ktlint-custom-rules

Additional rules for KtLint - Kotlin linter with build-in formatter

Idea

Custom rules allow to try new rules, test them and collect feedback. Once rules are polished, they will be pushed to KtLint and, hopefully, included into library.

Rules

IndentationRule

Verifies indentatin size.

• more intelligent than same rule from stable version (KtLint v.0.15.1)
• supports autocorrection

ClassAndFunctionHeaderFormatRule

Verifies class and function header formatting according to https://android.github.io/kotlin-guides/style.html#functions

Valid header example:

fun <T> Iterable<T>.joinToString(
    separator: CharSequence = ", ",
    prefix: CharSequence = "",
    postfix: CharSequence = ""
): String {
    // …
}

That format is required:

• header already takes more than one line
• header is longer than maximum allowed line length

Usage

See KtLint main page for details how to integrate KtLint

Once KtLint is configured, you have to add custom rules.

Gradle via custom tasks

build.gradle

repositories {
    maven {
      url "https://plugins.gradle.org/m2/"
    }
}

dependencies{
    ktlint 'com.github.MyDogTom:ktlint-custom-rules:v0.1.0-RC1'
}

Complete (KtLint + custom rules) Gradle configuration

build.gradle

apply plugin: "java"

repositories {
    jcenter()
    maven {
      url "https://plugins.gradle.org/m2/"
    }
}

configurations {
    ktlint
}

dependencies {
    ktlint "com.github.shyiko:ktlint:0.15.0"
    // additional 3rd party ruleset(s) can be specified here
    // just add them to the classpath (e.g. ktlint 'groupId:artifactId:version') and 
    // ktlint will pick them up
    ktlint 'com.github.MyDogTom:ktlint-custom-rules:v0.1.0-RC1'
}

task ktlint(type: JavaExec, group: "verification") {
    description = "Check Kotlin code style."
    classpath = configurations.ktlint
    main = "com.github.shyiko.ktlint.Main"
    args "src/**/*.kt"
    // to generate report in checkstyle format prepend following args:
    // "--reporter=plain", "--reporter=checkstyle,output=${buildDir}/ktlint.xml"
    // see https://github.com/shyiko/ktlint#usage for more
}
check.dependsOn ktlint

task ktlintFormat(type: JavaExec, group: "formatting") {
    description = "Fix Kotlin code style deviations."
    classpath = configurations.ktlint
    main = "com.github.shyiko.ktlint.Main"
    args "-F", "src/**/*.kt"
}

Requirements

ktlint-custom-rules:v0.1.0-RC1 requires KtLint v0.15.1

Feedback

Your feedback is very important. The entire idea of that repository is to run these rules on as many code bases as possible. Find and fix bugs.