Do not change config in place

src/mass/adapters/outbound/utils.py

@@ -186,12 +186,21 @@ def build_pipeline(  # noqa: PLR0913
         pipeline.append(pipeline_match_filters_stage(filters=filters))
 
     # turn the selected fields into a formatted pipeline $project
-    project: dict[str, int] = dict.fromkeys(
-        [
-            field.key if field.key == "id_" else f"content.{field.key}"
-            for field in selected_fields
-        ],
-        1,
+
+    project: dict[str, int] | None = (
+        dict.fromkeys(
+            (
+                "id_",
+                *(
+                    f"content.{field.key}"
+                    for field in selected_fields
+                    if field.key != "id_"
+                ),
+            ),
+            1,
+        )
+        if selected_fields
+        else None
     )
 
     # turn the sorting parameters into a formatted pipeline $sort

src/mass/core/query_handler.py

@@ -68,7 +68,7 @@ async def delete_resource(self, *, resource_id: str, class_name: str):  # noqa:
         except ResourceNotFoundError as err:
             raise self.ResourceNotFoundError(resource_id=resource_id) from err
 
-    async def handle_query(  # noqa: PLR0913, C901, D102
+    async def handle_query(  # noqa: D102, PLR0913
         self,
         *,
         class_name: str,
@@ -103,10 +103,6 @@ async def handle_query(  # noqa: PLR0913, C901, D102
         except KeyError as err:
             raise self.ClassNotConfiguredError(class_name=class_name) from err
 
-        # if id_ is not in selected_fields, add as first field
-        if selected_fields and not any(field.key == "id_" for field in selected_fields):
-            selected_fields.insert(0, models.FieldLabel(key="id_", name="ID"))
-
         # run the aggregation. Results will have {facets, count, hits} format
         aggregator = self._aggregator_collection.get_aggregator(class_name=class_name)
         for attempt in range(2):