Accept a coroutine in web.run_app

[asvetlov]

The proposal allows to execute async IO before creating an application

[samuelcolvin]

How does this differ from on_startup?

Surely too many options will for the default way to run a server will confuse new users?

[asvetlov]

It follows new asyncio API: https://docs.python.org/3.7/library/asyncio-task.html#asyncio.asyncio.run

[webknjaz]

Sounds reasonable, I'd like to see the implementation draft for it.

[asvetlov]

The change is easy:

if asyncio.iscoroutine(app):
    app = await app

in very beginning of run_app function.

Any volunteer?

[webknjaz]

it's say try/except instead

[asvetlov]

try:
     app = await app
except TypeError:
     pass

looks really strange for me

[webknjaz]

but follows EAFP

[asvetlov]

It is not forgiveness/permission problem but overloading accepted types.
In static typed language it should be two functions with the same name but different parameter types.

[webknjaz]

yeah, and there's functools.dispatch() for that it Python

[asvetlov]

singledispatch actually - that's the problem

[chuck1]

would this feature allow you to run the app asynchronously? in other words an async equivalent of the aiohttp.web.run_app function?

[asvetlov]

@chuck1 no. run_app instantiates and closes an event loop instance.

But you can run an app from in a coroutine by three lines of code, 2 for initializing and 1 for shutdown: https://docs.aiohttp.org/en/stable/web_advanced.html#application-runners

[asvetlov]

Done by #2765

[lock]

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[new issue]: https://github.com/aio-libs/aiohttp/issues/new