Fix favorite_lists returning null on cache miss and add regression coverage

care/emr/api/viewsets/favorites.py

@@ -23,10 +23,19 @@ class EMRFavoritesMixin:
     FAVORITE_RESOURCE = None
 
     def retrieve_facility_obj(self, obj):
+        """
+        Return the facility associated with the given object.
+        """
         return obj.facility
 
     @action(detail=False, methods=["GET"])
     def favorite_lists(self, request, *args, **kwargs):
+        """
+        Return the list of favorite list names for the current user.
+
+        Ensures that on cache miss the computed favorite lists are returned
+        immediately instead of returning a null response.
+        """
         user = self.request.user
 
         facility = kwargs.get("facility_external_id") or request.query_params.get(
@@ -56,10 +65,18 @@ def favorite_lists(self, request, *args, **kwargs):
                 favorite_lists_cache_key(user, self.FAVORITE_RESOURCE, facility),
                 favorite_list_obj,
             )
+            favorite_lists = favorite_list_obj
+
         return Response({"lists": favorite_lists})
 
     @action(detail=True, methods=["POST"])
     def add_favorite(self, request, *args, **kwargs):
+        """
+        Add the current object to the user's favorite list.
+
+        Inserts the object at the beginning of the list, trims the list
+        to the maximum allowed size, and updates the cache accordingly.
+        """
         request_data = FavoriteRequest(**request.data)
         favorite_list = request_data.favorite_list
         obj = self.get_object()
@@ -71,7 +88,6 @@ def add_favorite(self, request, *args, **kwargs):
             facility=self.retrieve_facility_obj(obj),
         )
         favorite_list_obj.favorites.insert(0, obj.id)
-        # trim favorites list to max allowed
         favorite_list_obj.favorites = list(dict.fromkeys(favorite_list_obj.favorites))[
             : settings.MAX_FAVORITES_PER_LIST
         ]
@@ -80,6 +96,12 @@ def add_favorite(self, request, *args, **kwargs):
 
     @action(detail=True, methods=["POST"])
     def remove_favorite(self, request, *args, **kwargs):
+        """
+        Remove the current object from the user's favorite list.
+
+        Deletes the favorite list entirely when it becomes empty and
+        clears all related cache entries.
+        """
         request_data = FavoriteRequest(**request.data)
         favorite_list = request_data.favorite_list
         obj = self.get_object()
@@ -93,6 +115,7 @@ def remove_favorite(self, request, *args, **kwargs):
         ).first()
         if not favorite_list_obj:
             raise ValidationError("Favorite List not found")
+
         favorite_list_obj_favorites = dict.fromkeys(favorite_list_obj.favorites)
         favorite_list_obj_favorites.pop(obj.id, None)
         if len(favorite_list_obj_favorites) == 0:
@@ -109,6 +132,7 @@ def remove_favorite(self, request, *args, **kwargs):
             )
             UserResourceFavorites.objects.filter(id=favorite_list_obj.id).delete()
             return Response({})
+
         favorite_list_obj.favorites = list(favorite_list_obj_favorites)
         favorite_list_obj.save(update_fields=["favorites"])
         return Response({})

care/emr/tests/test_favorites_api.py

@@ -238,6 +238,16 @@ def test_list_favorites_list(self):
                 "another_list",
             )
         )
+    def test_favorite_lists_returns_list_on_first_call(self):
+        # Ensure cache is empty
+        cache.delete(self.favorite_list_cache_key)
+
+        response = self.client.get(self.base_url + "favorite_lists/")
+
+        self.assertEqual(response.status_code, 200, response.content)
+        self.assertIn("lists", response.data)
+        self.assertIsNotNone(response.data["lists"])
+        self.assertIsInstance(response.data["lists"], list)
 
     def test_list_ordered_by_favorites(self):
         charge_item = self.create_charge_item_definition()

care/users/api/viewsets/plug_config.py

@@ -19,7 +19,7 @@ class PlugConfigViewset(
     def list(self, request, *args, **kwargs):
         # Cache data and return
         response = cache.get(self.cache_key)
-        if not response:
+        if response is None: # cache miss; allow cached empty list
             serializer = self.get_serializer(self.get_queryset(), many=True)
             response = serializer.data
             cache.set(self.cache_key, response)