Exploring Kotlin Symbol Processing (KSP)

Kotlin Symbol Processing (KSP) is an innovative tool developed by Google and JetBrains that enables developers to write lightweight compiler plugins for Kotlin. It is designed as a modern replacement for annotation processors like kapt, offering faster build times and better integration with the Kotlin compiler.

KSP enables tools and libraries to interact directly with Kotlin source code, allowing them to generate additional source files or perform analysis. This is extremely beneficial for libraries such as Room, Dagger, or Moshi that rely on code generation to function efficiently.

What is KSP?

Kotlin Symbol Processing is an API built to process Kotlin programs. Instead of relying on Java’s annotation processing system, KSP provides a Kotlin-first approach. Unlike kapt, which compiles Kotlin code to Java stubs before processing, KSP parses Kotlin code directly, giving access to the Kotlin AST (Abstract Syntax Tree) and making it significantly faster.

KSP is particularly useful for:

• Generating boilerplate code (e.g., data mappers, DAOs, serializers)
• Static analysis tools
• Generating dependency injection containers
• Frameworks that use metadata annotations

Benefits of Using KSP

1. Performance
   KSP avoids the Java stub generation process, resulting in faster incremental builds and a smoother development experience.
2. Full Kotlin Support
   Since KSP interacts directly with the Kotlin compiler frontend, it supports all Kotlin language features natively, including inline functions, coroutines, and more.
3. Simplified Setup
   Using KSP is straightforward. You only need to apply the KSP plugin and configure it in your Gradle build script.
4. Better Tooling Integration
   It’s officially supported by JetBrains and the Kotlin team, which means it is aligned with future Kotlin developments.

Basic Setup Example

To start using KSP, you need to include the plugin in your build.gradle.kts:

plugins {
    kotlin("jvm") version "1.9.0"
    id("com.google.devtools.ksp") version "1.9.0-1.0.13"
}

Then you can add dependencies for KSP processors like:

dependencies {
    implementation("com.squareup.moshi:moshi:1.14.0")
    ksp("com.squareup.moshi:moshi-kotlin-codegen:1.14.0")
}

After syncing your project, the KSP processor will generate the necessary files during compilation.

KSP vs kapt

Real-world Use Case: Room Database

Room now officially supports KSP, offering faster compile times. You can use the following dependency to enable it:

ksp("androidx.room:room-compiler:2.6.0")

Room’s KSP integration significantly speeds up builds, especially for large-scale applications.

Additional Resources

To explore more about KSP and stay updated with its latest changes, visit the official documentation provided by JetBrains.