Dagger 2.48

Dagger/Hilt KSP support

Dagger 2.48 includes the alpha release of the Dagger and Hilt KSP processors.

Instructions for using the Dagger/Hilt KSP processors can be found at https://dagger.dev/dev-guide/ksp.

In order to use Dagger’s KSP processor you will need to:

• Follow the basic setup to migrate Dagger’s processors from kapt to ksp (see https://dagger.dev/dev-guide/ksp#setup).
• Migrate any Dagger SPI plugins to the new Dagger SPI plugins API (with KSP support) (see https://dagger.dev/dev-guide/ksp#new-dagger-spi-plugin-with-ksp-support).
• Ensure that there are no kapt processors that generate classes that need to interact with Dagger (see https://dagger.dev/dev-guide/ksp#interaction-with-javackapt-processors).

Also note that Dagger’s KSP processors are still in the alpha stage. So far we’ve focused mainly on trying to ensure correctness rather than optimize performance. Please apply due diligence when enabling ksp and report any bugs or performance issues at https://github.com/google/dagger/issues. The current list of known issues can be found here.

There are also a few potentially breaking changes included with this release. These changes were made to better support Dagger usage with Kotlin sources, and make the migration from KAPT to KSP more seamless. We don’t expect these changes to affect most users. Please see below for more details.

Breaking changes

The dagger.ignoreProvisionKeyWildcards is now enabled by default

This may break apps that are providing the same binding with different wildcards, e.g. Foo<Bar> and Foo<? extends Bar>.

Fix: See https://dagger.dev/dev-guide/compiler-options#ignore-provision-key-wildcards for suggestions on how to fix this. If fixing is not an immediate option, you can still disable the flag with dagger.ignoreProvisionKeyWildcards=DISABLED.

@Binds assignability check

Unlike KAPT, KSP takes nullability into account when checking if a type is assignable to another type. This changes the behavior of Dagger’s @Binds usage validation such that a type that was assignable in KAPT may no longer be assignable in KSP. For example:

// Incorrect: this compiles successfully in KAPT but the compilation fails in KSP
@Binds fun bind(impl: FooImpl<Bar?>): Foo<Bar>

Fix: To fix this breakage, users should update the parameter or return type in the method such that they are actually assignable when taking nullability into account. For example:

// Correct: this compiles successfully in KAPT and KSP
@Binds fun bind(impl: FooImpl<Bar?>): Foo<Bar?>

Top-level @Module / @Inject classes can no longer be private

Top-level @Module or @Inject classes can no longer be private. This was previously allowed purely by accident (rather than being an officially supported feature) due to the way Kotlin’s private classes are represented as package-private in KAPT’s generated java stubs.

Fix: Replace the private visibility modifier with internal or public.

@Binds and @Provides methods can no longer be extension functions

Normally when we define an @Provides/@Binds function we put the dependencies in the parameter list:

@Module
abstract class BarModule {
    @Binds
    abstract fun bindsBar(@Marker foo: Foo): Bar
}

However, since the introduction of KAPT, it was also technically possible to define an @Provides/@Binds function using an extension function:

@Module
abstract class BarModule {
    @Binds
    abstract fun @receiver:Marker Foo.bindsBar(): Bar
}

This extension function syntax worked more by coincidence (rather than being an officially supported feature) due to the way extension functions are represented in KAPT’s generated java stubs. After review, we’ve decided not to support this feature anymore in KAPT or KSP. See more at #3990.

Fix: Use the traditional parameter approach rather than extension functions.

The use of abstract var properties are no longer allowed in components

A var property adds both a getter (aka request) method and a setter (aka injection) method for a binding. However, the setter method typically goes unused since there is rarely a case for needing both methods for a single binding. After discussion within the team, we’ve decided to ban abstract var properties in components.

Fix: Use fun (or val) for getter methods, use fun for setter methods.

Other changes

• Fixed #3995: Allow kotlin source to use java keywords as parameter names in KSP (2c31d66).
• Fixed #3991: Fixed error message when there are multiple @Inject + @AssistedInject constructors (9105ee671).
• Fixed #3992: Fixed crash crash when there are multiple @AssistedInject + @AssistedInject constructors (9105ee671.)
• Add a better error message when Hilt Gradle Plugin class loader conflicts with KSP's Gradle plugin. (3f7b9b5)