Full backward compatibility for Screen.

Extends the legacy `ViewRegistry.getFactoryForRendering` to handle any arbitrary `Screen` implementation, making every bit of code that works directly with `ViewRegistry.buildView` (including `DecorativeViewFactory`) future proof. Allows us to delete the legacy factory that had been created specifically for `BackStackScreen`.

Author: rjrjr

workflow-ui/core-android/api/core-android.api

@@ -48,13 +48,6 @@ public final class com/squareup/workflow1/ui/BackPressHandlerKt {
 	public static final fun setBackPressedHandler (Landroid/view/View;Lkotlin/jvm/functions/Function0;)V
 }
 
-public final class com/squareup/workflow1/ui/BackStackScreenLegacyViewFactory : com/squareup/workflow1/ui/ViewFactory {
-	public static final field INSTANCE Lcom/squareup/workflow1/ui/BackStackScreenLegacyViewFactory;
-	public fun buildView (Lcom/squareup/workflow1/ui/container/BackStackScreen;Lcom/squareup/workflow1/ui/ViewEnvironment;Landroid/content/Context;Landroid/view/ViewGroup;)Landroid/view/View;
-	public synthetic fun buildView (Ljava/lang/Object;Lcom/squareup/workflow1/ui/ViewEnvironment;Landroid/content/Context;Landroid/view/ViewGroup;)Landroid/view/View;
-	public fun getType ()Lkotlin/reflect/KClass;
-}
-
 public final class com/squareup/workflow1/ui/BuilderViewFactory : com/squareup/workflow1/ui/ViewFactory {
 	public fun <init> (Lkotlin/reflect/KClass;Lkotlin/jvm/functions/Function4;)V
 	public fun buildView (Ljava/lang/Object;Lcom/squareup/workflow1/ui/ViewEnvironment;Landroid/content/Context;Landroid/view/ViewGroup;)Landroid/view/View;
@@ -99,6 +92,13 @@ public final class com/squareup/workflow1/ui/LayoutScreenViewFactory : com/squar
 	public fun getType ()Lkotlin/reflect/KClass;
 }
 
+public final class com/squareup/workflow1/ui/LegacyFactoryForScreenType : com/squareup/workflow1/ui/ViewFactory {
+	public fun <init> ()V
+	public fun buildView (Lcom/squareup/workflow1/ui/Screen;Lcom/squareup/workflow1/ui/ViewEnvironment;Landroid/content/Context;Landroid/view/ViewGroup;)Landroid/view/View;
+	public synthetic fun buildView (Ljava/lang/Object;Lcom/squareup/workflow1/ui/ViewEnvironment;Landroid/content/Context;Landroid/view/ViewGroup;)Landroid/view/View;
+	public fun getType ()Lkotlin/reflect/KClass;
+}
+
 public final class com/squareup/workflow1/ui/NamedViewFactory : com/squareup/workflow1/ui/ViewFactory {
 	public static final field INSTANCE Lcom/squareup/workflow1/ui/NamedViewFactory;
 	public fun buildView (Lcom/squareup/workflow1/ui/Named;Lcom/squareup/workflow1/ui/ViewEnvironment;Landroid/content/Context;Landroid/view/ViewGroup;)Landroid/view/View;

workflow-ui/core-android/src/main/java/com/squareup/workflow1/ui/AndroidViewRegistry.kt

@@ -5,7 +5,6 @@ package com.squareup.workflow1.ui
 import android.content.Context
 import android.view.View
 import android.view.ViewGroup
-import com.squareup.workflow1.ui.container.BackStackScreen
 import com.squareup.workflow1.ui.container.EnvironmentScreen
 import com.squareup.workflow1.ui.container.EnvironmentScreenLegacyViewFactory
 import kotlin.reflect.KClass
@@ -36,14 +35,13 @@ public fun <RenderingT : Any> ViewRegistry.getFactoryForRendering(
   @Suppress("UNCHECKED_CAST")
   return getFactoryFor(rendering::class)
     ?: (rendering as? AndroidViewRendering<*>)?.viewFactory as? ViewFactory<RenderingT>
+    ?: (rendering as? Named<*>)?.let { NamedViewFactory as ViewFactory<RenderingT> }
     ?: (rendering as? AsScreen<*>)?.let { AsScreenLegacyViewFactory as ViewFactory<RenderingT> }
-    ?: (rendering as? BackStackScreen<*>)?.let {
-      BackStackScreenLegacyViewFactory as ViewFactory<RenderingT>
-    }
     ?: (rendering as? EnvironmentScreen<*>)?.let {
+      // Special handling to ensure the custom environment is in play before the view is built.
       EnvironmentScreenLegacyViewFactory as ViewFactory<RenderingT>
     }
-    ?: (rendering as? Named<*>)?.let { NamedViewFactory as ViewFactory<RenderingT> }
+    ?: (rendering as? Screen)?.let { LegacyFactoryForScreenType() as ViewFactory<RenderingT> }
     ?: throw IllegalArgumentException(
       "A ViewFactory should have been registered to display $rendering, " +
         "or that class should implement AndroidViewRendering."

workflow-ui/core-android/src/main/java/com/squareup/workflow1/ui/BackStackScreenLegacyViewFactory.kt

@@ -0,0 +1,26 @@
+package com.squareup.workflow1.ui
+
+import android.content.Context
+import android.view.View
+import android.view.ViewGroup
+
+@WorkflowUiExperimentalApi
+internal class LegacyFactoryForScreenType : ViewFactory<Screen> {
+  override val type = Screen::class
+
+  override fun buildView(
+    initialRendering: Screen,
+    initialViewEnvironment: ViewEnvironment,
+    contextForNewView: Context,
+    container: ViewGroup?
+  ): View {
+    val modernFactory = initialRendering.toViewFactory(initialViewEnvironment)
+    val holder = modernFactory.buildView(
+      initialRendering, initialViewEnvironment, contextForNewView, container
+    )
+    holder.view.bindShowRendering(initialRendering, initialViewEnvironment) { r, e ->
+      holder.runner.showRendering(r, e)
+    }
+    return holder.view
+  }
+}

workflow-ui/core-android/src/main/java/com/squareup/workflow1/ui/LegacyFactoryForScreenType.kt

@@ -42,7 +42,11 @@ public interface ScreenViewHolder<in ScreenT : Screen> {
 
     /**
      * Provides access to the [Screen] instance most recently shown in a [ScreenViewHolder]'s
-     * [view] via [show]. Call [showing] for more convenient access.
+     * [view] via [show], or through the legacy [View.showRendering] function.
+     * Call [showing] for more convenient access.
+     *
+     * If the host [View] is driven by a non-[Screen] rendering via the legacy
+     * [View.showRendering] function, it will be returned in an [AsScreen] wrapper.
      */
     public object Showing : ViewEnvironmentKey<Screen>(Screen::class) {
       override val default: Screen = ShowingNothing

workflow-ui/core-android/src/main/java/com/squareup/workflow1/ui/ScreenViewHolder.kt

@@ -114,25 +114,35 @@ public fun <RenderingT : Any> View.showRendering(
     }
 
     // Update the tag's rendering and viewEnvironment before calling
-    // the actual showRendering function.
-    workflowViewState = Started(rendering, viewEnvironment, viewState.showRendering)
+    // the actual showRendering function. Note that we update both the
+    // new Showing key and the old workflowViewState backing View.getRendering().
+    val updatedEnv = viewEnvironment + (Showing to asScreen(rendering))
+    workflowViewState = Started(rendering, updatedEnv, viewState.showRendering)
+
     viewState.showRendering.invoke(rendering, viewEnvironment)
   }
 }
 
 /**
- * **This will be deprecated in favor of [screenOrNull] very soon.**
- *
- * Returns the most recent rendering shown by this view cast to [RenderingT],
+ * Returns the most recent rendering [shown][showRendering] by this [View], cast to [RenderingT];
  * or null if [bindShowRendering] has never been called.
  *
+ * Note that this is tied strictly to calls to [showRendering], and does not reflect
+ * calls to [ScreenViewHolder.show], which is poised to replace that function. For
+ * reliable access to the latest rendering displayed by a View, use the [Showing]
+ * [ViewEnvironmentKey].
+ *
  * @throws ClassCastException if the current rendering is not of type [RenderingT]
  */
 @WorkflowUiExperimentalApi
-// @Deprecated(
-//   "Replaced by View.screenOrNull",
-//   ReplaceWith("screenOrNull", "com.squareup.workflow1.ui.screenOrNull")
-// )
+@Deprecated(
+  "Replaced by Showing in ViewEnvironment",
+  ReplaceWith(
+    "environmentOrNull?.get(Showing)",
+    "com.squareup.workflow1.ui.environmentOrNull",
+    "com.squareup.workflow1.ui.ScreenViewHolder.Companion.Showing"
+  )
+)
 public inline fun <reified RenderingT : Any> View.getRendering(): RenderingT? {
   // Can't use a val because of the parameter type.
   return when (val showing = workflowViewStateOrNull?.showing) {

workflow-ui/core-android/src/main/java/com/squareup/workflow1/ui/ViewShowRendering.kt

@@ -153,7 +153,7 @@ public class WorkflowSavedStateRegistryAggregator {
     } catch (e: IllegalArgumentException) {
       throw IllegalArgumentException(
         "Error registering SavedStateProvider: key \"$key\" is already in " +
-          "use on parent SavedStateRegistryOwner $parentOwner.\n" +
+          "use on parent SavedStateRegistryOwner $parentOwner. " +
           "This is most easily remedied by giving your container Screen rendering a unique " +
           "Compatible.compatibilityKey, perhaps by wrapping it with Named.",
         e

workflow-ui/core-android/src/main/java/com/squareup/workflow1/ui/androidx/WorkflowSavedStateRegistryAggregator.kt

@@ -6,10 +6,10 @@ import android.content.Context
 import android.view.View
 import android.view.ViewGroup
 import com.google.common.truth.Truth.assertThat
+import com.squareup.workflow1.ui.ScreenViewHolder.Companion.Showing
 import com.squareup.workflow1.ui.ViewRegistry.Entry
+import com.squareup.workflow1.ui.container.mockView
 import org.junit.Test
-import org.mockito.kotlin.doReturn
-import org.mockito.kotlin.eq
 import org.mockito.kotlin.mock
 import kotlin.reflect.KClass
 import kotlin.test.assertFailsWith
@@ -126,6 +126,23 @@ internal class LegacyAndroidViewRegistryTest {
     assertThat(overrideViewRenderingFactory.called).isTrue()
   }
 
+  @Test fun `buildView auto converts unwrapped Screen and updates Showing correctly`() {
+    val registry = ViewRegistry()
+    val view = registry.buildView(ScreenRendering)
+    view.start()
+    assertThat(view.getRendering<Any>()).isSameInstanceAs(ScreenRendering)
+    assertThat(view.environmentOrNull!![Showing]).isSameInstanceAs(ScreenRendering)
+  }
+
+  @Test fun `buildView auto converts wrapped Screen and updates Showing correctly`() {
+    val registry = ViewRegistry()
+    val rendering = Named(ScreenRendering, "fnord")
+    val view = registry.buildView(rendering)
+    view.start()
+    assertThat(compatible(view.getRendering()!!, rendering)).isTrue()
+    assertThat(compatible(view.environmentOrNull!![Showing], asScreen(rendering))).isTrue()
+  }
+
   @Test fun `ViewRegistry with no arguments infers type`() {
     val registry = ViewRegistry()
     assertTrue(registry.keys.isEmpty())
@@ -136,7 +153,11 @@ internal class LegacyAndroidViewRegistryTest {
   private object BazRendering
 
   private object ViewRendering : AndroidViewRendering<ViewRendering> {
-    override val viewFactory: TestViewFactory<ViewRendering> = TestViewFactory(ViewRendering::class)
+    override val viewFactory = TestViewFactory(ViewRendering::class)
+  }
+
+  private object ScreenRendering : AndroidScreen<ScreenRendering> {
+    override val viewFactory = TestScreenViewFactory(ScreenRendering::class)
   }
 
   private val overrideViewRenderingFactory = TestViewFactory(ViewRendering::class)
@@ -167,11 +188,23 @@ internal class LegacyAndroidViewRegistryTest {
       container: ViewGroup?
     ): View {
       called = true
-      return mock {
-        on {
-          getTag(eq(com.squareup.workflow1.ui.R.id.legacy_workflow_view_state))
-        } doReturn (WorkflowViewState.New(initialRendering, initialViewEnvironment, { _, _ -> }))
+      return mockView().also {
+        it.bindShowRendering(initialRendering, initialViewEnvironment) { _, _ -> }
       }
     }
   }
+
+  @OptIn(WorkflowUiExperimentalApi::class)
+  private class TestScreenViewFactory<R : Screen>(
+    override val type: KClass<R>
+  ) : ScreenViewFactory<R> {
+    override fun buildView(
+      initialRendering: R,
+      initialEnvironment: ViewEnvironment,
+      context: Context,
+      container: ViewGroup?
+    ): ScreenViewHolder<R> {
+      return ScreenViewHolder(initialEnvironment, mockView()) { _, _ -> }
+    }
+  }
 }