Hello,

You're right, explaining the difference between CANCELLED and CANCELLED_AND_NOTIFIED is gong to be hard and might be confusing. I also agree that there is no precedent for storing the history of something, and I don't like either the idea of having a futures factory (that was my first idea).

But, what about using callbacks? it is possible to add done callbacks, why can't we have a list of callbacks attached to each "public" state.

Something like:

Future.append_callback(self, state: "One of PENDING, RUNNING, CANCELLED, FINISHED", fn)