Add GetResponseAsyncCallable? / typing of MiddlewareMixin

[blueyed]

Given the following middleware, type checking fails:

error: Incompatible types in "await" (actual type "HttpResponse", expected type "Awaitable[Any]") [misc]
error: Returning Any from function declared to return "HttpResponse" [no-any-return]

from django.utils.decorators import async_only_middleware
from django.utils.deprecation import GetResponseCallable


@async_only_middleware
def my_middleware(get_response: "GetResponseCallable"):
    async def middleware(request: "HttpRequest") -> "HttpResponse":
        response = await get_response(request)
        # …
        return response
    return middleware

Adding and using AsyncGetResponseCallable fixes this:

diff --git i/django-stubs/utils/deprecation.pyi w/django-stubs/utils/deprecation.pyi
index e15e0ae0..fa5a8d5d 100644
--- i/django-stubs/utils/deprecation.pyi
+++ w/django-stubs/utils/deprecation.pyi
@@ -1,5 +1,5 @@
 from collections.abc import Callable
-from typing import Any, Protocol
+from typing import Any, Awaitable, Protocol

 from django.http.request import HttpRequest
 from django.http.response import HttpResponse
@@ -32,6 +32,9 @@ class DeprecationInstanceCheck(type):
 class GetResponseCallable(Protocol):
     def __call__(self, __request: HttpRequest) -> HttpResponse: ...

+class AsyncGetResponseCallable(Protocol):
+    def __call__(self, __request: HttpRequest) -> Awaitable[HttpResponse]: ...
+
 class MiddlewareMixin:
     get_response: GetResponseCallable
     def __init__(self, get_response: GetResponseCallable = ...) -> None: ...

This could also be handled in GetResponseCallable directly (via union), but would be less explicit then.

Maybe it is also a good idea to add support to it to MiddlewareMixin, where it would be typed based on the input of get_response passed to __init__ then.

[intgr]

Sounds good. I think this type should live in django.utils.decorators, not deprecation.

In fact, the sync_and_async_middleware, sync_only_middleware and async_only_middleware decorators could have a stricter bound to ensure that the decorated function accepts the correct type of argument.

[RyanWalker277]

In fact, the sync_and_async_middleware, sync_only_middleware and async_only_middleware decorators could have a stricter bound to ensure that the decorated function accepts the correct type of argument.

Looking at the definition here

https://github.com/django/django/blob/073b5fd40035759afaebe5c77de5269aee851643/django/utils/decorators.py#LL166-L190C16

sync_and_async_middleware, sync_only_middleware and async_only_middleware being decorators, take in a function and return the same so the type is preserved, hence the current definition looks good to me.

django-stubs/django-stubs/utils/decorators.pyi

Lines 17 to 19 in 04d5696

	def sync_and_async_middleware(func: _CallableType) -> _CallableType: ...
	def sync_only_middleware(func: _CallableType) -> _CallableType: ...
	def async_only_middleware(func: _CallableType) -> _CallableType: ...

Please let me know if I am missing something. I'll raise a PR adding the AsyncGetResponseCallable stub after this.

[intgr]

Huh? I think the #1425 PR is incomplete.

AsyncGetResponseCallable was added, but was not used anywhere. This isn't something that exists in Django, but the point was to use it to typehint Django's decorators, no?

[intgr]

• Fixed in Type django.utils.* against Django 4.2 #1575