Apollo compiler plugins

The Apollo compiler supports a wide range of options. For the cases where these options are not enough, you can use Apollo compiler plugins to modify the behaviour of the compiler.

Apollo compiler plugins allow to:

• Change the layout of the generated sources (name of the classes, package names, capitalization rules).

• Change the ids of operation for persisted queries.

• Transform the JavaPoet/KotlinPoet models.

• Transform the Apollo IR.

Implementing a compiler plugin

In this example we will implement a plugin that uses custom persisted queries ids registered on your backend.

The Apollo compiler use the ServiceLoader API to load plugins at runtime. Plugins need to be implemented in a separate module that is added to the classpath.

To start, create a new Gradle module and add apollo-compiler as a dependency to the module build.gradle[.kts] file. In this example, we'll use apollo-compiler-plugin as module name:

1// apollo-compiler-plugin/build.gradle.kts
2plugins {
3  id("org.jetbrains.kotlin.jvm")
4}
5
6dependencies {
7  // Add apollo-compiler as a compileOnly dependency
8  compileOnly("com.apollographql.apollo:apollo-compiler:4.3.0")  
9}

Next create your plugin in a src/main/kotlin/mypackage/MyPlugin file:

1class MyPlugin: ApolloCompilerPlugin {
2  override fun beforeCompilationStep(
3      environment: ApolloCompilerPluginEnvironment,
4      registry: ApolloCompilerRegistry,
5  ) {
6    // add your custom code here
7  }
8}

Make your plugin discoverable by ServiceLoader by adding a resource in src/main/resources/META-INF/services/com.apollographql.apollo.compiler.ApolloCompilerPlugin. This file contains the fully qualified name of your plugin:

1mypackage.MyPlugin

Adding a plugin to the Apollo compiler classpath

Use the Service.plugin() Gradle method to add the plugin to the Apollo compiler classpath:

1// app/build.gradle.kts
2plugins {
3  id("org.jetbrains.kotlin.jvm")
4  id("com.apollographql.apollo")
5}
6
7apollo {
8  service("service") {
9    packageName.set("com.example")
10    
11    // Add your plugin to the Apollo compiler classpath
12    plugin(project(":apollo-compiler-plugin"))
13  }
14}

The plugin code will now be invoked the next time the compiler is invoked.

Passing arguments to your Apollo compiler plugin

Because the compiler plugin runs in an isolated classpath, you can't use classes or data from your main build logic classpath.

In order to pass build-time arguments to your Apollo compiler plugin, use the argument() function:

1apollo {
2  service("service") {
3    packageName.set("com.example")
4    
5    // Add your plugin to the Apollo compiler classpath
6    plugin(project(":apollo-compiler-plugin")) {
7      argument("token", token)
8    }
9  }
10}

The arguments are available in ApolloCompilerPluginEnvironment.arguments:

1class MyPlugin: ApolloCompilerPlugin {
2  override fun beforeCompilationStep(
3      environment: ApolloCompilerPluginEnvironment,
4      registry: ApolloCompilerRegistry,
5  ) {
6    val token = environment.arguments.get("token") as String
7    
8    // add your custom code here
9  }
10}

Arguments must be serializable and be instances of classes accessible from the bootstrap classloader. In practice, built-in types and collections are supported.

Limitations

Because codegen is run in a separate classloader when using compiler plugins, it's not possible to use packageNameGenerator, operationIdGenerator or operationOutputGenerator at the same time as compiler plugins. If you want to use them, you'll have to:

• use ApolloCompilerRegistry.registerLayout() instead of packageNameGenerator

• use ApolloCompilerRegistry.registerOperationIdsGenerator() instead of operationIdGenerator and operationOutputGenerator

Other references

For other plugin APIs like layout, IR, JavaPoet and KotlinPoet transforms, check out the ApolloCompilerPlugin API docs

For more examples, check out the integration-tests.