Run `ruff` on `peg_generator`

[sobolevn]

We start to addopt ruff in Tools/ gradually, many folders already have some level of support:

cpython/.pre-commit-config.yaml

Lines 6 to 28 in 4357302

	name: Run Ruff (lint) on Doc/
	args: [--exit-non-zero-on-fix]
	files: ^Doc/
	- id: ruff
	name: Run Ruff (lint) on Lib/test/
	args: [--exit-non-zero-on-fix]
	files: ^Lib/test/
	- id: ruff
	name: Run Ruff (lint) on Tools/build/
	args: [--exit-non-zero-on-fix, --config=Tools/build/.ruff.toml]
	files: ^Tools/build/
	- id: ruff
	name: Run Ruff (lint) on Argument Clinic
	args: [--exit-non-zero-on-fix, --config=Tools/clinic/.ruff.toml]
	files: ^Tools/clinic/|Lib/test/test_clinic.py
	- id: ruff-format
	name: Run Ruff (format) on Doc/
	args: [--check]
	files: ^Doc/
	- id: ruff-format
	name: Run Ruff (format) on Tools/build/check_warnings.py
	args: [--check, --config=Tools/build/.ruff.toml]
	files: ^Tools/build/check_warnings.py

I propose adding this config to Tools/peg_generator:

extend = "../../.ruff.toml"  # Inherit the project-wide settings
extend-exclude = [
    # Generated files:
    "pegen/grammar_parser.py",
]

[lint]
select = [
    "F",  # Enable all pyflakes rules
    "I",  # Enable all isort rules
    "UP",  # Enable all pyupgrade rules by default
    "RUF100",  # Ban unused `# noqa` comments
    "PGH004",  # Ban blanket `# noqa` comments (only ignore specific error codes)
]
ignore = [
    # Unnecessary parentheses to functools.lru_cache: just leads to unnecessary churn.
    # https://github.com/python/cpython/pull/104684#discussion_r1199653347.
    "UP011",
    # Use format specifiers instead of %-style formatting.
    # Doesn't always make code more readable.
    "UP031",
    # Use f-strings instead of format specifiers.
    # Doesn't always make code more readable.
    "UP032",
    # Use PEP-604 unions rather than tuples for isinstance() checks.
    # Makes code slower and more verbose. https://github.com/astral-sh/ruff/issues/7871.
    "UP038",
]
unfixable = [
    # The autofixes sometimes do the wrong things for these;
    # it's better to have to manually look at the code and see how it needs fixing
    "F841",  # Detects unused variables
    "F601",  # Detects dictionaries that have duplicate keys
    "F602",  # Also detects dictionaries that have duplicate keys
]

It is based on https://github.com/python/cpython/blob/main/Tools/clinic/.ruff.toml

I've double checked the changed produced by it and did not find anything problematic.
So, let's give this a try!

Linked PRs

• gh-138281: Run ruff on Tools/peg_generator #138282
• [3.14] gh-138281: Run ruff on Tools/peg_generator (GH-138282) #138469
• [3.13] gh-138281: Run ruff on Tools/peg_generator (GH-138282) #138472
• gh-138281: Remove unused topsort and bump minimal version in peg_generator #138487