Create a widget protocol descriptor type

redwood-protocol-host/api/redwood-protocol-host.api

@@ -1,7 +1,6 @@
-public abstract interface class app/cash/redwood/protocol/host/GeneratedProtocolFactory : app/cash/redwood/protocol/host/ProtocolFactory {
+public abstract interface class app/cash/redwood/protocol/host/GeneratedHostProtocol : app/cash/redwood/protocol/host/ProtocolFactory {
 	public abstract fun createModifier (Lapp/cash/redwood/protocol/ModifierElement;)Lapp/cash/redwood/Modifier;
-	public abstract fun createNode-kyz2zXs (II)Lapp/cash/redwood/protocol/host/ProtocolNode;
-	public abstract fun widgetChildren-WCEpcRY (I)[I
+	public abstract fun widget-WCEpcRY (I)Lapp/cash/redwood/protocol/host/WidgetHostProtocol;
 }
 
 public final class app/cash/redwood/protocol/host/HostProtocolAdapter : app/cash/redwood/protocol/ChangesSink {
@@ -69,3 +68,8 @@ public final class app/cash/redwood/protocol/host/VersionKt {
 	public static final fun getHostRedwoodVersion ()Ljava/lang/String;
 }
 
+public abstract interface class app/cash/redwood/protocol/host/WidgetHostProtocol {
+	public abstract fun createNode-ou3jOuA (I)Lapp/cash/redwood/protocol/host/ProtocolNode;
+	public abstract fun getChildrenTags ()[I
+}
+

redwood-protocol-host/api/redwood-protocol-host.klib.api

@@ -14,10 +14,16 @@ abstract fun interface app.cash.redwood.protocol.host/UiEventSink { // app.cash.
     abstract fun sendEvent(app.cash.redwood.protocol.host/UiEvent) // app.cash.redwood.protocol.host/UiEventSink.sendEvent|sendEvent(app.cash.redwood.protocol.host.UiEvent){}[0]
 }
 
-abstract interface <#A: kotlin/Any> app.cash.redwood.protocol.host/GeneratedProtocolFactory : app.cash.redwood.protocol.host/ProtocolFactory<#A> { // app.cash.redwood.protocol.host/GeneratedProtocolFactory|null[0]
-    abstract fun createModifier(app.cash.redwood.protocol/ModifierElement): app.cash.redwood/Modifier // app.cash.redwood.protocol.host/GeneratedProtocolFactory.createModifier|createModifier(app.cash.redwood.protocol.ModifierElement){}[0]
-    abstract fun createNode(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/WidgetTag): app.cash.redwood.protocol.host/ProtocolNode<#A>? // app.cash.redwood.protocol.host/GeneratedProtocolFactory.createNode|createNode(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.WidgetTag){}[0]
-    abstract fun widgetChildren(app.cash.redwood.protocol/WidgetTag): kotlin/IntArray? // app.cash.redwood.protocol.host/GeneratedProtocolFactory.widgetChildren|widgetChildren(app.cash.redwood.protocol.WidgetTag){}[0]
+abstract interface <#A: kotlin/Any> app.cash.redwood.protocol.host/GeneratedHostProtocol : app.cash.redwood.protocol.host/ProtocolFactory<#A> { // app.cash.redwood.protocol.host/GeneratedHostProtocol|null[0]
+    abstract fun createModifier(app.cash.redwood.protocol/ModifierElement): app.cash.redwood/Modifier // app.cash.redwood.protocol.host/GeneratedHostProtocol.createModifier|createModifier(app.cash.redwood.protocol.ModifierElement){}[0]
+    abstract fun widget(app.cash.redwood.protocol/WidgetTag): app.cash.redwood.protocol.host/WidgetHostProtocol<#A>? // app.cash.redwood.protocol.host/GeneratedHostProtocol.widget|widget(app.cash.redwood.protocol.WidgetTag){}[0]
+}
+
+abstract interface <#A: kotlin/Any> app.cash.redwood.protocol.host/WidgetHostProtocol { // app.cash.redwood.protocol.host/WidgetHostProtocol|null[0]
+    abstract val childrenTags // app.cash.redwood.protocol.host/WidgetHostProtocol.childrenTags|{}childrenTags[0]
+        abstract fun <get-childrenTags>(): kotlin/IntArray? // app.cash.redwood.protocol.host/WidgetHostProtocol.childrenTags.<get-childrenTags>|<get-childrenTags>(){}[0]
+
+    abstract fun createNode(app.cash.redwood.protocol/Id): app.cash.redwood.protocol.host/ProtocolNode<#A> // app.cash.redwood.protocol.host/WidgetHostProtocol.createNode|createNode(app.cash.redwood.protocol.Id){}[0]
 }
 
 abstract interface app.cash.redwood.protocol.host/ProtocolMismatchHandler { // app.cash.redwood.protocol.host/ProtocolMismatchHandler|null[0]

redwood-protocol-host/src/commonMain/kotlin/app/cash/redwood/protocol/host/HostProtocolAdapter.kt

@@ -57,7 +57,7 @@ public class HostProtocolAdapter<W : Any>(
   private val leakDetector: LeakDetector,
 ) : ChangesSink {
   private val factory = when (factory) {
-    is GeneratedProtocolFactory -> factory
+    is GeneratedHostProtocol -> factory
   }
 
   private val nodes =
@@ -83,7 +83,8 @@ public class HostProtocolAdapter<W : Any>(
       val id = change.id
       when (change) {
         is Create -> {
-          val node = factory.createNode(id, change.tag) ?: continue
+          val widgetProtocol = factory.widget(change.tag) ?: continue
+          val node = widgetProtocol.createNode(id)
           val old = nodes.put(change.id.value, node)
           require(old == null) {
             "Insert attempted to replace existing widget with ID ${change.id.value}"

redwood-protocol-host/src/commonMain/kotlin/app/cash/redwood/protocol/host/NodeReuse.kt

@@ -31,15 +31,16 @@ import app.cash.redwood.protocol.host.HostProtocolAdapter.ReuseNode
  */
 @OptIn(RedwoodCodegenApi::class)
 internal fun shapesEqual(
-  factory: GeneratedProtocolFactory<*>,
+  factory: GeneratedHostProtocol<*>,
   a: ReuseNode<*>,
   b: ProtocolNode<*>,
 ): Boolean {
   if (!a.eligibleForReuse) return false // This node is ineligible.
   if (a.widgetTag == UnknownWidgetTag) return false // No 'Create' for this.
   if (b.widgetTag != a.widgetTag) return false // Widget types don't match.
 
-  val widgetChildren = factory.widgetChildren(a.widgetTag)
+  val widgetChildren = factory.widget(a.widgetTag)
+    ?.childrenTags
     ?: return true // Widget has no children.
 
   return widgetChildren.all { childrenTag ->
@@ -59,7 +60,7 @@ internal fun shapesEqual(
  */
 @OptIn(RedwoodCodegenApi::class)
 private fun childrenEqual(
-  factory: GeneratedProtocolFactory<*>,
+  factory: GeneratedHostProtocol<*>,
   aChildren: List<ReuseNode<*>>,
   bChildren: List<ProtocolNode<*>>,
   childrenTag: ChildrenTag,
@@ -81,15 +82,15 @@ private fun childrenEqual(
 /** Returns a hash of this node, or 0L if this node isn't eligible for reuse. */
 @OptIn(RedwoodCodegenApi::class)
 internal fun shapeHash(
-  factory: GeneratedProtocolFactory<*>,
+  factory: GeneratedHostProtocol<*>,
   node: ReuseNode<*>,
 ): Long {
   if (!node.eligibleForReuse) return 0L // This node is ineligible.
   if (node.widgetTag == UnknownWidgetTag) return 0L // No 'Create' for this.
 
   var result = node.widgetTag.value.toLong()
 
-  factory.widgetChildren(node.widgetTag)?.forEach { childrenTag ->
+  factory.widget(node.widgetTag)?.childrenTags?.forEach { childrenTag ->
     result = (result * 37L) + childrenTag
     var childCount = 0
     for (child in node.children) {
@@ -106,11 +107,11 @@ internal fun shapeHash(
 /** Returns the same hash as [shapeHash], but on an already-built [ProtocolNode]. */
 @OptIn(RedwoodCodegenApi::class)
 internal fun shapeHash(
-  factory: GeneratedProtocolFactory<*>,
+  factory: GeneratedHostProtocol<*>,
   node: ProtocolNode<*>,
 ): Long {
   var result = node.widgetTag.value.toLong()
-  factory.widgetChildren(node.widgetTag)?.forEach { childrenTag ->
+  factory.widget(node.widgetTag)?.childrenTags?.forEach { childrenTag ->
     result = (result * 37L) + childrenTag
     val children = node.children(ChildrenTag(childrenTag))
       ?: return@forEach // This acts like a 'continue'.

redwood-protocol-host/src/commonMain/kotlin/app/cash/redwood/protocol/host/ProtocolFactory.kt

@@ -35,20 +35,20 @@ public sealed interface ProtocolFactory<W : Any> {
 }
 
 /**
- * [ProtocolFactory] but containing codegen APIs.
+ * [ProtocolFactory] but containing codegen APIs for a schema.
  *
  * @suppress
  */
 @RedwoodCodegenApi
-public interface GeneratedProtocolFactory<W : Any> : ProtocolFactory<W> {
+public interface GeneratedHostProtocol<W : Any> : ProtocolFactory<W> {
   /**
-   * Create a new protocol node with [id] of the specified [tag].
+   * Look up host protocol information for a widget with the given [tag].
    *
    * Invalid [tag] values can either produce an exception or result in `null` being returned.
    * If `null` is returned, the caller should make every effort to ignore this node and
    * continue executing.
    */
-  public fun createNode(id: Id, tag: WidgetTag): ProtocolNode<W>?
+  public fun widget(tag: WidgetTag): WidgetHostProtocol<W>?
 
   /**
    * Create a new modifier from the specified [element].
@@ -57,12 +57,22 @@ public interface GeneratedProtocolFactory<W : Any> : ProtocolFactory<W> {
    * or result in the unit [`Modifier`][Modifier.Companion] being returned.
    */
   public fun createModifier(element: ModifierElement): Modifier
+}
+
+/**
+ * Protocol APIs for a widget definition.
+ *
+ * @suppress
+ */
+@RedwoodCodegenApi
+public interface WidgetHostProtocol<W : Any> {
+  /** Create an instance of this widget wrapped as a [ProtocolNode] with the given [id]. */
+  public fun createNode(id: Id): ProtocolNode<W>
 
   /**
-   * Look up known children tags for the given widget [tag]. These are stored as a bare [IntArray]
-   * for efficiency, but are otherwise an array of [ChildrenTag] instances.
-   *
-   * @return `null` when widget has no children
+   * Look up known children tags for this widget. These are stored as a bare [IntArray]
+   * for efficiency, but are otherwise an array of [ChildrenTag] instances. A value of
+   * `null` indicates no children.
    */
-  public fun widgetChildren(tag: WidgetTag): IntArray?
+  public val childrenTags: IntArray?
 }

redwood-protocol-host/src/commonTest/kotlin/app/cash/redwood/protocol/host/ProtocolFactoryTest.kt

@@ -60,7 +60,7 @@ class ProtocolFactoryTest {
     )
 
     val t = assertFailsWith<IllegalArgumentException> {
-      factory.createNode(Id(1), WidgetTag(345432))
+      factory.widget(WidgetTag(345432))
     }
     assertThat(t).hasMessage("Unknown widget tag 345432")
   }
@@ -76,8 +76,7 @@ class ProtocolFactoryTest {
       mismatchHandler = handler,
     )
 
-    assertThat(factory.createNode(Id(1), WidgetTag(345432))).isNull()
-
+    assertThat(factory.widget(WidgetTag(345432))).isNull()
     assertThat(handler.events.single()).isEqualTo("Unknown widget 345432")
   }
 
@@ -216,7 +215,7 @@ class ProtocolFactoryTest {
         RedwoodLazyLayout = RedwoodLazyLayoutTestingWidgetFactory(),
       ),
     )
-    val button = factory.createNode(Id(1), WidgetTag(4))!!
+    val button = factory.widget(WidgetTag(4))!!.createNode(Id(1))
 
     val t = assertFailsWith<IllegalArgumentException> {
       button.children(ChildrenTag(345432))
@@ -235,7 +234,7 @@ class ProtocolFactoryTest {
       mismatchHandler = handler,
     )
 
-    val button = factory.createNode(Id(1), WidgetTag(4))!!
+    val button = factory.widget(WidgetTag(4))!!.createNode(Id(1))
     assertThat(button.children(ChildrenTag(345432))).isNull()
 
     assertThat(handler.events.single()).isEqualTo("Unknown children 345432 for 4")
@@ -255,7 +254,7 @@ class ProtocolFactoryTest {
       ),
       json = json,
     )
-    val textInput = factory.createNode(Id(1), WidgetTag(5))!!
+    val textInput = factory.widget(WidgetTag(5))!!.createNode(Id(1))
 
     val throwingEventSink = UiEventSink { error(it) }
     textInput.apply(PropertyChange(Id(1), PropertyTag(2), JsonPrimitive("PT10S")), throwingEventSink)
@@ -271,7 +270,7 @@ class ProtocolFactoryTest {
         RedwoodLazyLayout = RedwoodLazyLayoutTestingWidgetFactory(),
       ),
     )
-    val button = factory.createNode(Id(1), WidgetTag(4))!!
+    val button = factory.widget(WidgetTag(4))!!.createNode(Id(1))
 
     val change = PropertyChange(Id(1), PropertyTag(345432))
     val eventSink = UiEventSink { throw UnsupportedOperationException() }
@@ -291,7 +290,7 @@ class ProtocolFactoryTest {
       ),
       mismatchHandler = handler,
     )
-    val button = factory.createNode(Id(1), WidgetTag(4))!!
+    val button = factory.widget(WidgetTag(4))!!.createNode(Id(1))
 
     button.apply(PropertyChange(Id(1), PropertyTag(345432))) { throw UnsupportedOperationException() }
 
@@ -312,7 +311,7 @@ class ProtocolFactoryTest {
       ),
       json = json,
     )
-    val textInput = factory.createNode(Id(1), WidgetTag(5))!!
+    val textInput = factory.widget(WidgetTag(5))!!.createNode(Id(1))
 
     val eventSink = RecordingUiEventSink()
     textInput.apply(PropertyChange(Id(1), PropertyTag(4), JsonPrimitive(true)), eventSink)