async/await for twisted ApplicationSession

From the version 16.4 twisted support async/await (py3.5+) https://twistedmatrix.com/documents/current/core/howto/defer-intro.html#coroutines-with-async-await

but it doesn’t work in crossbar (crossbar-0.15, autobahn-0.16.0, py3.5, twisted-16.4.1, txaio-2.5.1):

from autobahn.twisted.wamp import ApplicationSession
from autobahn.wamp.exception import ApplicationError


class AuthenticatorSession(ApplicationSession):
    async def onJoin(self, details):
        async def authenticate(realm, authid, details):
            ticket = details['ticket']
            ....
            return data['role']

        try:
            await self.register(authenticate, 'com.app.authenticate')
            self.log.info("Dynamic authenticator registered")
        except Exception as e:
            raise e

in logs i have warning: ...python3.5/site-packages/twisted/internet/defer.py:587: builtins.RuntimeWarning: coroutine 'onJoin' was never awaited

so, will be fine support this or if this is my fail - add example (re #653)

[oberstet]

Ah, right;) Ok, then as far as I see, there is actually 2 issues here:

1. txaio: add the ensureDeferred support to txaio.as_future
2. AB: actually use it (also in WebSocket code) 😉 as above grep shows, it is only used in onConnect right now, but it should be used in the other hooks as well …

Both can be done without breaking interfaces.

Does that make sense?

[oberstet]

async/await should be fully usable on Py3/Twisted now with Autobahn