denoland-deno/ext/web/03_abort_signal.js

// Copyright 2018-2022 the Deno authors. All rights reserved. MIT license.
"use strict";

// @ts-check
/// <reference path="../../core/internal.d.ts" />

((window) => {
  const webidl = window.__bootstrap.webidl;
  const { Event, setIsTrusted, defineEventHandler } = window.__bootstrap.event;
  const { EventTarget, listenerCount } = window.__bootstrap.eventTarget;
  const {
    SafeArrayIterator,
    SafeSetIterator,
    Set,
    SetPrototypeAdd,
    SetPrototypeDelete,
    Symbol,
    TypeError,
  } = window.__bootstrap.primordials;
  const { setTimeout, refTimer, unrefTimer } = window.__bootstrap.timers;

  const add = Symbol("[[add]]");
  const signalAbort = Symbol("[[signalAbort]]");
  const remove = Symbol("[[remove]]");
  const abortReason = Symbol("[[abortReason]]");
  const abortAlgos = Symbol("[[abortAlgos]]");
  const signal = Symbol("[[signal]]");
  const timerId = Symbol("[[timerId]]");

  const illegalConstructorKey = Symbol("illegalConstructorKey");

  class AbortSignal extends EventTarget {
    static abort(reason = undefined) {
      if (reason !== undefined) {
        reason = webidl.converters.any(reason);
      }
      const signal = new AbortSignal(illegalConstructorKey);
      signal[signalAbort](reason);
      return signal;
    }

    static timeout(millis) {
      const prefix = "Failed to call 'AbortSignal.timeout'";
      webidl.requiredArguments(arguments.length, 1, { prefix });
      millis = webidl.converters["unsigned long long"](millis, {
        enforceRange: true,
      });

      const signal = new AbortSignal(illegalConstructorKey);
      signal[timerId] = setTimeout(
        () => {
          signal[timerId] = null;
          signal[signalAbort](
            new DOMException("Signal timed out.", "TimeoutError"),
          );
        },
        millis,
      );
      unrefTimer(signal[timerId]);
      return signal;
    }

    [add](algorithm) {
      if (this.aborted) {
        return;
      }
      if (this[abortAlgos] === null) {
        this[abortAlgos] = new Set();
      }
      SetPrototypeAdd(this[abortAlgos], algorithm);
    }

    [signalAbort](
      reason = new DOMException("The signal has been aborted", "AbortError"),
    ) {
      if (this.aborted) {
        return;
      }
      this[abortReason] = reason;
      if (this[abortAlgos] !== null) {
        for (const algorithm of new SafeSetIterator(this[abortAlgos])) {
          algorithm();
        }
        this[abortAlgos] = null;
      }
      const event = new Event("abort");
      setIsTrusted(event, true);
      this.dispatchEvent(event);
    }

    [remove](algorithm) {
      this[abortAlgos] && SetPrototypeDelete(this[abortAlgos], algorithm);
    }

    constructor(key = null) {
      if (key != illegalConstructorKey) {
        throw new TypeError("Illegal constructor.");
      }
      super();
      this[abortReason] = undefined;
      this[abortAlgos] = null;
      this[timerId] = null;
      this[webidl.brand] = webidl.brand;
    }

    get aborted() {
      webidl.assertBranded(this, AbortSignalPrototype);
      return this[abortReason] !== undefined;
    }

    get reason() {
      webidl.assertBranded(this, AbortSignalPrototype);
      return this[abortReason];
    }

    throwIfAborted() {
      webidl.assertBranded(this, AbortSignalPrototype);
      if (this[abortReason] !== undefined) {
        throw this[abortReason];
      }
    }

    // `addEventListener` and `removeEventListener` have to be overriden in
    // order to have the timer block the event loop while there are listeners.
    // `[add]` and `[remove]` don't ref and unref the timer because they can
    // only be used by Deno internals, which use it to essentially cancel async
    // ops which would block the event loop.
    addEventListener(...args) {
      super.addEventListener(...new SafeArrayIterator(args));
      if (this[timerId] !== null && listenerCount(this, "abort") > 0) {
        refTimer(this[timerId]);
      }
    }

    removeEventListener(...args) {
      super.removeEventListener(...new SafeArrayIterator(args));
      if (this[timerId] !== null && listenerCount(this, "abort") === 0) {
        unrefTimer(this[timerId]);
      }
    }
  }
  defineEventHandler(AbortSignal.prototype, "abort");

  webidl.configurePrototype(AbortSignal);
  const AbortSignalPrototype = AbortSignal.prototype;

  class AbortController {
    [signal] = new AbortSignal(illegalConstructorKey);

    constructor() {
      this[webidl.brand] = webidl.brand;
    }

    get signal() {
      webidl.assertBranded(this, AbortControllerPrototype);
      return this[signal];
    }

    abort(reason) {
      webidl.assertBranded(this, AbortControllerPrototype);
      this[signal][signalAbort](reason);
    }
  }

  webidl.configurePrototype(AbortController);
  const AbortControllerPrototype = AbortController.prototype;

  webidl.converters["AbortSignal"] = webidl.createInterfaceConverter(
    "AbortSignal",
    AbortSignal.prototype,
  );

  function newSignal() {
    return new AbortSignal(illegalConstructorKey);
  }

  function follow(followingSignal, parentSignal) {
    if (followingSignal.aborted) {
      return;
    }
    if (parentSignal.aborted) {
      followingSignal[signalAbort](parentSignal.reason);
    } else {
      parentSignal[add](() =>
        followingSignal[signalAbort](parentSignal.reason)
      );
    }
  }

  window.__bootstrap.abortSignal = {
    AbortSignal,
    AbortController,
    AbortSignalPrototype,
    add,
    signalAbort,
    remove,
    follow,
    newSignal,
  };
})(this);