Feature Request: Allow Hilt to consume Dagger `@Component`s

Background

In my company, we expose our internal Android libraries as Dagger @Components. The rationally behind this pattern is that:

• we want to avoid conflicting binding (by exposing @Modules instead)
• we want a clear declaration of each library’s dependencies

In Hilt docs, Custom Components section, you state:

Consider if a non-Hilt (regular Dagger) component is sufficient

Still that use case seems not to be supported (yet) because:

1. I couldn’t find an API to property import a Dagger component (without re-writing all providers again). An equivalent to https://dagger.dev/api/2.22/dagger/Component.html#dependencies--
2. If by using Hilt compiler, you declare a @Module without an @InstallIn annotation (which will be the case for Dagger components), ~it fails~ (you can actually use @DisableInstallInCheck for this)

Use case

Allow Hilt components to somehow consume (inherit its exposed providers) Dagger @Components. If this is supported already, I couldn’t find any documentation or example about it.

For instance, one way we may support this is by providing a component in a Hilt module:

@Module
@InstallsOn(SingletonComponent::class)
object AppModule {

    // by providing an instance of `LoggerComponent`, Hilt will be smart enough to generate a provider `Logger` from it
    @Provides
    fun provideLoggerComponent(application: Application): LoggerComponent =
        DaggerLoggerComponent.create(application)

}

class MainActivity : Activity {

    @Inject
    lateinit var logger: Logger

    fun onCreate(savedInstanceState: Bundle) {
        super.onCreate(savedInstanceState)
        
        logger.log("onCreate")
    }

}

And from our library module:

@Component
interface LoggerComponent {

    val logger: Logger
    
    @Component.Factory
    interface Factory {
    
        fun create(@BindsInstance context: Context)
    
    }

}

interface Logger {

    fun log(log: String)
    
}

[gmazzo]

Good enough. We’ll probably build it internally then, let it mature to cover our needs, and then we’ll try to open source it as a third-party Hilt extension. We’ll let you know. Thanks!

[danysantiago]

Hi - If you open source it I will gladly take a look.

Two things to remember:

• Annotated your annotation API (@ImportDaggerComponent) with @GeneratesRootInput and remember to apply the hilt-compiler to the runtime project where this API is.
• Annotate the generated @Module with @OriginatingElement

Both of these are explained here: https://dagger.dev/hilt/creating-extensions

Also, plz don’t use @DaggerGenerated, that is internal not meant to be use by external code gens.