Working example of Dynamic Feature Modules (DFMs) with Circuit

[JohnBuhanan]

@ZacSweers Maybe a proper DynamicFeatureNavigator could become a Circuit artifact instead of my hacks?

Video of DFM:

DFMs.mp4

My nephew and I made a working example of DFMs with Circuit on a branch named dynamic in this project:
https://github.com/JamesBuhanan/Songify/tree/dynamic

Here are the main points:

1. Uses better-dynamic-features (BDF) from CashApp.
2. I implemented the DynamicApi from BDF like this for Circuit:

interface CircuitFeature : DynamicApi {
    fun presenterFactories(): Set<Presenter.Factory>
    fun uiFactories(): Set<Ui.Factory>
    fun injectFeature()
}

3. Each DFM has to make it's own CircuitFeature, e.g. home:

@DynamicImplementation
class HomeFeature : CircuitFeature {

    @Inject
    lateinit var presenterFactories: @JvmSuppressWildcards Set<Presenter.Factory>

    @Inject
    lateinit var uiFactories: @JvmSuppressWildcards Set<Ui.Factory>

    override fun presenterFactories(): Set<Presenter.Factory> {
        return presenterFactories
    }

    override fun uiFactories(): Set<Ui.Factory> {
        return uiFactories
    }

    override fun injectFeature() {
        DaggerHomeComponent
            .factory()
            .create(
                // from base `:app` module since this is a DFM that depends on `:app`
                requireNotNull(appComponent)
            )
            .inject(this)
    }
}

4. Every time a DFM is installed it will emit all DFMs here in the EntryPointActivity, and use them to build an instance of Circuit.

        val features by remember {
            splitInstallHelper.splitInstallManager.dynamicImplementations<CircuitFeature>()
        }.collectAsState(initial = emptyList())

        val circuit = Circuit.Builder()
            .apply {
                features.forEach {
                    it.injectFeature()

                    for (factory in it.presenterFactories()) {
                        addPresenterFactory(factory)
                    }
                    for (factory in it.uiFactories()) {
                        addUiFactory(factory)
                    }
                }
            }
            .build()

5. I made a DynamicNavigator that is hot garbage, but it works.

@Composable
internal fun rememberDynamicNavigator(
    delegate: Navigator,
    scope: CoroutineScope,
    splitInstallHelper: SplitInstallHelper,
): Navigator {
    return remember {
        DynamicNavigator(
            delegate = delegate,
            scope = scope,
            splitInstallHelper = splitInstallHelper,
        )
    }
}

internal class DynamicNavigator(
    private val delegate: Navigator,
    private val scope: CoroutineScope,
    private val splitInstallHelper: SplitInstallHelper
) : Navigator by delegate {
    override fun goTo(screen: Screen): Boolean {
        splitInstallHelper.requestInstall(screen, scope) {
            delegate.goTo(screen)
        }

        // It will show "route not available", but coincidentally we hide Circuit while showing installation progress bar, so it is fine lol.
        return true
    }
}

6. If you want to access resources inside a newly downloaded DFM, you must first call SplitCompat.install(). I don't know what is happening or if this can be automated somehow...

@CircuitInject(SearchScreen::class, FeatureScope::class)
@Composable
fun SearchView(
    state: SearchState,
    modifier: Modifier = Modifier,
) {
    // This is CRAZY.  Why do I have to do this just so we can access Resources from DFMs?
    val newContext =
        LocalContext.current.createPackageContext("com.songify", 0)
            .also { SplitCompat.install(it) }

    CompositionLocalProvider(
        LocalContext provides newContext
    ) {
        when (state) {
            is SearchState.Loading -> LoadingBar()
            is SearchState.Error -> toastEffect()(state.message)
            is SearchState.Success -> ShowSearch(state)
        }
    }
}

P.S.- The guys at CashApp said I should just pass dagger Components back or something? I don't grok.
cashapp/better-dynamic-features#126 (comment)