Remove state update warning for passive effect cleanup functions (facebook#18453)

Brian Vaughn · web-flow · commit 5ee0efe83276 · 2020-04-01T10:49:24.000-07:00
diff --git a/packages/react-reconciler/src/ReactFiberWorkLoop.js b/packages/react-reconciler/src/ReactFiberWorkLoop.js
@@ -160,7 +160,6 @@ import {
 import getComponentName from 'shared/getComponentName';
 import ReactStrictModeWarnings from './ReactStrictModeWarnings';
 import {
-  current as currentDebugFiberInDEV,
   isRendering as ReactCurrentDebugFiberIsRenderingInDEV,
   resetCurrentFiber as resetCurrentDebugFiberInDEV,
   setCurrentFiber as setCurrentDebugFiberInDEV,
@@ -2736,38 +2735,20 @@ function warnAboutUpdateOnUnmountedFiberInDEV(fiber) {
       didWarnStateUpdateForUnmountedComponent = new Set([componentName]);
     }
 
-    // If we are currently flushing passive effects, change the warning text.
     if (isFlushingPassiveEffects) {
+      // Do not warn if we are currently flushing passive effects!
+      //
       // React can't directly detect a memory leak, but there are some clues that warn about one.
       // One of these clues is when an unmounted React component tries to update its state.
       // For example, if a component forgets to remove an event listener when unmounting,
-      // that listener may be called later and try to update state, at which point React would warn about the potential leak.
-      //
-      // Warning signals like this are more useful if they're strong.
-      // For this reason, it's good to always avoid updating state from inside of an effect's cleanup function.
-      // Even when you know there is no potential leak, React has no way to know and so it will warn anyway.
-      // In most cases we suggest moving state updates to the useEffect() body instead.
-      // This works so long as the component is updating its own state (or the state of a descendant).
+      // that listener may be called later and try to update state,
+      // at which point React would warn about the potential leak.
       //
-      // However this will not work when a component updates its parent state in a cleanup function.
-      // If such a component is unmounted but its parent remains mounted, the state will be out of sync.
-      // For this reason, we avoid showing the warning if a component is updating an ancestor.
-      let currentTargetFiber = fiber;
-      while (currentTargetFiber !== null) {
-        // currentDebugFiberInDEV owns the effect destroy function currently being invoked.
-        if (
-          currentDebugFiberInDEV === currentTargetFiber ||
-          currentDebugFiberInDEV === currentTargetFiber.alternate
-        ) {
-          console.error(
-            "Can't perform a React state update from within a useEffect cleanup function. " +
-              'To fix, move state updates to the useEffect() body.%s',
-            getStackByFiberInDevAndProd(((currentDebugFiberInDEV: any): Fiber)),
-          );
-          break;
-        }
-        currentTargetFiber = currentTargetFiber.return;
-      }
+      // Warning signals are the most useful when they're strong.
+      // (So we should avoid false positive warnings.)
+      // Updating state from within an effect cleanup function is sometimes a necessary pattern, e.g.:
+      // 1. Updating an ancestor that a component had registered itself with on mount.
+      // 2. Resetting state when a component is hidden after going offscreen.
     } else {
       console.error(
         "Can't perform a React state update on an unmounted component. This " +
diff --git a/packages/react-reconciler/src/__tests__/ReactHooksWithNoopRenderer-test.internal.js b/packages/react-reconciler/src/__tests__/ReactHooksWithNoopRenderer-test.internal.js
@@ -1307,7 +1307,49 @@ describe('ReactHooksWithNoopRenderer', () => {
         });
       });
 
-      it('shows a warning when a component updates its own state from within passive unmount function', () => {
+      it('still warns if there are updates after pending passive unmount effects have been flushed', () => {
+        let updaterFunction;
+
+        function Component() {
+          Scheduler.unstable_yieldValue('Component');
+          const [state, setState] = React.useState(false);
+          updaterFunction = setState;
+          React.useEffect(() => {
+            Scheduler.unstable_yieldValue('passive create');
+            return () => {
+              Scheduler.unstable_yieldValue('passive destroy');
+            };
+          }, []);
+          return state;
+        }
+
+        act(() => {
+          ReactNoop.renderToRootWithID(<Component />, 'root', () =>
+            Scheduler.unstable_yieldValue('Sync effect'),
+          );
+        });
+        expect(Scheduler).toHaveYielded([
+          'Component',
+          'Sync effect',
+          'passive create',
+        ]);
+
+        ReactNoop.unmountRootWithID('root');
+        expect(Scheduler).toFlushAndYield(['passive destroy']);
+
+        act(() => {
+          expect(() => {
+            updaterFunction(true);
+          }).toErrorDev(
+            "Warning: Can't perform a React state update on an unmounted component. " +
+              'This is a no-op, but it indicates a memory leak in your application. ' +
+              'To fix, cancel all subscriptions and asynchronous tasks in a useEffect cleanup function.\n' +
+              '    in Component (at **)',
+          );
+        });
+      });
+
+      it('does not show a warning when a component updates its own state from within passive unmount function', () => {
         function Component() {
           Scheduler.unstable_yieldValue('Component');
           const [didLoad, setDidLoad] = React.useState(false);
@@ -1333,17 +1375,11 @@ describe('ReactHooksWithNoopRenderer', () => {
 
           // Unmount but don't process pending passive destroy function
           ReactNoop.unmountRootWithID('root');
-          expect(() => {
-            expect(Scheduler).toFlushAndYield(['passive destroy']);
-          }).toErrorDev(
-            "Warning: Can't perform a React state update from within a useEffect cleanup function. " +
-              'To fix, move state updates to the useEffect() body.\n' +
-              '    in Component (at **)',
-          );
+          expect(Scheduler).toFlushAndYield(['passive destroy']);
         });
       });
 
-      it('shows a warning when a component updates a childs state from within passive unmount function', () => {
+      it('does not show a warning when a component updates a childs state from within passive unmount function', () => {
         function Parent() {
           Scheduler.unstable_yieldValue('Parent');
           const updaterRef = React.useRef(null);
@@ -1378,13 +1414,7 @@ describe('ReactHooksWithNoopRenderer', () => {
 
           // Unmount but don't process pending passive destroy function
           ReactNoop.unmountRootWithID('root');
-          expect(() => {
-            expect(Scheduler).toFlushAndYield(['Parent passive destroy']);
-          }).toErrorDev(
-            "Warning: Can't perform a React state update from within a useEffect cleanup function. " +
-              'To fix, move state updates to the useEffect() body.\n' +
-              '    in Parent (at **)',
-          );
+          expect(Scheduler).toFlushAndYield(['Parent passive destroy']);
         });
       });
 
diff --git a/scripts/jest/matchers/toWarnDev.js b/scripts/jest/matchers/toWarnDev.js
@@ -1,6 +1,6 @@
 'use strict';
 
-const jestDiff = require('jest-diff').default;
+const jestDiff = require('jest-diff');
 const util = require('util');
 const shouldIgnoreConsoleError = require('../shouldIgnoreConsoleError');
 
