Argument 2 to "path" has incompatible type "_ASGIApplicationProtocol", with django url patterns

[deronnax]

This code:

# WebSocket URL patterns for chat rooms
websocket_urlpatterns = [
    django.urls.path(r"ws/chat/<int:turnaround_id>/", consumers.ChatConsumer.as_asgi()),
]

triggers this mypy error:

$ poetry run mypy --follow-imports=silent chat/routing.py
chat/routing.py:8: error: Argument 2 to "path" has incompatible type "_ASGIApplicationProtocol"; expected "Callable[..., HttpResponseBase]"  [arg-type]
chat/routing.py:8: note: "_ASGIApplicationProtocol.__call__" has type "Callable[[Arg(HTTPScope | WebSocketScope | LifespanScope, 'scope'), Arg(Callable[[], Awaitable[HTTPRequestEvent | HTTPDisconnectEvent | WebSocketConnectEvent | WebSocketReceiveEvent | WebSocketDisconnectEvent | LifespanStartupEvent | LifespanShutdownEvent]], 'receive'), Arg(Callable[[HTTPResponseStartEvent | HTTPResponseBodyEvent | HTTPResponseTrailersEvent | HTTPServerPushEvent | HTTPDisconnectEvent | WebSocketAcceptEvent | WebSocketSendEvent | WebSocketResponseStartEvent | WebSocketResponseBodyEvent | WebSocketCloseEvent | LifespanStartupCompleteEvent | LifespanStartupFailedEvent | LifespanShutdownCompleteEvent | LifespanShutdownFailedEvent], Awaitable[None]], 'send')], Awaitable[None]]"
Found 1 error in 1 file (checked 1 source file)

reveal type of (django.urls.path) is:

 Revealed type is "Overload(def (route: Union[builtins.str, django.utils.functional._StrPromise], view: def (*Any, **Any) -> django.http.response.HttpResponseBase, kwargs: builtins.dict[builtins.str, Any] =, name: builtins.str =) -> django.urls.resolvers.URLPattern, def (route: Union[builtins.str, django.utils.functional._StrPromise], view: def (*Any, **Any) -> typing.Coroutine[Any, Any, django.http.response.HttpResponseBase], kwargs: builtins.dict[builtins.str, Any] =, name: builtins.str =) -> django.urls.resolvers.URLPattern, def (route: Union[builtins.str, django.utils.functional._StrPromise], view: tuple[typing.Sequence[Union[django.urls.resolvers.URLResolver, django.urls.resolvers.URLPattern]], Union[builtins.str, None], Union[builtins.str, None]], kwargs: builtins.dict[builtins.str, Any] =, name: builtins.str =) -> django.urls.resolvers.URLResolver, def (route: Union[builtins.str, django.utils.functional._StrPromise], view: typing.Sequence[Union[django.urls.resolvers.URLResolver, builtins.str]], kwargs: builtins.dict[builtins.str, Any] =, name: builtins.str =) -> django.urls.resolvers.URLResolver)"

I don't know much about typing, I hope I gave all the informations you need. I am available for more information if needed.

[huynguyengl99]

Hi @deronnax, for this one, I’m afraid you’ll need to use the comment # type: ignore[arg-type] due to the incompatible type of Django’s path function when used with the as_asgi function from Django Channels. I’ve rewritten the path function in another package and will let you know when it’s ready to use, so just ignore it for now.

[deronnax]

OK, duly noted. Keep me updated

[deronnax]

I'm curious, where is this new typing happening (if it's publicly accessible). Also: why not fix current typing rather than go with a new package?

[huynguyengl99]

Hi @deronnax, initially I created this package because Django Channels does not have plans to provide official type annotations, following Django's current approach. I created this package to have typing support for myself (and others who want to use static type checkers). You can read my full proposal to introduce type annotations to Django Channels at django/channels#2155.

After that, I worked on the popular repo https://github.com/python/typeshed to create type annotations under that well-known repository, so others can continue the work in the future if I cannot maintain it. This work was done in PR python/typeshed#13939, which received feedback from Django and django-stubs core members. If the PR is accepted, we will have official types for Channels as types-channels on PyPI.

For now, while that PR is under review, I will update this package (published as channels-stubs) to serve as an alternative. The main purpose of this stubs/types package is to support another extension package I'm creating for Channels called Chanx, which requires some types from Channels, so I created the Channels types first.

For Chanx, you can check it out at https://pypi.org/project/chanx/. It has a fix for the problem you described by using from chanx.routing import include, path, re_path instead of the original django.urls, and includes additional extensions and features that are missing from Channels. However, I'm still developing it and consider it to be in beta mode. I will do more testing and bug fixes before making an official release (version 1+) when everything is stable.