Keywords: precompiled, plugin, pre-compiled

# Pre-compiled Script Plugins

version 9.4.0

A precompiled script plugin is a `.gradle.kts` (Kotlin DSL) or `.gradle` (Groovy DSL) script stored in a plugin source set (e.g. `buildSrc` or an included build like `build-logic`). Gradle automatically compiles it into a proper plugin class, packages it like a normal plugin, and assigns the plugin ID based on the file name.

For example, you place a script in `build-logic/src/main/kotlin/java-library-conventions.gradle.kts`:

    some-project/
    ├─ settings.gradle.kts
    ├─ build-logic/
    │  ├─ build.gradle.kts
    │  └─ src/
    │     └─ main/
    │        └─ kotlin/
    │           └─ java-library-conventions.gradle.kts  (1)
    └─ app/
       ├─ build.gradle.kts                              (2)
       └─ src/

1 | Pre-compiled script plugin
2 | Build file applies the plugin

Gradle automatically compiles that script into a plugin. The plugin ID is derived from the file name: `java-library-conventions.gradle.kts`.

You can now apply it in any build like a regular plugin. In the build file of the `app` project:

app/build.gradle.kts

    plugins {
        // Apply by ID derived from the file name:
        id("java-library-conventions")
    }

## Setting the plugin ID

The plugin ID for a precompiled script is derived from its file name and optional package declaration.

For example, a script named `code-quality.gradle(.kts)` located in `src/main/groovy` (or `src/main/kotlin`) without a package declaration would be exposed as the `code-quality` plugin:

buildSrc/build.gradle.kts

    plugins {
        `kotlin-dsl`
    }

app/build.gradle.kts

    plugins {
        id("code-quality")
    }

buildSrc/build.gradle

    plugins {
        id 'groovy-gradle-plugin'
    }

app/build.gradle

    plugins {
        id 'code-quality'
    }

On the other hand, a script named `code-quality.gradle.kts` located in `src/main/kotlin/my` with the package declaration `my` would be exposed as the `my.code-quality` plugin:

buildSrc/build.gradle.kts

    plugins {
        `kotlin-dsl`
    }

app/build.gradle.kts

    plugins {
        id("my.code-quality")
    }

When creating precompiled script plugins intended for settings or init scripts, the filename suffix determines where Gradle applies them:

- `.settings.gradle` or `.settings.gradle.kts` → interpreted as `Plugin<Settings>`

- `.init.gradle` or `.init.gradle.kts` → interpreted as `Plugin<Gradle>`

- `.gradle` or `.gradle.kts` → interpreted as the default `Plugin<Project>`

| Groovy pre-compiled script plugins cannot have packages.

## Making a plugin configurable using extensions

Extension objects are commonly used in plugins to expose configuration options and additional functionality to build scripts.

When you apply a plugin that defines an extension, you can access the extension object and configure its properties or call its methods to customize the behavior of the plugin or tasks provided by the plugin.

A Project has an associated ExtensionContainer object that contains all the settings and properties for the plugins that have been applied to the project. You can provide configuration for your plugin by adding an extension object to this container.

Let’s update our `greetings` example:

buildSrc/src/main/kotlin/greetings.gradle.kts

    // Create extension object
    interface GreetingPluginExtension {
        val message: Property<String>
    }

    // Add the 'greeting' extension object to project
    val extension = project.extensions.create<GreetingPluginExtension>("greeting")

buildSrc/src/main/groovy/greetings.gradle

    // Create extension object
    interface GreetingPluginExtension {
        Property<String> getMessage()
    }

    // Add the 'greeting' extension object to project
    def extension = project.extensions.create("greeting", GreetingPluginExtension)

You can set the value of the `message` property directly with `extension.message.set("Hi from Gradle,")`.

However, the `GreetingPluginExtension` object becomes available as a project property with the same name as the extension object. You can now access `message` like so:

buildSrc/src/main/kotlin/greetings.gradle.kts

    // Where the<GreetingPluginExtension>() is equivalent to project.extensions.getByType(GreetingPluginExtension::class.java)
    the<GreetingPluginExtension>().message.set("Hi from Gradle")

buildSrc/src/main/groovy/greetings.gradle

    extensions.findByType(GreetingPluginExtension).message.set("Hi from Gradle")

If you apply the `greetings` plugin, you can set the convention in your build script:

app/build.gradle.kts

    plugins {
        application
        id("greetings")
    }

    greeting {
        message = "Hello from Gradle"
    }

app/build.gradle

    plugins {
        id 'application'
        id('greetings')
    }

    configure(greeting) {
        message = "Hello from Gradle"
    }

## Adding default configuration as conventions

In plugins, you can define default values, also known as conventions, using the `project` object.

Convention properties are properties that are initialized with default values but can be overridden:

buildSrc/src/main/kotlin/greetings.gradle.kts

    // Create extension object
    interface GreetingPluginExtension {
        val message: Property<String>
    }

    // Add the 'greeting' extension object to project
    val extension = project.extensions.create<GreetingPluginExtension>("greeting")

    // Set a default value for 'message'
    extension.message.convention("Hello from Gradle")

buildSrc/src/main/groovy/greetings.gradle

    // Create extension object
    interface GreetingPluginExtension {
        Property<String> getMessage()
    }

    // Add the 'greeting' extension object to project
    def extension = project.extensions.create("greeting", GreetingPluginExtension)

    // Set a default value for 'message'
    extension.message.convention("Hello from Gradle")

`extension.message.convention(…​)` sets a convention for the `message` property of the extension. This convention specifies that the value of `message` should default to `"Hello from Gradle"`.

If the `message` property is not explicitly set, its value will be automatically set to `"Hello from Gradle"`.

## Mapping extension properties to task properties

Using an extension and mapping it to a custom task’s input/output properties is common in plugins.

In this example, the message property of the `GreetingPluginExtension` is mapped to the message property of the `GreetingTask` as an input:

buildSrc/src/main/kotlin/greetings.gradle.kts

    // Create extension object
    interface GreetingPluginExtension {
        val message: Property<String>
    }

    // Add the 'greeting' extension object to project
    val extension = project.extensions.create<GreetingPluginExtension>("greeting")

    // Set a default value for 'message'
    extension.message.convention("Hello from Gradle")

    // Create a greeting task
    abstract class GreetingTask : DefaultTask() {
        @Input
        val message = project.objects.property<String>()

        @TaskAction
        fun greet() {
            println("Message: ${message.get()}")
        }
    }

    // Register the task and set the convention
    tasks.register<GreetingTask>("hello") {
        message.convention(extension.message)
    }

buildSrc/src/main/groovy/greetings.gradle

    // Create extension object
    interface GreetingPluginExtension {
        Property<String> getMessage()
    }

    // Add the 'greeting' extension object to project
    def extension = project.extensions.create("greeting", GreetingPluginExtension)

    // Set a default value for 'message'
    extension.message.convention("Hello from Gradle")

    // Create a greeting task
    abstract class GreetingTask extends DefaultTask {
        @Input
        abstract Property<String> getMessage()

        @TaskAction
        void greet() {
            println("Message: ${message.get()}")
        }
    }

    // Register the task and set the convention
    tasks.register("hello", GreetingTask) {
        message.convention(extension.message)
    }

    $ ./gradlew -q hello

    Message: Hello from Gradle

This means that changes to the extension’s `message` property will trigger the task to be considered out-of-date, ensuring that the task is re-executed with the new message.

You can find out more about types that you can use in task implementations and extensions in Lazy Configuration.

## Applying external plugins

In order to apply an external plugin in a precompiled script plugin, it has to be added to the plugin project’s implementation classpath in the plugin’s build file:

buildSrc/build.gradle.kts

    plugins {
        `kotlin-dsl`
    }

    repositories {
        mavenCentral()
    }

    dependencies {
        implementation("com.bmuschko:gradle-docker-plugin:6.4.0")
    }

buildSrc/build.gradle

    plugins {
        id 'groovy-gradle-plugin'
    }

    repositories {
        mavenCentral()
    }

    dependencies {
        implementation 'com.bmuschko:gradle-docker-plugin:6.4.0'
    }

It can then be applied in the precompiled script plugin:

buildSrc/src/main/kotlin/my-plugin.gradle.kts

    plugins {
        id("com.bmuschko.docker-remote-api")
    }

buildSrc/src/main/groovy/my-plugin.gradle

    plugins {
        id 'com.bmuschko.docker-remote-api'
    }

The plugin version in this case is defined in the dependency declaration.

The `version "…​"` and `apply false` syntax are not supported in precompiled script plugins. The version for the plugin is determined by the version declared in the plugin’s build file. If a plugin needs to be on the classpath but not applied, it can be left out of the `plugins {}` block and only added as a dependency in the plugin’s build file.

## Example of a precompiled script plugin in the `Project` scope

You can see an example here.

## Example of a precompiled script plugin in the `Settings` scope

Precompiled script plugins can also target the `Settings` scope. The following example defines a simple plugin in a separate build called `settings-plugin`.

Configure plugin management for the plugin build:

settings-plugin/settings.gradle.kts

    pluginManagement {
        repositories {
            gradlePluginPortal()
            mavenCentral()
        }
    }

settings-plugin/settings.gradle

    pluginManagement {
        repositories {
            gradlePluginPortal()
            mavenCentral()
        }
    }

Set up the build to support precompiled script plugins:

settings-plugin/build.gradle.kts

    plugins {
        `kotlin-dsl`
    }

    repositories {
        mavenCentral()
        gradlePluginPortal()
    }

    dependencies {
        implementation("com.gradle:develocity-gradle-plugin:4.1")
    }

settings-plugin/build.gradle

    plugins {
        id('groovy-gradle-plugin')
    }

    repositories {
        mavenCentral()
        gradlePluginPortal()
    }

    dependencies {
        implementation('com.gradle:develocity-gradle-plugin:4.1')
    }

| Notice that we used the practice described in Applying external plugins.

Write the precompiled script plugin itself:

settings-plugin/src/main/kotlin/my-plugin.settings.gradle.kts

    plugins {
        id("com.gradle.develocity")
    }

settings-plugin/src/main/groovy/my-plugin.settings.gradle

    plugins {
        id('com.gradle.develocity')
    }

Because the file name ends with `.settings.gradle.kts`, Gradle compiles it into a plugin with a `Settings` scope. The plugin ID is `my-plugin`. You can use it as follows in a consumer project (root settings file of the consuming project):

settings.gradle.kts

    pluginManagement {
        repositories {
            mavenCentral()
            gradlePluginPortal()
        }
        includeBuild("./settings-plugin")
    }

    plugins {
        id("my-plugin")
    }

settings.gradle

    pluginManagement {
        repositories {
            mavenCentral()
            gradlePluginPortal()
        }
        includeBuild('./settings-plugin')
    }

    plugins {
        id('my-plugin')
    }

| Because the plugin was precompiled as a `Settings` plugin (the `.settings.gradle(.kts)` suffix), you apply it in the settings file’s `plugins {}` block, not in a project `build.gradle(.kts)` file.