# Mastering ktlint: A Guide to Crafting Your Own Rules

DevFeed: [Mastering ktlint: A Guide to Crafting Your Own Rules](<https://devfeed.tech/articles/mastering-ktlint-a-guide-to-crafting-your-own-rules-25116.md>)

Original publisher: [Read original article](<http://michaelevans.org/blog/2024/09/07/mastering-ktlint-a-guide-to-crafting-your-own-rules/>)

Author: Michael Evans

Published: 2024-09-07T15:49:37Z

Content type: tutorial

Language: en

Sources: [Gadget Habit](<https://devfeed.tech/sources/gadget-habit.md>)

Topics: [Kotlin](<https://devfeed.tech/topics/kotlin.md>), [Code quality](<https://devfeed.tech/topics/code-quality.md>), [Testing](<https://devfeed.tech/topics/testing.md>), [Gradle](<https://devfeed.tech/topics/gradle.md>), [Android](<https://devfeed.tech/topics/android.md>)

Tags: [android](<https://devfeed.tech/tags/android.md>), [code-quality](<https://devfeed.tech/tags/code-quality.md>), [coding](<https://devfeed.tech/tags/coding.md>), [gradle](<https://devfeed.tech/tags/gradle.md>), [gradle-plugin](<https://devfeed.tech/tags/gradle-plugin.md>), [guide](<https://devfeed.tech/tags/guide.md>), [kotlin](<https://devfeed.tech/tags/kotlin.md>), [module](<https://devfeed.tech/tags/module.md>), [test](<https://devfeed.tech/tags/test.md>), [tutorial](<https://devfeed.tech/tags/tutorial.md>)

## AI overview

This tutorial explains how to create a custom ktlint rule for Kotlin projects. The example detects Android Log statements, shows how to configure the ktlint Gradle plugin and dependencies, defines the rule, adds a test, integrates it into ktlint configuration, and runs ktlint to report findings.

## Source excerpt

Ktlint is a powerful linting tool for Kotlin code that helps maintain code quality and consistency. While it comes with a set of built-in rules, there may be cases where you want to create custom rules tailored to your project's specific requirements. In this tutorial, we'll walk you through the process of writing a custom ktlint rule that detects and removes Android Log statements from your Kotlin code. Prerequisites Before we dive into writing custom ktlint rules, ensure you have ktlint installed in your project. The tasks ktlintApplyToIdea and addKtlintCheckTask are provided by the ktlint Gradle plugin. If you haven't already, include the plugin in your project by adding the following to your build.gradle.kts file: 1 2 3 plugins { id("org.jlleitschuh.gradle.ktlint") version "<latest-version>" } Once the plugin is applied, run the following command to set up ktlint in your project: 1 ./gradlew ktlintApplyToIdea addKtlintCheckTask Writing a Custom ktlint Rule 1. Create a New Module To write a custom ktlint rule, start by creating a new module in your Kotlin project. 2. Set Up Your Project In your new module, make sure you have ktlint as a dependency. Add it to your build.gradle.kts or build.gradle file: 1 2 3 dependencies { ktlint("io.gitlab.arturbosch.detekt:detekt-formatting:<ktlint-version>") } 3. Define the ktlint Rule Now, let's define our custom rule. Create a Kotlin class that extends the Rule class and override the visit method to define the logic for your rule. In this example, we want to detect Android Log statements. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 import io.gitlab.arturbosch.detekt.api.Rule import org.jetbrains.kotlin.psi.KtCallExpression class LogStatementRule : Rule() { override fun visitCallExpression(expression: KtCallExpression) { if (expression.calleeExpression?.text == "Log" && expression.valueArguments.size == 1 ) { // Report a finding report( finding = "Found Android Log statement", documentable = expression ) } } } 4. Create a Test As w