Structural equality tests should use == or !=

org.openrewrite.kotlin.cleanup.EqualsMethodUsage

In Kotlin, == means structural equality and != structural inequality and both map to the left-side term’s equals() function. It is, therefore, redundant to call equals() as a function. Also, == and != are more general than equals() and !equals() because it allows either of both operands to be null. Developers using equals() instead of == or != is often the result of adapting styles from other languages like Java, where == means reference equality and != means reference inequality. The == and != operators are a more concise and elegant way to test structural equality than calling a function.

Recipe source

GitHub, Issue Tracker, Maven Central

groupId: org.openrewrite
artifactId: rewrite-kotlin
version: 1.14.0

Usage

This recipe has no required configuration options. It can be activated by adding a dependency on org.openrewrite:rewrite-kotlin:1.14.0 in your build file or by running a shell command (in which case no build changes are needed):

Add the following to your build.gradle file:

build.gradle

plugins {
    id("org.openrewrite.rewrite") version("6.12.0")
}

rewrite {
    activeRecipe("org.openrewrite.kotlin.cleanup.EqualsMethodUsage")
}

repositories {
    mavenCentral()
}

dependencies {
    rewrite("org.openrewrite:rewrite-kotlin:1.14.0")
}

Run gradle rewriteRun to run the recipe.

Create a file named init.gradle in the root of your project.

init.gradle

initscript {
    repositories {
        maven { url "https://plugins.gradle.org/m2" }
    }
    dependencies { classpath("org.openrewrite:plugin:6.12.0") }
}
rootProject {
    plugins.apply(org.openrewrite.gradle.RewritePlugin)
    dependencies {
        rewrite("org.openrewrite:rewrite-kotlin:1.14.0")
    }
    rewrite {
        activeRecipe("org.openrewrite.kotlin.cleanup.EqualsMethodUsage")
    }
    afterEvaluate {
        if (repositories.isEmpty()) {
            repositories {
                mavenCentral()
            }
        }
    }
}

Run gradle --init-script init.gradle rewriteRun to run the recipe.

Add the following to your pom.xml file:

pom.xml

<project>
  <build>
    <plugins>
      <plugin>
        <groupId>org.openrewrite.maven</groupId>
        <artifactId>rewrite-maven-plugin</artifactId>
        <version>5.29.0</version>
        <configuration>
          <activeRecipes>
            <recipe>org.openrewrite.kotlin.cleanup.EqualsMethodUsage</recipe>
          </activeRecipes>
        </configuration>
        <dependencies>
          <dependency>
            <groupId>org.openrewrite</groupId>
            <artifactId>rewrite-kotlin</artifactId>
            <version>1.14.0</version>
          </dependency>
        </dependencies>
      </plugin>
    </plugins>
  </build>
</project>

Run mvn rewrite:run to run the recipe.

shell

mvn -U org.openrewrite.maven:rewrite-maven-plugin:run -Drewrite.recipeArtifactCoordinates=org.openrewrite:rewrite-kotlin:RELEASE -Drewrite.activeRecipes=org.openrewrite.kotlin.cleanup.EqualsMethodUsage

You will need to have configured the Moderne CLI on your machine before you can run the following command.

shell