b5ed403bc4
When a single resource is preloaded twice in ngtsc, the second request would be recognized as in-flight in which case `undefined` would be returned, which signals to the compilation that is can resume synchronously. The compilation would then proceed immediately and call `load`, only to find out that the request is still in-flight which is not allowed. This commit caches the Promise of the in-flight fetch requests, such that subsequent preload requests can return the corresponding Promise instance. PR Close #27357
63 lines
1.7 KiB
TypeScript
63 lines
1.7 KiB
TypeScript
/**
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* @license
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* Copyright Google Inc. All Rights Reserved.
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*
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* Use of this source code is governed by an MIT-style license that can be
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* found in the LICENSE file at https://angular.io/license
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*/
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import * as fs from 'fs';
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import {ResourceLoader} from './annotations';
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/**
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* `ResourceLoader` which delegates to a `CompilerHost` resource loading method.
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*/
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export class HostResourceLoader implements ResourceLoader {
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private cache = new Map<string, string>();
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private fetching = new Map<string, Promise<void>>();
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constructor(private host: (url: string) => string | Promise<string>) {}
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preload(url: string): Promise<void>|undefined {
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if (this.cache.has(url)) {
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return undefined;
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} else if (this.fetching.has(url)) {
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return this.fetching.get(url);
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}
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const result = this.host(url);
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if (typeof result === 'string') {
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this.cache.set(url, result);
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return undefined;
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} else {
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const fetchCompletion = result.then(str => {
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this.fetching.delete(url);
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this.cache.set(url, str);
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});
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this.fetching.set(url, fetchCompletion);
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return fetchCompletion;
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}
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}
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load(url: string): string {
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if (this.cache.has(url)) {
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return this.cache.get(url) !;
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}
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const result = this.host(url);
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if (typeof result !== 'string') {
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throw new Error(`HostResourceLoader: host(${url}) returned a Promise`);
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}
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this.cache.set(url, result);
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return result;
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}
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}
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/**
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* `ResourceLoader` which directly uses the filesystem to resolve resources synchronously.
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*/
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export class FileResourceLoader implements ResourceLoader {
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load(url: string): string { return fs.readFileSync(url, 'utf8'); }
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}
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