Handle empty list for href and id in filter

Fix bug where empty list for the pulp_href__in or pulp_id__in filters
return all results instead of no results.

The problem is that when using FilterMethod, django-filter just simply
ignores None and empty set and returns the full list of results:

https://github.com/carltongibson/django-filter/blob/e4a70a667a0bf3882fd44b557bc76583d2c65cd1/django_filters/filters.py#L804-L805

There's no way to update the method to prevent this since this logic
happens before the method is called. Instead, this change moves the
method to the filter and adds a None check.

fixes pulp#4437

CHANGES/4437.bugfix

@@ -0,0 +1,2 @@
+Fixed bug where supplying an empty list for ``pulp_href__in`` or ``pulp_id__in`` would return all
+results instead of none.

pulpcore/filters.py

@@ -124,11 +124,19 @@ def filter(self, qs, value):
 
 
 class IdInFilter(BaseInFilter, filters.UUIDFilter):
-    pass
+    def filter(self, qs, value):
+        if value is None:
+            return qs
+        return qs.filter(pk__in=value)
 
 
 class HREFInFilter(BaseInFilter, filters.CharFilter):
-    pass
+    def filter(self, qs, value):
+        if value is None:
+            return qs
+
+        pks = [extract_pk(href) for href in value]
+        return qs.filter(pk__in=pks)
 
 
 class PulpTypeFilter(filters.ChoiceFilter):
@@ -271,7 +279,7 @@ class BaseFilterSet(filterset.FilterSet):
 
     help_text = {}
     pulp_id__in = IdInFilter(field_name="pk", lookup_expr="in")
-    pulp_href__in = HREFInFilter(field_name="pk", method="filter_pulp_href")
+    pulp_href__in = HREFInFilter(field_name="pk")
     q = ExpressionFilter()
 
     FILTER_DEFAULTS = {
@@ -307,11 +315,6 @@ class BaseFilterSet(filterset.FilterSet):
         "ne": _("not equal to"),
     }
 
-    def filter_pulp_href(self, queryset, name, value):
-        # Convert each href to a pk
-        pks = [extract_pk(href) for href in value]
-        return queryset.filter(pk__in=pks)
-
     @classmethod
     def get_filters(cls):
         filters = super().get_filters()

pulpcore/tests/functional/api/test_filter.py

@@ -87,6 +87,10 @@ def test_pulp_id_href_filter(
         redi_results = redirect_contentguard_api_client.list(**{filter: rbac_sample})
         assert redi_results.count == 0
 
+        # test out empty list
+        redi_results = redirect_contentguard_api_client.list(**{filter: []})
+        assert redi_results.count == 0
+
         # Test that filter fails when not a valid type
         with pytest.raises(ApiException) as exc:
             content_guards_api_client.list(**{filter: ["hello"]})