Since 3.8.0 ApplicationCommunicator cannot be constructed in a synchronous context

[riconnon]

#367 changed the initialisation of the task in ApplicationCommunicator from using asyncio.ensure_future to using asyncio.create_task

While is is generally a positive change and use of asyncio.create_task is generally preferred over low-level primitives like asyncio.ensure_future this has the side effect that, since asyncio.create_task uses asyncio.get_running_loop under the hood where asyncio.ensure_future used asyncio.get_event_loop, an ApplicationCommunicator can no longer be constructed outside of a coroutine or callback

In my test suite I'm using unittest with synchronous test functions and I have code to explicitly manage event loops and configure them for use using asyncio.set_event_loop

I've been able to workaround this using code like the following:

def _task():
    return ApplicationCommunicator(*args, **kwargs)
task = loop.create_task(_task())
while not task.done():
    pass
return task.result()

I wonder if this code could, instead, be calling asyncio.get_event_loop and calling loop.create_task instead of asyncio.create_task so that it works correctly in a synchronous context with an assigned event loop.

[graingert]

'asyncio.get_event_loop' is deprecated

perhaps we could make ApplicationCommunicator lazily bind the loop

[riconnon]

@graingert per the docs:

Deprecated since version 3.12: Deprecation warning is emitted if there is no current event loop. In some future Python release this will become an error.

The function is not deprecated but the behaviour of calling it when there is no current event loop is.

However, your idea of lazy binding does seem like it could work well either way.

[graingert]

in 3.14 it's deprecated, along with the whole policy system and set_event_loop etc.

edit: it got undeprecated this morning