From a48101688386855be96052176dbadb18583ea348 Mon Sep 17 00:00:00 2001
From: Sebastian Markbage <sema@fb.com>
Date: Sun, 20 Nov 2016 21:28:54 +0000
Subject: [PATCH] Preserve the original object when using replaceState

When we use only replace state we don't need to clone the object.
---
 scripts/fiber/tests-failing.txt               |  1 -
 scripts/fiber/tests-passing.txt               |  1 +
 .../shared/fiber/ReactFiberUpdateQueue.js     | 29 +++++++++++++------
 3 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/scripts/fiber/tests-failing.txt b/scripts/fiber/tests-failing.txt
index 712f9b98bd..c5979c37a4 100644
--- a/scripts/fiber/tests-failing.txt
+++ b/scripts/fiber/tests-failing.txt
@@ -114,7 +114,6 @@ src/renderers/shared/stack/reconciler/__tests__/ReactCompositeComponent-test.js
 * should warn about `setState` in render
 * should warn about `setState` in getChildContext
 * should update refs if shouldComponentUpdate gives false
-* should support objects with prototypes as state
 
 src/renderers/shared/stack/reconciler/__tests__/ReactCompositeComponentNestedState-test.js
 * should provide up to date values for props
diff --git a/scripts/fiber/tests-passing.txt b/scripts/fiber/tests-passing.txt
index 62b88a8aa7..27de2c82c3 100644
--- a/scripts/fiber/tests-passing.txt
+++ b/scripts/fiber/tests-passing.txt
@@ -1284,6 +1284,7 @@ src/renderers/shared/stack/reconciler/__tests__/ReactCompositeComponent-test.js
 * should allow access to findDOMNode in componentWillUnmount
 * context should be passed down from the parent
 * should replace state
+* should support objects with prototypes as state
 * should not warn about unmounting during unmounting
 * should only call componentWillUnmount once
 
diff --git a/src/renderers/shared/fiber/ReactFiberUpdateQueue.js b/src/renderers/shared/fiber/ReactFiberUpdateQueue.js
index 83d8542f51..784e8b8a6b 100644
--- a/src/renderers/shared/fiber/ReactFiberUpdateQueue.js
+++ b/src/renderers/shared/fiber/ReactFiberUpdateQueue.js
@@ -87,19 +87,30 @@ exports.callCallbacks = function(queue : UpdateQueue, context : any) : Error | n
   return firstError;
 };
 
+function getStateFromNode(node, instance, state, props) {
+  if (typeof node.partialState === 'function') {
+    const updateFn = node.partialState;
+    return updateFn.call(instance, state, props);
+  } else {
+    return node.partialState;
+  }
+}
+
 exports.mergeUpdateQueue = function(queue : UpdateQueue, instance : any, prevState : any, props : any) : any {
   let node : ?UpdateQueueNode = queue;
+  if (queue.isReplace) {
+    // replaceState is always first in the queue.
+    prevState = getStateFromNode(queue, instance, prevState, props);
+    node = queue.next;
+    if (!node) {
+      // If there is no more work, we replace the raw object instead of cloning.
+      return prevState;
+    }
+  }
   let state = Object.assign({}, prevState);
   while (node) {
-    state = node.isReplace ? null : state;
-    let partialState;
-    if (typeof node.partialState === 'function') {
-      const updateFn = node.partialState;
-      partialState = updateFn.call(instance, state, props);
-    } else {
-      partialState = node.partialState;
-    }
-    state = Object.assign(state || {}, partialState);
+    let partialState = getStateFromNode(node, instance, state, props);
+    Object.assign(state, partialState);
     node = node.next;
   }
   return state;