Errors sometimes not rethrown

Been tracking down this tricky bug that was causing some real-world pain 😢

RxJS version: 5.3.1 & 5.4.3

Code to reproduce:

Runnable version here.

Observable.of(0, Scheduler.async)
  .mergeMap(() =>
    Observable.combineLatest(Observable.of(0))
  )
  .subscribe(() => { throw new Error('uh oh'); });

Expected behavior:

Error is re-thrown asynchronously and can be handled by normal uncaught exception means. (window.onerror, uncaughtException).

Actual behavior:

Error gets swallowed.

Additional information:

combineLatest seems to be involved here—if you get rid of it, the example behaves as expected.

[matthewwithanm]

The TC39 observable discussions about errors are super interesting and important but can we keep this particular issue about RxJS 5? The current behavior is inconsistent, surprising, and a real source of pain. 😞

[shakyShane]

Would anyone happen to know how this is not considered a show-stopper given it’s so easy to reproduce?

https://jsbin.com/ribeyeyolo/edit?html,js,console