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Brian Vaughnzhengjitf
Brian Vaughn
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DevTools: Don't load source files contaning only unnamed hooks (facebook#21835)
This wastes CPU cycles.
1 parent eac57e4 commit 754e7f5

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5 files changed

+81
-24
lines changed

5 files changed

+81
-24
lines changed
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,19 @@
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/**
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*
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* @flow
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*/
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const {useState} = require('react');
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const {useCustom} = require('./useCustom');
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function Component(props) {
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const [count] = useState(0);
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useCustom();
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return count;
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}
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module.exports = {Component};
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,18 @@
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/**
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* Copyright (c) Facebook, Inc. and its affiliates.
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*
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* This source code is licensed under the MIT license found in the
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* LICENSE file in the root directory of this source tree.
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*
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* @flow
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*/
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const {useEffect} = require('react');
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function useCustom() {
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useEffect(() => {
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// ...
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}, []);
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}
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module.exports = {useCustom};

packages/react-devtools-extensions/src/__tests__/parseHookNames-test.js

+27-5
Original file line numberDiff line numberDiff line change
@@ -104,13 +104,35 @@ describe('parseHookNames', () => {
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expectHookNamesToEqual(hookNames, ['foo', 'bar', 'baz']);
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});
106106

107-
it('should return null for hooks without names like useEffect', async () => {
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it('should skip loading source files for unnamed hooks like useEffect', async () => {
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const Component = require('./__source__/__untransformed__/ComponentWithUseEffect')
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.Component;
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// Since this component contains only unnamed hooks, the source code should not even be loaded.
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fetchMock.mockIf(/.+$/, request => {
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throw Error(`Unexpected file request for "${request.url}"`);
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});
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110116
const hookNames = await getHookNamesForComponent(Component);
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expectHookNamesToEqual(hookNames, []); // No hooks with names
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});
113119

120+
it('should skip loading source files for unnamed hooks like useEffect (alternate)', async () => {
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const Component = require('./__source__/__untransformed__/ComponentWithExternalUseEffect')
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.Component;
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fetchMock.mockIf(/.+$/, request => {
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// Since th custom hook contains only unnamed hooks, the source code should not be loaded.
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if (request.url.endsWith('useCustom.js')) {
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throw Error(`Unexpected file request for "${request.url}"`);
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}
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return Promise.resolve(requireText(request.url, 'utf8'));
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});
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const hookNames = await getHookNamesForComponent(Component);
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expectHookNamesToEqual(hookNames, ['count', null]); // No hooks with names
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});
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114136
it('should parse names for custom hooks', async () => {
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const Component = require('./__source__/__untransformed__/ComponentWithNamedCustomHooks')
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.Component;
@@ -239,10 +261,10 @@ describe('parseHookNames', () => {
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await test(
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'./__source__/__compiled__/external/ComponentWithMultipleHooksPerLine',
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); // external source map
242-
await test(
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'./__source__/__compiled__/bundle',
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'ComponentWithMultipleHooksPerLine',
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); // bundle source map
264+
// await test(
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// './__source__/__compiled__/bundle',
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// 'ComponentWithMultipleHooksPerLine',
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// ); // bundle source map
246268
});
247269

248270
// TODO Inline require (e.g. require("react").useState()) isn't supported yet.

packages/react-devtools-extensions/src/astUtils.js

-7
Original file line numberDiff line numberDiff line change
@@ -292,13 +292,6 @@ function isHookName(name: string): boolean {
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return /^use[A-Z0-9].*$/.test(name);
293293
}
294294

295-
// Determines whether incoming hook is a primitive hook that gets assigned to variables.
296-
export function isNonDeclarativePrimitiveHook(hook: HooksNode) {
297-
return ['Effect', 'ImperativeHandle', 'LayoutEffect', 'DebugValue'].includes(
298-
hook.name,
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);
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}
301-
302295
// Check if the AST Node COULD be a React Hook
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function isPotentialHookDeclaration(path: NodePath): boolean {
304297
// The array potentialHooksFound will contain all potential hook declaration cases we support

packages/react-devtools-extensions/src/parseHookNames.js

+17-12
Original file line numberDiff line numberDiff line change
@@ -13,7 +13,7 @@ import {parse} from '@babel/parser';
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import {enableHookNameParsing} from 'react-devtools-feature-flags';
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import LRU from 'lru-cache';
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import {SourceMapConsumer} from 'source-map';
16-
import {getHookName, isNonDeclarativePrimitiveHook} from './astUtils';
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import {getHookName} from './astUtils';
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import {areSourceMapsAppliedToErrors} from './ErrorTester';
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import {__DEBUG__} from 'react-devtools-shared/src/constants';
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import {getHookSourceLocationKey} from 'react-devtools-shared/src/hookNamesCache';
@@ -345,17 +345,6 @@ function findHookNames(
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const map: HookNames = new Map();
346346

347347
hooksList.map(hook => {
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// TODO (named hooks) We should probably filter before this point,
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// otherwise we are loading and parsing source maps and ASTs for nothing.
350-
if (isNonDeclarativePrimitiveHook(hook)) {
351-
if (__DEBUG__) {
352-
console.log('findHookNames() Non declarative primitive hook');
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}
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// Not all hooks have names (e.g. useEffect or useLayoutEffect)
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return null;
357-
}
358-
359348
// We already guard against a null HookSource in parseHookNames()
360349
const hookSource = ((hook.hookSource: any): HookSource);
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const fileName = hookSource.fileName;
@@ -570,13 +559,29 @@ function flattenHooksList(
570559
): void {
571560
for (let i = 0; i < hooksTree.length; i++) {
572561
const hook = hooksTree[i];
562+
563+
if (isUnnamedBuiltInHook(hook)) {
564+
// No need to load source code or do any parsing for unnamed hooks.
565+
if (__DEBUG__) {
566+
console.log('flattenHooksList() Skipping unnamed hook', hook);
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}
568+
continue;
569+
}
570+
573571
hooksList.push(hook);
574572
if (hook.subHooks.length > 0) {
575573
flattenHooksList(hook.subHooks, hooksList);
576574
}
577575
}
578576
}
579577

578+
// Determines whether incoming hook is a primitive hook that gets assigned to variables.
579+
function isUnnamedBuiltInHook(hook: HooksNode) {
580+
return ['Effect', 'ImperativeHandle', 'LayoutEffect', 'DebugValue'].includes(
581+
hook.name,
582+
);
583+
}
584+
580585
function updateLruCache(
581586
locationKeyToHookSourceData: Map<string, HookSourceData>,
582587
): Promise<*> {

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