From c19b3ffae96ec57ae0aa143ce66e93f48c4e5301 Mon Sep 17 00:00:00 2001
From: Valentin Shergin <shergin@fb.com>
Date: Fri, 11 Sep 2020 09:19:44 -0700
Subject: [PATCH] Fabric: Communicating a reason why a commit was unsuccessful
 via ShadowTree::CommitStatus

Summary:
We need it to stop repeating to commit new shadow tree in `ShadowTree::commit` when a transaction cancels the commit.

Changelog: [Internal] Fabric-specific internal change.

Reviewed By: JoshuaGross, sammy-SC

Differential Revision: D23603959

fbshipit-source-id: d279fb3bf4190e860740a6450595d6f2fc3117f7
---
 .../react/renderer/mounting/ShadowTree.cpp     | 18 +++++++++++-------
 .../react/renderer/mounting/ShadowTree.h       | 13 +++++++++----
 .../react/renderer/uimanager/UIManager.cpp     | 13 +++++++------
 3 files changed, 27 insertions(+), 17 deletions(-)

diff --git a/ReactCommon/react/renderer/mounting/ShadowTree.cpp b/ReactCommon/react/renderer/mounting/ShadowTree.cpp
index 1c5cef2ecf9..59896ad7b1e 100644
--- a/ReactCommon/react/renderer/mounting/ShadowTree.cpp
+++ b/ReactCommon/react/renderer/mounting/ShadowTree.cpp
@@ -21,6 +21,8 @@
 namespace facebook {
 namespace react {
 
+using CommitStatus = ShadowTree::CommitStatus;
+
 /*
  * Generates (possibly) a new tree where all nodes with non-obsolete `State`
  * objects. If all `State` objects in the tree are not obsolete for the moment
@@ -260,7 +262,7 @@ MountingCoordinator::Shared ShadowTree::getMountingCoordinator() const {
   return mountingCoordinator_;
 }
 
-void ShadowTree::commit(
+CommitStatus ShadowTree::commit(
     ShadowTreeCommitTransaction transaction,
     bool enableStateReconciliation) const {
   SystraceSection s("ShadowTree::commit");
@@ -269,8 +271,10 @@ void ShadowTree::commit(
 
   while (true) {
     attempts++;
-    if (tryCommit(transaction, enableStateReconciliation)) {
-      return;
+
+    auto status = tryCommit(transaction, enableStateReconciliation);
+    if (status != CommitStatus::Failed) {
+      return status;
     }
 
     // After multiple attempts, we failed to commit the transaction.
@@ -279,7 +283,7 @@ void ShadowTree::commit(
   }
 }
 
-bool ShadowTree::tryCommit(
+CommitStatus ShadowTree::tryCommit(
     ShadowTreeCommitTransaction transaction,
     bool enableStateReconciliation) const {
   SystraceSection s("ShadowTree::tryCommit");
@@ -298,7 +302,7 @@ bool ShadowTree::tryCommit(
   RootShadowNode::Unshared newRootShadowNode = transaction(oldRootShadowNode);
 
   if (!newRootShadowNode) {
-    return false;
+    return CommitStatus::Cancelled;
   }
 
   if (enableStateReconciliation) {
@@ -330,7 +334,7 @@ bool ShadowTree::tryCommit(
     std::unique_lock<better::shared_mutex> lock(commitMutex_);
 
     if (rootShadowNode_ != oldRootShadowNode) {
-      return false;
+      return CommitStatus::Failed;
     }
 
     rootShadowNode_ = newRootShadowNode;
@@ -356,7 +360,7 @@ bool ShadowTree::tryCommit(
 
   notifyDelegatesOfUpdates();
 
-  return true;
+  return CommitStatus::Succeeded;
 }
 
 void ShadowTree::commitEmptyTree() const {
diff --git a/ReactCommon/react/renderer/mounting/ShadowTree.h b/ReactCommon/react/renderer/mounting/ShadowTree.h
index c4f6314b5b7..7b216a654a0 100644
--- a/ReactCommon/react/renderer/mounting/ShadowTree.h
+++ b/ReactCommon/react/renderer/mounting/ShadowTree.h
@@ -31,6 +31,12 @@ using ShadowTreeCommitTransaction = std::function<RootShadowNode::Unshared(
  */
 class ShadowTree final {
  public:
+  enum class CommitStatus {
+    Succeeded,
+    Failed,
+    Cancelled,
+  };
+
   /*
    * Creates a new shadow tree instance.
    */
@@ -53,17 +59,16 @@ class ShadowTree final {
   /*
    * Performs commit calling `transaction` function with a `oldRootShadowNode`
    * and expecting a `newRootShadowNode` as a return value.
-   * The `transaction` function can abort commit returning `nullptr`.
-   * Returns `true` if the operation finished successfully.
+   * The `transaction` function can cancel commit returning `nullptr`.
    */
-  bool tryCommit(
+  CommitStatus tryCommit(
       ShadowTreeCommitTransaction transaction,
       bool enableStateReconciliation = false) const;
 
   /*
    * Calls `tryCommit` in a loop until it finishes successfully.
    */
-  void commit(
+  CommitStatus commit(
       ShadowTreeCommitTransaction transaction,
       bool enableStateReconciliation = false) const;
 
diff --git a/ReactCommon/react/renderer/uimanager/UIManager.cpp b/ReactCommon/react/renderer/uimanager/UIManager.cpp
index 701e9e83ee4..a15aeb4ee6d 100644
--- a/ReactCommon/react/renderer/uimanager/UIManager.cpp
+++ b/ReactCommon/react/renderer/uimanager/UIManager.cpp
@@ -239,10 +239,10 @@ void UIManager::updateState(StateUpdate const &stateUpdate) const {
 
   shadowTreeRegistry_.visit(
       family->getSurfaceId(), [&](ShadowTree const &shadowTree) {
-        bool updateSucceeded = shadowTree.tryCommit(
-            [&](RootShadowNode::Shared const &oldRootShadowNode) {
-              return std::static_pointer_cast<
-                  RootShadowNode>(oldRootShadowNode->cloneTree(
+        auto status = shadowTree.tryCommit([&](RootShadowNode::Shared const
+                                                   &oldRootShadowNode) {
+          return std::static_pointer_cast<RootShadowNode>(
+              oldRootShadowNode->cloneTree(
                   *family, [&](ShadowNode const &oldShadowNode) {
                     auto newData =
                         callback(oldShadowNode.getState()->getDataPointer());
@@ -256,8 +256,9 @@ void UIManager::updateState(StateUpdate const &stateUpdate) const {
                         /* .state = */ newState,
                     });
                   }));
-            });
-        if (!updateSucceeded && stateUpdate.failureCallback) {
+        });
+        if (status != ShadowTree::CommitStatus::Succeeded &&
+            stateUpdate.failureCallback) {
           stateUpdate.failureCallback();
         }
       });