Implement async filter_queryset method

adrf/generics.py

@@ -31,7 +31,7 @@ async def aget_object(self):
         queryset lookups.  Eg if objects are referenced using multiple
         keyword arguments in the url conf.
         """
-        queryset = self.filter_queryset(self.get_queryset())
+        queryset = await self.afilter_queryset(self.get_queryset())
 
         # Perform the lookup filtering.
         lookup_url_kwarg = self.lookup_url_kwarg or self.lookup_field
@@ -51,6 +51,22 @@ async def aget_object(self):
 
         return obj
 
+    async def afilter_queryset(self, queryset):
+        """
+        Given a queryset, filter it with whichever filter backend is in use.
+        """
+        for backend in list(self.filter_backends):
+            backend_instance = backend()
+            if asyncio.iscoroutinefunction(backend_instance.filter_queryset):
+                queryset = await backend_instance.filter_queryset(
+                    self.request, queryset, self
+                )
+            else:
+                queryset = await sync_to_async(backend_instance.filter_queryset)(
+                    self.request, queryset, self
+                )
+        return queryset
+
     def paginate_queryset(self, queryset):
         """
         Return a single page of results, or `None` if pagination is disabled.

adrf/mixins.py

@@ -35,7 +35,7 @@ class ListModelMixin(mixins.ListModelMixin):
     """
 
     async def alist(self, *args, **kwargs):
-        queryset = self.filter_queryset(self.get_queryset())
+        queryset = await self.afilter_queryset(self.get_queryset())
 
         page = await self.apaginate_queryset(queryset)
         if page is not None: