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1337: Cache StatelessWorkflow.RenderContext in the StatefulWorkflow.RenderContext #1342

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Jun 10, 2025
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1337: Cache StatelessWorkflow.RenderContext in the StatefulWorkflow.RenderContext #1342

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13 changes: 1 addition & 12 deletions workflow-core/api/workflow-core.api
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Original file line number Diff line number Diff line change
Expand Up @@ -257,6 +257,7 @@ public final class com/squareup/workflow1/StatefulWorkflow$Companion {
}

public final class com/squareup/workflow1/StatefulWorkflow$RenderContext : com/squareup/workflow1/BaseRenderContext {
public final fun asStatelessRenderContext ()Lcom/squareup/workflow1/StatelessWorkflow$RenderContext;
public final fun eventHandler (Ljava/lang/String;Ljava/lang/Boolean;Lkotlin/jvm/functions/Function1;)Lkotlin/jvm/functions/Function0;
public static synthetic fun eventHandler$default (Lcom/squareup/workflow1/StatefulWorkflow$RenderContext;Ljava/lang/String;Ljava/lang/Boolean;Lkotlin/jvm/functions/Function1;ILjava/lang/Object;)Lkotlin/jvm/functions/Function0;
public fun getActionSink ()Lcom/squareup/workflow1/Sink;
Expand Down Expand Up @@ -288,17 +289,6 @@ public final class com/squareup/workflow1/StatelessWorkflow$RenderContext : com/
public fun runningSideEffect (Ljava/lang/String;Lkotlin/jvm/functions/Function2;)V
}

public final class com/squareup/workflow1/StatelessWorkflow$StatelessAsStatefulWorkflow : com/squareup/workflow1/StatefulWorkflow {
public fun <init> (Lcom/squareup/workflow1/StatelessWorkflow;)V
public final fun clearCache ()V
public synthetic fun initialState (Ljava/lang/Object;Lcom/squareup/workflow1/Snapshot;)Ljava/lang/Object;
public fun initialState (Ljava/lang/Object;Lcom/squareup/workflow1/Snapshot;)V
public synthetic fun render (Ljava/lang/Object;Ljava/lang/Object;Lcom/squareup/workflow1/StatefulWorkflow$RenderContext;)Ljava/lang/Object;
public fun render (Ljava/lang/Object;Lkotlin/Unit;Lcom/squareup/workflow1/StatefulWorkflow$RenderContext;)Ljava/lang/Object;
public synthetic fun snapshotState (Ljava/lang/Object;)Lcom/squareup/workflow1/Snapshot;
public fun snapshotState (Lkotlin/Unit;)Lcom/squareup/workflow1/Snapshot;
}

public final class com/squareup/workflow1/TypedWorker : com/squareup/workflow1/Worker {
public fun <init> (Lkotlin/reflect/KType;Lkotlinx/coroutines/flow/Flow;)V
public fun doesSameWorkAs (Lcom/squareup/workflow1/Worker;)Z
Expand Down Expand Up @@ -424,7 +414,6 @@ public final class com/squareup/workflow1/WorkflowTracerKt {

public final class com/squareup/workflow1/Workflows {
public static final fun RenderContext (Lcom/squareup/workflow1/BaseRenderContext;Lcom/squareup/workflow1/StatefulWorkflow;)Lcom/squareup/workflow1/StatefulWorkflow$RenderContext;
public static final fun RenderContext (Lcom/squareup/workflow1/BaseRenderContext;Lcom/squareup/workflow1/StatelessWorkflow;)Lcom/squareup/workflow1/StatelessWorkflow$RenderContext;
public static final fun action (Lcom/squareup/workflow1/StatefulWorkflow;Ljava/lang/String;Lkotlin/jvm/functions/Function1;)Lcom/squareup/workflow1/WorkflowAction;
public static final fun action (Lcom/squareup/workflow1/StatefulWorkflow;Lkotlin/jvm/functions/Function0;Lkotlin/jvm/functions/Function1;)Lcom/squareup/workflow1/WorkflowAction;
public static final fun action (Lcom/squareup/workflow1/StatelessWorkflow;Ljava/lang/String;Lkotlin/jvm/functions/Function1;)Lcom/squareup/workflow1/WorkflowAction;
Expand Down
14 changes: 14 additions & 0 deletions workflow-core/src/commonMain/kotlin/com/squareup/workflow1/StatefulWorkflow.kt
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Expand Up @@ -706,6 +706,20 @@ public abstract class StatefulWorkflow<
}
?: onFailedCast(name, CurrentStateT::class, state)
}

private var statelessContext: StatelessWorkflow.RenderContext<PropsT, OutputT>? = null

/**
* Fetch the [StatelessWorkflow.RenderContext] that is equivalent to this [RenderContext]
* with the `StateT` type erased.
*
* We cache this value so that it does not need to be continually recreated and will be stable
* for compose. See [statelessContext] for the instance.
*/
public fun asStatelessRenderContext(): StatelessWorkflow.RenderContext<PropsT, OutputT> =
statelessContext ?: StatelessWorkflow.RenderContext(this).also {
statelessContext = it
}
}

/**
Expand Down
58 changes: 4 additions & 54 deletions workflow-core/src/commonMain/kotlin/com/squareup/workflow1/StatelessWorkflow.kt
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Expand Up @@ -227,23 +227,9 @@ public abstract class StatelessWorkflow<PropsT, OutputT, out RenderingT> :
* Class type returned by [asStatefulWorkflow].
* See [statefulWorkflow] for the instance.
*/
inner class StatelessAsStatefulWorkflow :
private inner class StatelessAsStatefulWorkflow :
StatefulWorkflow<PropsT, Unit, OutputT, RenderingT>() {

/**
* We want to cache the render context so that we don't have to recreate it each time
* render() is called.
*/
private var cachedStatelessRenderContext:
StatelessWorkflow.RenderContext<PropsT, OutputT>? = null

/**
* We must know if the RenderContext we are passed (which is a StatefulWorkflow.RenderContext)
* has changed, so keep track of it.
*/
private var canonicalStatefulRenderContext:
StatefulWorkflow.RenderContext<PropsT, Unit, OutputT>? = null

override fun initialState(
props: PropsT,
snapshot: Snapshot?
Expand All @@ -254,37 +240,12 @@ public abstract class StatelessWorkflow<PropsT, OutputT, out RenderingT> :
renderState: Unit,
context: RenderContext<PropsT, Unit, OutputT>
): RenderingT {
// The `RenderContext` used *might* change - primarily in the case of our tests. E.g., The
// `RenderTester` uses a special NoOp context to render twice to test for idempotency.
// In order to support a changed render context but keep caching, we check to see if the
// instance passed in has changed.
if (cachedStatelessRenderContext == null || context !== canonicalStatefulRenderContext) {
// Recreate it if the StatefulWorkflow.RenderContext we are passed has changed.
cachedStatelessRenderContext = RenderContext(context, this@StatelessWorkflow)
}
canonicalStatefulRenderContext = context
// Pass the StatelessWorkflow.RenderContext to our StatelessWorkflow.
return render(renderProps, cachedStatelessRenderContext!!)
// Pass `asStatelessRenderContext()`. Caching for that will be handled by the
// `StatefulWorkflow.RenderContext` itself.
return render(renderProps, context.asStatelessRenderContext())
}

override fun snapshotState(state: Unit): Snapshot? = null

/**
* When we are finished with at least one node that holds on to this workflow instance,
* then we clear the cache. The reason we do that every time is that it *might* be the last
* node that is caching this instance, and if so, we do not want to leak these cached
* render contexts.
*
* Yes, that means that it might have to be re-created again when this instance is used
* multiple times. The current design for how we get a [StatefulWorkflow] from the
* [StatelessWorkflow] is a failed compromise between performance (caching) and type-safe
* brevity (erasing the `StateT` type from the concerns of [StatelessWorkflow]). It needs
* to be fixed with a bigger re-write (https://github.com/square/workflow-kotlin/issues/1337).
*/
fun clearCache() {
cachedStatelessRenderContext = null
canonicalStatefulRenderContext = null
}
}

private val statefulWorkflow: StatefulWorkflow<PropsT, Unit, OutputT, RenderingT> =
Expand Down Expand Up @@ -325,17 +286,6 @@ public abstract class StatelessWorkflow<PropsT, OutputT, out RenderingT> :
statefulWorkflow
}

/**
* Creates a `RenderContext` from a [BaseRenderContext] for the given [StatelessWorkflow].
*/
@Suppress("UNCHECKED_CAST")
public fun <PropsT, OutputT, RenderingT> RenderContext(
baseContext: BaseRenderContext<PropsT, *, OutputT>,
workflow: StatelessWorkflow<PropsT, OutputT, RenderingT>
): StatelessWorkflow.RenderContext<PropsT, OutputT> =
(baseContext as? StatelessWorkflow.RenderContext<PropsT, OutputT>)
?: StatelessWorkflow.RenderContext<PropsT, OutputT>(baseContext)

/**
* Returns a stateless [Workflow] via the given [render] function.
*
Expand Down
5 changes: 0 additions & 5 deletions workflow-runtime/src/commonMain/kotlin/com/squareup/workflow1/internal/WorkflowNode.kt
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Expand Up @@ -9,7 +9,6 @@ import com.squareup.workflow1.RuntimeConfig
import com.squareup.workflow1.RuntimeConfigOptions
import com.squareup.workflow1.RuntimeConfigOptions.PARTIAL_TREE_RENDERING
import com.squareup.workflow1.StatefulWorkflow
import com.squareup.workflow1.StatelessWorkflow
import com.squareup.workflow1.TreeSnapshot
import com.squareup.workflow1.Workflow
import com.squareup.workflow1.WorkflowAction
Expand Down Expand Up @@ -237,10 +236,6 @@ internal class WorkflowNode<PropsT, StateT, OutputT, RenderingT>(
fun cancel(cause: CancellationException? = null) {
coroutineContext.cancel(cause)
lastRendering = NullableInitBox()
(
cachedWorkflowInstance as?
StatelessWorkflow<PropsT, OutputT, RenderingT>.StatelessAsStatefulWorkflow
)?.clearCache()
}

/**
Expand Down
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