AppRoot

Marks an @AssistedInject presenter implementation as the application's root host, so the codegen processor can wire its bound interface into parentScope at compile time.

Without this annotation the consumer would have to manually write a Metro @BindingContainer that @Provides @SingleIn(parentScope) invokes the nested @AssistedFactory to instantiate the root presenter. With this annotation the processor emits all of that next to the implementation.

Example

@AppRoot(parentScope = ActivityScope::class)
@AssistedInject
class DefaultRootPresenter(
    @Assisted componentContext: ComponentContext,
    // ...
) : RootPresenter, ComponentContext by componentContext {

    @AssistedFactory
    fun interface Factory {
        fun create(componentContext: ComponentContext): DefaultRootPresenter
    }
}

The processor emits one file (<InterfaceName>BindingContainer.kt) into the implementation's <package>.di package. The file contains a @BindingContainer @ContributesTo(parentScope) object whose @Provides @SingleIn(parentScope) function takes a ComponentContext and the nested Factory, and returns the bound interface.

Bound interface inference

The processor reads the implementation's supertypes and picks the first non-marker interface as the bound type. Decompose's ComponentContext (commonly used as a delegate via ComponentContext by componentContext) is filtered out. Implementations that extend more than one non-marker interface are rejected at compile time.

Validation

The processor reports a compile error if any of the following hold:

• The annotated symbol is not a class.

• The class does not carry @AssistedInject.

• The class does not declare a nested @AssistedFactory interface.

• The nested factory does not have exactly one function whose single parameter is a ComponentContext and whose return type equals the implementation type.

• The class extends zero or more than one non-marker interface.