BaseEventLoop.create_server overload doesn't allow passing host with port=None

[timabroad]

The type stubs for BaseEventLoop.create_server (here) consist over two overloads:

# The first one specifies:
host: str | Sequence[str] | None = None,
port: int = ...,
sock: None = None,

# The second one specifies:
host: None = None,
port: None = None,
sock: socket = ...,

But the first of these causes a typing error if you pass None for the port (pyright playground), despite succeeding at runtime:

import asyncio

async def start():
    loop = asyncio.get_running_loop()

    await loop.create_server(asyncio.Protocol)
    await loop.create_server(asyncio.Protocol, 'localhost')
    await loop.create_server(asyncio.Protocol, 'localhost', 8080)
    await loop.create_server(asyncio.Protocol, 'localhost')
    await loop.create_server(asyncio.Protocol, 'localhost', None) # Argument of type "None" cannot be assigned to parameter "port" of type "int" in function "create_server".

This is documented as being valid as far back as Python 3.9. For some reason the 3.8 and earlier docs don't provide any details for the port parameter, though I'm not aware of any changes.

[srittau]

This doesn't make sense indeed. The reason for the two overloads is probably to ensure that exactly one of host/port and sock are specified. We just need a third overload (..., host: str | Sequence[str], port: int | None = None, ..., sock: None = None, ...) and the need to remove the default to port in the existing overload.

This is also one of the rare cases where having tests seems useful.

PR welcome!

[nightcityblade]

Hi, I'd like to work on this. I'll submit a PR shortly.

[nightcityblade]

I took a closer look at the three version-specific overload sets and won't be able to complete this within my current small-change window. Releasing it for someone else—sorry for the noise.