bug(LiveAnnouncer): not resolving promises

[Makatumba]

Description

Some LiveAnnouncer.announce('message') promises called more than once in sequence (with a delay < 100 ms) or in parallel are not resolved.

Reproduction

Use StackBlitz to reproduce your issue:
https://stackblitz.com/edit/angular-ivy-xn9hkc

Call LiveAnnouncer.announce('message') more than once in sequence (with a delay < 100 ms) or parallel.

Expected Behavior

All announce promises are either resolved or rejected.

Actual Behavior

Only the last announce promise is resolved. All promises before are never resolved.

Environment

• Angular: 13.3.0
• CDK/Material: 13.3.1
• Browser(s): Chrome Version 99.0.4844.51
• Operating System (e.g. Windows, macOS, Ubuntu): Windows

[Makatumba]

Implemented workaround:

Provide a fix service as LiveAnnouncer in app.module.ts

@NgModule({
  providers: [
    {provide: LiveAnnouncer, useClass: LiveAnnouncerFixService},
  ],
  bootstrap: [AppComponent],
})
export class AppModule {}

Extend LiveAnnouncer in LiveAnnouncerFixService

import { LiveAnnouncer } from '@angular/cdk/a11y';

export class LiveAnnouncerFixService extends LiveAnnouncer {
  private previousAnnouncementResolver: (value: PromiseLike<void> | void) => void = () => {};

  async announce(message: string, ...args: any[]): Promise<void> {
    let resolved = false;
    this.previousAnnouncementResolver();

    const promise = new Promise<void>(async (resolve) => {
      this.previousAnnouncementResolver = resolve;
      await this.superAnnounce(message, ...args);
      resolved = true;
      resolve();
    });

    setTimeout(() => {
      if (!resolved) {
        this.previousAnnouncementResolver();
      }
    }, 150);

    return promise;
  }

  private superAnnounce(message, ...args) {
    return super.announce(message, ...args);
  }
}

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