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Rewrite ReactFiberScheduler for better integration with Scheduler pac…
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…kage (#15151)

* Rewrite ReactFiberScheduler

Adds a new implementation of ReactFiberScheduler behind a feature flag.
We will maintain both implementations in parallel until the new one
is proven stable enough to replace the old one.

The main difference between the implementations is that the new one is
integrated with the Scheduler package's priority levels.

* Conditionally add fields to FiberRoot

Some fields only used by the old scheduler, and some by the new.

* Add separate build that enables new scheduler

* Re-enable skipped test

If synchronous updates are scheduled by a passive effect, that work
should be flushed synchronously, even if flushPassiveEffects is
called inside batchedUpdates.

* Passive effects have same priority as render

* Revert ability to cancel the current callback

React doesn't need this anyway because it never schedules callbacks if
it's already rendering.

* Revert change to FiberDebugPerf

Turns out this isn't neccessary.

* Fix ReactFiberScheduler dead code elimination

Should initialize to nothing, then assign the exports conditionally,
instead of initializing to the old exports and then reassigning to the
new ones.

* Don't yield before commit during sync error retry

* Call Scheduler.flushAll unconditionally in tests

Instead of wrapping in enableNewScheduler flag.
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acdlite authored Apr 2, 2019
1 parent aed0e1c commit 4d5cb64
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Showing 36 changed files with 4,754 additions and 1,207 deletions.
7 changes: 5 additions & 2 deletions packages/react-cache/src/LRU.js
Original file line number Diff line number Diff line change
Expand Up @@ -11,7 +11,10 @@ import * as Scheduler from 'scheduler';

// Intentionally not named imports because Rollup would
// use dynamic dispatch for CommonJS interop named imports.
const {unstable_scheduleCallback: scheduleCallback} = Scheduler;
const {
unstable_scheduleCallback: scheduleCallback,
unstable_IdlePriority: IdlePriority,
} = Scheduler;

type Entry<T> = {|
value: T,
Expand All @@ -34,7 +37,7 @@ export function createLRU<T>(limit: number) {
// The cache size exceeds the limit. Schedule a callback to delete the
// least recently used entries.
cleanUpIsScheduled = true;
scheduleCallback(cleanUp);
scheduleCallback(IdlePriority, cleanUp);
}
}

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Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@

let React;
let ReactTestRenderer;
let Scheduler;
let ReactDebugTools;
let act;

Expand All @@ -20,6 +21,7 @@ describe('ReactHooksInspectionIntegration', () => {
jest.resetModules();
React = require('react');
ReactTestRenderer = require('react-test-renderer');
Scheduler = require('scheduler');
act = ReactTestRenderer.act;
ReactDebugTools = require('react-debug-tools');
});
Expand Down Expand Up @@ -618,6 +620,8 @@ describe('ReactHooksInspectionIntegration', () => {

await LazyFoo;

Scheduler.flushAll();

let childFiber = renderer.root._currentFiber();
let tree = ReactDebugTools.inspectHooksOfFiber(childFiber);
expect(tree).toEqual([
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,8 @@

'use strict';

let ReactFeatureFlags;
let enableNewScheduler;
let React;
let ReactDOM;
let Scheduler;
Expand All @@ -19,6 +21,8 @@ describe('ReactDOMHooks', () => {
beforeEach(() => {
jest.resetModules();

ReactFeatureFlags = require('shared/ReactFeatureFlags');
enableNewScheduler = ReactFeatureFlags.enableNewScheduler;
React = require('react');
ReactDOM = require('react-dom');
Scheduler = require('scheduler');
Expand Down Expand Up @@ -97,15 +101,30 @@ describe('ReactDOMHooks', () => {
}

ReactDOM.render(<Foo />, container);
ReactDOM.unstable_batchedUpdates(() => {
_set(0); // Forces the effect to be flushed
expect(otherContainer.textContent).toBe('');
ReactDOM.render(<B />, otherContainer);
expect(otherContainer.textContent).toBe('');
});
expect(otherContainer.textContent).toBe('B');
expect(calledA).toBe(false); // It was in a batch
expect(calledB).toBe(true);

if (enableNewScheduler) {
// The old behavior was accidental; in the new scheduler, flushing passive
// effects also flushes synchronous work, even inside batchedUpdates.
ReactDOM.unstable_batchedUpdates(() => {
_set(0); // Forces the effect to be flushed
expect(otherContainer.textContent).toBe('A');
ReactDOM.render(<B />, otherContainer);
expect(otherContainer.textContent).toBe('A');
});
expect(otherContainer.textContent).toBe('B');
expect(calledA).toBe(true);
expect(calledB).toBe(true);
} else {
ReactDOM.unstable_batchedUpdates(() => {
_set(0); // Forces the effect to be flushed
expect(otherContainer.textContent).toBe('');
ReactDOM.render(<B />, otherContainer);
expect(otherContainer.textContent).toBe('');
});
expect(otherContainer.textContent).toBe('B');
expect(calledA).toBe(false); // It was in a batch
expect(calledB).toBe(true);
}
});

it('should not bail out when an update is scheduled from within an event handler', () => {
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@ let ReactDOM;
let Suspense;
let ReactCache;
let ReactTestUtils;
let Scheduler;
let TextResource;
let act;

Expand All @@ -26,6 +27,7 @@ describe('ReactDOMSuspensePlaceholder', () => {
ReactDOM = require('react-dom');
ReactCache = require('react-cache');
ReactTestUtils = require('react-dom/test-utils');
Scheduler = require('scheduler');
act = ReactTestUtils.act;
Suspense = React.Suspense;
container = document.createElement('div');
Expand Down Expand Up @@ -94,6 +96,8 @@ describe('ReactDOMSuspensePlaceholder', () => {

await advanceTimers(500);

Scheduler.flushAll();

expect(divs[0].current.style.display).toEqual('');
expect(divs[1].current.style.display).toEqual('');
// This div's display was set with a prop.
Expand All @@ -115,6 +119,8 @@ describe('ReactDOMSuspensePlaceholder', () => {

await advanceTimers(500);

Scheduler.flushAll();

expect(container.textContent).toEqual('ABC');
});

Expand Down Expand Up @@ -160,6 +166,8 @@ describe('ReactDOMSuspensePlaceholder', () => {

await advanceTimers(500);

Scheduler.flushAll();

expect(container.innerHTML).toEqual(
'<span style="display: inline;">Sibling</span><span style="">Async</span>',
);
Expand Down
Original file line number Diff line number Diff line change
Expand Up @@ -12,6 +12,7 @@
let React;
let ReactDOM;
let ReactDOMServer;
let Scheduler;

// These tests rely both on ReactDOMServer and ReactDOM.
// If a test only needs ReactDOMServer, put it in ReactServerRendering-test instead.
Expand All @@ -21,6 +22,7 @@ describe('ReactDOMServerHydration', () => {
React = require('react');
ReactDOM = require('react-dom');
ReactDOMServer = require('react-dom/server');
Scheduler = require('scheduler');
});

it('should have the correct mounting behavior (old hydrate API)', () => {
Expand Down Expand Up @@ -498,6 +500,7 @@ describe('ReactDOMServerHydration', () => {

jest.runAllTimers();
await Promise.resolve();
Scheduler.flushAll();
expect(element.textContent).toBe('Hello world');
});
});
16 changes: 16 additions & 0 deletions packages/react-dom/unstable-new-scheduler.js
Original file line number Diff line number Diff line change
@@ -0,0 +1,16 @@
/**
* Copyright (c) Facebook, Inc. and its affiliates.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*
* @flow
*/

'use strict';

const ReactDOM = require('./src/client/ReactDOM');

// TODO: decide on the top-level export form.
// This is hacky but makes it work with both Rollup and Jest.
module.exports = ReactDOM.default || ReactDOM;
39 changes: 39 additions & 0 deletions packages/react-reconciler/src/ReactFiberExpirationTime.js
Original file line number Diff line number Diff line change
Expand Up @@ -7,8 +7,17 @@
* @flow
*/

import type {ReactPriorityLevel} from './SchedulerWithReactIntegration';

import MAX_SIGNED_31_BIT_INT from './maxSigned31BitInt';

import {
ImmediatePriority,
UserBlockingPriority,
NormalPriority,
IdlePriority,
} from './SchedulerWithReactIntegration';

export type ExpirationTime = number;

export const NoWork = 0;
Expand Down Expand Up @@ -46,6 +55,8 @@ function computeExpirationBucket(
);
}

// TODO: This corresponds to Scheduler's NormalPriority, not LowPriority. Update
// the names to reflect.
export const LOW_PRIORITY_EXPIRATION = 5000;
export const LOW_PRIORITY_BATCH_SIZE = 250;

Expand Down Expand Up @@ -80,3 +91,31 @@ export function computeInteractiveExpiration(currentTime: ExpirationTime) {
HIGH_PRIORITY_BATCH_SIZE,
);
}

export function inferPriorityFromExpirationTime(
currentTime: ExpirationTime,
expirationTime: ExpirationTime,
): ReactPriorityLevel {
if (expirationTime === Sync) {
return ImmediatePriority;
}
if (expirationTime === Never) {
return IdlePriority;
}
const msUntil =
msToExpirationTime(expirationTime) - msToExpirationTime(currentTime);
if (msUntil <= 0) {
return ImmediatePriority;
}
if (msUntil <= HIGH_PRIORITY_EXPIRATION) {
return UserBlockingPriority;
}
if (msUntil <= LOW_PRIORITY_EXPIRATION) {
return NormalPriority;
}

// TODO: Handle LowPriority

// Assume anything lower has idle priority
return IdlePriority;
}
2 changes: 0 additions & 2 deletions packages/react-reconciler/src/ReactFiberReconciler.js
Original file line number Diff line number Diff line change
Expand Up @@ -43,7 +43,6 @@ import {
requestCurrentTime,
computeExpirationForFiber,
scheduleWork,
requestWork,
flushRoot,
batchedUpdates,
unbatchedUpdates,
Expand Down Expand Up @@ -300,7 +299,6 @@ export function updateContainer(

export {
flushRoot,
requestWork,
computeUniqueAsyncExpiration,
batchedUpdates,
unbatchedUpdates,
Expand Down
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