DNM: Convert the :sample app to Metro

**DO NOT MERGE:** Metro's aggregation (Anvil) features are not working for other KMP targets than JVM/Android yet. This maybe will be resolved in Kotlin 2.3: https://youtrack.jetbrains.com/issue/KT-75865 This PR, nonetheless, is a proof of concept of using Metro with App Platform in an application and how a migration could look like.

Migrate the `:sample` app from kotlin-inject to Metro. This change also renames "component" interfaces to "graph" interfaces.

Fixes #127

Author: vRallev

sample/app/build.gradle

@@ -12,7 +12,7 @@ plugins {
 // This extension comes from our published plugin.
 appPlatform {
     enableComposeUi true
-    enableKotlinInject true
+    enableMetro true
     enableModuleStructure true
     enableMoleculePresenters true
     addImplModuleDependencies true

sample/app/src/androidInstrumentedTest/kotlin/software/amazon/app/platform/sample/TestAndroidAppComponent.kt

@@ -0,0 +1,24 @@
+package software.amazon.app.platform.sample
+
+import android.app.Application
+import dev.zacsweers.metro.AppScope
+import dev.zacsweers.metro.DependencyGraph
+import dev.zacsweers.metro.Provides
+import software.amazon.app.platform.scope.RootScopeProvider
+
+/** Metro graph that is used in instrumented tests. */
+@DependencyGraph(AppScope::class)
+interface TestAndroidAppGraph {
+  /** The factory to create a new instance of [AndroidAppGraph]. */
+  @DependencyGraph.Factory
+  fun interface Factory {
+    /**
+     * Creates a new [AndroidAppGraph] instance. [application] and [rootScopeProvider] are provided
+     * in the [AndroidAppGraph] and can be injected.
+     */
+    fun create(
+      @Provides application: Application,
+      @Provides rootScopeProvider: RootScopeProvider,
+    ): TestAndroidAppGraph
+  }
+}

sample/app/src/androidInstrumentedTest/kotlin/software/amazon/app/platform/sample/TestAndroidAppGraph.kt

@@ -1,11 +1,13 @@
 package software.amazon.app.platform.sample
 
+import dev.zacsweers.metro.createGraphFactory
+
 /**
  * Application class that is used in instrumented tests. Note that it provides a
  * [TestAndroidApplication] instead of [AndroidApplication].
  */
 class TestAndroidApplication : AndroidApplication() {
-  override fun component(demoApplication: DemoApplication): AppComponent {
-    return TestAndroidAppComponent::class.create(this, demoApplication)
+  override fun metroGraph(demoApplication: DemoApplication): AppGraph {
+    return createGraphFactory<TestAndroidAppGraph.Factory>().create(this, demoApplication)
   }
 }

sample/app/src/androidInstrumentedTest/kotlin/software/amazon/app/platform/sample/TestAndroidApplication.kt

@@ -0,0 +1,29 @@
+package software.amazon.app.platform.sample
+
+import android.app.Application
+import dev.zacsweers.metro.AppScope
+import dev.zacsweers.metro.DependencyGraph
+import dev.zacsweers.metro.Provides
+import software.amazon.app.platform.scope.RootScopeProvider
+
+/**
+ * The final Android app graph.
+ *
+ * Note that [Application] is an Android specific type and classes living in the Android source
+ * folder can therefore inject [Application].
+ */
+@DependencyGraph(AppScope::class)
+interface AndroidAppGraph {
+  /** The factory to create a new instance of [AndroidAppGraph]. */
+  @DependencyGraph.Factory
+  fun interface Factory {
+    /**
+     * Creates a new [AndroidAppGraph] instance. [application] and [rootScopeProvider] are provided
+     * in the [AndroidAppGraph] and can be injected.
+     */
+    fun create(
+      @Provides application: Application,
+      @Provides rootScopeProvider: RootScopeProvider,
+    ): AndroidAppGraph
+  }
+}

sample/app/src/androidMain/kotlin/software/amazon/app/platform/sample/AndroidAppComponent.kt

@@ -1,6 +1,7 @@
 package software.amazon.app.platform.sample
 
 import android.app.Application
+import dev.zacsweers.metro.createGraphFactory
 import software.amazon.app.platform.scope.RootScopeProvider
 import software.amazon.app.platform.scope.Scope
 
@@ -16,12 +17,12 @@ open class AndroidApplication : Application(), RootScopeProvider {
     get() = demoApplication.rootScope
 
   override fun onCreate() {
-    demoApplication.create(component(demoApplication))
+    demoApplication.create(metroGraph(demoApplication))
     super.onCreate()
   }
 
-  /** Create the [AppComponent]. In UI tests we use a different instance. */
-  protected open fun component(demoApplication: DemoApplication): AppComponent {
-    return AndroidAppComponent::class.create(this, demoApplication)
+  /** Create the [AppGraph]. In UI tests we use a different instance. */
+  protected open fun metroGraph(demoApplication: DemoApplication): AppGraph {
+    return createGraphFactory<AndroidAppGraph.Factory>().create(this, demoApplication)
   }
 }

sample/app/src/androidMain/kotlin/software/amazon/app/platform/sample/AndroidAppGraph.kt

@@ -2,22 +2,21 @@ package software.amazon.app.platform.sample
 
 import android.app.Application
 import androidx.lifecycle.AndroidViewModel
+import dev.zacsweers.metro.AppScope
+import dev.zacsweers.metro.ContributesTo
 import kotlinx.coroutines.flow.StateFlow
 import software.amazon.app.platform.sample.template.SampleAppTemplate
 import software.amazon.app.platform.scope.RootScopeProvider
-import software.amazon.app.platform.scope.di.kotlinInjectComponent
-import software.amazon.lastmile.kotlin.inject.anvil.AppScope
-import software.amazon.lastmile.kotlin.inject.anvil.ContributesTo
+import software.amazon.app.platform.scope.di.metro.metroDependencyGraph
 
 /**
  * `ViewModel` that hosts the stream of templates and survives configuration changes. Note that we
  * use [application] to get access to the root scope.
  */
 class MainActivityViewModel(application: Application) : AndroidViewModel(application) {
 
-  private val component =
-    (application as RootScopeProvider).rootScope.kotlinInjectComponent<Component>()
-  private val templateProvider = component.templateProviderFactory.createTemplateProvider()
+  private val graph = (application as RootScopeProvider).rootScope.metroDependencyGraph<Graph>()
+  private val templateProvider = graph.templateProviderFactory.createTemplateProvider()
 
   /** The stream of templates that are rendered by [MainActivity]. */
   val templates: StateFlow<SampleAppTemplate> = templateProvider.templates
@@ -26,9 +25,9 @@ class MainActivityViewModel(application: Application) : AndroidViewModel(applica
     templateProvider.cancel()
   }
 
-  /** Component interface to give us access to objects from the app component. */
+  /** Graph interface to give us access to objects from the app graph. */
   @ContributesTo(AppScope::class)
-  interface Component {
+  interface Graph {
     /** Gives access to the [TemplateProvider.Factory] from the object graph. */
     val templateProviderFactory: TemplateProvider.Factory
   }

sample/app/src/androidMain/kotlin/software/amazon/app/platform/sample/AndroidApplication.kt

@@ -0,0 +1,21 @@
+package software.amazon.app.platform.sample
+
+import dev.zacsweers.metro.AppScope
+import dev.zacsweers.metro.ContributesTo
+import dev.zacsweers.metro.ForScope
+import dev.zacsweers.metro.Multibinds
+import software.amazon.app.platform.scope.Scoped
+import software.amazon.app.platform.scope.coroutine.CoroutineScopeScoped
+
+/**
+ * Shared interface for the app graph. The final graphs live in the platform specific source folders
+ * in order to have access to platform specific code.
+ */
+@ContributesTo(AppScope::class)
+interface AppGraph {
+  /** All [Scoped] instances part of the app scope. */
+  @ForScope(AppScope::class) @Multibinds(allowEmpty = true) val appScopedInstances: Set<Scoped>
+
+  /** The coroutine scope that runs as long as the app scope is alive. */
+  @ForScope(AppScope::class) val appScopeCoroutineScopeScoped: CoroutineScopeScoped
+}