Implement on top of concurrent.futures

[wmertens]

I have tried to use aplus, but I couldn't make it run the error handler when an exception occurred such as a typo in the called code.

I then switched to concurrent.futures (the backported one) and that works fine for exceptions, but I miss the Promises/A+ interface, especially being able to transparently return a new promise as the result of a promise.

[xogeny]

Could you be a bit more specific about what you'd like aplus to do? A test case would be great. I suspect it can be done (and still satisfy the A+ spec).

[xogeny]

And implementing on top of concurrent.futures is probably a good idea. I just don't know much about it. The problem is that Python doesn't really lend itself so well to this kind of thing without a standard way of dealing with queueing of work to be done.

[wmertens]

Well, I tried to use aplus.background(lambda: somefunction(foo)).then(...) in various ways, but code errors did not throw exceptions.

When instead I did

   import futures
   executor = futures.ThreadPoolExecutor(max_workers=100)
    f = executor.submit(somefunction, foo)

    def cb(f):
        if f.exception() is not None:
            log.warn("FAIL: {}".format(f.exception()))
        else:
            log.info("Success: {}".format(f.result()))
    f.add_done_callback(cb)

Much uglier than Promises/A+, but it works...

[xogeny]

Thanks for your feedback. I don't expect to have time in the near term to look into this. But I'll keep this open. Perhaps someone else will come along and implement something here. I'd gladly accept a pull request.