change get_user to use a protocol requiring a session (#522)

* change get_user to use a protocol requiring a session
define a "_HasSession" protocol, and update contrib.auth.get_user to use it
get_user only requires a session field, and idiomatic django testing frequently calls get_user with a TestClient

* run black

* use union for get_user instead of a protocol

* create tests for get_user typechecking

* properly import test client

django-stubs/contrib/auth/__init__.pyi

@@ -7,12 +7,11 @@ from django.core.handlers.wsgi import WSGIRequest
 from django.db.models.base import Model
 from django.db.models.options import Options
 from django.http.request import HttpRequest
+from django.test.client import Client
 
-from .signals import (
-    user_logged_in as user_logged_in,
-    user_logged_out as user_logged_out,
-    user_login_failed as user_login_failed,
-)
+from .signals import user_logged_in as user_logged_in
+from .signals import user_logged_out as user_logged_out
+from .signals import user_login_failed as user_login_failed
 
 SESSION_KEY: str
 BACKEND_SESSION_KEY: str
@@ -27,7 +26,7 @@ def login(
 ) -> None: ...
 def logout(request: HttpRequest) -> None: ...
 def get_user_model() -> Type[Model]: ...
-def get_user(request: HttpRequest) -> Union[AbstractBaseUser, AnonymousUser]: ...
+def get_user(request: Union[HttpRequest, Client]) -> Union[AbstractBaseUser, AnonymousUser]: ...
 def get_permission_codename(action: str, opts: Options) -> str: ...
 def update_session_auth_hash(request: HttpRequest, user: AbstractBaseUser) -> None: ...
 

django-stubs/views/generic/edit.pyi

@@ -8,7 +8,7 @@ from typing_extensions import Literal
 
 from django.http import HttpRequest, HttpResponse
 
-_FormT = TypeVar('_FormT', bound=BaseForm)
+_FormT = TypeVar("_FormT", bound=BaseForm)
 
 class AbstractFormMixin(ContextMixin):
     initial: Dict[str, Any] = ...

tests/typecheck/contrib/auth/test_misc.yml

@@ -0,0 +1,15 @@
+-   case: test_request_session
+    main: |
+      from django.contrib.auth import get_user
+      from django.contrib.sessions.middleware import SessionMiddleware
+      from django.http import HttpRequest
+
+      request = HttpRequest()
+      SessionMiddleware().process_request(request)
+      get_user(request)
+-   case: test_client_session
+    main: |
+        from django.contrib.auth import get_user
+        from django.test import Client
+
+        get_user(Client())