chore: Migrate from flake8 to ruff

[GabDug]

I have made things!

Ruff now includes flake8-pyi rules has well as the flake8-no-pep420 rule.

To simplify the dev experience, I propose to use ruff to replace these flake8 rules, thus completely removing the need for flake8.

Migration notes:

• PYI037 is not implemented but UP007 checks for Optional usage instead of union type
• PYI022 is equivalent to UP035

[intgr]

Last time I checked, Ruff PYI* group was still missing a few checks that flake8-pyi has.

Can you please compile a list of relevant checks that Ruff is missing? Then we can make an informed decision on whether we want to drop flake8-pyi.

[GabDug]

Ruff implemented PYI rules.
flake8-pyi implemented Y rules.

Missing rule	Description	Alternative
PYI022	Do not use typing if available in stdlib (e.g. prefer builtins.list over typing.List, collections.Counter over typing.Counter, etc.).	UP035
PYI023	Where there is no detriment to backwards compatibility, import objects such as ClassVar and NoReturn from typing rather than typing_extensions.	UP035
PYI027	Removed from flake8-pyi	PYI022, thus UP035
PYI028	Use class-based NamedTuple instead of assignment-based	UP014
PYI031	TypedDicts should use class-based syntax instead of assignment-based syntax wherever possible. (In situations where this is not possible, such as if a field is a Python keyword or an invalid identifier, this error will not be emitted.)	UP014
PYI037	Use PEP 604 syntax instead of typing.Union and typing.Optional. E.g. use str | int instead of Union[str, int], and use str | None instead of Optional[str].	UP007
PYI038	Use from collections.abc import Set as AbstractSet instead of from typing import AbstractSet.	Not sure, may be covered in UP035
PYI039	Use str instead of typing.Text.	UP019
PYI040	Never explicitly inherit from object, as all classes implicitly inherit from object in Python 3.	UP004
PYI057	Do not use typing.ByteString or collections.abc.ByteString. These types have unclear semantics, and are deprecated; use typing_extensions.Buffer or a union such as bytes | bytearray | memoryview instead. See PEP 688 for more details.	None, recently added rule

We may need to tweak target-version and/or ignores, as UP may not be enabled with a 3.8 target.

[intgr]

Thanks!

We may need to tweak target-version and/or ignores, as UP may not be enabled with a 3.8 target.

Let's not do that. Bumping target-version can cause real compatibility issues in .py files like the mypy plugin or django_stubs_ext, which are executed in the Python runtime, and we still want to support Python 3.8.

While many of the missing flake8-pyi rules do exist as UP* rules in Ruff, flake8-pyi is more eager in adopting updates because type checkers support newer features than the Python runtime. It's still a bit unclear how much we lose from to that. Most common ones are already covered by the target-version = "py38" level, so it's not a big loss.

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Still, I don't see a downside to keeping flake8-pyi in parallel with Ruff either. Typeshed project uses both as well. Any third opinions?

[intgr]

No-one has voiced any opinions or concerns. Let's keep this as proposed and drop flake8-pyi then. Worst case I see is that we'll be using some imports of compatibility aliases, no big deal.