fix: Handle None return during link creation

capella2polarion/converters/link_converter.py

@@ -75,6 +75,13 @@ def create_links_for_work_item(
                     new: cabc.Iterable[str]
                     if isinstance(refs, common.ElementList):
                         new = refs.by_uuid  # type: ignore[assignment]
+                    elif refs is None:
+                        logger.info(
+                            'For model element %r attribute "%s" is not set',
+                            obj._short_repr_(),
+                            link_config.capella_attr,
+                        )
+                        continue
                     else:
                         assert hasattr(refs, "uuid"), "No 'uuid' on value"
                         new = [refs.uuid]
@@ -86,14 +93,11 @@ def create_links_for_work_item(
                         self._create(work_item.id, role_id, new, {})
                     )
             except Exception as error:
-                error_text = f"{type(error).__name__} {str(error)}"
-                link_errors.extend(
-                    [
-                        f"Requested attribute: {link_config.capella_attr}",
-                        error_text,
-                        "--------",
-                    ]
+                error_message = make_link_logging_message(
+                    f"{type(error).__name__} {str(error)}",
+                    link_config.capella_attr,
                 )
+                link_errors.extend(error_message)
 
         if link_errors:
             for link_error in link_errors:
@@ -382,11 +386,20 @@ def _sorted_unordered_html_list(
 
 def _resolve_attribute(
     obj: common.GenericElement | diag.Diagram, attr_id: str
-) -> common.ElementList[common.GenericElement] | common.GenericElement:
+) -> common.ElementList[common.GenericElement] | common.GenericElement | None:
     attr_name, _, map_id = attr_id.partition(".")
     objs = getattr(obj, attr_name)
-    if map_id:
+    if map_id and objs is not None:
         if isinstance(objs, common.GenericElement):
             return _resolve_attribute(objs, map_id)
         objs = objs.map(map_id)
     return objs
+
+
+def make_link_logging_message(message: str, capella_attr: str) -> list[str]:
+    """Return a list of strings for a link logging message."""
+    return [
+        f"Requested attribute: {capella_attr!r}",
+        message,
+        "--------",
+    ]

tests/test_elements.py

@@ -453,17 +453,22 @@ def test_create_links_custom_exchanges_resolver(
         assert links == [expected]
 
     @staticmethod
-    def test_create_links_missing_attribute(
+    def test_create_links_logs_error_when_no_uuid_is_found_on_value(
         base_object: BaseObjectContainer, caplog: pytest.LogCaptureFixture
     ):
         expected = (
             "Link creation for \"<FakeModelObject 'Fake 1' (uuid1)>\" failed:"
-            "\n\tRequested attribute: attribute"
+            "\n\tRequested attribute: 'attribute'"
             "\n\tAssertionError No 'uuid' on value"
             "\n\t--------"
         )
+        no_uuid = FakeModelObject("")
+        del no_uuid.uuid
+        base_object.mc.converter_session["uuid1"].capella_element.attribute = (
+            no_uuid
+        )
 
-        with caplog.at_level(logging.DEBUG):
+        with caplog.at_level(logging.ERROR):
             link_serializer = link_converter.LinkSerializer(
                 base_object.pw.polarion_data_repo,
                 base_object.mc.converter_session,
@@ -475,13 +480,36 @@ def test_create_links_missing_attribute(
         assert not links
         assert caplog.messages[0] == expected
 
+    @staticmethod
+    def test_create_links_logs_warning_model_element_behind_attribute_is_none(
+        base_object: BaseObjectContainer, caplog: pytest.LogCaptureFixture
+    ):
+        expected = (
+            "For model element \"<FakeModelObject 'Fake 1' (uuid1)>\" "
+            'attribute "attribute" is not set'
+        )
+
+        with caplog.at_level(logging.INFO):
+            link_serializer = link_converter.LinkSerializer(
+                base_object.pw.polarion_data_repo,
+                base_object.mc.converter_session,
+                base_object.pw.polarion_params.project_id,
+                base_object.c2pcli.capella_model,
+            )
+            links = link_serializer.create_links_for_work_item("uuid1")
+
+        assert not links
+        assert len(caplog.records) == 1
+        assert caplog.records[0].levelno == 20
+        assert caplog.records[0].message == expected
+
     @staticmethod
     def test_create_links_no_new_links_with_errors(
         base_object: BaseObjectContainer, caplog: pytest.LogCaptureFixture
     ):
         expected = (
             "Link creation for \"<FakeModelObject 'Fake 2' (uuid2)>\" failed:"
-            "\n\tRequested attribute: non_existent_attr"
+            "\n\tRequested attribute: 'non_existent_attr'"
             "\n\t"
         )
 
@@ -532,7 +560,7 @@ def test_create_links_with_new_links_and_errors(
         expected = (
             "Link creation for \"<FakeModelObject 'Fake 2' (uuid2)>\" "
             "partially successful. Some links were not created:"
-            "\n\tRequested attribute: non_existent_attr"
+            "\n\tRequested attribute: 'non_existent_attr'"
             "\n\t"
         )