tools/import-normalizer/persons_tree.py

@@ -193,6 +193,12 @@ def _attach_person_ids(tree_persons: list[dict], raw_dicts: list[dict]) -> None:
     parse_register and _parse_row both keep exactly the rows that have a last name.
     """
     register = _persons.parse_register(raw_dicts)
+    if len(tree_persons) != len(register):
+        raise ValueError(
+            "person_id propagation requires equal length: "
+            f"{len(tree_persons)} tree persons vs {len(register)} register persons "
+            "(the positional zip would otherwise silently truncate and mis-join ids)"
+        )
     for tree_person, register_person in zip(tree_persons, register):
         tree_person["personId"] = register_person.person_id
 

tools/import-normalizer/tests/test_persons_tree.py

@@ -454,6 +454,26 @@ def test_attach_person_ids_propagates_register_slug():
     assert tree_persons[1]["personId"] == "de-gruyter-eugenie"
 
 
+def test_attach_person_ids_raises_on_length_divergence():
+    # The propagation is a positional zip; if tree_persons and the register drift in
+    # length (e.g. a future filter change), zip would silently truncate and mis-join ids.
+    # The guard must fail loudly instead.
+    raw_dicts = [
+        {"generation": "G 1", "last_name": "de Gruyter", "first_name": "Walter",
+         "maiden_name": "", "birth_date": "", "birth_place": "",
+         "death_date": "", "death_place": "", "spouse": "", "notes": ""},
+        # second register row has a last name -> parse_register keeps it ...
+        {"generation": "G 1", "last_name": "de Gruyter", "first_name": "Eugenie",
+         "maiden_name": "Müller", "birth_date": "", "birth_place": "",
+         "death_date": "", "death_place": "", "spouse": "", "notes": ""},
+    ]
+    # ... but the tree side only has one person -> lengths diverge.
+    tree_persons = [persons_tree._parse_row(2, raw_dicts[0])]
+    import pytest
+    with pytest.raises(ValueError, match="length"):
+        persons_tree._attach_person_ids(tree_persons, raw_dicts)
+
+
 def test_attach_person_ids_carries_register_collision_suffix():
     # when two register rows slug-collide, the register suffixes the ids (-1, -2);
     # those exact suffixed ids must reach the tree persons, never a recomputed bare slug