Fix lambda function logic when all detections are filtered out

Currently, if all detected shapes have labels that aren't mapped, then the
mapping is not applied at all.

changelog.d/20250113_122208_roman_filter_out_all_detections.md

@@ -0,0 +1,5 @@
+### Fixed
+
+- Fixed incorrect results being returned from lambda functions when all
+  detected shapes have labels that aren't mapped.
+  (<https://github.com/cvat-ai/cvat/pull/8931>)

cvat/apps/lambda_manager/tests/test_lambda.py

@@ -1101,6 +1101,18 @@ def test_api_v2_lambda_functions_create_detector_without_mapping(self):
         )
         self.assertEqual(response.status_code, status.HTTP_200_OK)
 
+    def test_api_v2_lambda_functions_create_detector_all_shapes_unmapped(self):
+        data = {
+            "task": self.main_task["id"],
+            "frame": 0,
+            "mapping": {"person": {"name": "person"}},
+        }
+        response = self._post_request(
+            f"{LAMBDA_FUNCTIONS_PATH}/{id_function_detector}", self.admin, data
+        )
+        self.assertEqual(response.status_code, status.HTTP_200_OK)
+        self.assertEqual(response.json(), [])
+
     def test_api_v2_lambda_functions_create_detector_without_task(self):
         data = {
             "frame": 0,

cvat/apps/lambda_manager/views.py

@@ -479,8 +479,6 @@ def validate_attributes_mapping(attributes_mapping, model_attributes, db_attribu
 
         response = self.gateway.invoke(self, payload)
 
-        response_filtered = []
-
         def check_attr_value(value, db_attr):
             if db_attr is None:
                 return False
@@ -509,6 +507,8 @@ def transform_attributes(input_attributes, attr_mapping, db_attributes):
             return attributes
 
         if self.kind == FunctionKind.DETECTOR:
+            response_filtered = []
+
             for item in response:
                 item_label = item["label"]
                 if item_label not in mapping:
@@ -534,7 +534,8 @@ def transform_attributes(input_attributes, attr_mapping, db_attributes):
                             db_label.attributespec_set.values(),
                         )
                 response_filtered.append(item)
-                response = response_filtered
+
+            response = response_filtered
 
         return response