Add support for AbortController/AbortSignal (#4757)

cli/js/globals.ts

@@ -2,6 +2,8 @@
 
 import "./lib.deno.shared_globals.d.ts";
 
+import * as abortController from "./web/abort_controller.ts";
+import * as abortSignal from "./web/abort_signal.ts";
 import * as blob from "./web/blob.ts";
 import * as consoleTypes from "./web/console.ts";
 import * as promiseTypes from "./web/promise.ts";
@@ -207,6 +209,8 @@ export const windowOrWorkerGlobalScopeMethods = {
 // Other properties shared between WindowScope and WorkerGlobalScope
 export const windowOrWorkerGlobalScopeProperties = {
   console: writable(new consoleTypes.Console(core.print)),
+  AbortController: nonEnumerable(abortController.AbortControllerImpl),
+  AbortSignal: nonEnumerable(abortSignal.AbortSignalImpl),
   Blob: nonEnumerable(blob.DenoBlob),
   File: nonEnumerable(domFile.DomFileImpl),
   CustomEvent: nonEnumerable(customEvent.CustomEventImpl),

cli/js/lib.deno.shared_globals.d.ts

@@ -1256,6 +1256,16 @@ declare class CustomEvent<T = any> extends Event {
   readonly detail: T;
 }
 
+/** A controller object that allows you to abort one or more DOM requests as and
+ * when desired. */
+declare class AbortController {
+  /** Returns the AbortSignal object associated with this object. */
+  readonly signal: AbortSignal;
+  /** Invoking this method will set this object's AbortSignal's aborted flag and
+   * signal to any observers that the associated activity is to be aborted. */
+  abort(): void;
+}
+
 interface AbortSignalEventMap {
   abort: Event;
 }
@@ -1263,10 +1273,8 @@ interface AbortSignalEventMap {
 /** A signal object that allows you to communicate with a DOM request (such as a
  * Fetch) and abort it if required via an AbortController object. */
 interface AbortSignal extends EventTarget {
-  /**
-   * Returns true if this AbortSignal's AbortController has signaled to abort,
-   * and false otherwise.
-   */
+  /** Returns true if this AbortSignal's AbortController has signaled to abort,
+   * and false otherwise. */
   readonly aborted: boolean;
   onabort: ((this: AbortSignal, ev: Event) => any) | null;
   addEventListener<K extends keyof AbortSignalEventMap>(

cli/js/tests/abort_controller_test.ts

@@ -0,0 +1,56 @@
+import { unitTest, assert, assertEquals } from "./test_util.ts";
+
+unitTest(function basicAbortController() {
+  const controller = new AbortController();
+  assert(controller);
+  const { signal } = controller;
+  assert(signal);
+  assertEquals(signal.aborted, false);
+  controller.abort();
+  assertEquals(signal.aborted, true);
+});
+
+unitTest(function signalCallsOnabort() {
+  const controller = new AbortController();
+  const { signal } = controller;
+  let called = false;
+  signal.onabort = (evt): void => {
+    assert(evt);
+    assertEquals(evt.type, "abort");
+    called = true;
+  };
+  controller.abort();
+  assert(called);
+});
+
+unitTest(function signalEventListener() {
+  const controller = new AbortController();
+  const { signal } = controller;
+  let called = false;
+  signal.addEventListener("abort", function (ev) {
+    assert(this === signal);
+    assertEquals(ev.type, "abort");
+    called = true;
+  });
+  controller.abort();
+  assert(called);
+});
+
+unitTest(function onlyAbortsOnce() {
+  const controller = new AbortController();
+  const { signal } = controller;
+  let called = 0;
+  signal.addEventListener("abort", () => called++);
+  signal.onabort = (): void => {
+    called++;
+  };
+  controller.abort();
+  assertEquals(called, 2);
+  controller.abort();
+  assertEquals(called, 2);
+});
+
+unitTest(function controllerHasProperToString() {
+  const actual = Object.prototype.toString.call(new AbortController());
+  assertEquals(actual, "[object AbortController]");
+});

cli/js/tests/unit_tests.ts

@@ -4,6 +4,7 @@
 //
 // Test runner automatically spawns subprocesses for each required permissions combination.
 
+import "./abort_controller_test.ts";
 import "./blob_test.ts";
 import "./body_test.ts";
 import "./buffer_test.ts";

cli/js/web/abort_controller.ts

@@ -0,0 +1,23 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+import { AbortSignalImpl, signalAbort } from "./abort_signal.ts";
+
+export class AbortControllerImpl implements AbortController {
+  #signal = new AbortSignalImpl();
+
+  get signal(): AbortSignal {
+    return this.#signal;
+  }
+
+  abort(): void {
+    this.#signal[signalAbort]();
+  }
+
+  get [Symbol.toStringTag](): string {
+    return "AbortController";
+  }
+}
+
+Object.defineProperty(AbortControllerImpl, "name", {
+  value: "AbortController",
+  configurable: true,
+});

cli/js/web/abort_signal.ts

@@ -0,0 +1,58 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+import { EventImpl } from "./event.ts";
+import { EventTargetImpl } from "./event_target.ts";
+
+export const add = Symbol("add");
+export const signalAbort = Symbol("signalAbort");
+export const remove = Symbol("remove");
+
+export class AbortSignalImpl extends EventTargetImpl implements AbortSignal {
+  #aborted?: boolean;
+  #abortAlgorithms = new Set<() => void>();
+
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  onabort: ((this: AbortSignal, ev: Event) => any) | null = null;
+
+  [add](algorithm: () => void): void {
+    this.#abortAlgorithms.add(algorithm);
+  }
+
+  [signalAbort](): void {
+    if (this.#aborted) {
+      return;
+    }
+    this.#aborted = true;
+    for (const algorithm of this.#abortAlgorithms) {
+      algorithm();
+    }
+    this.#abortAlgorithms.clear();
+    this.dispatchEvent(new EventImpl("abort"));
+  }
+
+  [remove](algorithm: () => void): void {
+    this.#abortAlgorithms.delete(algorithm);
+  }
+
+  constructor() {
+    super();
+    this.addEventListener("abort", (evt: Event) => {
+      const { onabort } = this;
+      if (typeof onabort === "function") {
+        onabort.call(this, evt);
+      }
+    });
+  }
+
+  get aborted(): boolean {
+    return Boolean(this.#aborted);
+  }
+
+  get [Symbol.toStringTag](): string {
+    return "AbortSignal";
+  }
+}
+
+Object.defineProperty(AbortSignalImpl, "name", {
+  value: "AbortSignal",
+  configurable: true,
+});