Gradle中useBuildCache使用及kapt缓存Dagger2的安全性咨询

Great question! Let's dive into this—both the Kotlin Gradle Plugin's build cache and kapt caching for Dagger 2 are fantastic ways to speed up your builds, and I've got plenty of real-world experience to share here.

核心问题：缓存Dagger 2的Kapt任务是否安全？ #

Short answer: Absolutely, it's safe—and this is backed by years of community practice and Dagger's design principles. Here's why:

• Dagger 2's annotation processor is 100% deterministic. Given the exact same input (source code with Dagger annotations, dependency versions, module configurations), it will always generate identical output classes (like *_Factory, Dagger*Component, etc.). There's no randomness, environment-dependent logic, or hidden side effects in its code generation process.
• While Gradle can't automatically map all kapt inputs/outputs out of the box, Dagger's input-output relationship is crystal clear. As long as your annotated classes, modules, and components don't change, the generated code won't either—making it a perfect candidate for caching.

如何启用Kapt缓存？ #

To turn on caching for Dagger's kapt tasks, add this to your Gradle build script:

kapt {
    useBuildCache = true
}

If you need more granular control (e.g., only cache specific kapt tasks), you can target the task types directly:

tasks.withType(org.jetbrains.kotlin.gradle.tasks.KaptGenerateStubs) {
    outputs.cacheIf { true }
}
tasks.withType(org.jetbrains.kotlin.gradle.internal.KaptExecution) {
    outputs.cacheIf { true }
}

关键注意事项 #

• Stick to Dagger 2.16 or newer. Earlier versions had a few edge cases with caching, but 2.16+ has been widely tested and confirmed to work flawlessly with build caching.
• If you're using custom annotation processors alongside Dagger, you'll need to evaluate their determinism separately—but Dagger alone is safe.
• Combine this with the new Kotlin Gradle Plugin's build cache features, and you'll see even bigger gains in build speed. The plugin's cache works seamlessly with kapt caching to avoid redundant work across your entire build pipeline.

内容的提问来源于stack exchange，提问作者Efi MK