From ca51dc6288eb8c8df197239cd53dff649da4e50d Mon Sep 17 00:00:00 2001
From: Joshua Gross <joshuagross@fb.com>
Date: Tue, 29 Sep 2020 16:35:44 -0700
Subject: [PATCH] Fix mutation sorting function

Summary:
The sorting function currently forms a partial ordering, not a total ordering. This can cause problems with certain sequences of immediate or conflicting mutations, leading to UI corruption or crashes.

Changelog: [Internal]

Reviewed By: shergin

Differential Revision: D24002668

fbshipit-source-id: edc9b4c1e3104897cb0c5fd6da563ec43d800494
---
 .../LayoutAnimationKeyFrameManager.h           | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/ReactCommon/react/renderer/animations/LayoutAnimationKeyFrameManager.h b/ReactCommon/react/renderer/animations/LayoutAnimationKeyFrameManager.h
index e6aba6e3c07..891d25d46d1 100644
--- a/ReactCommon/react/renderer/animations/LayoutAnimationKeyFrameManager.h
+++ b/ReactCommon/react/renderer/animations/LayoutAnimationKeyFrameManager.h
@@ -308,6 +308,14 @@ static inline bool shouldFirstComeBeforeSecondMutation(
       return true;
     }
 
+    // Update comes last, before deletes
+    if (rhs.type == ShadowViewMutation::Type::Update) {
+      return true;
+    }
+    if (lhs.type == ShadowViewMutation::Type::Update) {
+      return false;
+    }
+
     // Remove comes before insert
     if (lhs.type == ShadowViewMutation::Type::Remove &&
         rhs.type == ShadowViewMutation::Type::Insert) {
@@ -317,6 +325,16 @@ static inline bool shouldFirstComeBeforeSecondMutation(
         lhs.type == ShadowViewMutation::Type::Insert) {
       return false;
     }
+
+    // Create comes before insert
+    if (lhs.type == ShadowViewMutation::Type::Create &&
+        rhs.type == ShadowViewMutation::Type::Insert) {
+      return true;
+    }
+    if (rhs.type == ShadowViewMutation::Type::Create &&
+        lhs.type == ShadowViewMutation::Type::Insert) {
+      return false;
+    }
   } else {
     // Make sure that removes on the same level are sorted - highest indices
     // must come first.