Ktlint Gradle

Provides a convenient wrapper plugin over the ktlint project.

Latest plugin version: 9.4.1

This plugin creates convenient tasks in your Gradle project that run ktlint checks or do code auto format.

The plugin can be applied to any project, but only activates if that project has the kotlin plugin applied. The assumption being that you would not want to lint code you weren't compiling.

Table of content

• Supported Kotlin plugins
• How to use
  • Minimal support versions
  • Ktlint plugin
    • Simple setup
    • Using new plugin API
    • How to apply to all subprojects
  • Intellij IDEA plugin
    • Simple setup
    • Using new plugin API
  • Plugin configuration
    • Setting reports output directory
    • Customer reporters
  • Samples
• Task details
  • Main tasks
  • Additional tasks
• FAQ
• Developers
  • Importing the project
  • Building the project
• Links

Supported Kotlin plugins

This plugin supports the following kotlin plugins:

• "kotlin"
• "kotlin-android"
• "kotlin-multiplatform"
• project kotlin script files
• "org.jetbrains.kotlin.js"

If you know any new Kotlin plugin that is not in this list - please, open a new issue.

How to use

Minimal supported versions

This plugin was written using the new API available for the Gradle script Kotlin builds. This API is available in new versions of Gradle.

Minimal supported Gradle version: 5.4.1

Minimal supported ktlint version: 0.22.0

Ktlint plugin

Simple setup

Build script snippet for use in all Gradle versions:

Groovy

buildscript {
  repositories {
    maven {
      url "https://plugins.gradle.org/m2/"
    }
  }
  dependencies {
    classpath "org.jlleitschuh.gradle:ktlint-gradle:<current_version>"
  }
}

apply plugin: "org.jlleitschuh.gradle.ktlint"

Kotlin

buildscript {
  repositories {
    maven("https://plugins.gradle.org/m2/")
  }
  dependencies {
    classpath("org.jlleitschuh.gradle:ktlint-gradle:<current_version>")
  }
}

apply(plugin = "org.jlleitschuh.gradle.ktlint")

Using new plugin API

Build script snippet for new, incubating, plugin mechanism introduced in Gradle 2.1:

plugins {
  id "org.jlleitschuh.gradle.ktlint" version "<current_version>"
}

Applying to subprojects

Optionally apply plugin to all project modules:

Groovy

subprojects {
    apply plugin: "org.jlleitschuh.gradle.ktlint" // Version should be inherited from parent
    
    // Optionally configure plugin
    ktlint {
       debug = true
    }
}

Kotlin

subprojects {
    apply(plugin = "org.jlleitschuh.gradle.ktlint") // Version should be inherited from parent
    
    // Optionally configure plugin
    ktlint {
       debug.set(true)
    }
}

IntelliJ Idea Only Plugin

Note: This plugin is automatically applied by the main ktlint plugin.

This plugin just adds special tasks that can generate IntelliJ IDEA codestyle rules using ktlint.

Idea plugin simple setup

For all Gradle versions:

Use the same buildscript logic as above, but with this instead of the above suggested apply line.

apply plugin: "org.jlleitschuh.gradle.ktlint-idea"

Idea plugin setup using new plugin API

Build script snippet for new, incubating, plugin mechanism introduced in Gradle 2.1:

plugins {
  id("org.jlleitschuh.gradle.ktlint-idea") version "<current_version>"
}

Configuration

The following configuration block is optional.

If you don't configure this the defaults defined in the KtlintExtension object will be used.

The version of ktlint used by default may change between patch versions of this plugin. If you don't want to inherit these changes then make sure you lock your version here.

Groovy

import org.jlleitschuh.gradle.ktlint.reporter.ReporterType

ktlint {
    version = "0.22.0"
    debug = true
    verbose = true
    android = false
    outputToConsole = true
    outputColorName = "RED"
    ignoreFailures = true
    enableExperimentalRules = true
    additionalEditorconfigFile = file("/some/additional/.editorconfig")
    disabledRules = ["final-newline"]
    reporters {
        reporter "plain"
        reporter "checkstyle"
        
        customReporters {
            "csv" {
                fileExtension = "csv"
                dependency = project(":project-reporters:csv-reporter")
            }
            "yaml" {
                fileExtension = "yml"
                dependency = "com.example:ktlint-yaml-reporter:1.0.0"
            }
        }
    }
    kotlinScriptAdditionalPaths {
        include fileTree("scripts/")
    }
    filter {
        exclude("**/generated/**")
        include("**/kotlin/**")
    }
}

dependencies {
    ktlintRuleset "com.github.username:rulseset:master-SNAPSHOT"
    ktlintRuleset files("/path/to/custom/rulseset.jar")
    ktlintRuleset project(":chore:project-ruleset") 
}

or in kotlin script:

Kotlin

import org.jlleitschuh.gradle.ktlint.reporter.ReporterType

ktlint {
    version.set("0.22.0")
    debug.set(true)
    verbose.set(true)
    android.set(false)
    outputToConsole.set(true)
    outputColorName.set("RED")
    ignoreFailures.set(true)
    enableExperimentalRules.set(true)
    additionalEditorconfigFile.set(file("/some/additional/.editorconfig"))
    disabledRules.set(setOf("final-newline"))
    reporters {
        reporter(ReporterType.PLAIN)
        reporter(ReporterType.CHECKSTYLE)
        
        customReporters {
            register("csv") {
                fileExtension = "csv"
                dependency = project(":project-reporters:csv-reporter")
            }
            register("yaml") {
                fileExtension = "yml"
                dependency = "com.example:ktlint-yaml-reporter:1.0.0"
            }
        }
    }
    kotlinScriptAdditionalPaths {
        include(fileTree("scripts/"))
    }
    filter {
        exclude("**/generated/**")
        include("**/kotlin/**")
    }
}

dependencies {
    ktlintRuleset("com.github.username:rulseset:master-SNAPSHOT")
    ktlintRuleset(files("/path/to/custom/rulseset.jar"))
    ktlintRuleset(project(":chore:project-ruleset")) 
}

Setting reports output directory

It is possible also to define different from default output directory for generated reports (by default it is "build/reports/ktlint"):

Groovy

tasks.withType(org.jlleitschuh.gradle.ktlint.KtlintCheckTask) {
    reporterOutputDir = project.layout.buildDirectory.dir("other/location/$name")
}

Kotlin script

tasks.withType<org.jlleitschuh.gradle.ktlint.KtlintCheckTask>() {
    reporterOutputDir.set(
        project.layout.buildDirectory.dir("other/location/$name")
    )
}

Custom reporters

Note: If Ktlint custom reporter creates report output file internally, for example:

class CsvReporter(
    private val out: PrintStream
) : Reporter {
    override fun onLintError(file: String, err: LintError, corrected: Boolean) {
        val line = "$file;${err.line};${err.col};${err.ruleId};${err.detail};$corrected"
        out.println(line)
        File("some_other_file.txt").write(line) // <-- Here!!!
    }
}

"some_other_file.txt" won't be captured as task output. This may lead to the problem, that task will always be not "UP_TO_DATE" and caching will not work.

Samples

This repository provides the following examples of how to set up this plugin:

• android-app - applies plugin to android application project
• kotlin-gradle - applies plugin to plain Kotlin project that uses groovy in build.gradle files
• kotlin-js - applies plugin to kotlin js project
• kotlin-ks - applies plugin to plain Kotlin project that uses Kotlin DSL in build.gradle.kts files
• kotlin-multiplatform-common - applies plugin to Kotlin common multiplatform module
• kotlin-multiplatform-js - applies plugin to Kotlin JavaScript multiplatform module
• kotlin-multiplatform-jvm - applies plugin to Kotlin JVM multiplatform module
• kotlin-rulesets-using - adds custom example ruleset
• kotlin-reporter-using - adds custom example reporter

Tasks Added

Main tasks

This plugin adds two maintasks to every source set: ktlint[source set name]SourceSetCheck and ktlint[source set name]SourceSetFormat. Additionally, a simple ktlintCheck task has also been added that checks all of the source sets for that project. Similarly, a ktlintFormat task has been added that formats all of the source sets.

Additionally plugin adds two task for project kotlin script files: ktlintKotlinScriptCheck and ktlintKotlinScriptFormat.

Additional helper tasks

Following additional tasks are added:

• ktlintApplyToIdea - The task generates IntelliJ IDEA (or Android Studio) Kotlin style files in the project .idea/ folder. Note that this task will overwrite the existing style file.
• ktlintApplyToIdeaGlobally - The task generates IntelliJ IDEA (or Android Studio) Kotlin style files in the user home IDEA (or Android Studio) settings folder. Note that this task will overwrite the existing style file.
• addKtlintCheckGitPreCommitHook - adds Git pre-commit hook, that runs ktlint check over staged files.
• addKtlintFormatGitPreCommitHook - adds Git pre-commit hook, that runs ktlint format over staged files and adds fixed files back to commit.

All these additional tasks are always added only to the root project.

FAQ

• Is it possible to not stop task execution if some of the subprojects tasks failed?

Yes. Just use gradle --continue option:

$ ./gradlew --continue ktlintCheck

• Can I mix old plugin and new plugin API setup in my project (see simple-setup and using new plugin API setup)?

No. These approaches are not equivalent to how they work. The problem that the plugin may not find some of the kotlin plugins if both approaches are used in the project configuration. Especially it is related to the Android plugin.

• Does plugin check change files incrementally?

Yes, check tasks support it. On the first run, the task will check all files in the source set, on subsequent runs it will check only added/modified files.

Format tasks do not check files incrementally.

• I could not filter dynamically attached sources that are located outside of the project dir.

Gradle based filtering are only working for files located inside project (subproject) folder, see gradle/gradle#3417 To filter files outside project dir, use:

exclude { element -> element.file.path.contains("generated/") }

• Running KtLint fails with strange exception (for example, check #383)

Ensure you are not pinning Kotlin version for "ktlint*" configurations added by plugin.

KtLint relies on Kotlin compiler to parse source files. Each version of KtLint are build using specific Kotlin version.

To exclude "ktlint*" Gradle configurations from Kotlin version pinning - use following approach:

configurations.all {
    if (!name.startsWith("ktlint")) {
        resolutionStrategy {
            eachDependency {
                // Force Kotlin to our version
                if (requested.group == "org.jetbrains.kotlin") {
                    useVersion("1.3.72")
                }
            }
        }
    }
}

Developers

Importing

Import the settings.gradle.kts file into your IDE.

To enable the Android sample either define the ANDROID_HOME environmental variable or add a local.properties file to the project root folder with the following content:

sdk.dir=<android-sdk-location>

Building

Building the plugin: ./plugin/gradlew build

On how to run the current plugin snapshot check on sample projects: ./gradlew ktlintCheck

Running tests from IDEA IDE

To run tests in IDEA IDE, firstly you need to run following gradle task (or after any dependency change):

$ ./plugin/gradlew pluginUnderTestMetadata

Optionally you can add this step test run configuration.

Links

Ktlint Gradle Plugin on the Gradle Plugin Registry