Optimize Modifier serialization in guest code (#2253)

* Optimize Modifier serialization in guest code

I learned that encoding a type as a JsonElement and then
encoding that as JSON is significantly less efficient than
going directly from the type to JSON. This is due to some
inefficient code in the internals of kotlinx.serialization.

Skipping this intermediate step is useful on its own, but it
also turns out to be significantly more efficient in practice.

* Fix sample code

* Delete unused generated code

* Drop an obsolete test

* Return a pair from ProtocolWidgetSystemFactory

* Generate the tag and serializer as a single symbol

* Don't encode ',null' unnecessarily

CHANGELOG.md

@@ -6,6 +6,7 @@
 New:
 - Source-based schema parser is now the default. The `useFir` Gradle property has been removed.
 - Introduce a `LoadingStrategy` interface to manage `LazyList` preloading.
+- Optimize encoding modifiers in Kotlin/JS.
 
 Changed:
 - In Treehouse, events from the UI are now serialized on a background thread. This means that there is both a delay and a thread change between when a UI binding sends an event and when that object is converted to JSON. All arguments to events must not be mutable and support property reads on any thread. Best practice is for all event arguments to be completely immutable.

redwood-protocol-guest/api/redwood-protocol-guest.api

@@ -4,7 +4,7 @@ public final class app/cash/redwood/protocol/guest/DefaultGuestProtocolAdapter :
 	public synthetic fun <init> (Lkotlinx/serialization/json/Json;Ljava/lang/String;Lapp/cash/redwood/protocol/guest/ProtocolWidgetSystemFactory;Lapp/cash/redwood/protocol/guest/ProtocolMismatchHandler;Lkotlin/jvm/internal/DefaultConstructorMarker;)V
 	public fun appendAdd-ARs5Qwk (IIILapp/cash/redwood/protocol/guest/ProtocolWidget;)V
 	public fun appendCreate-kyz2zXs (II)V
-	public fun appendModifierChange-z3jyS0k (ILjava/util/List;)V
+	public fun appendModifierChange-z3jyS0k (ILapp/cash/redwood/Modifier;)V
 	public fun appendMove-HpxY78w (IIIII)V
 	public fun appendPropertyChange-DxQz5cw (IILkotlinx/serialization/KSerializer;Ljava/lang/Object;)V
 	public fun appendPropertyChange-M7EZMwg (III)V
@@ -25,7 +25,7 @@ public final class app/cash/redwood/protocol/guest/DefaultGuestProtocolAdapter :
 public abstract interface class app/cash/redwood/protocol/guest/GuestProtocolAdapter : app/cash/redwood/protocol/EventSink {
 	public abstract fun appendAdd-ARs5Qwk (IIILapp/cash/redwood/protocol/guest/ProtocolWidget;)V
 	public abstract fun appendCreate-kyz2zXs (II)V
-	public abstract fun appendModifierChange-z3jyS0k (ILjava/util/List;)V
+	public abstract fun appendModifierChange-z3jyS0k (ILapp/cash/redwood/Modifier;)V
 	public abstract fun appendMove-HpxY78w (IIIII)V
 	public abstract fun appendPropertyChange-DxQz5cw (IILkotlinx/serialization/KSerializer;Ljava/lang/Object;)V
 	public abstract fun appendPropertyChange-M7EZMwg (III)V
@@ -81,6 +81,7 @@ public final class app/cash/redwood/protocol/guest/ProtocolWidgetChildren : app/
 public abstract interface class app/cash/redwood/protocol/guest/ProtocolWidgetSystemFactory {
 	public abstract fun create (Lapp/cash/redwood/protocol/guest/GuestProtocolAdapter;Lapp/cash/redwood/protocol/guest/ProtocolMismatchHandler;)Lapp/cash/redwood/widget/WidgetSystem;
 	public static synthetic fun create$default (Lapp/cash/redwood/protocol/guest/ProtocolWidgetSystemFactory;Lapp/cash/redwood/protocol/guest/GuestProtocolAdapter;Lapp/cash/redwood/protocol/guest/ProtocolMismatchHandler;ILjava/lang/Object;)Lapp/cash/redwood/widget/WidgetSystem;
+	public abstract fun modifierTagAndSerializationStrategy (Lapp/cash/redwood/Modifier$Element;)Lkotlin/Pair;
 }
 
 public final class app/cash/redwood/protocol/guest/VersionKt {

redwood-protocol-guest/api/redwood-protocol-guest.klib.api

@@ -19,7 +19,7 @@ abstract interface app.cash.redwood.protocol.guest/GuestProtocolAdapter : app.ca
     abstract fun <#A1: kotlin/Any?> appendPropertyChange(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/PropertyTag, kotlinx.serialization/KSerializer<#A1>, #A1) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendPropertyChange|appendPropertyChange(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.PropertyTag;kotlinx.serialization.KSerializer<0:0>;0:0){0§<kotlin.Any?>}[0]
     abstract fun appendAdd(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/ChildrenTag, kotlin/Int, app.cash.redwood.protocol.guest/ProtocolWidget) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendAdd|appendAdd(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.ChildrenTag;kotlin.Int;app.cash.redwood.protocol.guest.ProtocolWidget){}[0]
     abstract fun appendCreate(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/WidgetTag) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendCreate|appendCreate(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.WidgetTag){}[0]
-    abstract fun appendModifierChange(app.cash.redwood.protocol/Id, kotlin.collections/List<app.cash.redwood.protocol/ModifierElement>) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendModifierChange|appendModifierChange(app.cash.redwood.protocol.Id;kotlin.collections.List<app.cash.redwood.protocol.ModifierElement>){}[0]
+    abstract fun appendModifierChange(app.cash.redwood.protocol/Id, app.cash.redwood/Modifier) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendModifierChange|appendModifierChange(app.cash.redwood.protocol.Id;app.cash.redwood.Modifier){}[0]
     abstract fun appendMove(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/ChildrenTag, kotlin/Int, kotlin/Int, kotlin/Int) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendMove|appendMove(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.ChildrenTag;kotlin.Int;kotlin.Int;kotlin.Int){}[0]
     abstract fun appendPropertyChange(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/PropertyTag, kotlin/Boolean) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendPropertyChange|appendPropertyChange(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.PropertyTag;kotlin.Boolean){}[0]
     abstract fun appendPropertyChange(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/PropertyTag, kotlin/UInt) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.appendPropertyChange|appendPropertyChange(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.PropertyTag;kotlin.UInt){}[0]
@@ -53,6 +53,7 @@ abstract interface app.cash.redwood.protocol.guest/ProtocolWidget : app.cash.red
 }
 
 abstract interface app.cash.redwood.protocol.guest/ProtocolWidgetSystemFactory { // app.cash.redwood.protocol.guest/ProtocolWidgetSystemFactory|null[0]
+    abstract fun <#A1: app.cash.redwood/Modifier.Element> modifierTagAndSerializationStrategy(#A1): kotlin/Pair<app.cash.redwood.protocol/ModifierTag, kotlinx.serialization/SerializationStrategy<#A1>?> // app.cash.redwood.protocol.guest/ProtocolWidgetSystemFactory.modifierTagAndSerializationStrategy|modifierTagAndSerializationStrategy(0:0){0§<app.cash.redwood.Modifier.Element>}[0]
     abstract fun create(app.cash.redwood.protocol.guest/GuestProtocolAdapter, app.cash.redwood.protocol.guest/ProtocolMismatchHandler = ...): app.cash.redwood.widget/WidgetSystem<kotlin/Unit> // app.cash.redwood.protocol.guest/ProtocolWidgetSystemFactory.create|create(app.cash.redwood.protocol.guest.GuestProtocolAdapter;app.cash.redwood.protocol.guest.ProtocolMismatchHandler){}[0]
 }
 
@@ -71,7 +72,7 @@ final class app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter : app.ca
     final fun <#A1: kotlin/Any?> appendPropertyChange(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/PropertyTag, kotlinx.serialization/KSerializer<#A1>, #A1) // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.appendPropertyChange|appendPropertyChange(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.PropertyTag;kotlinx.serialization.KSerializer<0:0>;0:0){0§<kotlin.Any?>}[0]
     final fun appendAdd(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/ChildrenTag, kotlin/Int, app.cash.redwood.protocol.guest/ProtocolWidget) // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.appendAdd|appendAdd(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.ChildrenTag;kotlin.Int;app.cash.redwood.protocol.guest.ProtocolWidget){}[0]
     final fun appendCreate(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/WidgetTag) // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.appendCreate|appendCreate(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.WidgetTag){}[0]
-    final fun appendModifierChange(app.cash.redwood.protocol/Id, kotlin.collections/List<app.cash.redwood.protocol/ModifierElement>) // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.appendModifierChange|appendModifierChange(app.cash.redwood.protocol.Id;kotlin.collections.List<app.cash.redwood.protocol.ModifierElement>){}[0]
+    final fun appendModifierChange(app.cash.redwood.protocol/Id, app.cash.redwood/Modifier) // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.appendModifierChange|appendModifierChange(app.cash.redwood.protocol.Id;app.cash.redwood.Modifier){}[0]
     final fun appendMove(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/ChildrenTag, kotlin/Int, kotlin/Int, kotlin/Int) // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.appendMove|appendMove(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.ChildrenTag;kotlin.Int;kotlin.Int;kotlin.Int){}[0]
     final fun appendPropertyChange(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/PropertyTag, kotlin/Boolean) // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.appendPropertyChange|appendPropertyChange(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.PropertyTag;kotlin.Boolean){}[0]
     final fun appendPropertyChange(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/PropertyTag, kotlin/UInt) // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.appendPropertyChange|appendPropertyChange(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.PropertyTag;kotlin.UInt){}[0]

redwood-protocol-guest/src/commonMain/kotlin/app/cash/redwood/protocol/guest/DefaultGuestProtocolAdapter.kt

@@ -15,6 +15,7 @@
  */
 package app.cash.redwood.protocol.guest
 
+import app.cash.redwood.Modifier
 import app.cash.redwood.RedwoodCodegenApi
 import app.cash.redwood.protocol.Change
 import app.cash.redwood.protocol.ChangesSink
@@ -41,7 +42,7 @@ import kotlinx.serialization.json.JsonPrimitive
 public class DefaultGuestProtocolAdapter(
   public override val json: Json = Json.Default,
   hostVersion: RedwoodVersion,
-  widgetSystemFactory: ProtocolWidgetSystemFactory,
+  private val widgetSystemFactory: ProtocolWidgetSystemFactory,
   private val mismatchHandler: ProtocolMismatchHandler = ProtocolMismatchHandler.Throwing,
 ) : GuestProtocolAdapter {
   private var nextValue = Id.Root.value + 1
@@ -111,13 +112,22 @@ public class DefaultGuestProtocolAdapter(
     changes.add(PropertyChange(id, tag, JsonPrimitive(value)))
   }
 
-  public override fun appendModifierChange(
-    id: Id,
-    elements: List<ModifierElement>,
-  ) {
+  override fun appendModifierChange(id: Id, value: Modifier) {
+    val elements = mutableListOf<ModifierElement>()
+
+    value.forEach { element ->
+      elements += modifierElement(element)
+    }
+
     changes.add(ModifierChange(id, elements))
   }
 
+  private fun <T : Modifier.Element> modifierElement(element: T): ModifierElement {
+    val (tag, serializer) = widgetSystemFactory.modifierTagAndSerializationStrategy(element)
+    if (serializer == null) return ModifierElement(tag)
+    return ModifierElement(tag, json.encodeToJsonElement(serializer, element))
+  }
+
   public override fun appendAdd(
     id: Id,
     tag: ChildrenTag,

redwood-protocol-guest/src/commonMain/kotlin/app/cash/redwood/protocol/guest/GuestProtocolAdapter.kt

@@ -15,12 +15,12 @@
  */
 package app.cash.redwood.protocol.guest
 
+import app.cash.redwood.Modifier
 import app.cash.redwood.RedwoodCodegenApi
 import app.cash.redwood.protocol.ChangesSink
 import app.cash.redwood.protocol.ChildrenTag
 import app.cash.redwood.protocol.EventSink
 import app.cash.redwood.protocol.Id
-import app.cash.redwood.protocol.ModifierElement
 import app.cash.redwood.protocol.PropertyTag
 import app.cash.redwood.protocol.WidgetTag
 import app.cash.redwood.widget.Widget
@@ -106,7 +106,7 @@ public interface GuestProtocolAdapter : EventSink {
   @RedwoodCodegenApi
   public fun appendModifierChange(
     id: Id,
-    elements: List<ModifierElement>,
+    value: Modifier,
   )
 
   @RedwoodCodegenApi

redwood-protocol-guest/src/commonMain/kotlin/app/cash/redwood/protocol/guest/ProtocolWidgetSystemFactory.kt

@@ -15,12 +15,22 @@
  */
 package app.cash.redwood.protocol.guest
 
+import app.cash.redwood.Modifier
+import app.cash.redwood.RedwoodCodegenApi
+import app.cash.redwood.protocol.ModifierTag
 import app.cash.redwood.widget.WidgetSystem
+import kotlinx.serialization.SerializationStrategy
 
 public interface ProtocolWidgetSystemFactory {
   /** Create a new [WidgetSystem] connected to a host via [guestAdapter]. */
   public fun create(
     guestAdapter: GuestProtocolAdapter,
     mismatchHandler: ProtocolMismatchHandler = ProtocolMismatchHandler.Throwing,
   ): WidgetSystem<Unit>
+
+  /** The serialization strategy is null if the modifier is stateless. */
+  @RedwoodCodegenApi
+  public fun <T : Modifier.Element> modifierTagAndSerializationStrategy(
+    element: T,
+  ): Pair<ModifierTag, SerializationStrategy<T>?>
 }

redwood-tooling-codegen/src/main/kotlin/app/cash/redwood/tooling/codegen/protocolCodegen.kt

@@ -37,7 +37,6 @@ internal fun ProtocolSchemaSet.generateFileSpecs(type: ProtocolCodegenType): Lis
     when (type) {
       Guest -> {
         add(generateProtocolWidgetSystemFactory(this@generateFileSpecs))
-        add(generateComposeProtocolModifierSerialization(this@generateFileSpecs))
         for (dependency in all) {
           add(generateProtocolWidgetFactory(dependency, host = schema))
           generateProtocolModifierSerializers(dependency, host = schema)?.let { add(it) }