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https://github.com/zebrajr/react.git
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d9659e499e
Removes support for using arbitrary promises as the type of a React
element. Instead, promises must be wrapped in React.lazy. This gives us
flexibility later if we need to change the protocol.
The reason is that promises do not provide a way to call their
constructor multiple times. For example:
const promiseForA = new Promise(resolve => {
fetchA(a => resolve(a));
});
Given a reference to `promiseForA`, there's no way to call `fetchA`
again. Calling `then` on the promise doesn't run the constructor again;
it only attaches another listener.
In the future we will likely introduce an API like `React.eager` that
is similar to `lazy` but eagerly calls the constructor. That gives us
the ability to call the constructor multiple times. E.g. to increase
the priority, or to retry if the first operation failed.
43 lines
1011 B
JavaScript
43 lines
1011 B
JavaScript
/**
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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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export type Thenable<T, R> = {
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then(resolve: (T) => mixed, reject: (mixed) => mixed): R,
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};
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export type LazyComponent<T> = {
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$$typeof: Symbol | number,
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_ctor: () => Thenable<T, mixed>,
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_status: 0 | 1 | 2,
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_result: any,
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};
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type ResolvedLazyComponentThenable<T> = {
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$$typeof: Symbol | number,
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_ctor: () => Thenable<T, mixed>,
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_status: 1,
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_result: any,
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};
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export const Pending = 0;
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export const Resolved = 1;
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export const Rejected = 2;
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export function getResultFromResolvedLazyComponent<T>(
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lazyComponent: ResolvedLazyComponentThenable<T>,
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): T {
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return lazyComponent._result;
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}
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export function refineResolvedLazyComponent<T>(
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lazyComponent: LazyComponent<T>,
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): ResolvedLazyComponentThenable<T> | null {
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return lazyComponent._status === Resolved ? lazyComponent._result : null;
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}
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