Properly use declaration-site type variance

org.openrewrite.staticanalysis.DeclarationSiteTypeVariance

Currently, Java requires use-site type variance, so if someone has Function<IN, OUT> method parameter, it should rather be Function<? super IN, ? extends OUT>. Unfortunately, it is not easy to notice that ? super and ? extends is missing, so this recipe adds it where that would improve the situation.

Recipe source

GitHub, Issue Tracker, Maven Central

• groupId: org.openrewrite.recipe

• artifactId: rewrite-static-analysis

• version: 1.5.0

Options

Type	Name	Description	Example
List	variantTypes	A list of well-known classes that have in/out type variance.	java.util.function.Function<IN, OUT>
List	excludedBounds	Optional. A list of bounds that should not receive explicit variance. Globs supported.	java.lang.*
Boolean	excludeFinalClasses	Optional. If true, do not add ? extends variance to final classes. ? super variance will be added regardless of finality.

Usage

This recipe has required configuration parameters. Recipes with required configuration parameters cannot be activated directly. To activate this recipe you must create a new recipe which fills in the required parameters. In your rewrite.yml create a new recipe with a unique name. For example: com.yourorg.DeclarationSiteTypeVarianceExample. Here's how you can define and customize such a recipe within your rewrite.yml:

rewrite.yml

---
type: specs.openrewrite.org/v1beta/recipe
name: com.yourorg.DeclarationSiteTypeVarianceExample
displayName: Properly use declaration-site type variance example
recipeList:
  - org.openrewrite.staticanalysis.DeclarationSiteTypeVariance:
      variantTypes: java.util.function.Function<IN, OUT>
      excludedBounds: java.lang.*

Now that com.yourorg.DeclarationSiteTypeVarianceExample has been defined activate it and take a dependency on org.openrewrite.recipe:rewrite-static-analysis:1.5.0 in your build file:

Gradle

1. Add the following to your build.gradle file:

build.gradle

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

rewrite {
    activeRecipe("com.yourorg.DeclarationSiteTypeVarianceExample")
}

repositories {
    mavenCentral()
}

dependencies {
    rewrite("org.openrewrite.recipe:rewrite-static-analysis:1.5.0")
}

2. Run gradle rewriteRun to run the recipe.

Maven

1. 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>com.yourorg.DeclarationSiteTypeVarianceExample</recipe>
          </activeRecipes>
        </configuration>
        <dependencies>
          <dependency>
            <groupId>org.openrewrite.recipe</groupId>
            <artifactId>rewrite-static-analysis</artifactId>
            <version>1.5.0</version>
          </dependency>
        </dependencies>
      </plugin>
    </plugins>
  </build>
</project>

2. Run mvn rewrite:run to run the recipe.

Moderne CLI

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

shell

mod run . --recipe DeclarationSiteTypeVarianceExample

See how this recipe works across multiple open-source repositories

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Please contact Moderne for more information about safely running the recipes on your own codebase in a private SaaS.

Contributors

Jonathan Schneider, Tim te Beek, Sam Snyder, Knut Wannheden