Fabric: ShadowTree::completeByReplacingShadowNode

Summary: This method is the core of the future features: `setNativeProps` and `LocalState`.

Reviewed By: sahrens

Differential Revision: D13114789

fbshipit-source-id: 2138496c43c171fe27784b1959d86d6eec4638ee

ReactCommon/fabric/uimanager/ShadowTree.cpp

@@ -98,6 +98,35 @@ bool ShadowTree::complete(
   return complete(oldRootShadowNode, newRootShadowNode);
 }
 
+bool ShadowTree::completeByReplacingShadowNode(
+    const SharedShadowNode &oldShadowNode,
+    const SharedShadowNode &newShadowNode) const {
+  auto rootShadowNode = getRootShadowNode();
+  std::vector<std::reference_wrapper<const ShadowNode>> ancestors;
+  oldShadowNode->constructAncestorPath(*rootShadowNode, ancestors);
+
+  if (ancestors.size() == 0) {
+    return false;
+  }
+
+  auto oldChild = oldShadowNode;
+  auto newChild = newShadowNode;
+
+  SharedShadowNodeUnsharedList sharedChildren;
+
+  for (const auto &ancestor : ancestors) {
+    auto children = ancestor.get().getChildren();
+    std::replace(children.begin(), children.end(), oldChild, newChild);
+
+    sharedChildren = std::make_shared<SharedShadowNodeList>(children);
+
+    oldChild = ancestor.get().shared_from_this();
+    newChild = oldChild->clone(ShadowNodeFragment{.children = sharedChildren});
+  }
+
+  return complete(sharedChildren);
+}
+
 bool ShadowTree::complete(
     const SharedRootShadowNode &oldRootShadowNode,
     const UnsharedRootShadowNode &newRootShadowNode) const {

ReactCommon/fabric/uimanager/ShadowTree.h

@@ -77,6 +77,16 @@ class ShadowTree final {
    */
   bool complete(const SharedShadowNodeUnsharedList &rootChildNodes) const;
 
+  /*
+   * Replaces a given old shadow node with a new one in the tree by cloning all
+   * nodes on the path to the root node and then complete the tree.
+   * Can be called from any thread.
+   * Returns `true` if the operation finished successfully.
+   */
+  bool completeByReplacingShadowNode(
+      const SharedShadowNode &oldShadowNode,
+      const SharedShadowNode &newShadowNode) const;
+
   /*
    * Returns a root shadow node that represents the last committed three.
    */