takeUntil unclear on how to coerce type

[keithamus]

takeUntil's IDL is as follows:

interface Observable {
  // takeUntil() can consume promises, iterables, async iterables, and other
  // observables.
  Observable takeUntil(any notifier);
}

However the first thing the spec for takeUntil(notifier) does with notifier, in step 2.3 is:

Subscribe to notifier given notifierObserver and options.

Subscribe assumes the given observer is an Observable. So I think there's a missing step to coerce an any to an Observable. Perhaps this is missing because from(any value) has yet to be specced? Additionally it looks as though Chrome's implementation just expects takeUntil() to recieve an Observable.

---

This is tracked in https://issues.chromium.org/issues/40282760 but I'm bringing it here also.

[domfarolino]

So I think there's a missing step to coerce an any to an Observable. Perhaps this is missing because from(any value) has yet to be specced

Exactly!

Additionally it looks as though Chrome's implementation just expects takeUntil() to recieve an Observable.

Right, we don't use from() + any because it is not finished being implemented for all of the planned coercions yet.