Cancellation of promise collections about promise HOT 3 CLOSED

Bumped into this a few days ago.

In my opinion, the collection functions should accept an optional argument to define the cancellable behavior, with these possible values:

• NEVER: never cancels upstream promises; this is the default, legacy behavior, to avoid BC.
• ON_CANCEL: try and cancel upstream promises when the downstream promise is cancelled.
• ON_REJECT: try and cancel upstream promises when the downstream promise is cancelled or rejected.
• ALWAYS: always try and cancel upstream promises.

Here are the effect of ALWAYS behavior with different functions when the downstream promise is fulfilled:

• all, reduce, map: does nothing,
• race, some, any: cancels all upstream promises that haven't been fulfilled or rejected.

I'm not sure how to handle resolve() when it generates an ExtendedPromiseInterface for an existing Promise.

from promise.

Implemented in #36

from promise.

Released in v2.3.0.

from promise.