From 4162f6026c2f560f286e7853f4929cd5e0135bdd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastian=20Markb=C3=A5ge?= <sebastian@calyptus.eu>
Date: Fri, 15 Mar 2019 15:54:22 -0700
Subject: [PATCH] Add feature flag to disable yielding (#15119)

---
 .../ReactDOMFiberAsync-test.internal.js       | 52 +++++++++++++++++++
 .../src/ReactFiberScheduler.js                |  9 +++-
 packages/shared/ReactFeatureFlags.js          |  3 ++
 .../forks/ReactFeatureFlags.native-fb.js      |  1 +
 .../forks/ReactFeatureFlags.native-oss.js     |  1 +
 .../forks/ReactFeatureFlags.persistent.js     |  1 +
 .../forks/ReactFeatureFlags.test-renderer.js  |  1 +
 .../ReactFeatureFlags.test-renderer.www.js    |  1 +
 .../shared/forks/ReactFeatureFlags.www.js     |  1 +
 9 files changed, 68 insertions(+), 2 deletions(-)

diff --git a/packages/react-dom/src/__tests__/ReactDOMFiberAsync-test.internal.js b/packages/react-dom/src/__tests__/ReactDOMFiberAsync-test.internal.js
index 69013757ae8fb..c3e83a5795400 100644
--- a/packages/react-dom/src/__tests__/ReactDOMFiberAsync-test.internal.js
+++ b/packages/react-dom/src/__tests__/ReactDOMFiberAsync-test.internal.js
@@ -10,6 +10,7 @@
 'use strict';
 
 const React = require('react');
+const Fragment = React.Fragment;
 let ReactFeatureFlags = require('shared/ReactFeatureFlags');
 
 let ReactDOM;
@@ -659,4 +660,55 @@ describe('ReactDOMFiberAsync', () => {
       expect(formSubmitted).toBe(true);
     });
   });
+
+  describe('Disable yielding', () => {
+    beforeEach(() => {
+      jest.resetModules();
+      ReactFeatureFlags = require('shared/ReactFeatureFlags');
+      ReactFeatureFlags.disableYielding = true;
+      ReactFeatureFlags.debugRenderPhaseSideEffectsForStrictMode = false;
+      ReactDOM = require('react-dom');
+      Scheduler = require('scheduler');
+    });
+
+    it('wont yield during a render if yielding is disabled', () => {
+      class A extends React.Component {
+        render() {
+          Scheduler.yieldValue('A');
+          return <div>{this.props.children}</div>;
+        }
+      }
+
+      class B extends React.Component {
+        render() {
+          Scheduler.yieldValue('B');
+          return <div>{this.props.children}</div>;
+        }
+      }
+
+      class C extends React.Component {
+        render() {
+          Scheduler.yieldValue('C');
+          return <div>{this.props.children}</div>;
+        }
+      }
+
+      let root = ReactDOM.unstable_createRoot(container);
+
+      root.render(
+        <Fragment>
+          <A />
+          <B />
+          <C />
+        </Fragment>,
+      );
+
+      expect(Scheduler).toHaveYielded([]);
+
+      Scheduler.unstable_flushNumberOfYields(2);
+      // Even though we just flushed two yields, we should have rendered
+      // everything without yielding when the flag is on.
+      expect(Scheduler).toHaveYielded(['A', 'B', 'C']);
+    });
+  });
 });
diff --git a/packages/react-reconciler/src/ReactFiberScheduler.js b/packages/react-reconciler/src/ReactFiberScheduler.js
index fdd42867b31d3..e24e2ad714803 100644
--- a/packages/react-reconciler/src/ReactFiberScheduler.js
+++ b/packages/react-reconciler/src/ReactFiberScheduler.js
@@ -63,6 +63,7 @@ import {
   replayFailedUnitOfWorkWithInvokeGuardedCallback,
   warnAboutDeprecatedLifecycles,
   enableSuspenseServerRenderer,
+  disableYielding,
 } from 'shared/ReactFeatureFlags';
 import getComponentName from 'shared/getComponentName';
 import invariant from 'shared/invariant';
@@ -2019,7 +2020,7 @@ function onSuspend(
   msUntilTimeout: number,
 ): void {
   root.expirationTime = rootExpirationTime;
-  if (msUntilTimeout === 0 && !shouldYield()) {
+  if (msUntilTimeout === 0 && (disableYielding || !shouldYield())) {
     // Don't wait an additional tick. Commit the tree immediately.
     root.pendingCommitExpirationTime = suspendedExpirationTime;
     root.finishedWork = finishedWork;
@@ -2233,7 +2234,11 @@ function performAsyncWork(didTimeout) {
       } while (root !== firstScheduledRoot);
     }
   }
-  performWork(NoWork, true);
+  let isYieldy = true;
+  if (disableYielding) {
+    isYieldy = false;
+  }
+  performWork(NoWork, isYieldy);
 }
 
 function performSyncWork() {
diff --git a/packages/shared/ReactFeatureFlags.js b/packages/shared/ReactFeatureFlags.js
index b9e249914b1ad..95108e7d96239 100644
--- a/packages/shared/ReactFeatureFlags.js
+++ b/packages/shared/ReactFeatureFlags.js
@@ -45,6 +45,9 @@ export function addUserTimingListener() {
 // Disable javascript: URL strings in href for XSS protection.
 export const disableJavaScriptURLs = false;
 
+// Disables yielding during render in Concurrent Mode. Used for debugging only.
+export const disableYielding = false;
+
 // React Fire: prevent the value and checked attributes from syncing
 // with their related DOM properties
 export const disableInputAttributeSyncing = false;
diff --git a/packages/shared/forks/ReactFeatureFlags.native-fb.js b/packages/shared/forks/ReactFeatureFlags.native-fb.js
index c1de808b851bc..64db95b8d8484 100644
--- a/packages/shared/forks/ReactFeatureFlags.native-fb.js
+++ b/packages/shared/forks/ReactFeatureFlags.native-fb.js
@@ -25,6 +25,7 @@ export const warnAboutShorthandPropertyCollision = false;
 export const enableSchedulerDebugging = false;
 export const debugRenderPhaseSideEffectsForStrictMode = true;
 export const disableJavaScriptURLs = false;
+export const disableYielding = false;
 export const disableInputAttributeSyncing = false;
 export const replayFailedUnitOfWorkWithInvokeGuardedCallback = __DEV__;
 export const warnAboutDeprecatedLifecycles = true;
diff --git a/packages/shared/forks/ReactFeatureFlags.native-oss.js b/packages/shared/forks/ReactFeatureFlags.native-oss.js
index edfe1f5e220d0..a5cfb3d29435d 100644
--- a/packages/shared/forks/ReactFeatureFlags.native-oss.js
+++ b/packages/shared/forks/ReactFeatureFlags.native-oss.js
@@ -21,6 +21,7 @@ export const enableProfilerTimer = __PROFILE__;
 export const enableSchedulerTracing = __PROFILE__;
 export const enableSuspenseServerRenderer = false;
 export const disableJavaScriptURLs = false;
+export const disableYielding = false;
 export const disableInputAttributeSyncing = false;
 export const enableStableConcurrentModeAPIs = false;
 export const warnAboutShorthandPropertyCollision = false;
diff --git a/packages/shared/forks/ReactFeatureFlags.persistent.js b/packages/shared/forks/ReactFeatureFlags.persistent.js
index 7b8fb48083cbb..692864b4cfd57 100644
--- a/packages/shared/forks/ReactFeatureFlags.persistent.js
+++ b/packages/shared/forks/ReactFeatureFlags.persistent.js
@@ -21,6 +21,7 @@ export const enableProfilerTimer = __PROFILE__;
 export const enableSchedulerTracing = __PROFILE__;
 export const enableSuspenseServerRenderer = false;
 export const disableJavaScriptURLs = false;
+export const disableYielding = false;
 export const disableInputAttributeSyncing = false;
 export const enableStableConcurrentModeAPIs = false;
 export const warnAboutShorthandPropertyCollision = false;
diff --git a/packages/shared/forks/ReactFeatureFlags.test-renderer.js b/packages/shared/forks/ReactFeatureFlags.test-renderer.js
index 7153ac8c29903..7239941035bc5 100644
--- a/packages/shared/forks/ReactFeatureFlags.test-renderer.js
+++ b/packages/shared/forks/ReactFeatureFlags.test-renderer.js
@@ -21,6 +21,7 @@ export const enableProfilerTimer = false;
 export const enableSchedulerTracing = false;
 export const enableSuspenseServerRenderer = false;
 export const disableJavaScriptURLs = false;
+export const disableYielding = false;
 export const disableInputAttributeSyncing = false;
 export const enableStableConcurrentModeAPIs = false;
 export const warnAboutShorthandPropertyCollision = false;
diff --git a/packages/shared/forks/ReactFeatureFlags.test-renderer.www.js b/packages/shared/forks/ReactFeatureFlags.test-renderer.www.js
index 660f3c19d754a..096494b839ef7 100644
--- a/packages/shared/forks/ReactFeatureFlags.test-renderer.www.js
+++ b/packages/shared/forks/ReactFeatureFlags.test-renderer.www.js
@@ -24,6 +24,7 @@ export const enableStableConcurrentModeAPIs = false;
 export const enableSchedulerDebugging = false;
 export const warnAboutDeprecatedSetNativeProps = false;
 export const disableJavaScriptURLs = false;
+export const disableYielding = false;
 export const enableEventAPI = true;
 
 // Only used in www builds.
diff --git a/packages/shared/forks/ReactFeatureFlags.www.js b/packages/shared/forks/ReactFeatureFlags.www.js
index f967402adc871..e47428a52a3c3 100644
--- a/packages/shared/forks/ReactFeatureFlags.www.js
+++ b/packages/shared/forks/ReactFeatureFlags.www.js
@@ -17,6 +17,7 @@ export const {
   replayFailedUnitOfWorkWithInvokeGuardedCallback,
   warnAboutDeprecatedLifecycles,
   disableJavaScriptURLs,
+  disableYielding,
   disableInputAttributeSyncing,
   warnAboutShorthandPropertyCollision,
   warnAboutDeprecatedSetNativeProps,