Apollo compiler plugins
Compiler plugins are currently experimental in Apollo Kotlin. If you have feedback on them, please let us know via GitHub issues or in the Kotlin Slack community.
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:
// apollo-compiler-plugin/build.gradle.ktsplugins {id("org.jetbrains.kotlin.jvm")}dependencies {// Add apollo-compiler as a dependencyimplementation("com.apollographql.apollo3:apollo-compiler:4.0.0-beta.7")}
Next create your plugin in a src/main/kotlin/mypackage/MyPlugin
file:
package mypackageimport com.apollographql.apollo3.compiler.OperationOutputGeneratorimport com.apollographql.apollo3.compiler.ApolloCompilerPluginimport com.apollographql.apollo3.compiler.operationoutput.OperationDescriptorimport com.apollographql.apollo3.compiler.operationoutput.OperationIdclass MyPlugin: ApolloCompilerPlugin {override fun operationIds(descriptors: List<OperationDescriptor>): List<OperationId> {// This assumes the returned ids are in the same order as the descriptorsreturn registerOperations(descriptors).withIndex().map { OperationId(it.value, descriptors[it.index].name) }}/*** Send operations to a remote server and return the server persisted ids*/fun registerOperations(descriptors: List<OperationDescriptor>): List<String> {// ...}}
Next, create an ApolloCompilerPluginProvider
. This is the entry point of compiler plugins. It is loaded using the ServiceLoader API.
class MyPluginProvider: ApolloCompilerPluginProvider {override fun create(environment: ApolloCompilerPluginEnvironment): ApolloCompilerPlugin {return MyPlugin()}}
Make your plugin discoverable by ServiceLoader by adding a resource in src/main/resources/META-INF/services/com.apollographql.apollo3.compiler.ApolloCompilerPluginProvider
. This file contains the fully qualified name of your plugin:
mypackage.MyPluginProvider
ⓘ NOTE
The name of the resource file is important. It must be com.apollographql.apollo3.compiler.ApolloCompilerPluginProvider
and be in the META-INF/services
folder. This is how ServiceLoader
looks up plugins at runtime.
Adding a plugin to the Apollo compiler classpath
Use the Service.plugin()
Gradle method to add the plugin to the Apollo compiler classpath:
// app/build.gradle.ktsplugins {id("org.jetbrains.kotlin.jvm")id("com.apollographql.apollo3")}apollo {service("service") {packageName.set("com.example")// Add your plugin to the Apollo compiler classpathplugin(project(":apollo-compiler-plugin"))}}
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:
apollo {service("service") {packageName.set("com.example")// Add your plugin to the Apollo compiler classpathplugin(project(":apollo-compiler-plugin")) {argument("token", token)}}}
The arguments are available in ApolloCompilerPluginEnvironment.arguments
:
class MyPluginProvider: ApolloCompilerPluginProvider {override fun create(environment: ApolloCompilerPluginEnvironment): ApolloCompilerPlugin {return MyPlugin(environment.arguments.get("token") as String)}}
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
ApolloCompilerPlugin.layout()
instead ofpackageNameGenerator
- use
ApolloCompilerPlugin.operationIds()
instead ofoperationIdGenerator
andoperationOutputGenerator
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.