Implement host-side protocol widget reuse

This does not yet support sending the detach flag from the guest.
cashapp · Dec 10, 2024 · 0dd3844 · 0dd3844
1 parent 660d72f
commit 0dd3844
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Showing 3 changed files with 84 additions and 7 deletions.
diff --git a/...protocol-host/src/commonMain/kotlin/app/cash/redwood/protocol/host/HostProtocolAdapter.kt b/...protocol-host/src/commonMain/kotlin/app/cash/redwood/protocol/host/HostProtocolAdapter.kt
@@ -36,7 +36,6 @@ import app.cash.redwood.protocol.RedwoodVersion
 import app.cash.redwood.protocol.WidgetTag
 import app.cash.redwood.widget.ChangeListener
 import app.cash.redwood.widget.Widget
-import kotlin.collections.mutableMapOf
 import kotlin.native.ObjCName
 
 /**
@@ -107,10 +106,12 @@ public class HostProtocolAdapter<W : Any>(
             }
 
             is Remove -> {
-              for (childIndex in change.index until change.index + change.count) {
-                val child = children.nodes[childIndex]
-                child.visitIds(removeNodeById)
-                poolOrDetach(child)
+              if (!change.detach) {
+                for (childIndex in change.index until change.index + change.count) {
+                  val child = children.nodes[childIndex]
+                  child.visitIds(removeNodeById)
+                  poolOrDetach(child)
+                }
               }
               children.remove(change.index, change.count)
             }

diff --git a/...ocol-host/src/commonTest/kotlin/app/cash/redwood/protocol/host/HostProtocolAdapterTest.kt b/...ocol-host/src/commonTest/kotlin/app/cash/redwood/protocol/host/HostProtocolAdapterTest.kt
@@ -29,6 +29,7 @@ import app.cash.redwood.protocol.PropertyChange
 import app.cash.redwood.protocol.PropertyTag
 import app.cash.redwood.protocol.WidgetTag
 import app.cash.redwood.protocol.guest.guestRedwoodVersion
+import app.cash.redwood.testing.WidgetValue
 import app.cash.redwood.widget.MutableListChildren
 import assertk.assertFailure
 import assertk.assertThat
@@ -37,7 +38,9 @@ import assertk.assertions.isEqualTo
 import assertk.assertions.isInstanceOf
 import assertk.assertions.message
 import com.example.redwood.testapp.protocol.host.TestSchemaProtocolFactory
+import com.example.redwood.testapp.testing.TestRowValue
 import com.example.redwood.testapp.testing.TestSchemaTestingWidgetFactory
+import com.example.redwood.testapp.testing.TextValue
 import com.example.redwood.testapp.widget.TestSchemaWidgetSystem
 import kotlin.test.Test
 import kotlin.test.assertFailsWith
@@ -204,9 +207,10 @@ class HostProtocolAdapterTest {
   }
 
   @Test fun entireSubtreeRemoved() {
+    val container = MutableListChildren<WidgetValue>()
     val host = HostProtocolAdapter(
       guestVersion = guestRedwoodVersion,
-      container = MutableListChildren(),
+      container = container,
       factory = TestSchemaProtocolFactory(
         widgetSystem = TestSchemaWidgetSystem(
           TestSchema = TestSchemaTestingWidgetFactory(),
@@ -263,4 +267,69 @@ class HostProtocolAdapterTest {
       .message()
       .isEqualTo("Unknown widget ID 3")
   }
+
+  @Test fun detachAndAdd() {
+    val container = MutableListChildren<WidgetValue>()
+    val host = HostProtocolAdapter(
+      guestVersion = guestRedwoodVersion,
+      container = container,
+      factory = TestSchemaProtocolFactory(
+        widgetSystem = TestSchemaWidgetSystem(
+          TestSchema = TestSchemaTestingWidgetFactory(),
+          RedwoodLayout = RedwoodLayoutTestingWidgetFactory(),
+          RedwoodLazyLayout = RedwoodLazyLayoutTestingWidgetFactory(),
+        ),
+      ),
+      eventSink = ::error,
+      leakDetector = LeakDetector.none(),
+    )
+
+    // TestRow {
+    //   TestRow {
+    //     Text("hello")
+    host.sendChanges(
+      listOf(
+        // TestRow
+        Create(Id(1), WidgetTag(1)),
+        ModifierChange(Id(1)),
+        // TestRow
+        Create(Id(2), WidgetTag(1)),
+        ModifierChange(Id(2)),
+        // Text
+        Create(Id(3), WidgetTag(3)),
+        PropertyChange(Id(3), WidgetTag(3), PropertyTag(1), JsonPrimitive("hello")),
+        ModifierChange(Id(3)),
+        Add(Id(2), ChildrenTag(1), Id(3), 0),
+        Add(Id(1), ChildrenTag(1), Id(2), 0),
+        Add(Id.Root, ChildrenTag.Root, Id(1), 0),
+      ),
+    )
+
+    host.sendChanges(
+      listOf(
+        // Detach inner TestRow.
+        Remove(Id(1), ChildrenTag(1), 0, 1, detach = true),
+        // Remove outer TestRow.
+        Remove(Id.Root, ChildrenTag.Root, 0, 1),
+        // New outer TestRow.
+        Create(Id(4), WidgetTag(1)),
+        ModifierChange(Id(4)),
+        Add(Id.Root, ChildrenTag.Root, Id(4), 0),
+        // Re-attach inner TestRow.
+        Add(Id(4), ChildrenTag(1), Id(2), 0),
+      ),
+    )
+
+    assertThat(container.single().value).isEqualTo(
+      TestRowValue(
+        children = listOf(
+          TestRowValue(
+            children = listOf(
+              TextValue(text = "hello"),
+            ),
+          ),
+        ),
+      ),
+    )
+  }
 }
diff --git a/redwood-protocol/src/commonMain/kotlin/app/cash/redwood/protocol/protocol.kt b/redwood-protocol/src/commonMain/kotlin/app/cash/redwood/protocol/protocol.kt
@@ -248,6 +248,12 @@ public sealed interface ChildrenChange : Change {
     private val _tag: Int,
     public val index: Int,
     public val count: Int,
+    /**
+     * When true, the associated nodes should only be detached from the tree with the expectation
+     * that a future [Add] will re-attach them. Otherwise, nodes should be detached and fully
+     * removed for garbage collection.
+     */
+    public val detach: Boolean = false,
   ) : ChildrenChange {
     override val id: Id get() = Id(_id)
     override val tag: ChildrenTag get() = ChildrenTag(_tag)
@@ -258,7 +264,8 @@ public sealed interface ChildrenChange : Change {
         tag: ChildrenTag,
         index: Int,
         count: Int,
-      ): Remove = Remove(id.value, tag.value, index, count)
+        detach: Boolean = false,
+      ): Remove = Remove(id.value, tag.value, index, count, detach)
     }
   }
 }