From 67387c3c91a743f89dcdbfac9d4e9456c25573b8 Mon Sep 17 00:00:00 2001
From: Samuel Susla <samuelsusla@meta.com>
Date: Tue, 12 Sep 2023 06:55:37 -0700
Subject: [PATCH] Implement findDescendantNode without cloning the tree
 (#39356)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/39356

changelog: [internal]

`findDescendantNode` shouldn't clone the tree.

Reviewed By: javache

Differential Revision: D49095341

fbshipit-source-id: 4cd6aa6f9ba0f96d708e6a6c6b0cd55f03d8b5b1
---
 .../tests/StateReconciliationTest.cpp         | 24 ++++++++++++-------
 1 file changed, 16 insertions(+), 8 deletions(-)

diff --git a/packages/react-native/ReactCommon/react/renderer/mounting/tests/StateReconciliationTest.cpp b/packages/react-native/ReactCommon/react/renderer/mounting/tests/StateReconciliationTest.cpp
index 9b74efad03ee0c..bba5f9a5b533b6 100644
--- a/packages/react-native/ReactCommon/react/renderer/mounting/tests/StateReconciliationTest.cpp
+++ b/packages/react-native/ReactCommon/react/renderer/mounting/tests/StateReconciliationTest.cpp
@@ -36,23 +36,31 @@ class DummyShadowTreeDelegate : public ShadowTreeDelegate {
       bool mountSynchronously) const override{};
 };
 
-inline const ShadowNode* findDescendantNode(
+namespace {
+const ShadowNode* findDescendantNode(
     const ShadowNode& shadowNode,
     const ShadowNodeFamily& family) {
-  const ShadowNode* result = nullptr;
-  shadowNode.cloneTree(family, [&](const ShadowNode& oldShadowNode) {
-    result = &oldShadowNode;
-    return oldShadowNode.clone({});
-  });
-  return result;
+  if (&shadowNode.getFamily() == &family) {
+    return &shadowNode;
+  }
+
+  for (auto childNode : shadowNode.getChildren()) {
+    auto descendant = findDescendantNode(*childNode, family);
+    if (descendant != nullptr) {
+      return descendant;
+    }
+  }
+
+  return nullptr;
 }
 
-inline const ShadowNode* findDescendantNode(
+const ShadowNode* findDescendantNode(
     const ShadowTree& shadowTree,
     const ShadowNodeFamily& family) {
   return findDescendantNode(
       *shadowTree.getCurrentRevision().rootShadowNode, family);
 }
+} // namespace
 
 TEST(StateReconciliationTest, testStateReconciliation) {
   auto builder = simpleComponentBuilder();