react-native/Libraries/Performance/PureComponentDebug.js

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/**
* Copyright (c) 2013-present, Facebook, Inc.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*
* @flow
* @format
*/
'use strict';
const React = require('React');
opaque type DoNotCommitUsageOfPureComponentDebug = {};
/**
* Identifies which prop or state changes triggered a re-render of a PureComponent. Usage:
*
* Change `extends React.PureComponent` to `extends PureComponentDebug` or inject it
* everywhere by putting this line in your app setup:
*
* React.PureComponent = require('PureComponentDebug');
*
* Should only be used for local testing, and will trigger a flow failure if you try to
* commit any usages.
*/
class PureComponentDebug<
P: DoNotCommitUsageOfPureComponentDebug,
S: ?Object = void,
> extends React.Component<P, S> {
shouldComponentUpdate(nextProps: P, nextState: S): boolean {
const tag = this.constructor.name;
let ret = false;
const prevPropsKeys = Object.keys(this.props);
const nextPropsKeys = Object.keys(nextProps);
if (prevPropsKeys.length !== nextPropsKeys.length) {
ret = true;
console.warn(
'PureComponentDebug: different prop keys',
tag,
prevPropsKeys.filter(key => !nextPropsKeys.includes(key)),
nextPropsKeys.filter(key => !prevPropsKeys.includes(key)),
);
}
const prevStateKeys = Object.keys(this.state || {});
const nextStateKeys = Object.keys(nextState || {});
if (prevStateKeys.length !== nextStateKeys.length) {
ret = true;
console.warn(
'PureComponentDebug: different state keys',
tag,
prevStateKeys.filter(key => !nextStateKeys.includes(key)),
nextStateKeys.filter(key => !prevStateKeys.includes(key)),
);
}
for (const key in this.props) {
if (this.props[key] !== nextProps[key]) {
ret = true;
console.warn('PureComponentDebug: different prop values', tag, key);
}
}
for (const key in this.state) {
if (this.state[key] !== (nextState || {})[key]) {
ret = true;
console.warn('PureComponentDebug: different state values', tag, key);
}
}
return ret;
}
}
module.exports = PureComponentDebug;