Make fromPromise support promise cancellation?

[felixfbecker]

Many non-standard promise implementations support a promise.cancel() method that cancels the promise:

• WinJS (used in Visual Studio Code)
• Angular 1 ($timeout has cancel())
• Bluebird (if enabled)

The only way to currently convert these to Observables is to write by hand:

return new Observable(subscriber => {
  const promise = foo();
  Observable.fromPromise(promise).subscribe(subscriber);
  return () => promise.cancel();
})

Would there be any downside to have PromiseObservable check if the promise has a cancel method, and if present, invoke it on unsubscription?

[staltz]

I think this is a good idea to consider.

[MychaelZ]

How is this not supported?

[felixfbecker]

I have since changed my opinion on this. The standard way to cancel Promises in JS is AbortSignal now. Angular 1, WinJS and Bluebird are rarely used anymore.

[kwonoj]

Closing as core team trying to follow spec complaint abortsignal.