Don't change type of HttpRequest.user if type has been changed by subclassing (#415)

* Don't change type of HttpRequest.user if type has been changed by subclassing

* Asserts for typing

* Add tests

* Add description of HttpRequest subclassing to README

* Dummy to rebuild travis

README.md

@@ -90,19 +90,24 @@ You can use strings instead: `'QuerySet[MyModel]'` and `'Manager[MyModel]'`, thi
 
 Currently we [are working](https://github.com/django/django/pull/12405) on providing `__class_getitem__` to the classes where we need them.
 
-### How can I use HttpRequest with custom user model?
+### How can I create a HttpRequest that's guaranteed to have an authenticated user?
 
-You can subclass standard request like so:
+Django's built in `HttpRequest` has the attribute `user` that resolves to the type
+```python
+Union[User, AnonymousUser]
+```
+where `User` is the user model specified by the `AUTH_USER_MODEL` setting.
 
+If you want a `HttpRequest` that you can type-annotate with where you know that the user is authenticated you can subclass the normal `HttpRequest` class like so:
 ```python
 from django.http import HttpRequest
 from my_user_app.models import MyUser
 
-class MyRequest(HttpRequest):
+class AuthenticatedHttpRequest(HttpRequest):
     user: MyUser
 ```
 
-And then use `MyRequest` instead of standard `HttpRequest` inside your project.
+And then use `AuthenticatedHttpRequest` instead of the standard `HttpRequest` for when you know that the user is authenticated. For example in views using the `@login_required` decorator.
 
 
 ## Related projects

mypy_django_plugin/transformers/request.py

@@ -8,6 +8,22 @@ from mypy_django_plugin.lib import helpers
 
 
 def set_auth_user_model_as_type_for_request_user(ctx: AttributeContext, django_context: DjangoContext) -> MypyType:
+    # Imported here because django isn't properly loaded yet when module is loaded
+    from django.contrib.auth.base_user import AbstractBaseUser
+    from django.contrib.auth.models import AnonymousUser
+
+    abstract_base_user_info = helpers.lookup_class_typeinfo(helpers.get_typechecker_api(ctx), AbstractBaseUser)
+    anonymous_user_info = helpers.lookup_class_typeinfo(helpers.get_typechecker_api(ctx), AnonymousUser)
+
+    # This shouldn't be able to happen, as we managed to import the models above.
+    assert abstract_base_user_info is not None
+    assert anonymous_user_info is not None
+
+    if ctx.default_attr_type != UnionType([Instance(abstract_base_user_info, []), Instance(anonymous_user_info, [])]):
+        # Type has been changed from the default in django-stubs.
+        # I.e. HttpRequest has been subclassed and user-type overridden, so let's leave it as is.
+        return ctx.default_attr_type
+
     auth_user_model = django_context.settings.AUTH_USER_MODEL
     user_cls = django_context.apps_registry.get_model(auth_user_model)
     user_info = helpers.lookup_class_typeinfo(helpers.get_typechecker_api(ctx), user_cls)
@@ -15,12 +31,4 @@ def set_auth_user_model_as_type_for_request_user(ctx: AttributeContext, django_c
     if user_info is None:
         return ctx.default_attr_type
 
-    # Imported here because django isn't properly loaded yet when module is loaded
-    from django.contrib.auth.models import AnonymousUser
-
-    anonymous_user_info = helpers.lookup_class_typeinfo(helpers.get_typechecker_api(ctx), AnonymousUser)
-    if anonymous_user_info is None:
-        # This shouldn't be able to happen, as we managed to import the model above...
-        return Instance(user_info, [])
-
     return UnionType([Instance(user_info, []), Instance(anonymous_user_info, [])])

test-data/typecheck/test_request.yml

@@ -27,3 +27,28 @@
             reveal_type(request.user) # N: Revealed type is 'django.contrib.auth.models.User'
     custom_settings: |
         INSTALLED_APPS = ('django.contrib.contenttypes', 'django.contrib.auth')
+-   case: subclass_request_not_changed_user_type
+    disable_cache: true
+    main: |
+        from django.http.request import HttpRequest
+        class MyRequest(HttpRequest):
+            foo: int # Just do something
+
+        request = MyRequest()
+        reveal_type(request.user) # N: Revealed type is 'Union[django.contrib.auth.models.User, django.contrib.auth.models.AnonymousUser]'
+    custom_settings: |
+        INSTALLED_APPS = ('django.contrib.contenttypes', 'django.contrib.auth')
+
+-   case: subclass_request_changed_user_type
+    disable_cache: true
+    main: |
+        from django.http.request import HttpRequest
+        from django.contrib.auth.models import User
+        class MyRequest(HttpRequest):
+            user: User # Override the type of user
+
+        request = MyRequest()
+        reveal_type(request.user) # N: Revealed type is 'django.contrib.auth.models.User'
+    custom_settings: |
+        INSTALLED_APPS = ('django.contrib.contenttypes', 'django.contrib.auth')
+