BREAKING: Release ComponentTree through binder when RecyclerCollectio…

…nComponent's @OnDetached is called.

Summary:
When RecyclerCollectionComponent's onDetached() callback is called, we should release ComponentTrees in the sections as well. Add a method called `release` in Binder.java that RecyclerCollectionComponent can access it to release ComponentTrees under the hood.

The release() method in ComponentTreeHolder has been removed in D14183719, but I think we need to add it back. It's not just used to triggering OnDetached method, but also used to remove the pending runnables posted in the handlers(https://fburl.com/4spmzpwu).

Reviewed By: pasqualeanatriello

Differential Revision: D13848269

fbshipit-source-id: 0060ddb8cc0341cf7963e0b5fb4982bc1f9675f4

litho-it/src/test/java/com/facebook/litho/widget/RecyclerBinderTest.java

@@ -5046,6 +5046,49 @@ public void testOnAttachedOnDetachedWithViewportChanged() {
     }
   }
 
+  @Test
+  public void testItemsOnDetached() {
+    final int childHeightPx = 20;
+    final int widthPx = 200;
+    final int heightPx = 200;
+
+    mRecyclerBinder = new RecyclerBinder.Builder().rangeRatio(RANGE_RATIO).build(mComponentContext);
+    final RecyclerView rv = mock(RecyclerView.class);
+    mRecyclerBinder.mount(rv);
+
+    final List<RenderInfo> renderInfos = new ArrayList<>();
+    final List<TestComponent> components = new ArrayList<>();
+    for (int i = 0; i < 200; i++) {
+      final TestComponent component =
+          TestAttachDetachComponent.create(mComponentContext).heightPx(childHeightPx).build();
+      components.add(component);
+      final Component child = Column.create(mComponentContext).child(component).build();
+      renderInfos.add(ComponentRenderInfo.create().component(child).build());
+    }
+    mRecyclerBinder.insertRangeAt(0, renderInfos);
+    mRecyclerBinder.notifyChangeSetComplete(true, NO_OP_CHANGE_SET_COMPLETE_CALLBACK);
+
+    Size size = new Size();
+    int widthSpec = SizeSpec.makeSizeSpec(widthPx, SizeSpec.EXACTLY);
+    int heightSpec = SizeSpec.makeSizeSpec(heightPx, SizeSpec.EXACTLY);
+    mRecyclerBinder.measure(size, widthSpec, heightSpec, null);
+
+    mLayoutThreadShadowLooper.runToEndOfTasks();
+    ShadowLooper.runUiThreadTasks();
+
+    mRecyclerBinder.detach();
+
+    final int rangeSize = heightPx / childHeightPx;
+    final int rangeStart = 0;
+    final int rangeTotal = (int) (rangeSize + (RANGE_RATIO * rangeSize));
+    for (int i = rangeStart; i <= rangeStart + rangeTotal; i++) {
+      assertThat(components.get(i).wasOnDetachedCalled()).isTrue();
+    }
+    for (int i = rangeStart + rangeTotal + 1; i < 200; i++) {
+      assertThat(components.get(i).wasOnDetachedCalled()).isFalse();
+    }
+  }
+
   private RecyclerBinder createRecyclerBinderWithMockAdapter(RecyclerView.Adapter adapterMock) {
     return new RecyclerBinder.Builder()
         .rangeRatio(RANGE_RATIO)

litho-sections-widget/src/main/java/com/facebook/litho/sections/widget/RecyclerCollectionComponentSpec.java

@@ -42,6 +42,7 @@
 import com.facebook.litho.annotations.LayoutSpec;
 import com.facebook.litho.annotations.OnCreateInitialState;
 import com.facebook.litho.annotations.OnCreateLayout;
+import com.facebook.litho.annotations.OnDetached;
 import com.facebook.litho.annotations.OnEvent;
 import com.facebook.litho.annotations.OnTrigger;
 import com.facebook.litho.annotations.OnUpdateState;
@@ -399,6 +400,11 @@ static void onScroll(
     sectionTree.requestFocusOnRoot(position);
   }
 
+  @OnDetached
+  static void onDetached(ComponentContext c, @State Binder<RecyclerView> binder) {
+    binder.detach();
+  }
+
   private static class RecyclerCollectionOnScrollListener extends OnScrollListener {
 
     private final RecyclerCollectionEventsController mEventsController;

litho-sections-widget/src/main/java/com/facebook/litho/sections/widget/SectionBinderTarget.java

@@ -202,6 +202,11 @@ public boolean supportsBackgroundChangeSets() {
     return mUseBackgroundChangeSets;
   }
 
+  @Override
+  public void detach() {
+    mRecyclerBinder.detach();
+  }
+
   public void clear() {
     if (mUseBackgroundChangeSets) {
       mRecyclerBinder.clearAsync();

litho-widget/src/main/java/com/facebook/litho/widget/Binder.java

@@ -101,4 +101,7 @@ void measure(
    * view and the first item will need to be measured to determine the height of the view.
    */
   void setCanMeasure(boolean canMeasure);
+
+  /** Detach items under the hood. */
+  void detach();
 }

litho-widget/src/main/java/com/facebook/litho/widget/RecyclerBinder.java

@@ -633,6 +633,20 @@ public void setCanMeasure(boolean canMeasure) {
     mCanMeasure = canMeasure;
   }
 
+  @Override
+  public void detach() {
+    final List<ComponentTreeHolder> toDetach = new ArrayList<>();
+    synchronized (this) {
+      for (int i = 0, size = mComponentTreeHolders.size(); i < size; i++) {
+        toDetach.add(mComponentTreeHolders.get(i));
+      }
+    }
+
+    for (int i = 0, size = toDetach.size(); i < size; i++) {
+      toDetach.get(i).acquireStateAndReleaseTree();
+    }
+  }
+
   @UiThread
   public void notifyItemRenderCompleteAt(int position, final long timestampMillis) {
     final ComponentTreeHolder holder = mComponentTreeHolders.get(position);