Use global state for hasForceUpdate instead of persisting to queue (#12808)

* Use global state for `hasForceUpdate` instead of persisting to queue

Fixes a bug where `hasForceUpdate` was not reset on commit.

Ideally we'd use a tuple and return `hasForceUpdate` from
`processUpdateQueue`.

* Remove underscore and add comment

* Remove temporary variables

packages/react-reconciler/src/ReactFiberClassComponent.js

@@ -32,6 +32,8 @@ import {StrictMode} from './ReactTypeOfMode';
 import {
   enqueueUpdate,
   processUpdateQueue,
+  checkHasForceUpdateAfterProcessing,
+  resetHasForceUpdateBeforeProcessing,
   createUpdate,
   ReplaceState,
   ForceUpdate,
@@ -235,14 +237,6 @@ export default function(
     newState,
     newContext,
   ) {
-    if (
-      workInProgress.updateQueue !== null &&
-      workInProgress.updateQueue.hasForceUpdate
-    ) {
-      // If forceUpdate was called, disregard sCU.
-      return true;
-    }
-
     const instance = workInProgress.stateNode;
     const ctor = workInProgress.type;
     if (typeof instance.shouldComponentUpdate === 'function') {
@@ -789,6 +783,8 @@ export default function(
       }
     }
 
+    resetHasForceUpdateBeforeProcessing();
+
     const oldState = workInProgress.memoizedState;
     let newState = (instance.state = oldState);
     let updateQueue = workInProgress.updateQueue;
@@ -806,10 +802,7 @@ export default function(
       oldProps === newProps &&
       oldState === newState &&
       !hasContextChanged() &&
-      !(
-        workInProgress.updateQueue !== null &&
-        workInProgress.updateQueue.hasForceUpdate
-      )
+      !checkHasForceUpdateAfterProcessing()
     ) {
       // If an update was already in progress, we should schedule an Update
       // effect even though we're bailing out, so that cWU/cDU are called.
@@ -828,14 +821,16 @@ export default function(
       newState = workInProgress.memoizedState;
     }
 
-    const shouldUpdate = checkShouldComponentUpdate(
-      workInProgress,
-      oldProps,
-      newProps,
-      oldState,
-      newState,
-      newContext,
-    );
+    const shouldUpdate =
+      checkHasForceUpdateAfterProcessing() ||
+      checkShouldComponentUpdate(
+        workInProgress,
+        oldProps,
+        newProps,
+        oldState,
+        newState,
+        newContext,
+      );
 
     if (shouldUpdate) {
       // In order to support react-lifecycles-compat polyfilled components,
@@ -922,6 +917,8 @@ export default function(
       }
     }
 
+    resetHasForceUpdateBeforeProcessing();
+
     const oldState = workInProgress.memoizedState;
     let newState = (instance.state = oldState);
     let updateQueue = workInProgress.updateQueue;
@@ -940,10 +937,7 @@ export default function(
       oldProps === newProps &&
       oldState === newState &&
       !hasContextChanged() &&
-      !(
-        workInProgress.updateQueue !== null &&
-        workInProgress.updateQueue.hasForceUpdate
-      )
+      !checkHasForceUpdateAfterProcessing()
     ) {
       // If an update was already in progress, we should schedule an Update
       // effect even though we're bailing out, so that cWU/cDU are called.
@@ -977,14 +971,16 @@ export default function(
       }
     }
 
-    const shouldUpdate = checkShouldComponentUpdate(
-      workInProgress,
-      oldProps,
-      newProps,
-      oldState,
-      newState,
-      newContext,
-    );
+    const shouldUpdate =
+      checkHasForceUpdateAfterProcessing() ||
+      checkShouldComponentUpdate(
+        workInProgress,
+        oldProps,
+        newProps,
+        oldState,
+        newState,
+        newContext,
+      );
 
     if (shouldUpdate) {
       // In order to support react-lifecycles-compat polyfilled components,

packages/react-reconciler/src/ReactUpdateQueue.js

@@ -131,9 +131,6 @@ export type UpdateQueue<State> = {
 
   firstCapturedEffect: Update<State> | null,
   lastCapturedEffect: Update<State> | null,
-
-  // TODO: Workaround for lack of tuples. Could use global state instead.
-  hasForceUpdate: boolean,
 };
 
 export const UpdateState = 0;
@@ -141,6 +138,11 @@ export const ReplaceState = 1;
 export const ForceUpdate = 2;
 export const CaptureUpdate = 3;
 
+// Global state that is reset at the beginning of calling `processUpdateQueue`.
+// It should only be read right after calling `processUpdateQueue`, via
+// `checkHasForceUpdateAfterProcessing`.
+let hasForceUpdate = false;
+
 let didWarnUpdateInsideUpdate;
 let currentlyProcessingQueue;
 export let resetCurrentlyProcessingQueue;
@@ -164,7 +166,6 @@ export function createUpdateQueue<State>(baseState: State): UpdateQueue<State> {
     lastEffect: null,
     firstCapturedEffect: null,
     lastCapturedEffect: null,
-    hasForceUpdate: false,
   };
   return queue;
 }
@@ -183,8 +184,6 @@ function cloneUpdateQueue<State>(
     firstCapturedUpdate: null,
     lastCapturedUpdate: null,
 
-    hasForceUpdate: false,
-
     firstEffect: null,
     lastEffect: null,
 
@@ -423,7 +422,7 @@ function getStateFromUpdate<State>(
       return Object.assign({}, prevState, partialState);
     }
     case ForceUpdate: {
-      queue.hasForceUpdate = true;
+      hasForceUpdate = true;
       return prevState;
     }
   }
@@ -437,6 +436,8 @@ export function processUpdateQueue<State>(
   instance: any,
   renderExpirationTime: ExpirationTime,
 ): void {
+  hasForceUpdate = false;
+
   if (
     queue.expirationTime === NoWork ||
     queue.expirationTime > renderExpirationTime
@@ -595,6 +596,14 @@ function callCallback(callback, context) {
   callback.call(context);
 }
 
+export function resetHasForceUpdateBeforeProcessing() {
+  hasForceUpdate = false;
+}
+
+export function checkHasForceUpdateAfterProcessing(): boolean {
+  return hasForceUpdate;
+}
+
 export function commitUpdateQueue<State>(
   finishedWork: Fiber,
   finishedQueue: UpdateQueue<State>,

packages/react-reconciler/src/__tests__/ReactIncremental-test.internal.js

@@ -1115,6 +1115,29 @@ describe('ReactIncremental', () => {
     expect(ops).toEqual(['Foo', 'Bar', 'Baz', 'Bar', 'Baz']);
   });
 
+  it('should clear forceUpdate after update is flushed', () => {
+    let a = 0;
+
+    class Foo extends React.PureComponent {
+      render() {
+        const msg = `A: ${a}, B: ${this.props.b}`;
+        ReactNoop.yield(msg);
+        return msg;
+      }
+    }
+
+    const foo = React.createRef(null);
+    ReactNoop.render(<Foo ref={foo} b={0} />);
+    expect(ReactNoop.flush()).toEqual(['A: 0, B: 0']);
+
+    a = 1;
+    foo.current.forceUpdate();
+    expect(ReactNoop.flush()).toEqual(['A: 1, B: 0']);
+
+    ReactNoop.render(<Foo ref={foo} b={0} />);
+    expect(ReactNoop.flush()).toEqual([]);
+  });
+
   xit('can call sCU while resuming a partly mounted component', () => {
     let ops = [];