model.base: fix ConstrainedList.clear() atomicity

basyx/aas/model/base.py

@@ -1311,6 +1311,10 @@ def extend(self, values: Iterable[_T]) -> None:
  self._item_add_hook(v, self._list + v_list[:idx])
  self._list = self._list + v_list
 
+ def clear(self) -> None:
+ # clear() repeatedly deletes the last item by default, making it not atomic
+ del self[:]
+
  @overload
  def __getitem__(self, index: int) -> _T: ...
 

test/model/test_base.py

@@ -1213,7 +1213,15 @@ def hook(itm: int, _list: List[int]) -> None:
  self.assertEqual(c_list, [1, 2, 3])
  with self.assertRaises(ValueError):
  c_list.clear()
- self.assertEqual(c_list, [1, 2, 3])
+ # the default clear() implementation seems to repeatedly delete the last item until the list is empty
+ # in this case, the last item is 3, which cannot be deleted because it is > 2, thus leaving it unclear whether
+ # clear() really is atomic. to work around this, the list is reversed, making 1 the last item, and attempting
+ # to clear again.
+ c_list.reverse()
+ with self.assertRaises(ValueError):
+ c_list.clear()
+ self.assertEqual(c_list, [3, 2, 1])
+ c_list.reverse()
  del c_list[0:2]
  self.assertEqual(c_list, [3])