hunk.code_window:         messages.push({ frame: this.frame - outerFrame, notification: errorNotification(error) });
         },
         () => {
           messages.push({ frame: this.frame - outerFrame, notification: COMPLETE_NOTIFICATION });
  
hunk.labels: keep keep replace keep
hunk.after_edit:       complete: () => {
  
hunk.file_path: src/internal/testing/TestScheduler.ts
hunk.type: replace
file: import { Observable } from './Observable';
  import { EmptyError } from './util/EmptyError';
  import { SafeSubscriber } from './Subscriber';
  
  export interface FirstValueFromConfig<T> {
    defaultValue: T;
  }
  
  export function firstValueFrom<T, D>(source: Observable<T>, config: FirstValueFromConfig<D>): Promise<T | D>;
  export function firstValueFrom<T>(source: Observable<T>): Promise<T>;
  
  /**
   * Converts an observable to a promise by subscribing to the observable,
   * and returning a promise that will resolve as soon as the first value
   * arrives from the observable. The subscription will then be closed.
   *
   * If the observable stream completes before any values were emitted, the
   * returned promise will reject with {@link EmptyError} or will resolve
   * with the default value if a default was specified.
   *
   * If the observable stream emits an error, the returned promise will reject
   * with that error.
   *
   * **WARNING**: Only use this with observables you *know* will emit at least one value,
   * *OR* complete. If the source observable does not emit one value or complete, you will
   * end up with a promise that is hung up, and potentially all of the state of an
   * async function hanging out in memory. To avoid this situation, look into adding
   * something like {@link timeout}, {@link take}, {@link takeWhile}, or {@link takeUntil}
   * amongst others.
   *
   * ## Example
   *
   * Wait for the first value from a stream and emit it from a promise in
   * an async function
   *
   * ```ts
   * import { interval, firstValueFrom } from 'rxjs';
   *
   * async function execute() {
   *   const source$ = interval(2000);
   *   const firstNumber = await firstValueFrom(source$);
   *   console.log(`The first number is ${ firstNumber }`);
   * }
   *
   * execute();
   *
   * // Expected output:
   * // 'The first number is 0'
   * ```
   *
   * @see {@link lastValueFrom}
   *
   * @param source the observable to convert to a promise
   * @param config a configuration object to define the `defaultValue` to use if the source completes without emitting a value
   */
  export function firstValueFrom<T, D>(source: Observable<T>, config?: FirstValueFromConfig<D>): Promise<T | D> {
    const hasConfig = typeof config === 'object';
    return new Promise<T | D>((resolve, reject) => {
      const subscriber = new SafeSubscriber<T>({
        next: (value) => {
          resolve(value);
          subscriber.unsubscribe();
        },
        error: reject,
        complete: () => {
          if (hasConfig) {
            resolve(config!.defaultValue);
          } else {
            reject(new EmptyError());
          }
        },
      });
      source.subscribe(subscriber);
    });
  }
  