KTLINT

ktlint is a single binary with both linter & formatter included. All you need is to drop it in (no need to get overwhelmed while choosing among dozens of code style options ). fiber_manual_record. Can I have my own rules on top of ktlint? Absolutely, "no configuration" doesn't mean "no extensibility".

KTLINT

ktlint is a single binary with both linter & formatter included. All you need is to drop it in (no need to get overwhelmed while choosing among dozens of code style options ). fiber_manual_record. Can I have my own rules on top of ktlint? Absolutely, "no configuration" doesn't mean "no extensibility".

KTLINT

ktlint is a single binary with both linter & formatter included. All you need is to drop it in (no need to get overwhelmed while choosing among dozens of code style options ). fiber_manual_record. Can I have my own rules on top of ktlint? Absolutely, "no configuration" doesn't mean "no extensibility".

KTLINT

ktlint is a single binary with both linter & formatter included. All you need is to drop it in (no need to get overwhelmed while choosing among dozens of code style options ). fiber_manual_record. Can I have my own rules on top of ktlint? Absolutely, "no configuration" doesn't mean "no extensibility".

KTLINT

ktlint is a single binary with both linter & formatter included. All you need is to drop it in (no need to get overwhelmed while choosing among dozens of code style options ). fiber_manual_record. Can I have my own rules on top of ktlint? Absolutely, "no configuration" doesn't mean "no extensibility".

KTLINT

ktlint is a single binary with both linter & formatter included. All you need is to drop it in (no need to get overwhelmed while choosing among dozens of code style options ). fiber_manual_record. Can I have my own rules on top of ktlint? Absolutely, "no configuration" doesn't mean "no extensibility".

KTLINT

ktlint is a single binary with both linter & formatter included. All you need is to drop it in (no need to get overwhelmed while choosing among dozens of code style options ). fiber_manual_record. Can I have my own rules on top of ktlint? Absolutely, "no configuration" doesn't mean "no extensibility".

KTLINT

ktlint is a single binary with both linter & formatter included. All you need is to drop it in (no need to get overwhelmed while choosing among dozens of code style options ). fiber_manual_record. Can I have my own rules on top of ktlint? Absolutely, "no configuration" doesn't mean "no extensibility".

KTLINT

ktlint is a single binary with both linter & formatter included. All you need is to drop it in (no need to get overwhelmed while choosing among dozens of code style options ). fiber_manual_record. Can I have my own rules on top of ktlint? Absolutely, "no configuration" doesn't mean "no extensibility".

KTLINT

ktlint is a single binary with both linter & formatter included. All you need is to drop it in (no need to get overwhelmed while choosing among dozens of code style options ). fiber_manual_record. Can I have my own rules on top of ktlint? Absolutely, "no configuration" doesn't mean "no extensibility".

KTLINT

ktlint is a single binary with both linter & formatter included. All you need is to drop it in (no need to get overwhelmed while choosing among dozens of code style options ). fiber_manual_record. Can I have my own rules on top of ktlint? Absolutely, "no configuration" doesn't mean "no extensibility".

KTLINT

ktlint is a single binary with both linter & formatter included. All you need is to drop it in (no need to get overwhelmed while choosing among dozens of code style options ). fiber_manual_record. Can I have my own rules on top of ktlint? Absolutely, "no configuration" doesn't mean "no extensibility".

KTLINT

ktlint is a single binary with both linter & formatter included. All you need is to drop it in (no need to get overwhelmed while choosing among dozens of code style options ). fiber_manual_record. Can I have my own rules on top of ktlint? Absolutely, "no configuration" doesn't mean "no extensibility".

KTLINT

ktlint is a single binary with both linter & formatter included. All you need is to drop it in (no need to get overwhelmed while choosing among dozens of code style options ). fiber_manual_record. Can I have my own rules on top of ktlint? Absolutely, "no configuration" doesn't mean "no extensibility".

KTLINT

ktlint is a single binary with both linter & formatter included. All you need is to drop it in (no need to get overwhelmed while choosing among dozens of code style options ). fiber_manual_record. Can I have my own rules on top of ktlint? Absolutely, "no configuration" doesn't mean "no extensibility".

__

ktlint

Getting Started Rules FAQ GitHub Getting Started Rules FAQ GitHub

ktlint

An anti-bikeshedding Kotlin linter with built-in formatter.

Getting Started

Command Line Maven Gradle

INSTALLATION

curl -sSLO https://github.com/pinterest/ktlint/releases/download/0.35.0/ktlint && chmod a+x ktlint # you can also download ktlint manually from https://github.com/pinterest/ktlint/releases # another option is "brew install ktlint" # verify PGP signature (optional but recommended) curl -sS https://keybase.io/pinterestandroid/pgp_keys.asc | gpg --import curl -sSLO https://github.com/pinterest/ktlint/releases/download/0.35.0/ktlint.asc gpg --verify ktlint.asc

USAGE

# check the style of all Kotlin files inside the current dir (recursively) # (hidden folders will be skipped)

$ ktlint

src/main/kotlin/Main.kt:10:10: Unused import # check only certain locations (prepend ! to negate the pattern) $ ktlint "src/**/*.kt" "!src/**/*Test.kt" # auto-correct style violations # (if some errors cannot be fixed automatically they will be printed to stderr) $ ktlint -F "src/**/*.kt" # print style violations grouped by file $ ktlint --reporter=plain?group_by_file # print style violations as usual + create report in checkstyle format $ ktlint --reporter=plain --reporter=checkstyle,output=ktlint-report-in-checkstyle-format.xml # install git hook to automatically check files for style violations on commit $ ktlint --install-git-pre-commit-hook

INTEGRATION

Add the following snippet to pom.xml (inside ...)

org.apache.maven.plugins maven-antrun-plugin 1.7

ktlint

verify

run

ktlint-format

run

com.pinterest ktlint 0.35.0

USAGE

# check code style (it's also bound to "mvn verify") $ mvn antrun:run@ktlint src/main/kotlin/Main.kt:10:10: Unused import # fix code style deviations (runs built-in formatter) $ mvn antrun:run@ktlint-format

INTEGRATION

PLUGINS (RECOMMENDED) There are few community-driven plugins (in order of appearance): * jlleitschuh/ktlint-gradle

Gradle plugin that

automatically creates check and format tasks for project Kotlin sources, supports different kotlin plugins and Gradle build caching. * jeremymailen/kotlinter-gradle

Gradle plugin

featuring incremental build support, file reports, .kt & .kts source

support.

* diffplug/spotless

Spotless is not really a plugin, it's a standalone project that happens to have a built-in ktlint support. In addition to linting/formatting kotlin code it allows you to keep license headers, markdown documentation, etc. in check.

WITHOUT PLUGINS

Add the following snippet to build.gradle apply plugin: "java"

repositories {

jcenter()

}

configurations {

ktlint

}

dependencies {

ktlint "com.pinterest:ktlint:0.35.0" // additional 3rd party ruleset(s) can be specified here // just add them to the classpath (ktlint 'groupId:artifactId:version') and // ktlint will pick them up

}

task ktlint(type: JavaExec, group: "verification") { description = "Check Kotlin code style." main = "com.pinterest.ktlint.Main" classpath = configurations.ktlint

args "src/**/*.kt"

// to generate report in checkstyle format prepend following args: // "--reporter=plain", "--reporter=checkstyle,output=${buildDir}/ktlint.xml" // see https://github.com/pinterest/ktlint#usage for more

}

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

}

USAGE

# check code style (it's also bound to "gradle check")

$ gradle ktlint

src/main/kotlin/Main.kt:10:10: Unused import # fix code style deviations (runs built-in formatter) $ gradle ktlintFormat

Rules

4 SPACES FOR INDENTATION*.

Do.

data class C(

val a: Any,

val b: Any = 0,

val c: Any

) {}

Don't.

data class C(val a: Any,

val b: Any = 0,

val c: Any) {

}

* Starting from 0.8.0

value of

indent_size specified under section in .editorconfig takes precedence (if any). Official recommendation is to use 4 spaces, though. (see #43

for details)

NO SEMICOLONS.

Do.

val v = ""

println(v)

// semicolons used to separate multiple statements on the same line are OK // try avoid though fn({ v -> println(v); v * 10 })

Don't.

val v = "";

println(v);

NO WILDCARD / UNUSED IMPORTS.

Do.

import io.vertx.core.Vertx import com.google.Guice import com.google.Injector

Don't.

import io.vertx.core.* import com.google.inject.* import pkg.UnusedClass NO CONSECUTIVE BLANK LINES.

Do.

class A {}

class B {}

Don't.

// this in not a Python and you are not in PEP 8 realm

class A {}

class B {}

NO TRAILING WHITESPACES.

Do.

class A {}

class B {}

Don't.

class A {}⋅⋅⋅

class B {}⋅

* If you don't use EditorConfig it's a good time to start.

NO UNIT RETURNS.

Do.

fun f() {}

Don't.

fun f(): Unit {}

NO EMPTY CLASS BODIES.

Do.

class A

interface B

Don't.

class A {}

interface B {}

CONSISTENT STRING TEMPLATES.

Do.

val a = "class = ${String::class}" val b = "not $a"

Don't.

val a = "class = ${String::class.toString()}" val b = "not ${a}" CONSISTENT ORDER OF MODIFIERS.

Do.

internal abstract class A { protected open val v = "" internal open suspend fun f(v: Any): Any = "" public lateinit var lv: String abstract tailrec fun findFixPoint(x: Double = 1.0): Double

}

class B : A() {

public override val v = "" suspend override fun f(v: Any): Any = "" tailrec override fun findFixPoint(x: Double): Double = if (x == Math.cos(x)) x else findFixPoint(Math.cos(x))

}

Don't.

abstract internal class A { open protected val v = "" open suspend internal fun f(v: Any): Any = "" lateinit public var lv: String tailrec abstract fun findFixPoint(x: Double = 1.0): Double

}

class B : A() {

override public val v = "" override suspend fun f(v: Any): Any = "" override tailrec fun findFixPoint(x: Double): Double = if (x == Math.cos(x)) x else findFixPoint(Math.cos(x))

}

CONSISTENT SPACING.

Do.

val short = ""

val long = ""

val v = a - b * c class A : B, C {}

if (true) {}

@file:JvmName("Main")

class A : B

call(object : C() {}) fun fn(@field:F a: Any, b: Any, c: Any): Any val v: String = str() if (ok) { /* .. */ } fn({ v -> f(v) * g(v) }) emptyList().find { true }!!.hashCode() find { it.default ?: false }?.phone

Don't.

// multiple spaces after "val long" for vertical alignment

val short = ""

val long  = ""

// no spacing around operators

val v=a-b*c

// no space after the comma class A : B,C {} // no spacing after keyword ("if" in this case)

if(true) {}

// incorrect spacing around ":" @file: JvmName("Main")

class A:B

call(object: C() {}) fun fn(@field: F a:Any, b:Any, c:Any):Any val v:String = str() // missing spacing around "{" and before "}" if (true){/* .. */} // missing spacing after "{" and before "}" fn({v -> f(v) * g(v)}!!) // unnecessary space after "}" emptyList().find { true } !!.hashCode() find { it.default ?: false } ?.phone

FAQ

_FIBER_MANUAL_RECORD_WHY SHOULD I USE KTLINT?

SIMPLICITY.

Spending time on configuration (& maintenance down the road) of hundred-line long style config file(s) is counter-productive. Instead of wasting your energy on something that has no business value - focus on what really matters (not debating whether to use tabs or spaces). By using ktlint you put the importance of code clarity and community conventions over personal preferences. This makes things easier for people reading your code as well as frees you from having to document & explain what style potential contributor(s) have to follow. ktlint is a single binary with both linter & formatter included. All you need is to drop it in (no need to get overwhelmed while choosing among dozens of code style options

).

_FIBER_MANUAL_RECORD_CAN I HAVE MY OWN RULES ON TOP OF KTLINT? Absolutely, "no configuration" doesn't mean "no extensibility". You can add your own ruleset(s) to discover potential bugs, check for

anti-patterns, etc.

See Creating A Ruleset

on GitHub.

_FIBER_MANUAL_RECORD_HOW DO I SUPPRESS AN ERROR? This is meant primarily as an escape latch for the rare cases when ktlint is not able to produce the correct result (please report any such instances using GitHub Issues

).

To disable a specific rule you'll need to turn on the verbose mode (ktlint --verbose ...). At the end of each line you'll see an error code. Use it as an argument for ktlint-disable directive (shown

below).

import package.* // ktlint-disable no-wildcard-imports /* ktlint-disable no-wildcard-imports */

import package.a.*

import package.b.*

/* ktlint-enable no-wildcard-imports */ To disable all checks: import package.* // ktlint-disable _FIBER_MANUAL_RECORD_HOW DO I GLOBALLY DISABLE A RULE? See the EditorConfig

section on GitHub.

You may also use the --disabled_rules command line flag.

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