From 79ef5f9b0f7d48bf029a5b2b8dc7ef63fbe82fc0 Mon Sep 17 00:00:00 2001
From: Valentin Shergin <shergin@fb.com>
Date: Wed, 4 Sep 2019 23:14:49 -0700
Subject: [PATCH] Fabric: `UIManager::findShadowNodeByTag_DEPRECATED`

Summary: The mehtod implements the core functionality of finding a shadow node by given tag.

Reviewed By: zackargyle, JoshuaGross, mdvacca

Differential Revision: D17175955

fbshipit-source-id: 5cfbb80b2d4e54a33ca9c20a21988df4de54c800
---
 ReactCommon/fabric/uimanager/UIManager.cpp | 41 ++++++++++++++++++++++
 ReactCommon/fabric/uimanager/UIManager.h   |  8 +++++
 2 files changed, 49 insertions(+)

diff --git a/ReactCommon/fabric/uimanager/UIManager.cpp b/ReactCommon/fabric/uimanager/UIManager.cpp
index ee0e812eb5a..d0ed76dbd73 100644
--- a/ReactCommon/fabric/uimanager/UIManager.cpp
+++ b/ReactCommon/fabric/uimanager/UIManager.cpp
@@ -191,6 +191,47 @@ void UIManager::dispatchCommand(
   }
 }
 
+static ShadowNode::Shared findShadowNodeByTagRecursively(
+    ShadowNode::Shared const &parentShadowNode,
+    Tag tag) {
+  if (parentShadowNode->getTag() == tag) {
+    return parentShadowNode;
+  }
+
+  for (ShadowNode::Shared const &shadowNode : parentShadowNode->getChildren()) {
+    auto result = findShadowNodeByTagRecursively(shadowNode, tag);
+    if (result) {
+      return result;
+    }
+  }
+
+  return nullptr;
+}
+
+ShadowNode::Shared UIManager::findShadowNodeByTag_DEPRECATED(Tag tag) const {
+  auto shadowNode = ShadowNode::Shared{};
+
+  shadowTreeRegistry_.enumerate([&](ShadowTree const &shadowTree, bool &stop) {
+    auto rootShadowNode = ShadowNode::Shared{};
+    // This is tricky.
+    // The public interface of `ShadowTree` discourages accessing a stored
+    // pointer to a root node because of the possible data race.
+    // To work around this, we ask for a commit and immediately cancel it
+    // returning `nullptr` instead of a new shadow tree.
+    shadowTree.tryCommit([&](SharedRootShadowNode const &oldRootShadowNode) {
+      rootShadowNode = oldRootShadowNode;
+      return nullptr;
+    });
+
+    shadowNode = findShadowNodeByTagRecursively(rootShadowNode, tag);
+    if (shadowNode) {
+      stop = true;
+    }
+  });
+
+  return shadowNode;
+}
+
 void UIManager::setComponentDescriptorRegistry(
     const SharedComponentDescriptorRegistry &componentDescriptorRegistry) {
   componentDescriptorRegistry_ = componentDescriptorRegistry;
diff --git a/ReactCommon/fabric/uimanager/UIManager.h b/ReactCommon/fabric/uimanager/UIManager.h
index 5ba848f87ce..781ac4bd1a3 100644
--- a/ReactCommon/fabric/uimanager/UIManager.h
+++ b/ReactCommon/fabric/uimanager/UIManager.h
@@ -97,6 +97,14 @@ class UIManager {
       std::string const &commandName,
       folly::dynamic const args) const;
 
+  /*
+   * Iterates over all shadow nodes which are parts of all registered surfaces
+   * and find the one that has given `tag`. Returns `nullptr` if the node wasn't
+   * found. This is a temporary workaround that should not be used in any core
+   * functionality.
+   */
+  ShadowNode::Shared findShadowNodeByTag_DEPRECATED(Tag tag) const;
+
   ShadowTreeRegistry const &getShadowTreeRegistry() const;
 
   SharedComponentDescriptorRegistry componentDescriptorRegistry_;