You provided an invalid object where a stream was expected error in Module Federation environment

Bug Report

Current Behavior

switchMap (and other mapping operators) might not work correctly in Module Federation environment.

Code like:

this
  .getSomeObservable()
  .pipe(
    switchMap(() => this.getOtherObservable()) // switching here causes the error
  ).subscribe()

Will cause : You provided an invalid object where a stream was expected error in Module Federation environment exception

Expected behavior

Mapping operators should work and recognise

Reproduction

I was not able yet to reproduce it with a repo I could publicly push. This is explanation from the app I'm maintaining.

I've migrated one app to MFE Architecture using Module Federation and mysteriously looking error is thrown at runtime:

You provided an invalid object where a stream was expected error. You can provide an Observable, Promise, Array, or Iterable.

The code that causes it looks like this:

this
  .getSomeObservable()
  .pipe(
    switchMap(() => this.getOtherObservable()) // switching here causes the error
  ).subscribe()

However I was pretty sure code was ok...

When analysing stack trace, error originates from:

https://github.com/ReactiveX/rxjs/blob/6.6.7/src/internal/util/subscribeTo.ts

export const subscribeTo = <T>(result: ObservableInput<T>): (subscriber: Subscriber<T>) => Subscription | void => {
  if (!!result && typeof result[Symbol_observable] === 'function') {
    return subscribeToObservable(result as any);
  } else if (isArrayLike(result)) {
    return subscribeToArray(result);
  } else if (isPromise(result)) {
    return subscribeToPromise(result as Promise<any>);
  } else if (!!result && typeof result[Symbol_iterator] === 'function') {
    return subscribeToIterable(result as any);
  } else {
    const value = isObject(result) ? 'an invalid object' : `'${result}'`;
    const msg = `You provided ${value} where a stream was expected.`
      + ' You can provide an Observable, Promise, Array, or Iterable.';
    throw new TypeError(msg);
  }
};

In my case, result is of type BehaviorSubject.

However, when I compared stack trace when app is running in non-federated to federated, the issue is here:

https://github.com/ReactiveX/rxjs/blob/6.6.7/src/internal/innerSubscribe.ts#L110

  if (result instanceof Observable) {
    return result.subscribe(innerSubscriber);
  }

Without module federation, this if is truthy, when I look at prototypes, deeper I can find Observable.

However in federated environment, this expression is falsy.

The good news it that refactoring to:

this
  .getSomeObservable()
  .subscribe(() => this.getOtherObservable().subscribe())

does not throw error any more.

Environment

• RxJS version: 6.6.7
• Build configuration: webpack@5.50.0

Start with src/internal/util/subscribeTo.ts and src/internal/innerSubscribe.ts, then investigate the reported BehaviorSubject case under RxJS 6.6.7 with webpack 5.50 Module Federation. Reproduce the federated and non-federated behavior if possible; done means switchMap and other mapping operators accept the returned observable without the invalid-object error.