152 lines
4.0 KiB
TypeScript
152 lines
4.0 KiB
TypeScript
// Copyright 2018-2023 the Deno authors. All rights reserved. MIT license.
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// This module is browser compatible.
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import { deferred } from "./deferred.ts";
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/**
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* Make Promise abortable with the given signal.
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*
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* @example
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* ```typescript
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* import { abortable } from "https://deno.land/std@$STD_VERSION/async/mod.ts";
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* import { delay } from "https://deno.land/std@$STD_VERSION/async/mod.ts";
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*
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* const p = delay(1000);
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* const c = new AbortController();
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* setTimeout(() => c.abort(), 100);
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*
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* // Below throws `DOMException` after 100 ms
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* await abortable(p, c.signal);
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* ```
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*/
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export function abortable<T>(p: Promise<T>, signal: AbortSignal): Promise<T>;
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/**
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* Make AsyncIterable abortable with the given signal.
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*
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* @example
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* ```typescript
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* import { abortable } from "https://deno.land/std@$STD_VERSION/async/mod.ts";
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* import { delay } from "https://deno.land/std@$STD_VERSION/async/mod.ts";
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*
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* const p = async function* () {
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* yield "Hello";
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* await delay(1000);
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* yield "World";
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* };
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* const c = new AbortController();
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* setTimeout(() => c.abort(), 100);
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*
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* // Below throws `DOMException` after 100 ms
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* // and items become `["Hello"]`
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* const items: string[] = [];
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* for await (const item of abortable(p(), c.signal)) {
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* items.push(item);
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* }
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* ```
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*/
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export function abortable<T>(
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p: AsyncIterable<T>,
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signal: AbortSignal,
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): AsyncGenerator<T>;
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export function abortable<T>(
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p: Promise<T> | AsyncIterable<T>,
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signal: AbortSignal,
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): Promise<T> | AsyncIterable<T> {
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if (p instanceof Promise) {
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return abortablePromise(p, signal);
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} else {
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return abortableAsyncIterable(p, signal);
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}
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}
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/**
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* Make Promise abortable with the given signal.
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*
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* @example
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* ```typescript
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* import { abortablePromise } from "https://deno.land/std@$STD_VERSION/async/mod.ts";
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*
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* const request = fetch("https://example.com");
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*
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* const c = new AbortController();
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* setTimeout(() => c.abort(), 100);
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*
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* const p = abortablePromise(request, c.signal);
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*
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* // The below throws if the request didn't resolve in 100ms
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* await p;
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* ```
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*/
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export function abortablePromise<T>(
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p: Promise<T>,
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signal: AbortSignal,
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): Promise<T> {
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if (signal.aborted) {
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return Promise.reject(createAbortError(signal.reason));
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}
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const waiter = deferred<never>();
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const abort = () => waiter.reject(createAbortError(signal.reason));
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signal.addEventListener("abort", abort, { once: true });
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return Promise.race([
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waiter,
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p.finally(() => {
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signal.removeEventListener("abort", abort);
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}),
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]);
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}
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/**
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* Make AsyncIterable abortable with the given signal.
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*
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* @example
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* ```typescript
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* import { abortableAsyncIterable } from "https://deno.land/std@$STD_VERSION/async/mod.ts";
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* import { delay } from "https://deno.land/std@$STD_VERSION/async/mod.ts";
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*
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* const p = async function* () {
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* yield "Hello";
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* await delay(1000);
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* yield "World";
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* };
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* const c = new AbortController();
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* setTimeout(() => c.abort(), 100);
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*
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* // Below throws `DOMException` after 100 ms
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* // and items become `["Hello"]`
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* const items: string[] = [];
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* for await (const item of abortableAsyncIterable(p(), c.signal)) {
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* items.push(item);
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* }
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* ```
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*/
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export async function* abortableAsyncIterable<T>(
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p: AsyncIterable<T>,
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signal: AbortSignal,
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): AsyncGenerator<T> {
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if (signal.aborted) {
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throw createAbortError(signal.reason);
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}
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const waiter = deferred<never>();
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const abort = () => waiter.reject(createAbortError(signal.reason));
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signal.addEventListener("abort", abort, { once: true });
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const it = p[Symbol.asyncIterator]();
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while (true) {
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const { done, value } = await Promise.race([waiter, it.next()]);
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if (done) {
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signal.removeEventListener("abort", abort);
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return;
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}
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yield value;
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}
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}
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// This `reason` comes from `AbortSignal` thus must be `any`.
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// deno-lint-ignore no-explicit-any
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function createAbortError(reason?: any): DOMException {
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return new DOMException(
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reason ? `Aborted: ${reason}` : "Aborted",
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"AbortError",
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);
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}
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