
control_statement
rule when methods with keyword names are used.
Marcelo Fabri #1946 -
Fix false positives in
for_where
rule when pattern matching (if case
) is used.
Marcelo Fabri #1968 -
Fix false positives in
unused_closure_parameter
rule when closure is wrapped in parentheses.
JP Simard #1979
0.24.0: Timed Dry
Breaking
-
SwiftLint now requires Xcode 9 and Swift 3.2+ to build.
Marcelo Fabri -
Remove
SwiftExpressionKind.other
.
Marcelo Fabri
Enhancements
-
Add
sorted_first_last
opt-in rule to encourage usingmin()
ormax()
oversorted().first
orsorted().last
.
Tom Quist #1932 -
Add
quick_discouraged_focused_test
opt-in rule which warns against focused tests in Quick tests.
Ornithologist Coder #1905 -
Add
override_in_extension
opt-in rule that warns against overriding declarations in anextension
.
Marcelo Fabri #1884 -
Add
[f,x]{describe, context, itBehavesLike}
toquick_discouraged_call
rule.
Ornithologist Coder #1903 -
Add
quick_discouraged_pending_test
opt-in rule which warns against pending tests in Quick tests.
Ornithologist Coder #1909 -
Speed up equality tests for
[Rule]
andConfiguration
values.
JP Simard -
Make
Configuration
conform toHashable
.
JP Simard -
Speed up reading cached results by about 200%.
JP Simard -
Add
catch
to the statements checked by thecontrol_statement
rule.
JP Simard -
Make
sorted_imports
correctable.
Samuel Susla JP Simard #1822 -
Make
sorted_imports
only validate within "groups" of imports on directly adjacent lines.
Samuel Susla JP Simard #1822
Bug Fixes
-
Extend
first_where
andcontains_over_first_not_nil
rules to also detect cases where calls tofilter
andfirst
are parenthesized.
Tom Quist -
Correct equality tests for
Configuration
values. They previously didn't account forwarningThreshold
orcachePath
.
JP Simard -
Fix false positive in
multiline_parameters
rule when parameter is a closure with default value.
Ornithologist Coder #1912 -
Fix caching on Linux.
JP Simard -
Fix crashes due to races.
JP Simard -
Fix
String.characters
deprecation warnings when compiling with Swift 4.0.2.
JP Simard
0.24.1 - Jan 8, 2018
Breaking
- None.
Enhancements
-
Invalidate cache when Swift patch version changes.
Norio Nomura -
Add
private_action
opt-in rule which warns against public @IBAction methods.
Ornithologist Coder #1931 -
Add
yoda_condition
opt-in rule which warns when Yoda conditions are used. That is, when the constant portion of the expression is on the left side of a conditional statement.
Daniel Metzing #1924 -
Indentation can now be specified via a configuration file.
Noah McCann RubenSandwich #319 -
Add
required_enum_case
opt-in rule which allows enums that conform to protocols to require one or more cases. Useful for result enums.
Donald Ritter -
Add
discouraged_object_literal
opt-in rule which encourages initializers over object literals.
Ornithologist Coder #1987 -
Adds
prefixed_toplevel_constant
opt-in rule which encourages top-level constants to be prefixed byk
.
Ornithologist Coder #1907 -
Added
explicit_acl
opt-in rule to enforce explicit access control levels.
Josep Rodriguez #1822
Bug Fixes
-
Fix false positives in
control_statement
rule when methods with keyword names are used.
Marcelo Fabri #1946 -
Fix false positives in
for_where
rule when pattern matching (if case
) is used.
Marcelo Fabri #1968 -
Fix false positives in
unused_closure_parameter
rule when closure is wrapped in parentheses.
JP Simard #1979
0.24.0 - Nov 10, 2017
Breaking
-
SwiftLint now requires Xcode 9 and Swift 3.2+ to build.
Marcelo Fabri -
Remove
SwiftExpressionKind.other
.
Marcelo Fabri
Enhancements
-
Add
sorted_first_last
opt-in rule to encourage usingmin()
ormax()
oversorted().first
orsorted().last
.
Tom Quist #1932 -
Add
quick_discouraged_focused_test
opt-in rule which warns against focused tests in Quick tests.
Ornithologist Coder #1905 -
Add
override_in_extension
opt-in rule that warns against overriding declarations in anextension
.
Marcelo Fabri #1884 -
Add
[f,x]{describe, context, itBehavesLike}
toquick_discouraged_call
rule.
Ornithologist Coder #1903 -
Add
quick_discouraged_pending_test
opt-in rule which warns against pending tests in Quick tests.
Ornithologist Coder #1909 -
Speed up equality tests for
[Rule]
andConfiguration
values.
JP Simard -
Make
Configuration
conform toHashable
.
JP Simard -
Speed up reading cached results by about 200%.
JP Simard -
Add
catch
to the statements checked by thecontrol_statement
rule.
JP Simard -
Make
sorted_imports
correctable.
Samuel Susla JP Simard #1822 -
Make
sorted_imports
only validate within "groups" of imports on directly adjacent lines.
Samuel Susla JP Simard #1822
Bug Fixes
-
Extend
first_where
andcontains_over_first_not_nil
rules to also detect cases where calls tofilter
andfirst
are parenthesized.
Tom Quist -
Correct equality tests for
Configuration
values. They previously didn't account forwarningThreshold
orcachePath
.
JP Simard -
Fix false positive in
multiline_parameters
rule when parameter is a closure with default value.
Ornithologist Coder #1912 -
Fix caching on Linux.
JP Simard -
Fix crashes due to races.
JP Simard -
Fix
String.characters
deprecation warnings when compiling with Swift 4.0.2.
JP Simard