Fix: apply ordering after annotating tag document count (#12238)

src/documents/tests/test_tag_hierarchy.py

@@ -147,6 +147,16 @@ class TestTagHierarchy(APITestCase):
         assert serializer.data  # triggers serialization
         assert "document_count_filter" in context
 
+    def test_tag_list_can_order_by_document_count_with_children(self) -> None:
+        self.document.tags.add(self.child)
+
+        response = self.client.get(
+            "/api/tags/",
+            {"ordering": "document_count"},
+        )
+
+        assert response.status_code == 200
+
     def test_cannot_set_parent_to_self(self):
         tag = Tag.objects.create(name="Selfie")
         resp = self.client.patch(

src/documents/views.py

@@ -487,13 +487,13 @@ class TagViewSet(PermissionsAwareDocumentCountMixin, ModelViewSet):
             user = getattr(getattr(self, "request", None), "user", None)
             children_source = list(
                 annotate_document_count_for_related_queryset(
-                    Tag.objects.filter(pk__in=descendant_pks | {t.pk for t in all_tags})
-                    .select_related("owner")
-                    .order_by(*ordering),
+                    Tag.objects.filter(
+                        pk__in=descendant_pks | {t.pk for t in all_tags},
+                    ).select_related("owner"),
                     through_model=self.document_count_through,
                     related_object_field=self.document_count_source_field,
                     user=user,
-                ),
+                ).order_by(*ordering),
             )
         else:
             children_source = all_tags