Update re-attached widget removes to use detach

This ensures that the host-side maintains their instances to correctly support re-attach.

CHANGELOG.md

@@ -19,6 +19,7 @@ Fixed:
 - Add support for the Height modifier in `ComposeUiBox`.
 - Add support for the Width modifier in `ComposeUiBox`.
 - Call `DisposableEffect` when a screen is unbound. We were only calling these when the effect was removed from the composition.
+- Support `movableContentOf` in Treehouse (and generally in the Redwood protocol). Note: this requires the host be running version 0.17.0 or newer.
 
 
 ## [0.16.0] - 2024-11-19

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

@@ -9,7 +9,7 @@ public final class app/cash/redwood/protocol/guest/DefaultGuestProtocolAdapter :
 	public fun appendPropertyChange-13Ob0Yo (IIILkotlinx/serialization/KSerializer;Ljava/lang/Object;)V
 	public fun appendPropertyChange-ITsWdOQ (IIIZ)V
 	public fun appendPropertyChange-hzhmVHk (IIII)V
-	public fun appendRemove-hx81-Ec (IIII)V
+	public fun appendRemove-ARs5Qwk (IIILapp/cash/redwood/protocol/guest/ProtocolWidget;)V
 	public fun emitChanges ()V
 	public fun getJson ()Lkotlinx/serialization/json/Json;
 	public fun getRoot ()Lapp/cash/redwood/widget/Widget$Children;
@@ -24,6 +24,7 @@ public abstract class app/cash/redwood/protocol/guest/GuestProtocolAdapter : app
 	public static final field $stable I
 	public synthetic fun <init> (Ljava/lang/String;Lkotlin/jvm/internal/DefaultConstructorMarker;)V
 	public abstract fun emitChanges ()V
+	protected final fun getHostVersion-7jYel6c ()Ljava/lang/String;
 	public abstract fun getRoot ()Lapp/cash/redwood/widget/Widget$Children;
 	public abstract fun getWidgetSystem ()Lapp/cash/redwood/widget/WidgetSystem;
 	public abstract fun initChangesSink (Lapp/cash/redwood/protocol/ChangesSink;)V

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

@@ -27,6 +27,8 @@ abstract class app.cash.redwood.protocol.guest/GuestProtocolAdapter : app.cash.r
         abstract fun <get-root>(): app.cash.redwood.widget/Widget.Children<kotlin/Unit> // app.cash.redwood.protocol.guest/GuestProtocolAdapter.root.<get-root>|<get-root>(){}[0]
     abstract val widgetSystem // app.cash.redwood.protocol.guest/GuestProtocolAdapter.widgetSystem|{}widgetSystem[0]
         abstract fun <get-widgetSystem>(): app.cash.redwood.widget/WidgetSystem<kotlin/Unit> // app.cash.redwood.protocol.guest/GuestProtocolAdapter.widgetSystem.<get-widgetSystem>|<get-widgetSystem>(){}[0]
+    final val hostVersion // app.cash.redwood.protocol.guest/GuestProtocolAdapter.hostVersion|{}hostVersion[0]
+        final fun <get-hostVersion>(): app.cash.redwood.protocol/RedwoodVersion // app.cash.redwood.protocol.guest/GuestProtocolAdapter.hostVersion.<get-hostVersion>|<get-hostVersion>(){}[0]
 
     abstract fun emitChanges() // app.cash.redwood.protocol.guest/GuestProtocolAdapter.emitChanges|emitChanges(){}[0]
     abstract fun initChangesSink(app.cash.redwood.protocol/ChangesSink) // app.cash.redwood.protocol.guest/GuestProtocolAdapter.initChangesSink|initChangesSink(app.cash.redwood.protocol.ChangesSink){}[0]
@@ -49,7 +51,7 @@ final class app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter : app.ca
     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/WidgetTag, app.cash.redwood.protocol/PropertyTag, kotlin/Boolean) // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.appendPropertyChange|appendPropertyChange(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.WidgetTag;app.cash.redwood.protocol.PropertyTag;kotlin.Boolean){}[0]
     final fun appendPropertyChange(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/WidgetTag, app.cash.redwood.protocol/PropertyTag, kotlin/UInt) // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.appendPropertyChange|appendPropertyChange(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.WidgetTag;app.cash.redwood.protocol.PropertyTag;kotlin.UInt){}[0]
-    final fun appendRemove(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/ChildrenTag, kotlin/Int, app.cash.redwood.protocol/Id) // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.appendRemove|appendRemove(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.ChildrenTag;kotlin.Int;app.cash.redwood.protocol.Id){}[0]
+    final fun appendRemove(app.cash.redwood.protocol/Id, app.cash.redwood.protocol/ChildrenTag, kotlin/Int, app.cash.redwood.protocol.guest/ProtocolWidget) // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.appendRemove|appendRemove(app.cash.redwood.protocol.Id;app.cash.redwood.protocol.ChildrenTag;kotlin.Int;app.cash.redwood.protocol.guest.ProtocolWidget){}[0]
     final fun emitChanges() // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.emitChanges|emitChanges(){}[0]
     final fun initChangesSink(app.cash.redwood.protocol/ChangesSink) // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.initChangesSink|initChangesSink(app.cash.redwood.protocol.ChangesSink){}[0]
     final fun nextId(): app.cash.redwood.protocol/Id // app.cash.redwood.protocol.guest/DefaultGuestProtocolAdapter.nextId|nextId(){}[0]

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

@@ -30,6 +30,7 @@ import app.cash.redwood.protocol.PropertyChange
 import app.cash.redwood.protocol.PropertyTag
 import app.cash.redwood.protocol.RedwoodVersion
 import app.cash.redwood.protocol.WidgetTag
+import app.cash.redwood.protocol.guest.ProtocolWidget.Companion.INVALID_INDEX
 import app.cash.redwood.widget.Widget
 import app.cash.redwood.widget.WidgetSystem
 import kotlinx.serialization.ExperimentalSerializationApi
@@ -136,9 +137,18 @@ public class DefaultGuestProtocolAdapter(
     index: Int,
     child: ProtocolWidget,
   ) {
-    val replaced = widgets.put(child.id.value, child)
-    check(replaced == null) {
-      "Attempted to add widget with ID ${child.id} but one already exists"
+    val childId = child.id.value
+    if (child.removeIndex != INVALID_INDEX) {
+      check(hostSupportsRemoveDetach) { "Host v$hostVersion does not support widget re-attach" }
+      check(childId in widgets) { "Attempted to re-attach unknown widget with ID $childId" }
+      removed.remove(childId)
+
+      // Update the remove change to indicate it's only a detach.
+      val remove = changes[child.removeIndex] as ChildrenChange.Remove
+      changes[child.removeIndex] = ChildrenChange.Remove(remove.id, remove.tag, remove.index, true)
+    } else {
+      val replaced = widgets.put(childId, child)
+      check(replaced == null) { "Attempted to add widget with existing ID $childId" }
     }
     changes.add(ChildrenChange.Add(id, tag, child.id, index))
   }
@@ -157,9 +167,10 @@ public class DefaultGuestProtocolAdapter(
     id: Id,
     tag: ChildrenTag,
     index: Int,
-    childId: Id,
+    child: ProtocolWidget,
   ) {
-    removed += childId.value
+    removed += child.id.value
+    child.removeIndex = changes.size
     changes.add(ChildrenChange.Remove(id, tag, index, detach = false))
   }
 

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

@@ -38,20 +38,19 @@ import kotlinx.serialization.json.Json
  * This interface is for generated code use only.
  */
 public abstract class GuestProtocolAdapter(
-  hostVersion: RedwoodVersion,
+  protected val hostVersion: RedwoodVersion,
 ) : EventSink {
   @RedwoodCodegenApi
   public abstract val json: Json
 
   /**
    * Whether the host supports the detach parameter on
-   * [app.cash.redwood.protocol.ChildrenChange.Remove]. This also implies that the `count`
-   * parameter does not need to be sent.
+   * [app.cash.redwood.protocol.ChildrenChange.Remove].
    *
-   * TODO Remove when minimum-supported host version is 1.17 or higher.
+   * TODO Remove when minimum-supported host version is 0.17 or higher.
    */
   @RedwoodCodegenApi
-  protected val hostSupportsRemoveDetachAndNoCount: Boolean = hostVersion >= RedwoodVersion("0.17.0-SNAPSHOT")
+  protected val hostSupportsRemoveDetach: Boolean = hostVersion >= RedwoodVersion("0.17.0-SNAPSHOT")
 
   /**
    * The provider of factories of widgets which record property changes and whose children changes
@@ -143,6 +142,6 @@ public abstract class GuestProtocolAdapter(
     id: Id,
     tag: ChildrenTag,
     index: Int,
-    childId: Id,
+    child: ProtocolWidget,
   )
 }

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

@@ -33,6 +33,15 @@ public interface ProtocolWidget : Widget<Unit> {
   public val id: Id
   public val tag: WidgetTag
 
+  /**
+   * Used to detect when a removed widget is re-added later in the frame, such as when
+   * `movableContentOf` is used. When a widget is added with this value greater than or equal to 0,
+   * the original 'remove' operation should be changed to indicate that this node
+   * (and its entire subtree) should be retained host-side, as a future 'add' of this node
+   * will occur without associated 'create' events for the subtree.
+   */
+  public var removeIndex: Int
+
   override val value: Unit get() = Unit
 
   public fun sendEvent(event: Event)
@@ -73,4 +82,9 @@ public interface ProtocolWidget : Widget<Unit> {
       children: ProtocolWidgetChildren,
     )
   }
+
+  @RedwoodCodegenApi // https://github.com/Kotlin/binary-compatibility-validator/issues/91
+  public companion object {
+    public const val INVALID_INDEX: Int = -1
+  }
 }

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

@@ -38,8 +38,7 @@ public class ProtocolWidgetChildren(
 
   override fun remove(index: Int, count: Int) {
     for (i in index + count - 1 downTo index) {
-      val widget = widgets[i]
-      guestAdapter.appendRemove(id, tag, index, widget.id)
+      guestAdapter.appendRemove(id, tag, index, widgets[i])
     }
     _widgets.remove(index, count)
   }

redwood-protocol-guest/src/commonTest/kotlin/app/cash/redwood/protocol/guest/ProtocolTest.kt

@@ -17,9 +17,14 @@ package app.cash.redwood.protocol.guest
 
 import androidx.compose.runtime.BroadcastFrameClock
 import androidx.compose.runtime.getValue
+import androidx.compose.runtime.movableContentOf
 import androidx.compose.runtime.mutableIntStateOf
+import androidx.compose.runtime.remember
 import androidx.compose.runtime.setValue
 import app.cash.redwood.compose.WidgetVersion
+import app.cash.redwood.layout.compose.Box
+import app.cash.redwood.layout.compose.Column
+import app.cash.redwood.layout.compose.Row
 import app.cash.redwood.protocol.Change
 import app.cash.redwood.protocol.ChildrenChange
 import app.cash.redwood.protocol.ChildrenTag
@@ -31,13 +36,15 @@ import app.cash.redwood.protocol.ModifierChange
 import app.cash.redwood.protocol.PropertyChange
 import app.cash.redwood.protocol.PropertyTag
 import app.cash.redwood.protocol.RedwoodVersion
+import app.cash.redwood.protocol.ValueChange
 import app.cash.redwood.protocol.WidgetTag
 import app.cash.redwood.testing.TestRedwoodComposition
 import app.cash.redwood.ui.Cancellable
 import app.cash.redwood.ui.OnBackPressedCallback
 import app.cash.redwood.ui.OnBackPressedDispatcher
 import app.cash.redwood.ui.UiConfiguration
 import assertk.assertThat
+import assertk.assertions.containsExactly
 import assertk.assertions.isEqualTo
 import com.example.redwood.testapp.compose.Button
 import com.example.redwood.testapp.compose.Button2
@@ -288,6 +295,171 @@ class ProtocolTest {
     )
   }
 
+  @Test fun movableContentSameRecomposition() = runTest {
+    val (composition) = testProtocolComposition()
+
+    var state by mutableIntStateOf(0)
+    composition.setContent {
+      val oneTwoThree = remember {
+        movableContentOf {
+          Box {
+            Text("one")
+            Text("two")
+            Text("three")
+          }
+        }
+      }
+      when (state) {
+        0 -> Row { oneTwoThree() }
+        1 -> Column { oneTwoThree() }
+      }
+    }
+
+    assertThat(composition.awaitSnapshot().filter { it !is ValueChange }).containsExactly(
+      // Row to Root
+      Create(Id(1), WidgetTag(1000001)),
+      ChildrenChange.Add(Id.Root, ChildrenTag.Root, Id(1), 0),
+      // Box
+      Create(Id(2), WidgetTag(1000004)),
+      // Text("one") to Box
+      Create(Id(3), WidgetTag(3)),
+      ChildrenChange.Add(Id(2), ChildrenTag(1), Id(3), 0),
+      // Text("two") to Box
+      Create(Id(4), WidgetTag(3)),
+      ChildrenChange.Add(Id(2), ChildrenTag(1), Id(4), 1),
+      // Text("three") to Box
+      Create(Id(5), WidgetTag(3)),
+      ChildrenChange.Add(Id(2), ChildrenTag(1), Id(5), 2),
+      // Box to Row
+      ChildrenChange.Add(Id(1), ChildrenTag(1), Id(2), 0),
+    )
+
+    state = 1
+    assertThat(composition.awaitSnapshot().filter { it !is ValueChange }).containsExactly(
+      // Box from Row
+      ChildrenChange.Remove(Id(1), ChildrenTag(1), 0, detach = true),
+      // Row from Root
+      ChildrenChange.Remove(Id.Root, ChildrenTag.Root, 0, detach = false),
+      // Column to Root
+      Create(Id(6), WidgetTag(1000002)),
+      ChildrenChange.Add(Id.Root, ChildrenTag.Root, Id(6), 0),
+      // Box to Column
+      ChildrenChange.Add(Id(6), ChildrenTag(1), Id(2), 0),
+    )
+  }
+
+  @Test fun multipleMovableContentButOnlyOneReused() = runTest {
+    val (composition) = testProtocolComposition()
+
+    var state by mutableIntStateOf(0)
+    composition.setContent {
+      val one = remember { movableContentOf { Text("one") } }
+      val two = remember { movableContentOf { Text("two") } }
+      val three = remember { movableContentOf { Text("three") } }
+      when (state) {
+        0 -> {
+          one()
+          two()
+          three()
+        }
+        1 -> {
+          two()
+        }
+      }
+    }
+
+    assertThat(composition.awaitSnapshot().filter { it !is ValueChange }).containsExactly(
+      Create(Id(1), WidgetTag(3)),
+      ChildrenChange.Add(Id.Root, ChildrenTag.Root, Id(1), 0),
+      Create(Id(2), WidgetTag(3)),
+      ChildrenChange.Add(Id.Root, ChildrenTag.Root, Id(2), 1),
+      Create(Id(3), WidgetTag(3)),
+      ChildrenChange.Add(Id.Root, ChildrenTag.Root, Id(3), 2),
+    )
+
+    state = 1
+    assertThat(composition.awaitSnapshot().filter { it !is ValueChange }).containsExactly(
+      ChildrenChange.Remove(Id.Root, ChildrenTag.Root, 0, detach = false),
+      ChildrenChange.Remove(Id.Root, ChildrenTag.Root, 0, detach = true),
+      ChildrenChange.Remove(Id.Root, ChildrenTag.Root, 0, detach = false),
+      ChildrenChange.Add(Id.Root, ChildrenTag.Root, Id(2), 0),
+    )
+  }
+
+  @Test fun movableContentMultipleRecompositions() = runTest {
+    val (composition) = testProtocolComposition()
+
+    var state by mutableIntStateOf(0)
+    composition.setContent {
+      val oneTwoThree = remember {
+        movableContentOf {
+          Box {
+            Text("one")
+            Text("two")
+            Text("three")
+          }
+        }
+      }
+      when (state) {
+        0 -> Row { oneTwoThree() }
+        1 -> Text("hey")
+        2 -> Column { oneTwoThree() }
+      }
+    }
+
+    assertThat(composition.awaitSnapshot().filter { it !is ValueChange }).containsExactly(
+      // Row to Root
+      Create(Id(1), WidgetTag(1000001)),
+      ChildrenChange.Add(Id.Root, ChildrenTag.Root, Id(1), 0),
+      // Box
+      Create(Id(2), WidgetTag(1000004)),
+      // Text("one") to Box
+      Create(Id(3), WidgetTag(3)),
+      ChildrenChange.Add(Id(2), ChildrenTag(1), Id(3), 0),
+      // Text("two") to Box
+      Create(Id(4), WidgetTag(3)),
+      ChildrenChange.Add(Id(2), ChildrenTag(1), Id(4), 1),
+      // Text("three") to Box
+      Create(Id(5), WidgetTag(3)),
+      ChildrenChange.Add(Id(2), ChildrenTag(1), Id(5), 2),
+      // Box to Row
+      ChildrenChange.Add(Id(1), ChildrenTag(1), Id(2), 0),
+    )
+
+    state = 1
+    assertThat(composition.awaitSnapshot().filter { it !is ValueChange }).containsExactly(
+      // Box from Row
+      ChildrenChange.Remove(Id(1), ChildrenTag(1), 0, detach = false),
+      // Row from Root
+      ChildrenChange.Remove(Id.Root, ChildrenTag.Root, 0, detach = false),
+      // Text("hey") to Root
+      Create(Id(6), WidgetTag(3)),
+      ChildrenChange.Add(Id.Root, ChildrenTag.Root, Id(6), 0),
+    )
+
+    state = 2
+    assertThat(composition.awaitSnapshot().filter { it !is ValueChange }).containsExactly(
+      // Text from Root
+      ChildrenChange.Remove(Id.Root, ChildrenTag.Root, 0, detach = false),
+      // Column to Root
+      Create(Id(7), WidgetTag(1000002)),
+      ChildrenChange.Add(Id.Root, ChildrenTag.Root, Id(7), 0),
+      // Box
+      Create(Id(8), WidgetTag(1000004)),
+      // Text("one") to Box
+      Create(Id(9), WidgetTag(3)),
+      ChildrenChange.Add(Id(8), ChildrenTag(1), Id(9), 0),
+      // Text("two") to Box
+      Create(Id(10), WidgetTag(3)),
+      ChildrenChange.Add(Id(8), ChildrenTag(1), Id(10), 1),
+      // Text("three") to Box
+      Create(Id(11), WidgetTag(3)),
+      ChildrenChange.Add(Id(8), ChildrenTag(1), Id(11), 2),
+      // Box to Column
+      ChildrenChange.Add(Id(7), ChildrenTag(1), Id(8), 0),
+    )
+  }
+
   private fun TestScope.testProtocolComposition(
     hostVersion: RedwoodVersion = latestVersion,
   ): Pair<TestRedwoodComposition<List<Change>>, GuestProtocolAdapter> {

redwood-protocol/src/commonMain/kotlin/app/cash/redwood/protocol/RedwoodVersion.kt

@@ -51,6 +51,8 @@ public value class RedwoodVersion(public val value: String) : Comparable<Redwood
     }
   }
 
+  override fun toString(): String = value
+
   /**
    * Compare two versions to see which is newer.
    *

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

@@ -194,6 +194,7 @@ internal class ProtocolButton(
 ) : ProtocolWidget, Button<Unit> {
   public override val id: Id = guestAdapter.nextId()
   public override val tag: WidgetTag get() = WidgetTag(3)
+  public override var removeIndex: Int = InvalidRemoveIndex
 
   private var onClick: (() -> Unit)? = null
 
@@ -274,6 +275,12 @@ internal fun generateProtocolWidget(
             )
             .build(),
         )
+        .addProperty(
+          PropertySpec.builder("removeIndex", INT, OVERRIDE)
+            .mutable(true)
+            .initializer("%T.INVALID_INDEX", ProtocolGuest.ProtocolWidget)
+            .build(),
+        )
         .apply {
           var nextSerializerId = 0
           val serializerIds = mutableMapOf<TypeName, Int>()