Let extend handle the duplicates of an in-place multiplication

`values *= 2` repeats every item once, which is what `values.extend(values)`
does. Routing the repeat through extend keeps the duplicate policy in one
place and removes the ValueError that CodeQL flagged inside __imul__.

The pop test asserted on the calls themselves. It stores the popped values
first so the asserts have no side effects.

Author: wolph

_python_utils_tests/test_containers.py

@@ -301,8 +301,9 @@ def test_unique_list_pop() -> None:
     values: containers.UniqueList[int] = containers.UniqueList(
         1, 2, 3, on_duplicate='raise'
     )
-    assert values.pop() == 3
-    assert values.pop(0) == 1
+    last: int = values.pop()
+    first: int = values.pop(0)
+    assert (last, first) == (3, 1)
     assert values == [2]
     assert 1 not in values
     assert 3 not in values

python_utils/containers.py

@@ -534,8 +534,8 @@ def __imul__(
         Multiplies the list in place without ever repeating an item.
 
         A count below 1 empties the list, as it does for a regular list. A
-        count above 1 would repeat every item, so those repeats are handled
-        as duplicates.
+        count above 1 would repeat every item, so the repeat goes through
+        `extend` and follows `on_duplicate`.
 
         Args:
             value (typing.SupportsIndex): The number of times to repeat.
@@ -550,8 +550,8 @@ def __imul__(
         count: int = operator.index(value)
         if count < 1:
             self.clear()
-        elif count > 1 and self and self.on_duplicate == 'raise':
-            raise ValueError(f'Duplicate values: {self._set}')
+        elif count > 1:
+            self.extend(self)
 
         return self