Add close state to finally operator?

@matthewwithanm presented a scenerio here that I think we can address with a non-breaking change to the finally operator.

That is that we could provide, as an argument to finally’s callback, a flag of some sort to declare whether or not it was finalized because of error, complete or unsubscribe.

Strawman:

source$.finally((type: string) => {
  switch(type) {
    case 'complete':
      doThing1();
      break;
    case 'error':
      doThing2();
      break;
    case 'unsubscribe':
      doThing3();
      break;
  }
})

The only additional thing I can think of is additionally providing the error in the event of an error, but I’m not sure how helpful that would be.

Thoughts?

[matthewwithanm]

@martinsik We wound up with basically the same thing. I think you need to wrap your operator body in a defer() though. Otherwise you’re using the same completed and errored variables for every subscription and once one errors they all will.

[martinsik]

@matthewwithanm You’re right, it should be wrapped inside defer.