Test for parent param not allowed at node

src/calliope/preprocess/model_data.py

@@ -365,11 +365,17 @@ def _get_relevant_node_refs(self, techs_dict: AttrDict, node: str) -> list[str]:
             ):
                 techs_dict.set_key(key, val + ":" + node)
 
-        for tech_dict in techs_dict.values():
+        for tech_name, tech_dict in techs_dict.items():
             if tech_dict is None or not tech_dict.get("active", True):
                 continue
             else:
+                if "parent" in tech_dict.keys():
+                    raise exceptions.ModelError(
+                        f"(nodes, {node}), (techs, {tech_name}) | Defining a technology `parent` at a node is not supported; "
+                        "limit yourself to defining this parameter within `techs` or `tech_groups`"
+                    )
                 refs.update(tech_dict.keys())
+
         return list(refs)
 
     def _param_dict_to_array(self, param_name: str, param_data: Param) -> xr.DataArray:

tests/test_model_data.py

@@ -336,6 +336,20 @@ def test_get_relevant_node_refs_no_ts_data(
         refs = model_data_factory._get_relevant_node_refs(techs_dict, "A")
         assert set(refs) == set(["key1", "key2", "key3"])
 
+    def test_get_relevant_node_refs_parent_at_node_not_supported(
+        self, model_data_factory: ModelDataFactory
+    ):
+        techs_dict = AttrDict(
+            {"bar": {"key1": 1}, "foo": {"parent": "foobar"}, "baz": None}
+        )
+        with pytest.raises(exceptions.ModelError) as excinfo:
+            model_data_factory._get_relevant_node_refs(techs_dict, "A")
+
+        assert check_error_or_warning(
+            excinfo,
+            "(nodes, A), (techs, foo) | Defining a technology `parent` at a node is not supported",
+        )
+
     def test_param_dict_to_array_with_defaults(
         self, model_data_factory: ModelDataFactory
     ):