Reimplemented Workers using side effects (GUWT).

samples/dungeon/app/src/main/java/com/squareup/sample/dungeon/DungeonAppWorkflow.kt

@@ -26,6 +26,7 @@ import com.squareup.workflow.Snapshot
 import com.squareup.workflow.StatefulWorkflow
 import com.squareup.workflow.action
 import com.squareup.workflow.renderChild
+import com.squareup.workflow.runningWorker
 import com.squareup.workflow.ui.WorkflowUiExperimentalApi
 import com.squareup.workflow.ui.modal.AlertContainerScreen
 

samples/dungeon/app/src/main/java/com/squareup/sample/dungeon/GameSessionWorkflow.kt

@@ -31,6 +31,7 @@ import com.squareup.workflow.WorkflowAction
 import com.squareup.workflow.WorkflowAction.Companion.noAction
 import com.squareup.workflow.WorkflowAction.Updater
 import com.squareup.workflow.action
+import com.squareup.workflow.runningWorker
 import com.squareup.workflow.ui.WorkflowUiExperimentalApi
 import com.squareup.workflow.ui.modal.AlertContainerScreen
 import com.squareup.workflow.ui.modal.AlertScreen

samples/dungeon/common/src/main/java/com/squareup/sample/dungeon/AiWorkflow.kt

@@ -28,6 +28,7 @@ import com.squareup.workflow.Snapshot
 import com.squareup.workflow.StatefulWorkflow
 import com.squareup.workflow.Worker
 import com.squareup.workflow.action
+import com.squareup.workflow.runningWorker
 import com.squareup.workflow.transform
 import kotlinx.coroutines.ExperimentalCoroutinesApi
 import kotlinx.coroutines.flow.transform

samples/dungeon/common/src/main/java/com/squareup/sample/dungeon/GameWorkflow.kt

@@ -36,6 +36,7 @@ import com.squareup.workflow.StatefulWorkflow
 import com.squareup.workflow.Worker
 import com.squareup.workflow.action
 import com.squareup.workflow.renderChild
+import com.squareup.workflow.runningWorker
 import kotlinx.coroutines.delay
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.flow

samples/dungeon/timemachine-shakeable/src/main/java/com/squareup/sample/timemachine/shakeable/ShakeableTimeMachineWorkflow.kt

@@ -28,6 +28,7 @@ import com.squareup.workflow.StatefulWorkflow
 import com.squareup.workflow.WorkflowAction
 import com.squareup.workflow.WorkflowAction.Updater
 import com.squareup.workflow.action
+import com.squareup.workflow.runningWorker
 import kotlin.time.Duration
 import kotlin.time.ExperimentalTime
 

samples/hello-terminal/hello-terminal-app/src/main/java/com/squareup/sample/helloterminal/BlinkingCursorWorkflow.kt

@@ -20,6 +20,7 @@ import com.squareup.workflow.Snapshot
 import com.squareup.workflow.StatefulWorkflow
 import com.squareup.workflow.Worker
 import com.squareup.workflow.action
+import com.squareup.workflow.runningWorker
 import kotlinx.coroutines.delay
 
 /**

samples/hello-terminal/hello-terminal-app/src/main/java/com/squareup/sample/helloterminal/HelloTerminalWorkflow.kt

@@ -29,6 +29,7 @@ import com.squareup.workflow.StatefulWorkflow
 import com.squareup.workflow.WorkflowAction
 import com.squareup.workflow.action
 import com.squareup.workflow.renderChild
+import com.squareup.workflow.runningWorker
 
 private typealias HelloTerminalAction = WorkflowAction<TerminalProps, State, ExitCode>
 

samples/hello-terminal/todo-terminal-app/src/main/java/com/squareup/sample/hellotodo/EditTextWorkflow.kt

@@ -12,6 +12,7 @@ import com.squareup.workflow.RenderContext
 import com.squareup.workflow.Snapshot
 import com.squareup.workflow.StatefulWorkflow
 import com.squareup.workflow.action
+import com.squareup.workflow.runningWorker
 
 class EditTextWorkflow : StatefulWorkflow<EditTextProps, EditTextState, String, String>() {
 

samples/hello-terminal/todo-terminal-app/src/main/java/com/squareup/sample/hellotodo/TodoWorkflow.kt

@@ -31,6 +31,7 @@ import com.squareup.workflow.Snapshot
 import com.squareup.workflow.StatefulWorkflow
 import com.squareup.workflow.WorkflowAction
 import com.squareup.workflow.action
+import com.squareup.workflow.runningWorker
 
 private typealias TodoAction = WorkflowAction<TerminalProps, TodoList, Nothing>
 

samples/tictactoe/common/src/main/java/com/squareup/sample/authworkflow/AuthWorkflow.kt

@@ -36,6 +36,7 @@ import com.squareup.workflow.StatefulWorkflow
 import com.squareup.workflow.Workflow
 import com.squareup.workflow.WorkflowAction
 import com.squareup.workflow.WorkflowAction.Updater
+import com.squareup.workflow.runningWorker
 import com.squareup.workflow.rx2.asWorker
 import com.squareup.workflow.ui.WorkflowUiExperimentalApi
 import com.squareup.workflow.ui.backstack.BackStackScreen

samples/tictactoe/common/src/main/java/com/squareup/sample/gameworkflow/RunGameWorkflow.kt

@@ -46,6 +46,7 @@ import com.squareup.workflow.StatefulWorkflow
 import com.squareup.workflow.Workflow
 import com.squareup.workflow.WorkflowAction
 import com.squareup.workflow.WorkflowAction.Updater
+import com.squareup.workflow.runningWorker
 import com.squareup.workflow.rx2.asWorker
 import com.squareup.workflow.ui.WorkflowUiExperimentalApi
 import com.squareup.workflow.ui.modal.AlertContainerScreen

samples/tictactoe/common/src/test/java/com/squareup/sample/mainworkflow/MainWorkflowTest.kt

@@ -11,6 +11,7 @@ import com.squareup.workflow.Worker
 import com.squareup.workflow.Workflow
 import com.squareup.workflow.action
 import com.squareup.workflow.rendering
+import com.squareup.workflow.runningWorker
 import com.squareup.workflow.stateless
 import com.squareup.workflow.testing.launchForTestingFromStartWith
 import com.squareup.workflow.ui.WorkflowUiExperimentalApi

workflow-core/api/workflow-core.api

@@ -33,14 +33,12 @@ public abstract interface class com/squareup/workflow/RenderContext {
 	public abstract fun onEvent (Lkotlin/jvm/functions/Function1;)Lkotlin/jvm/functions/Function1;
 	public abstract fun renderChild (Lcom/squareup/workflow/Workflow;Ljava/lang/Object;Ljava/lang/String;Lkotlin/jvm/functions/Function1;)Ljava/lang/Object;
 	public abstract fun runningSideEffect (Ljava/lang/String;Lkotlin/jvm/functions/Function1;)V
-	public abstract fun runningWorker (Lcom/squareup/workflow/Worker;Ljava/lang/String;Lkotlin/jvm/functions/Function1;)V
 }
 
 public final class com/squareup/workflow/RenderContext$DefaultImpls {
 	public static fun makeActionSink (Lcom/squareup/workflow/RenderContext;)Lcom/squareup/workflow/Sink;
 	public static fun onEvent (Lcom/squareup/workflow/RenderContext;Lkotlin/jvm/functions/Function1;)Lkotlin/jvm/functions/Function1;
 	public static synthetic fun renderChild$default (Lcom/squareup/workflow/RenderContext;Lcom/squareup/workflow/Workflow;Ljava/lang/Object;Ljava/lang/String;Lkotlin/jvm/functions/Function1;ILjava/lang/Object;)Ljava/lang/Object;
-	public static synthetic fun runningWorker$default (Lcom/squareup/workflow/RenderContext;Lcom/squareup/workflow/Worker;Ljava/lang/String;Lkotlin/jvm/functions/Function1;ILjava/lang/Object;)V
 }
 
 public abstract interface class com/squareup/workflow/Sink {
@@ -213,12 +211,9 @@ public final class com/squareup/workflow/Workflows {
 	public static final fun contraMap (Lcom/squareup/workflow/Sink;Lkotlin/jvm/functions/Function1;)Lcom/squareup/workflow/Sink;
 	public static final fun getIdentifier (Lcom/squareup/workflow/Workflow;)Lcom/squareup/workflow/WorkflowIdentifier;
 	public static final fun getWorkflowIdentifier (Lkotlin/reflect/KClass;)Lcom/squareup/workflow/WorkflowIdentifier;
-	public static final fun impostorWorkflowIdentifier (Lkotlin/reflect/KClass;Lcom/squareup/workflow/WorkflowIdentifier;)Lcom/squareup/workflow/WorkflowIdentifier;
 	public static final fun invoke (Lcom/squareup/workflow/EventHandler;)V
 	public static final fun makeEventSink (Lcom/squareup/workflow/RenderContext;Lkotlin/jvm/functions/Function2;)Lcom/squareup/workflow/Sink;
 	public static final fun mapRendering (Lcom/squareup/workflow/Workflow;Lkotlin/jvm/functions/Function1;)Lcom/squareup/workflow/Workflow;
-	public static final fun onWorkerOutput (Lcom/squareup/workflow/RenderContext;Lcom/squareup/workflow/Worker;Ljava/lang/String;Lkotlin/jvm/functions/Function1;)V
-	public static synthetic fun onWorkerOutput$default (Lcom/squareup/workflow/RenderContext;Lcom/squareup/workflow/Worker;Ljava/lang/String;Lkotlin/jvm/functions/Function1;ILjava/lang/Object;)V
 	public static final fun renderChild (Lcom/squareup/workflow/RenderContext;Lcom/squareup/workflow/Workflow;Ljava/lang/Object;Ljava/lang/String;)Ljava/lang/Object;
 	public static final fun renderChild (Lcom/squareup/workflow/RenderContext;Lcom/squareup/workflow/Workflow;Ljava/lang/String;)Ljava/lang/Object;
 	public static final fun renderChild (Lcom/squareup/workflow/RenderContext;Lcom/squareup/workflow/Workflow;Ljava/lang/String;Lkotlin/jvm/functions/Function1;)Ljava/lang/Object;
@@ -227,6 +222,7 @@ public final class com/squareup/workflow/Workflows {
 	public static synthetic fun renderChild$default (Lcom/squareup/workflow/RenderContext;Lcom/squareup/workflow/Workflow;Ljava/lang/String;Lkotlin/jvm/functions/Function1;ILjava/lang/Object;)Ljava/lang/Object;
 	public static final fun rendering (Lcom/squareup/workflow/Workflow$Companion;Ljava/lang/Object;)Lcom/squareup/workflow/Workflow;
 	public static final fun runningWorker (Lcom/squareup/workflow/RenderContext;Lcom/squareup/workflow/Worker;Ljava/lang/String;)V
+	public static final fun runningWorker (Lcom/squareup/workflow/RenderContext;Lcom/squareup/workflow/Worker;Lkotlin/reflect/KType;Ljava/lang/String;Lkotlin/jvm/functions/Function1;)V
 	public static synthetic fun runningWorker$default (Lcom/squareup/workflow/RenderContext;Lcom/squareup/workflow/Worker;Ljava/lang/String;ILjava/lang/Object;)V
 	public static final fun sendAndAwaitApplication (Lcom/squareup/workflow/Sink;Lcom/squareup/workflow/WorkflowAction;Lkotlin/coroutines/Continuation;)Ljava/lang/Object;
 	public static final fun stateful (Lcom/squareup/workflow/Workflow$Companion;Ljava/lang/Object;Lkotlin/jvm/functions/Function2;)Lcom/squareup/workflow/StatefulWorkflow;

workflow-core/src/main/java/com/squareup/workflow/LifecycleWorker.kt

@@ -73,6 +73,5 @@ abstract class LifecycleWorker : Worker<Nothing> {
   /**
    * Equates [LifecycleWorker]s that have the same concrete class.
    */
-  override fun doesSameWorkAs(otherWorker: Worker<*>): Boolean =
-    this::class == otherWorker::class
+  override fun doesSameWorkAs(otherWorker: Worker<*>): Boolean = true
 }

workflow-core/src/main/java/com/squareup/workflow/RenderContext.kt

@@ -21,6 +21,8 @@ package com.squareup.workflow
 
 import com.squareup.workflow.WorkflowAction.Companion.noAction
 import com.squareup.workflow.WorkflowAction.Updater
+import kotlin.reflect.KType
+import kotlin.reflect.typeOf
 
 /**
  * Facilities for a [Workflow] to interact with other [Workflow]s and the outside world from inside
@@ -109,19 +111,6 @@ interface RenderContext<out PropsT, StateT, in OutputT> {
     handler: (ChildOutputT) -> WorkflowAction<PropsT, StateT, OutputT>
   ): ChildRenderingT
 
-  /**
-   * Ensures [worker] is running. When the [Worker] emits an output, [handler] is called
-   * to determine the [WorkflowAction] to take. When the worker finishes, nothing happens (although
-   * another render pass may be triggered).
-   *
-   * @param key An optional string key that is used to distinguish between identical [Worker]s.
-   */
-  fun <T> runningWorker(
-    worker: Worker<T>,
-    key: String = "",
-    handler: (T) -> WorkflowAction<PropsT, StateT, OutputT>
-  )
-
   /**
    * Ensures [sideEffect] is running with the given [key].
    *
@@ -196,12 +185,62 @@ fun <PropsT, StateT, OutputT> RenderContext<PropsT, StateT, OutputT>.runningWork
   worker: Worker<Nothing>,
   key: String = ""
 ) {
-  // Need to cast to Any so the compiler doesn't complain about unreachable code.
-  runningWorker(worker as Worker<Any>, key) {
+  runningWorker(worker, key) {
+    // The compiler thinks this code is unreachable, and it is correct. But we have to pass a lambda
+    // here so we might as well check at runtime as well.
+    @Suppress("UNREACHABLE_CODE", "ThrowableNotThrown")
     throw AssertionError("Worker<Nothing> emitted $it")
   }
 }
 
+/**
+ * Ensures [worker] is running. When the [Worker] emits an output, [handler] is called
+ * to determine the [WorkflowAction] to take. When the worker finishes, nothing happens (although
+ * another render pass may be triggered).
+ *
+ * Like workflows, workers are kept alive across multiple render passes if they're the same type,
+ * and different workers of distinct types can be run concurrently. However, unlike workflows,
+ * workers are compared by their _declared_ type, not their actual type. This means that if you
+ * pass a worker stored in a variable to this function, the type that will be used to compare the
+ * worker will be the type of the variable, not the type of the object the variable refers to.
+ *
+ * @param key An optional string key that is used to distinguish between identical [Worker]s.
+ */
+@OptIn(ExperimentalStdlibApi::class)
+/* ktlint-disable parameter-list-wrapping */
+inline fun <T, reified W : Worker<T>, PropsT, StateT, OutputT>
+    RenderContext<PropsT, StateT, OutputT>.runningWorker(
+  worker: W,
+  key: String = "",
+  noinline handler: (T) -> WorkflowAction<PropsT, StateT, OutputT>
+) {
+/* ktlint-enable parameter-list-wrapping */
+  runningWorker(worker, typeOf<W>(), key, handler)
+}
+
+/**
+ * Ensures [worker] is running. When the [Worker] emits an output, [handler] is called
+ * to determine the [WorkflowAction] to take. When the worker finishes, nothing happens (although
+ * another render pass may be triggered).
+ *
+ * @param workerType `typeOf<W>()`
+ * @param key An optional string key that is used to distinguish between identical [Worker]s.
+ */
+@OptIn(ExperimentalStdlibApi::class)
+@PublishedApi
+/* ktlint-disable parameter-list-wrapping */
+internal fun <T, PropsT, StateT, OutputT>
+    RenderContext<PropsT, StateT, OutputT>.runningWorker(
+  worker: Worker<T>,
+  workerType: KType,
+  key: String = "",
+  handler: (T) -> WorkflowAction<PropsT, StateT, OutputT>
+) {
+/* ktlint-enable parameter-list-wrapping */
+  val workerWorkflow = WorkerWorkflow<T>(workerType, key)
+  renderChild(workerWorkflow, props = worker, key = key, handler = handler)
+}
+
 /**
  * Alternative to [RenderContext.actionSink] that allows externally defined
  * event types to be mapped to anonymous [WorkflowAction]s.
@@ -223,8 +262,8 @@ fun <EventT, PropsT, StateT, OutputT> RenderContext<PropsT, StateT, OutputT>.mak
     "Use runningWorker",
     ReplaceWith("runningWorker(worker, key, handler)", "com.squareup.workflow.runningWorker")
 )
-fun <PropsT, StateT, OutputT, T> RenderContext<PropsT, StateT, OutputT>.onWorkerOutput(
+inline fun <PropsT, StateT, OutputT, reified T> RenderContext<PropsT, StateT, OutputT>.onWorkerOutput(
   worker: Worker<T>,
   key: String = "",
-  handler: (T) -> WorkflowAction<PropsT, StateT, OutputT>
+  noinline handler: (T) -> WorkflowAction<PropsT, StateT, OutputT>
 ) = runningWorker(worker, key, handler)

workflow-core/src/main/java/com/squareup/workflow/Sink.kt

@@ -18,6 +18,7 @@
 
 package com.squareup.workflow
 
+import com.squareup.workflow.WorkflowAction.Updater
 import kotlinx.coroutines.flow.Flow
 import kotlinx.coroutines.flow.collect
 import kotlinx.coroutines.suspendCancellableCoroutine
@@ -104,15 +105,18 @@ suspend fun <
       action: WorkflowAction<PropsT, StateT, OutputT>
     ) {
   suspendCancellableCoroutine<Unit> { continuation ->
-    val resumingAction = action<PropsT, StateT, OutputT>({ "sendAndAwaitExecution($action)" }) {
-      // Don't execute anything if the caller was cancelled while we were in the queue.
-      if (!continuation.isActive) return@action
+    val resumingAction = object : WorkflowAction<PropsT, StateT, OutputT> {
+      override fun toString(): String = "sendAndAwaitApplication($action)"
+      override fun Updater<PropsT, StateT, OutputT>.apply() {
+        // Don't execute anything if the caller was cancelled while we were in the queue.
+        if (!continuation.isActive) return
 
-      with(action) {
-        // Forward our Updater to the real action.
-        apply()
+        with(action) {
+          // Forward our Updater to the real action.
+          apply()
+        }
+        continuation.resume(Unit)
       }
-      continuation.resume(Unit)
     }
     send(resumingAction)
   }

workflow-core/src/main/java/com/squareup/workflow/Worker.kt

@@ -154,19 +154,20 @@ interface Worker<out OutputT> {
   fun run(): Flow<OutputT>
 
   /**
-   * Override this method to define equivalence between [Worker]s.
+   * Override this method to define equivalence between [Worker]s. The default implementation
+   * returns true if this worker's class is the same as [otherWorker]'s class.
    *
    * At the end of every render pass, the set of [Worker]s that were requested by the workflow are
-   * compared to the set from the last render pass using this method. Equivalent workers are allowed
-   * to keep running. New workers are started ([run] is called and the returned [Flow] is
-   * collected). Old workers are cancelled by cancelling their collecting coroutines.
+   * compared to the set from the last render pass using this method. Workers are compared by their
+   * _declared_ type. Equivalent workers are allowed to keep running. New workers are started ([run]
+   * is called and the returned [Flow] is collected). Old workers are cancelled by cancelling their
+   * collecting coroutines. Workers for which [doesSameWorkAs] returns false will also be restarted.
    *
    * Implementations of this method should not be based on object identity. For example, a [Worker]
    * that performs a network request might check that two workers are requests to the same endpoint
    * and have the same request data.
    *
-   * Most implementations of this method will check for concrete type equality, and then match
-   * on constructor parameters.
+   * Most implementations of this method should compare constructor parameters.
    *
    * E.g:
    *
@@ -384,23 +385,18 @@ fun <T, R> Worker<T>.transform(
 
 /**
  * A generic [Worker] implementation that defines equivalent workers as those having equivalent
- * [type]s. This is used by all the [Worker] builder functions.
+ * [outputType]s. This is used by all the [Worker] builder functions.
  */
 @PublishedApi
 internal class TypedWorker<OutputT>(
-  private val type: KType,
+  private val outputType: KType,
   private val work: Flow<OutputT>
 ) : Worker<OutputT> {
-
   override fun run(): Flow<OutputT> = work
-
-  override fun doesSameWorkAs(otherWorker: Worker<*>): Boolean =
-    otherWorker is TypedWorker && otherWorker.type == type
-
-  override fun toString(): String = "TypedWorker($type)"
+  override fun toString(): String = "TypedWorker($outputType)"
 }
 
-private class TimerWorker(
+private data class TimerWorker(
   private val delayMs: Long,
   private val key: String
 ) : Worker<Unit> {
@@ -412,17 +408,14 @@ private class TimerWorker(
 
   override fun doesSameWorkAs(otherWorker: Worker<*>): Boolean =
     otherWorker is TimerWorker && otherWorker.key == key
-
-  override fun toString(): String = "TimerWorker(delayMs=$delayMs)"
 }
 
 private object FinishedWorker : Worker<Nothing> {
   override fun run(): Flow<Nothing> = emptyFlow()
-  override fun doesSameWorkAs(otherWorker: Worker<*>): Boolean = otherWorker === FinishedWorker
   override fun toString(): String = "FinishedWorker"
 }
 
-private class WorkerWrapper<T, R>(
+private data class WorkerWrapper<T, R>(
   private val wrapped: Worker<T>,
   private val flow: Flow<R>
 ) : Worker<R> {