Do not force django.contrib.* dependencies (#535)

* Do not force django.contrib.* dependencies

Fixes #428.
Fixes #534.

* Add one more test with contenttypes installed, but auth not

mypy_django_plugin/django/context.py

@@ -148,6 +148,8 @@ class DjangoContext:
         raise ValueError("No primary key defined")
 
     def get_expected_types(self, api: TypeChecker, model_cls: Type[Model], *, method: str) -> Dict[str, MypyType]:
+        contenttypes_in_apps = self.apps_registry.is_installed("django.contrib.contenttypes")
+        if contenttypes_in_apps:
             from django.contrib.contenttypes.fields import GenericForeignKey
 
         expected_types = {}
@@ -192,7 +194,7 @@ class DjangoContext:
 
                     expected_types[field_name] = model_set_type
 
-            elif isinstance(field, GenericForeignKey):
+            elif contenttypes_in_apps and isinstance(field, GenericForeignKey):
                 # it's generic, so cannot set specific model
                 field_name = field.name
                 gfk_info = helpers.lookup_class_typeinfo(api, field.__class__)

mypy_django_plugin/transformers/request.py

@@ -8,6 +8,9 @@ from mypy_django_plugin.lib import helpers
 
 
 def set_auth_user_model_as_type_for_request_user(ctx: AttributeContext, django_context: DjangoContext) -> MypyType:
+    if not django_context.apps_registry.is_installed("django.contrib.auth"):
+        return ctx.default_attr_type
+
     # 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

tests/typecheck/test_request.yml

@@ -27,6 +27,24 @@
             reveal_type(request.user) # N: Revealed type is 'django.contrib.auth.models.User'
     custom_settings: |
         INSTALLED_APPS = ('django.contrib.contenttypes', 'django.contrib.auth')
+-   case: request_object_user_without_auth_and_contenttypes_apps
+    disable_cache: true
+    main: |
+        from django.http.request import HttpRequest
+        request = HttpRequest()
+        reveal_type(request.user) # N: Revealed type is 'Union[django.contrib.auth.base_user.AbstractBaseUser, django.contrib.auth.models.AnonymousUser]'
+        if request.user.is_authenticated:
+            reveal_type(request.user) # N: Revealed type is 'django.contrib.auth.base_user.AbstractBaseUser'
+-   case: request_object_user_without_auth_but_with_contenttypes_apps
+    disable_cache: true
+    main: |
+        from django.http.request import HttpRequest
+        request = HttpRequest()
+        reveal_type(request.user) # N: Revealed type is 'Union[django.contrib.auth.base_user.AbstractBaseUser, django.contrib.auth.models.AnonymousUser]'
+        if request.user.is_authenticated:
+            reveal_type(request.user) # N: Revealed type is 'django.contrib.auth.base_user.AbstractBaseUser'
+    custom_settings: |
+        INSTALLED_APPS = ('django.contrib.contenttypes',)
 -   case: subclass_request_not_changed_user_type
     disable_cache: true
     main: |