added exception for array of objects field filter

src/dso_api/dynamic_api/filters/parser.py

@@ -417,6 +417,16 @@ def _translate_raw_value(  # noqa: C901
                 # or ?ligtInPanden=... references their identifier as foreign key.
                 return filter_input.raw_value
 
+            if field_schema.is_array_of_objects:
+                try:
+                    items = field_schema["items"]
+                    parser = SCALAR_PARSERS[items.get("format") or items["type"]]
+                except KeyError as e:
+                    raise ValidationError(
+                        f"Array of objects field '{filter_part.name}' "
+                        f"should be filtered on with a .subfield"
+                    ) from e
+
             if field_schema.is_array:
                 items = field_schema["items"]
                 parser = SCALAR_PARSERS[items.get("format") or items["type"]]

src/tests/test_dynamic_api/views/test_api_filters.py

@@ -20,6 +20,19 @@ def test_no_such_field(api_client, afval_dataset, filled_router):
         reason = response.data["invalid-params"][0]["reason"]
         assert reason == "Field 'nonexistent' does not exist"
 
+    @staticmethod
+    def test_array_of_objects_field(api_client, bag_dataset, filled_router):
+        """Prove that not filtering on a subfield of an array of objects will crash."""
+        response = api_client.get("/v1/bag/verblijfsobjecten/?gebruiksdoel=test")
+        data = read_response_json(response)
+
+        assert response.status_code == HTTP_400_BAD_REQUEST, data
+        reason = data["invalid-params"][0]["reason"]
+        assert (
+            reason
+            == "Array of objects field 'gebruiksdoel' should be filtered on with a .subfield"
+        )
+
     @staticmethod
     @pytest.mark.parametrize(
         "url",