Share the slicing code between replaced leaves and unchanged children

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: hryhoriiK97

packages/react-native/ReactCommon/react/renderer/mounting/internal/sliceChildShadowNodeViewPairs.cpp

@@ -264,42 +264,18 @@ bool sliceChangedChildShadowNodeViewPairsRecursively(
       continue;
     }
 
-    if (oldChildShadowNode.getTag() != newChildShadowNode.getTag() ||
+    // A child whose tag or order index changed can still be listed if it is a
+    // leaf that doesn't form a view, like the raw text of a `Text` whose
+    // string changed: it has no mount index, so it doesn't shift the views
+    // around it, and both lists are sorted by order index at the end.
+    bool isReplaced =
+        oldChildShadowNode.getTag() != newChildShadowNode.getTag() ||
         oldChildShadowNode.getOrderIndex() !=
-            newChildShadowNode.getOrderIndex()) {
-      // A replaced leaf that doesn't form a view (like the raw text of a
-      // `Text` whose string changed) has no mount index, so both nodes can be
-      // listed as they are without shifting the views around them.
-      if (!oldChildShadowNode.getChildren().empty() ||
-          !newChildShadowNode.getChildren().empty()) {
-        return false;
-      }
-      auto oldLeafSlice = sliceChild(
-          oldShadowNode,
-          oldChildShadowNode,
-          ShadowView(oldChildShadowNode),
-          oldLayoutOffset);
-      auto newLeafSlice = sliceChild(
-          newShadowNode,
-          newChildShadowNode,
-          ShadowView(newChildShadowNode),
-          newLayoutOffset);
-      if (oldLeafSlice.isConcreteView || newLeafSlice.isConcreteView) {
-        return false;
-      }
-      addChildSlice(
-          oldPairList,
-          oldStartOfStaticIndex,
-          scope,
-          oldLeafSlice,
-          oldChildShadowNode);
-      addChildSlice(
-          newPairList,
-          newStartOfStaticIndex,
-          scope,
-          newLeafSlice,
-          newChildShadowNode);
-      continue;
+            newChildShadowNode.getOrderIndex();
+    if (isReplaced &&
+        (!oldChildShadowNode.getChildren().empty() ||
+         !newChildShadowNode.getChildren().empty())) {
+      return false;
     }
 
     auto oldChildSlice = sliceChild(
@@ -314,7 +290,12 @@ bool sliceChangedChildShadowNodeViewPairsRecursively(
         newLayoutOffset);
     bool isStatic = newChildSlice.shadowView.layoutMetrics.positionType ==
         PositionType::Static;
-    if (oldChildSlice.isConcreteView != newChildSlice.isConcreteView ||
+    if (isReplaced) {
+      if (oldChildSlice.isConcreteView || newChildSlice.isConcreteView) {
+        return false;
+      }
+    } else if (
+        oldChildSlice.isConcreteView != newChildSlice.isConcreteView ||
         oldChildSlice.areChildrenFlattened !=
             newChildSlice.areChildrenFlattened ||
         (oldChildSlice.shadowView.layoutMetrics.positionType ==
@@ -335,7 +316,7 @@ bool sliceChangedChildShadowNodeViewPairsRecursively(
         newChildSlice,
         newChildShadowNode);
 
-    if (!newChildSlice.areChildrenFlattened) {
+    if (isReplaced || !newChildSlice.areChildrenFlattened) {
       continue;
     }
     if (isStatic) {