From 26731ea9671837899de80d7e71db0df93d5ca64f Mon Sep 17 00:00:00 2001
From: Andrew Clark <acdlite@fb.com>
Date: Sun, 30 Oct 2016 22:44:52 -0700
Subject: [PATCH] unstable_batchedUpdates should return value of callback

---
 src/renderers/dom/fiber/ReactDOMFiber.js           | 4 ++--
 src/renderers/shared/fiber/ReactFiberReconciler.js | 5 ++++-
 src/renderers/shared/fiber/ReactFiberScheduler.js  | 4 ++--
 3 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/src/renderers/dom/fiber/ReactDOMFiber.js b/src/renderers/dom/fiber/ReactDOMFiber.js
index 6d59e5aed7..08fd6d7c59 100644
--- a/src/renderers/dom/fiber/ReactDOMFiber.js
+++ b/src/renderers/dom/fiber/ReactDOMFiber.js
@@ -165,8 +165,8 @@ var ReactDOM = {
     return DOMRenderer.findHostInstance(component);
   },
 
-  unstable_batchedUpdates(fn : Function) : void {
-    DOMRenderer.batchedUpdates(fn);
+  unstable_batchedUpdates<A>(fn : () => A) : A {
+    return DOMRenderer.batchedUpdates(fn);
   },
 
 };
diff --git a/src/renderers/shared/fiber/ReactFiberReconciler.js b/src/renderers/shared/fiber/ReactFiberReconciler.js
index f14559dfa8..7708e04c59 100644
--- a/src/renderers/shared/fiber/ReactFiberReconciler.js
+++ b/src/renderers/shared/fiber/ReactFiberReconciler.js
@@ -68,7 +68,10 @@ export type Reconciler<C, I, TI> = {
   updateContainer(element : ReactElement<any>, container : OpaqueNode) : void,
   unmountContainer(container : OpaqueNode) : void,
   performWithPriority(priorityLevel : PriorityLevel, fn : Function) : void,
-  batchedUpdates(fn: Function) : void,
+  /* eslint-disable no-undef */
+  // FIXME: ESLint complains about type parameter
+  batchedUpdates<A>(fn : () => A) : A,
+  /* eslint-enable no-undef */
 
   // Used to extract the return value from the initial render. Legacy API.
   getPublicRootInstance(container : OpaqueNode) : (ReactComponent<any, any, any> | TI | I | null),
diff --git a/src/renderers/shared/fiber/ReactFiberScheduler.js b/src/renderers/shared/fiber/ReactFiberScheduler.js
index dbd6d3e7ce..ca942f6269 100644
--- a/src/renderers/shared/fiber/ReactFiberScheduler.js
+++ b/src/renderers/shared/fiber/ReactFiberScheduler.js
@@ -681,11 +681,11 @@ module.exports = function<T, P, I, TI, C>(config : HostConfig<T, P, I, TI, C>) {
     }
   }
 
-  function batchedUpdates(fn: Function) {
+  function batchedUpdates<A>(fn : () => A) : A {
     const prev = shouldBatchUpdates;
     shouldBatchUpdates = true;
     try {
-      fn();
+      return fn();
     } finally {
       shouldBatchUpdates = prev;
     }