Enable Ruff pyupgrade (UP) rule

[mwtoews]

This enables Ruff's pyupgrade (UP) rule.

The associated fixes are automated (no manual edits) and are either UP007 or UP045.

[JamesParrott]

I'm not really a fan of this rule Mike, but this has exposed a gap in our testing, so thanks very much!

I don;t know why the Python 3.9 tests have passed when given Python 3.10 Type Expression syntax (| instead of Union).

Python 3.9.23 (main, Jun  4 2025, 17:36:12) [MSC v.1929 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> x: str | int
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for |: 'type' and 'type'

So I don't think that syntax has been backported? Surely Ruff or Pyupgrade check the project metadata: requires-python = ">=3.9"?

[JamesParrott]

Oh I see, it's because of the future import.

Python 3.9.1 (default, Jan  3 2021, 22:36:18) [MSC v.1928 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> x: int | None
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for |: 'type' and 'NoneType'
>>> from __future__ import annotations
>>> x: int | None

[JamesParrott]

The tests do enforce Python 3.9 syntax: https://github.com/JamesParrott/IronPyShp/actions/runs/17095556570

[JamesParrott]

Merged! I wasn't a fan of having hundreds of Unions and Optionals either. I'm warming to what PyUpgrade's trying to do.

[mwtoews]

I'm warming to what PyUpgrade's trying to do.

Likewise, I wasn't initially keen on these changes, but am seeing that it is a simpler mark-up in the long run. And correct, I forgot to mention that from __future__ import annotations allows | syntax for oldish Python versions.