run_app has incorrect typing

[iawells]

🐞 Describe the bug

async def _run_app(app: Union[Application, Awaitable[Application]], *,
                   host: Optional[str]=None,

The documentation is a bit woolly:

"host (str) – TCP/IP host or a sequence of hosts for HTTP server. Default is '0.0.0.0' if port has been specified or if path is not supplied."

('(str)' excludes 'None' and excludes 'a sequence of hosts'. Also, I don't think you mean 'sequence' literally.)

But it's clear from reading the code that an iterable of strings is planned for (along with several other types).

I would think you want Optional[Union[str, Iterable[str]]] - though given the following code it's maybe unclear if you think other types are also acceptable.

💡 To Reproduce

Write some code like this and then run it though mypy

from aiohttp.web import run_app

hosts: List[str] = ['a', 'b']

run_app(host=hosts)

💡 Expected behavior

If a list of strings is acceptable, then the attribute is wrong. I'm surprised mypy didn't spot it during CI, actually.

📋 Your version of the Python

$ python --version
Python 3.6.9

📋 Your version of the aiohttp/yarl/multidict distributions

$ python -m pip show aiohttp
Name: aiohttp
Version: 3.6.2

$ python -m pip show multidict
Name: multidict
Version: 4.7.6

$ python -m pip show yarl
Name: yarl
Version: 1.5.1

[WisdomPill]

Hello @iawells !

Nice catch!
Can you open a PR to address the issue?

[WisdomPill]

Otherwise I can step in and do it

[derlih]

@asvetlov shouldn't this issue be closed?

[asvetlov]

Yes, sure!