From c0d27de37eec7b6860387e35dae4dfc455d4b6e2 Mon Sep 17 00:00:00 2001
From: "Andrew Chen (Eng)" <ayc@fb.com>
Date: Wed, 21 Mar 2018 14:21:37 -0700
Subject: [PATCH] Fix removal of virtual nodes in FabricReconciler

Reviewed By: mdvacca

Differential Revision: D7338949

fbshipit-source-id: 31263c138689f9b3f59deb26851132df04b8a823
---
 .../react/fabric/FabricReconciler.java        | 19 +++++++++----------
 .../facebook/react/uimanager/ViewAtIndex.java | 11 ++++++++++-
 2 files changed, 19 insertions(+), 11 deletions(-)

diff --git a/ReactAndroid/src/main/java/com/facebook/react/fabric/FabricReconciler.java b/ReactAndroid/src/main/java/com/facebook/react/fabric/FabricReconciler.java
index eba24f2754..cc851c228f 100644
--- a/ReactAndroid/src/main/java/com/facebook/react/fabric/FabricReconciler.java
+++ b/ReactAndroid/src/main/java/com/facebook/react/fabric/FabricReconciler.java
@@ -89,12 +89,11 @@ public class FabricReconciler {
     // If a View is not re-ordered, then the ReactTag is deleted (ReactShadowNode and native View
     // are released from memory)
     List<Integer> tagsToDelete = new LinkedList<>();
-    int[] indicesToRemove = new int[prevList.size() - firstRemovedOrAddedViewIndex];
-    int indicesToRemoveIndex = 0;
-    for (int j = firstRemovedOrAddedViewIndex; j < prevList.size(); j++) {
+    List<Integer> indicesToRemove = new LinkedList<>();
+    for (int j = prevList.size() - 1; j >= firstRemovedOrAddedViewIndex; j--) {
       ReactShadowNode nodeToRemove = prevList.get(j);
       if (nodeToRemove.isVirtual()) continue;
-      indicesToRemove[indicesToRemoveIndex++] = j;
+      indicesToRemove.add(0, j);
       if (!addedTags.contains(nodeToRemove.getReactTag())) {
         tagsToDelete.add(nodeToRemove.getReactTag());
         // TODO: T26729293 since we are not cloning ReactShadowNode's we need to "manually" remove
@@ -103,21 +102,21 @@ public class FabricReconciler {
       }
     }
 
-    int[] tagsToDeleteArray = ArrayUtils.copyListToArray(tagsToDelete);
-    ViewAtIndex[] viewsToAddArray = viewsToAdd.toArray(new ViewAtIndex[viewsToAdd.size()]);
-
     // TODO (t27180994): Mutate views synchronously on main thread
-    if (indicesToRemove.length > 0 || viewsToAddArray.length > 0 || tagsToDeleteArray.length > 0) {
+    if (!(indicesToRemove.isEmpty() && viewsToAdd.isEmpty() && tagsToDelete.isEmpty())) {
+      int[] indicesToRemoveArray = ArrayUtils.copyListToArray(indicesToRemove);
+      ViewAtIndex[] viewsToAddArray = viewsToAdd.toArray(new ViewAtIndex[viewsToAdd.size()]);
+      int[] tagsToDeleteArray = ArrayUtils.copyListToArray(tagsToDelete);
       if (DEBUG) {
         Log.d(
             TAG,
             "manageChildren.enqueueManageChildren parent: " + parent.getReactTag() +
-                "\n\tIndices2Remove: " + Arrays.toString(indicesToRemove) +
+                "\n\tIndices2Remove: " + Arrays.toString(indicesToRemoveArray) +
                 "\n\tViews2Add: " + Arrays.toString(viewsToAddArray) +
                 "\n\tTags2Delete: " + Arrays.toString(tagsToDeleteArray));
       }
       uiViewOperationQueue.enqueueManageChildren(
-        parent.getReactTag(), indicesToRemove, viewsToAddArray, tagsToDeleteArray);
+        parent.getReactTag(), indicesToRemoveArray, viewsToAddArray, tagsToDeleteArray);
     }
   }
 
diff --git a/ReactAndroid/src/main/java/com/facebook/react/uimanager/ViewAtIndex.java b/ReactAndroid/src/main/java/com/facebook/react/uimanager/ViewAtIndex.java
index ef2a914d3c..c242d7c310 100644
--- a/ReactAndroid/src/main/java/com/facebook/react/uimanager/ViewAtIndex.java
+++ b/ReactAndroid/src/main/java/com/facebook/react/uimanager/ViewAtIndex.java
@@ -29,8 +29,17 @@ public class ViewAtIndex {
     mIndex = index;
   }
 
+  @Override
+  public boolean equals(Object obj) {
+    if (obj == null || obj.getClass() != getClass()) {
+      return false;
+    }
+    ViewAtIndex other = (ViewAtIndex) obj;
+    return mIndex == other.mIndex && mTag == other.mTag;
+  }
+
   @Override
   public String toString() {
-    return "[" + mIndex + ", " + mTag + "]";
+    return "[" + mTag + ", " + mIndex + "]";
   }
 }