Kotlin Help

KSP quickstart

Get a sample processor to check out.

Create a processor of your own

  1. Create an empty gradle project.

  2. Specify version 1.5.30 of the Kotlin plugin in the root project for use in other project modules:

plugins { kotlin("jvm") version "1.5.30" apply false } buildscript { dependencies { classpath(kotlin("gradle-plugin", version = "1.5.30")) } }
  1. Add a module for hosting the processor.

  2. In the module's build.gradle.kts file, do the following:

    • Apply Kotlin plugin

    • Add the KSP API to the dependencies block.

plugins { kotlin("jvm") } repositories { mavenCentral() } dependencies { implementation("com.google.devtools.ksp:symbol-processing-api:1.5.30-1.0.0-beta09") }
  1. You'll need to implement com.google.devtools.ksp.processing.SymbolProcessor and com.google.devtools.ksp.processing.SymbolProcessorProvider. Your implementation of SymbolProcessorProvider will be loaded as a service to instantiate the SymbolProcessor you implement. Note the following:

  • Implement SymbolProcessorProvider.create() to create a SymbolProcessor. Dependencies your processor needs (e.g. CodeGenerator, processor options) are passed through the parameters of SymbolProcessorProvider.create().

  • Your main logic should be in the SymbolProcessor.process() method.

  • Use resolver.getSymbolsWithAnnotation() to get the symbols you want to process, given the fully-qualified name of an annotation.

  • A common use case for KSP is to implement a customized visitor (interface com.google.devtools.ksp.symbol.KSVisitor) for operating on symbols. A simple template visitor is com.google.devtools.ksp.symbol.KSDefaultVisitor.

  • For sample implementations of the SymbolProcessorProvider and SymbolProcessor interfaces, see the following files in the sample project.
    • src/main/kotlin/BuilderProcessor.kt
    • src/main/kotlin/TestProcessor.kt
  • After writing your own processor, register your processor provider to the package by including its fully-qualified name in resources/META-INF/services/com.google.devtools.ksp.processing.SymbolProcessorProvider.

Use your own processor in a project

Setup using Kotlin DSL

  1. Create another module that contains a workload where you want to try out your processor.

pluginManagement { repositories { gradlePluginPortal() } }
  1. In the new module's build.gradle.kts, do the following:
    • Apply the com.google.devtools.ksp plugin with the specified version.

    • Add ksp(<your processor>) to the list of dependencies.

  2. Run ./gradlew build. You can find the generated code under build/generated/source/ksp.

Here's a sample build.gradle.kts to apply the KSP plugin to a workload:

plugins { id("com.google.devtools.ksp") version "1.5.30-1.0.0-beta09" kotlin("jvm") } version = "1.0-SNAPSHOT" repositories { mavenCentral() } dependencies { implementation(kotlin("stdlib-jdk8")) implementation(project(":test-processor")) ksp(project(":test-processor")) }

Setup using Groovy

  1. Create another module that contains a workload where you want to try out your processor.

pluginManagement { repositories { gradlePluginPortal() } }
  1. In your projects build.gradle file add a plugins block containing the ksp plugin:

plugins { id "com.google.devtools.ksp" version "1.5.30-1.0.0-beta09" }
  1. In the modules build.gradle, add the following:

    • Apply the com.google.devtools.ksp plugin:

    apply plugin: 'com.google.devtools.ksp'
    • Add ksp <your processor> to the list of dependencies.

    dependencies { implementation "org.jetbrains.kotlin:kotlin-stdlib:$kotlin_version" implementation project(":test-processor") ksp project(":test-processor") }

Pass Options to Processors

Processor options in SymbolProcessorEnvironment.options are specified in gradle build scripts:

ksp { arg("option1", "value1") arg("option2", "value2") ... }

Make IDE Aware Of Generated Code

By default, IntelliJ or other IDEs don't know about the generated code and therefore references to those generated symbols will be marked unresolvable. To make, for example, IntelliJ be able to reason about the generated symbols, the following paths need to be marked as generated source root:

build/generated/ksp/main/kotlin/ build/generated/ksp/main/java/

and perhaps also resource directory if your IDE supports them:


It may also be necessary to configure these directories in your KSP consumer module build.gradle.kts:

kotlin { sourceSets.main { kotlin.srcDir("build/generated/ksp/main/kotlin") } sourceSets.test { kotlin.srcDir("build/generated/ksp/test/kotlin") } }
Last modified: 16 September 2021