Expose RecyclerBinder's Commit Policy through DynamicConfig

Summary:
# Problem

Today we don't have the ability to modify any configurations we set to the `RecyclerBinder` once they have been initialized. We don't want to allow all the configurations to be mutable, but `rangeRatio` and `commitPolicy` should be allowed to change throughout a production's interaction.

# Solution
Expose the configurations we allow to change through `DynamicConfig`. Today I'm only going to allow `commitPolicy` to be modified.

I recommend that the configuration changed to be exposed through `RecyclerCollectionComponent` through `Trigger`.

Reviewed By: astreet

Differential Revision: D16674728

fbshipit-source-id: 89277591adddcaae9dc23fcbf905c3e069410fd9

litho-it/src/test/java/com/facebook/litho/sections/SectionTreeTest.java

@@ -1125,5 +1125,8 @@ public void requestFocusWithOffset(int index, int offset) {}
     public boolean supportsBackgroundChangeSets() {
       return mSupportsBackgroundChangeSets;
     }
+
+    @Override
+    public void changeConfig(DynamicConfig dynamicConfig) {}
   }
 }

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

@@ -2526,6 +2526,52 @@ public void testInsertAsync_AsyncMode() {
     assertThat(holder.isTreeValid()).isTrue();
   }
 
+  @Test
+  public void testInsertAsync_PolicyChangeMode() {
+    final RecyclerBinder recyclerBinder =
+        new RecyclerBinder.Builder().rangeRatio(RANGE_RATIO).build(mComponentContext);
+    recyclerBinder.setCommitPolicy(RecyclerBinder.CommitPolicy.LAYOUT_BEFORE_INSERT);
+
+    final Component component =
+        TestDrawableComponent.create(mComponentContext).widthPx(100).heightPx(100).build();
+    final ComponentRenderInfo renderInfo =
+        ComponentRenderInfo.create().component(component).build();
+
+    recyclerBinder.measure(
+        new Size(), makeSizeSpec(1000, EXACTLY), makeSizeSpec(1000, EXACTLY), null);
+    recyclerBinder.insertItemAtAsync(0, renderInfo);
+
+    final Component secondComponent =
+        TestDrawableComponent.create(mComponentContext).widthPx(100).heightPx(100).build();
+    final ComponentRenderInfo secondRenderInfo =
+        ComponentRenderInfo.create().component(secondComponent).build();
+    recyclerBinder.setCommitPolicy(RecyclerBinder.CommitPolicy.IMMEDIATE);
+    recyclerBinder.insertItemAtAsync(1, secondRenderInfo);
+
+    recyclerBinder.notifyChangeSetCompleteAsync(true, NO_OP_CHANGE_SET_COMPLETE_CALLBACK);
+
+    assertThat(recyclerBinder.getItemCount()).isEqualTo(0);
+    assertThat(recyclerBinder.getRangeCalculationResult()).isNull();
+
+    mLayoutThreadShadowLooper.runToEndOfTasks();
+
+    assertThat(recyclerBinder.getItemCount()).isEqualTo(2);
+    assertThat(recyclerBinder.getRangeCalculationResult()).isNotNull();
+
+    final ComponentTreeHolder holder = recyclerBinder.getComponentTreeHolderAt(0);
+    assertThat(holder.getRenderInfo().getComponent()).isEqualTo(component);
+    assertThat(holder.hasCompletedLatestLayout()).isTrue();
+    assertThat(holder.isTreeValid()).isTrue();
+
+    final Component thirdComponent =
+        TestDrawableComponent.create(mComponentContext).widthPx(100).heightPx(100).build();
+    final ComponentRenderInfo thirdRenderInfo =
+        ComponentRenderInfo.create().component(thirdComponent).build();
+    recyclerBinder.insertItemAtAsync(2, thirdRenderInfo);
+    recyclerBinder.notifyChangeSetCompleteAsync(true, NO_OP_CHANGE_SET_COMPLETE_CALLBACK);
+    assertThat(recyclerBinder.getItemCount()).isEqualTo(3);
+  }
+
   @Test
   public void testMultipleInsertAsyncs_AsyncMode() {
     final RecyclerBinder recyclerBinder =

litho-sections-core/src/main/java/com/facebook/litho/sections/BatchedTarget.java

@@ -171,6 +171,11 @@ public boolean supportsBackgroundChangeSets() {
     return mTarget.supportsBackgroundChangeSets();
   }
 
+  @Override
+  public void changeConfig(DynamicConfig dynamicConfig) {
+    mTarget.changeConfig(dynamicConfig);
+  }
+
   private void maybeLogRequestFocusWithOffset(int index, int offset) {
     if (ENABLE_LOGGER && mComponentInfoSparseArray.size() != 0) {
       mSectionsDebugLogger.logRequestFocusWithOffset(

litho-sections-core/src/main/java/com/facebook/litho/sections/SectionTree.java

@@ -55,6 +55,7 @@
 import com.facebook.litho.sections.config.SectionsConfiguration;
 import com.facebook.litho.sections.logger.SectionsDebugLogger;
 import com.facebook.litho.widget.ChangeSetCompleteCallback;
+import com.facebook.litho.widget.RecyclerBinder.CommitPolicy;
 import com.facebook.litho.widget.RenderInfo;
 import com.facebook.litho.widget.SectionsDebug;
 import com.facebook.litho.widget.SmoothScrollAlignmentType;
@@ -142,6 +143,18 @@ void notifyChangeSetComplete(
      * @return whether this target supports applying change sets from a background thread.
      */
     boolean supportsBackgroundChangeSets();
+
+    /** Notify this target that a new set of configurations is applied. */
+    void changeConfig(DynamicConfig dynamicConfig);
+
+    class DynamicConfig {
+
+      public final @CommitPolicy int mChangeSetsCommitPolicy;
+
+      public DynamicConfig(@CommitPolicy int changeSetsCommitPolicy) {
+        mChangeSetsCommitPolicy = changeSetsCommitPolicy;
+      }
+    }
   }
 
   private static final String EMPTY_STRING = "";
@@ -426,6 +439,20 @@ public void setLoadEventsHandler(LoadEventsHandler loadEventsHandler) {
     mLoadEventsHandler = loadEventsHandler;
   }
 
+  /**
+   * Set a new set of configurations to the {@link Target}. Only those allowed to be modified will
+   * be included in {@link Target.DynamicConfig}.
+   */
+  public void setTargetConfig(Target.DynamicConfig dynamicConfig) {
+    if (mUseBackgroundChangeSets) {
+      synchronized (this) {
+        // applyChangeSetsToTargetUnchecked() in background will be computed in a synchronized
+        // block, and the config is only updated after the ongoing computation is completed.
+        mTarget.changeConfig(dynamicConfig);
+      }
+    }
+  }
+
   private void refreshRecursive(Section section) {
     section.refresh(section.getScopedContext());
 

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

@@ -63,6 +63,7 @@
 import com.facebook.litho.widget.PTRRefreshEvent;
 import com.facebook.litho.widget.Recycler;
 import com.facebook.litho.widget.RecyclerBinder;
+import com.facebook.litho.widget.RecyclerBinder.CommitPolicy;
 import com.facebook.litho.widget.RecyclerEventsController;
 import com.facebook.litho.widget.StickyHeaderControllerFactory;
 import com.facebook.litho.widget.ViewportInfo;
@@ -407,6 +408,14 @@ static void onScroll(
     sectionTree.requestFocusOnRoot(position);
   }
 
+  @OnTrigger(RecyclerDynamicConfigEvent.class)
+  static void onRecyclerConfigChanged(
+      ComponentContext c,
+      @FromTrigger @CommitPolicy int commitPolicy,
+      @State SectionTree sectionTree) {
+    sectionTree.setTargetConfig(new SectionTree.Target.DynamicConfig(commitPolicy));
+  }
+
   @OnDetached
   static void onDetached(ComponentContext c, @State Binder<RecyclerView> binder) {
     binder.detach();

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

@@ -0,0 +1,28 @@
+/*
+ * Copyright 2019-present Facebook, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.facebook.litho.sections.widget;
+
+import com.facebook.litho.annotations.Event;
+import com.facebook.litho.widget.RecyclerBinder.CommitPolicy;
+
+/**
+ * An event that is triggered when a new set of configurations, which are allowed to be dynamic, is
+ * applied to {@link com.facebook.litho.sections.SectionTree.Target}.
+ */
+@Event
+public class RecyclerDynamicConfigEvent {
+  public @CommitPolicy int commitPolicy;
+}

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 changeConfig(DynamicConfig dynamicConfig) {
+    mRecyclerBinder.setCommitPolicy(dynamicConfig.mChangeSetsCommitPolicy);
+  }
+
   @Override
   public void detach() {
     mRecyclerBinder.detach();

litho-testing/src/main/java/com/facebook/litho/testing/sections/TestTarget.java

@@ -197,6 +197,9 @@ public boolean supportsBackgroundChangeSets() {
     return false;
   }
 
+  @Override
+  public void changeConfig(DynamicConfig dynamicConfig) {}
+
   public void clear() {
     mOperations.clear();
     mNumChanges = 0;

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

@@ -34,6 +34,7 @@
 import android.view.View;
 import android.view.ViewGroup;
 import android.view.ViewTreeObserver;
+import androidx.annotation.AnyThread;
 import androidx.annotation.IntDef;
 import androidx.annotation.UiThread;
 import androidx.annotation.VisibleForTesting;
@@ -3273,8 +3274,8 @@ private int getActualChildrenHeightSpec(final ComponentTreeHolder treeHolder) {
     return mLayoutInfo.getChildHeightSpec(mLastHeightSpec, treeHolder.getRenderInfo());
   }
 
-  @VisibleForTesting
-  void setCommitPolicy(@CommitPolicy int commitPolicy) {
+  @AnyThread
+  public void setCommitPolicy(@CommitPolicy int commitPolicy) {
     mCommitPolicy = commitPolicy;
   }
 
@@ -3310,7 +3311,7 @@ private AsyncInsertOperation createAsyncInsertOperation(int position, RenderInfo
    */
   @IntDef({CommitPolicy.IMMEDIATE, CommitPolicy.LAYOUT_BEFORE_INSERT})
   @Retention(RetentionPolicy.SOURCE)
-  @interface CommitPolicy {
+  public @interface CommitPolicy {
     int IMMEDIATE = 0;
     int LAYOUT_BEFORE_INSERT = 1;
   }