UP045 fixes Optional[Optional[x]] to x | None | None

[johncassil]

Summary

Nesting is not taken care of in the conversion:

Optional[Optional[str]] yields str | None | None

This might be related to #18508

Version

ruff 0.12.1 (32c5418 2025-06-26)

[ntBre]

Hmm, I thought #18508 was supposed to be closed by #18572, which came out the day after 0.12.1, but I can still reproduce this on 0.12.7, regardless. Thanks for the report!

[ntBre]

I guess this isn't quite as catastrophic as None | None alone:

>>> None | None
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for |: 'NoneType' and 'NoneType'
>>> int | None | None
int | None

But I think we handle nesting in these rules in other cases, so it may still be worth handling here.