Here's an example: in Bluebird, cancelation doesn't
propagate upstream. After registering onCancel in a
promise constructor, you have to call .cancel() on
that exact promise object. Calling .cancel() in any
child promise created with .then() or .catch() will
not abort the work, rendering the feature useless for
the most common use case!
True cancelation must propagate upstream, prevent
all pending work, and immediately free resources and memory.
Interesting! This must be new. Bluebird didn't have upstream cancelation last time I checked. Now it might actually be viable. Should update the readme. Thanks!
Unfortunately it's still not viable in the browser due to its size, promises too easily get converted into non-cancelables, and worst of all, async/await forces native promises. If you want cancelable coroutines, you're forced to roll a generator-based implementation such as what Posterus provides.
