Adds DjangoFilterBackend option for filter_backends (#154)

* Support DjangoFilterBackend for filter_backends

* Add django-filter requirement to setup.py

* Redo base filter as protocol

* Add standard BaseFilterBackend as an option

* Try doing model type work on BaseFilterProtocol

* Update generics.pyi

* Add invariant type variable for BaseFilterProtocol

* Add type variable to BaseFilterProtocol

Co-authored-by: Nikita Sobolev <[email protected]>

Author: palfrey

rest_framework-stubs/generics.pyi

@@ -11,6 +11,7 @@ from rest_framework.response import Response
 from rest_framework.serializers import BaseSerializer
 
 _MT_co = TypeVar("_MT_co", bound=Model, covariant=True)
+_MT_inv = TypeVar("_MT_inv", bound=Model)
 
 def get_object_or_404(
     queryset: Union[Type[_MT_co], Manager[_MT_co], QuerySet[_MT_co]], *filter_args: Any, **filter_kwargs: Any
@@ -19,12 +20,19 @@ def get_object_or_404(
 class UsesQuerySet(Protocol[_MT_co]):
     def get_queryset(self) -> QuerySet[_MT_co]: ...
 
+# Can't just use BaseFilterBackend because there's also things like django_filters.rest_framework.DjangoFilterBackend that are
+# valid options but don't extend it
+class BaseFilterProtocol(Protocol[_MT_inv]):
+    def filter_queryset(self, request: Request, queryset: QuerySet[_MT_inv], view: views.APIView) -> QuerySet[_MT_inv]: ...
+    def get_schema_fields(self, view: views.APIView) -> List[Any]: ...
+    def get_schema_operation_parameters(self, view: views.APIView): ...
+
 class GenericAPIView(views.APIView, UsesQuerySet[_MT_co]):
     queryset: Optional[Union[QuerySet[_MT_co], Manager[_MT_co]]] = ...
     serializer_class: Optional[Type[BaseSerializer]] = ...
     lookup_field: str = ...
     lookup_url_kwarg: Optional[str] = ...
-    filter_backends: Sequence[Type[BaseFilterBackend]] = ...
+    filter_backends: Sequence[Union[Type[BaseFilterBackend], Type[BaseFilterProtocol[_MT_co]]]] = ...
     pagination_class: Optional[Type[BasePagination]] = ...
     def get_object(self) -> _MT_co: ...
     def get_serializer(self, *args: Any, **kwargs: Any) -> BaseSerializer[_MT_co]: ...

tests/typecheck/test_filters.yml

@@ -0,0 +1,35 @@
+-   case: basic_filters
+    main: |
+        from rest_framework.mixins import CreateModelMixin
+        from rest_framework.generics import GenericAPIView
+        from rest_framework.serializers import BaseSerializer, ModelSerializer
+        from rest_framework.filters import OrderingFilter
+        from django.db.models import Model
+
+        class MyModel(Model):
+            pass
+
+        class MyView(GenericAPIView):
+            filter_backends = [OrderingFilter]
+
+-   case: django_filters
+    main: |
+        from rest_framework.mixins import CreateModelMixin
+        from rest_framework.generics import GenericAPIView
+        from rest_framework.views import APIView
+        from rest_framework.serializers import BaseSerializer, ModelSerializer
+        from django.db.models import Model
+
+        class MyModel(Model):
+            pass
+
+        class MyFilterBackend:
+            def filter_queryset(self, request, queryset, view):
+                pass
+            def get_schema_fields(self, view):
+                pass
+            def get_schema_operation_parameters(self, view):
+                pass
+
+        class MyView(GenericAPIView):
+            filter_backends = [MyFilterBackend]