hunk.code_window:         observer.error(err);
         }
         const subscription = self.subscribe(
           (x) => {
             try {
               if (messageFilter(x)) {
                 observer.next(x);
               }
  
hunk.labels: keep keep keep replace replace keep keep keep keep
hunk.after_edit:       const subscription = self.subscribe({
           next: (x) => {
  
hunk.file_path: src/internal/observable/dom/WebSocketSubject.ts
hunk.type: replace
file: import { Observable } from '../Observable';
  import { Unsubscribable, ObservableInput, ObservedValueOf } from '../types';
  import { innerFrom } from './innerFrom';
  import { EMPTY } from './empty';
  
  /**
   * Creates an Observable that uses a resource which will be disposed at the same time as the Observable.
   *
   * <span class="informal">Use it when you catch yourself cleaning up after an Observable.</span>
   *
   * `using` is a factory operator, which accepts two functions. First function returns a disposable resource.
   * It can be an arbitrary object that implements `unsubscribe` method. Second function will be injected with
   * that object and should return an Observable. That Observable can use resource object during its execution.
   * Both functions passed to `using` will be called every time someone subscribes - neither an Observable nor
   * resource object will be shared in any way between subscriptions.
   *
   * When Observable returned by `using` is subscribed, Observable returned from the second function will be subscribed
   * as well. All its notifications (nexted values, completion and error events) will be emitted unchanged by the output
   * Observable. If however someone unsubscribes from the Observable or source Observable completes or errors by itself,
   * the `unsubscribe` method on resource object will be called. This can be used to do any necessary clean up, which
   * otherwise would have to be handled by hand. Note that complete or error notifications are not emitted when someone
   * cancels subscription to an Observable via `unsubscribe`, so `using` can be used as a hook, allowing you to make
   * sure that all resources which need to exist during an Observable execution will be disposed at appropriate time.
   *
   * @see {@link defer}
   *
   * @param {function(): ISubscription} resourceFactory A function which creates any resource object
   * that implements `unsubscribe` method.
   * @param {function(resource: ISubscription): Observable<T>} observableFactory A function which
   * creates an Observable, that can use injected resource object.
   * @return {Observable<T>} An Observable that behaves the same as Observable returned by `observableFactory`, but
   * which - when completed, errored or unsubscribed - will also call `unsubscribe` on created resource object.
   */
  export function using<T extends ObservableInput<any>>(
    resourceFactory: () => Unsubscribable | void,
    observableFactory: (resource: Unsubscribable | void) => T | void
  ): Observable<ObservedValueOf<T>> {
    return new Observable<ObservedValueOf<T>>((subscriber) => {
      const resource = resourceFactory();
      const result = observableFactory(resource);
      const source = result ? innerFrom(result) : EMPTY;
      source.subscribe(subscriber);
      return () => {
        // NOTE: Optional chaining did not work here.
        // Related TS Issue: https://github.com/microsoft/TypeScript/issues/40818
        if (resource) {
          resource.unsubscribe();
        }
      };
    });
  }
  