ComposeWorkflow sketch

gradle/libs.versions.toml

@@ -68,6 +68,8 @@ material = "1.11.0"
 mockito-core = "3.12.4"
 mockito-kotlin = "3.2.0"
 
+molecule = "2.0.0"
+
 mockk = "1.13.9"
 robolectric = "4.10.3"
 
@@ -226,6 +228,8 @@ lanterna = "com.googlecode.lanterna:lanterna:3.1.1"
 mockito-core = { module = "org.mockito:mockito-core", version.ref = "mockito-core" }
 mockito-kotlin = { module = "org.mockito.kotlin:mockito-kotlin", version.ref = "mockito-kotlin" }
 
+molecule = { module = "app.cash.molecule:molecule-runtime", version.ref = "molecule" }
+
 mockk = { module = "io.mockk:mockk", version.ref = "mockk" }
 
 reactivestreams = "org.reactivestreams:reactive-streams:1.0.4"

workflow-ui/compose-tooling/dependencies/releaseRuntimeClasspath.txt

@@ -73,16 +73,19 @@ androidx.startup:startup-runtime:1.1.1
 androidx.tracing:tracing:1.0.0
 androidx.transition:transition:1.5.1
 androidx.versionedparcelable:versionedparcelable:1.1.1
+app.cash.molecule:molecule-runtime-android:2.0.0
+app.cash.molecule:molecule-runtime:2.0.0
 com.google.guava:listenablefuture:1.0
 com.squareup.okio:okio-jvm:3.3.0
 com.squareup.okio:okio:3.3.0
+org.jetbrains.compose.runtime:runtime:1.6.10
 org.jetbrains.kotlin:kotlin-bom:1.9.24
-org.jetbrains.kotlin:kotlin-stdlib-common:1.9.24
+org.jetbrains.kotlin:kotlin-stdlib-common:2.0.0
 org.jetbrains.kotlin:kotlin-stdlib-jdk7:1.9.24
 org.jetbrains.kotlin:kotlin-stdlib-jdk8:1.9.24
-org.jetbrains.kotlin:kotlin-stdlib:1.9.24
-org.jetbrains.kotlinx:kotlinx-coroutines-android:1.7.3
-org.jetbrains.kotlinx:kotlinx-coroutines-bom:1.7.3
-org.jetbrains.kotlinx:kotlinx-coroutines-core-jvm:1.7.3
-org.jetbrains.kotlinx:kotlinx-coroutines-core:1.7.3
+org.jetbrains.kotlin:kotlin-stdlib:2.0.0
+org.jetbrains.kotlinx:kotlinx-coroutines-android:1.8.1
+org.jetbrains.kotlinx:kotlinx-coroutines-bom:1.8.1
+org.jetbrains.kotlinx:kotlinx-coroutines-core-jvm:1.8.1
+org.jetbrains.kotlinx:kotlinx-coroutines-core:1.8.1
 org.jetbrains:annotations:23.0.0

workflow-ui/compose/api/compose.api

@@ -17,6 +17,14 @@ public final class com/squareup/workflow1/ui/compose/ComposeScreenKt {
 	public static final fun ComposeScreen (Lkotlin/jvm/functions/Function2;)Lcom/squareup/workflow1/ui/compose/ComposeScreen;
 }
 
+public abstract interface class com/squareup/workflow1/ui/compose/ComposeWorkflow {
+	public abstract fun render (Landroidx/compose/runtime/Composer;I)Ljava/lang/Object;
+}
+
+public abstract interface class com/squareup/workflow1/ui/compose/ComposeWorkflowWithProps {
+	public abstract fun render (Ljava/lang/Object;Landroidx/compose/runtime/Composer;I)Ljava/lang/Object;
+}
+
 public final class com/squareup/workflow1/ui/compose/CompositionRootKt {
 	public static final fun withCompositionRoot (Lcom/squareup/workflow1/ui/compose/ScreenComposableFactoryFinder;Lkotlin/jvm/functions/Function3;)Lcom/squareup/workflow1/ui/compose/ScreenComposableFactoryFinder;
 }
@@ -64,6 +72,20 @@ public final class com/squareup/workflow1/ui/compose/ScreenComposableFactoryKt {
 	public static final fun toComposableFactory (Lcom/squareup/workflow1/ui/Screen;Lcom/squareup/workflow1/ui/ViewEnvironment;)Lcom/squareup/workflow1/ui/compose/ScreenComposableFactory;
 }
 
+public final class com/squareup/workflow1/ui/compose/State {
+	public static final field $stable I
+	public fun <init> (Lcom/squareup/workflow1/Worker;Ljava/lang/Object;)V
+	public final fun component1 ()Lcom/squareup/workflow1/Worker;
+	public final fun component2 ()Ljava/lang/Object;
+	public final fun copy (Lcom/squareup/workflow1/Worker;Ljava/lang/Object;)Lcom/squareup/workflow1/ui/compose/State;
+	public static synthetic fun copy$default (Lcom/squareup/workflow1/ui/compose/State;Lcom/squareup/workflow1/Worker;Ljava/lang/Object;ILjava/lang/Object;)Lcom/squareup/workflow1/ui/compose/State;
+	public fun equals (Ljava/lang/Object;)Z
+	public final fun getLatestRendering ()Ljava/lang/Object;
+	public final fun getRenderings ()Lcom/squareup/workflow1/Worker;
+	public fun hashCode ()I
+	public fun toString ()Ljava/lang/String;
+}
+
 public final class com/squareup/workflow1/ui/compose/TextControllerAsMutableStateKt {
 	public static final fun asMutableState (Lcom/squareup/workflow1/ui/TextController;Landroidx/compose/runtime/Composer;I)Landroidx/compose/runtime/MutableState;
 }

workflow-ui/compose/build.gradle.kts

@@ -54,6 +54,7 @@ dependencies {
   implementation(libs.androidx.lifecycle.compose)
   implementation(libs.androidx.lifecycle.core)
   implementation(libs.kotlinx.coroutines.core)
+  implementation(libs.molecule)
   implementation(libs.squareup.okio)
 
   implementation(project(":workflow-core"))

workflow-ui/compose/dependencies/releaseRuntimeClasspath.txt

@@ -67,16 +67,19 @@ androidx.startup:startup-runtime:1.1.1
 androidx.tracing:tracing:1.0.0
 androidx.transition:transition:1.5.1
 androidx.versionedparcelable:versionedparcelable:1.1.1
+app.cash.molecule:molecule-runtime-android:2.0.0
+app.cash.molecule:molecule-runtime:2.0.0
 com.google.guava:listenablefuture:1.0
 com.squareup.okio:okio-jvm:3.3.0
 com.squareup.okio:okio:3.3.0
+org.jetbrains.compose.runtime:runtime:1.6.10
 org.jetbrains.kotlin:kotlin-bom:1.9.24
-org.jetbrains.kotlin:kotlin-stdlib-common:1.9.24
+org.jetbrains.kotlin:kotlin-stdlib-common:2.0.0
 org.jetbrains.kotlin:kotlin-stdlib-jdk7:1.9.24
 org.jetbrains.kotlin:kotlin-stdlib-jdk8:1.9.24
-org.jetbrains.kotlin:kotlin-stdlib:1.9.24
-org.jetbrains.kotlinx:kotlinx-coroutines-android:1.7.3
-org.jetbrains.kotlinx:kotlinx-coroutines-bom:1.7.3
-org.jetbrains.kotlinx:kotlinx-coroutines-core-jvm:1.7.3
-org.jetbrains.kotlinx:kotlinx-coroutines-core:1.7.3
+org.jetbrains.kotlin:kotlin-stdlib:2.0.0
+org.jetbrains.kotlinx:kotlinx-coroutines-android:1.8.1
+org.jetbrains.kotlinx:kotlinx-coroutines-bom:1.8.1
+org.jetbrains.kotlinx:kotlinx-coroutines-core-jvm:1.8.1
+org.jetbrains.kotlinx:kotlinx-coroutines-core:1.8.1
 org.jetbrains:annotations:23.0.0

workflow-ui/compose/src/main/java/com/squareup/workflow1/ui/compose/ComposeWorkflow.kt

@@ -0,0 +1,77 @@
+package com.squareup.workflow1.ui.compose
+
+import androidx.compose.runtime.Composable
+import app.cash.molecule.RecompositionMode.Immediate
+import app.cash.molecule.launchMolecule
+import com.squareup.workflow1.SessionWorkflow
+import com.squareup.workflow1.Snapshot
+import com.squareup.workflow1.Worker
+import com.squareup.workflow1.Workflow
+import com.squareup.workflow1.WorkflowExperimentalApi
+import com.squareup.workflow1.action
+import com.squareup.workflow1.asWorker
+import com.squareup.workflow1.runningWorker
+import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.flow.drop
+
+/**
+ * - Note that `RenderT` can be our old friends `Screen`, `Overlay`,
+ *   `MarketStackScreen`, etc.
+ *
+ * - For `OutputT`, pass a `MutableStateFlow` as a prop and
+ *   consume it as a worker. Perhaps we can provide some sugar
+ *   for that, but I don't think it needs to be part of the
+ *   fundamental machinery
+ *
+ * - Snapshots: TBD. [Easy enough to put a `SavedStateRegistry` in place.](https://docs.google.com/presentation/d/1JTN3PpFG27b06OqKEOdHXZSos8wHck3y9T4pRvwpir8/edit#slide=id.g149ba2e5ba1_0_204)
+ *   Tricky bit is that Snapshot really wants you to read and
+ *   write `ByteString`, with support provided for `Parcelable`.
+ *   How do we get `SavedStateRegistry` to play nice with that?
+ *   Maybe `SavedStateRegistryOwner` and `SavedStateController`
+ *   are flexible enough. Not excited about this.
+ */
+public fun interface ComposeWorkflow<out RenderT> {
+  @Composable public fun render(): RenderT
+}
+
+public fun interface ComposeWorkflowWithProps<in PropsT, out RenderT> {
+  @Composable public fun render(propsT: PropsT): RenderT
+}
+
+@PublishedApi
+internal data class State<RenderT>(
+  val renderings: Worker<RenderT>,
+  val latestRendering: RenderT
+)
+
+public inline fun <reified RenderT> ComposeWorkflow<RenderT>.asWorkflow(): Workflow<Unit, Nothing, RenderT> {
+  @OptIn(WorkflowExperimentalApi::class)
+  return object : SessionWorkflow<Unit, State<RenderT>, Nothing, RenderT>() {
+    val rootPresenter = this@asWorkflow
+
+    override fun initialState(
+      props: Unit,
+      snapshot: Snapshot?,
+      workflowScope: CoroutineScope
+    ): State<RenderT> {
+      val stateFlow = workflowScope.launchMolecule(mode = Immediate) { rootPresenter.render() }
+      val worker: Worker<RenderT> = stateFlow.drop(1).asWorker()
+      return State(worker, stateFlow.value)
+    }
+
+    override fun render(
+      renderProps: Unit,
+      renderState: State<RenderT>,
+      context: RenderContext
+    ): RenderT {
+      context.runningWorker(renderState.renderings) {
+        action("nextRendering") {
+          state = state.copy(latestRendering = it)
+        }
+      }
+      return renderState.latestRendering
+    }
+
+    override fun snapshotState(state: State<RenderT>): Snapshot? = null
+  }
+}