use ruff as linter

[mattijn]

This PR add ruff as linter over flake8. This in order to work towards a complete pyproject.toml-based build, see corresponding PR #3007.

I've moved the flake8 configuration to the corresponding ruff section in the pyproject.toml file. I tried to synchronize the same tests for now. But still had to apply some fixes in the code to get in sync

• This PR include code fixes for B028, B904, B006 and B018.
• I've excluded TID252 (relative imports) and B905 (valid from python>3.10).
• E203, E266 and W503 checks are not yet available in ruff, see Implement remaining pycodestyle rules astral-sh/ruff#2402, so these cannot be excluded yet (as they were for flake8).

Ready for review.

[mattijn]

I cannot assign you as reviewer @binste, but would you be willing to check this?

[binste]

Sure! Always happy to review.

Thank you for tackling this and also for going through the rules to see what is available! I'm amazed by the speed of ruff and how many rules are already implemented... Maybe we can even use it as a replacement for black at one point: astral-sh/ruff#1904

Looks mostly good to me. Added some smaller code suggestions. Could you also replace the mention of flake8 in contributing.md?

[binste]

Suggested change

	raise SchemaValidationError(self, err) from err
	# We do not raise `from err` as else the resulting
	# traceback is very long as it contains part
	# of the Vega-Lite schema. It would also first
	# show the less helpful ValidationError instead of
	# the more user friendly SchemaValidationError
	raise SchemaValidationError(self, err) from None

[mattijn]

I've modified your suggestion a little bit to raise from None instead of raise # noqa: B904. I'm not entirely sure if that leads to the same behavior. Do you have an example how you checked this?

[binste]

Double-checked and that works as well. It gives the same traceback as in master which is good. I tested it with:

import altair as alt
from vega_datasets import data

(
    alt.Chart(data.barley())
    .mark_bar()
    .encode(
        x=alt.X("variety", unknown=2),
        y=alt.Y("sum(yield)", stack="asdf"),
    )
)

[binste]

Suggested change

	raise SchemaValidationError(self, err) from err
	# We do not raise `from err` as else the resulting
	# traceback is very long as it contains part
	# of the Vega-Lite schema. It would also first
	# show the less helpful ValidationError instead of
	# the more user friendly SchemaValidationError
	raise SchemaValidationError(self, err) from None

[mattijn]

Same change as above, raise from None instead of rase # noqa: B904

[mattijn]

Thanks for the review @binste. I've one inline question remaining.

[mattijn]

Hm, it seems there are some sync issues with VSCode replies. Let me respond using the replies on github website.

[mattijn]

Maybe we can even use it as a replacement for black at one point: astral-sh/ruff#1904

Hm, didn't realize this, but I think we can remove black for format suggestions already? The link you refer to is on ruff autoformat, but I don't think we have black autoformat enabled?

In that case black --check . should raise the same as ruff check ., agree? Or I miss something here?

[binste]

I didn't find any options for ruff to enable checks on code formatting. Also tested it on some code where black correctly shows an error but ruff does not. The FAQ state that "As a project, Ruff is designed to be used alongside Black and, as such, will defer implementing stylistic lint rules that are obviated by autoformatting." So I'd assume that the checking comes hand-in-hand with the autoformat capability and we need to wait for that.

[binste]

Looks good! This inspired me to start using ruff at work as well.

[mattijn]

Thanks @binste! Great that the insights here is more useful than this PR alone👍.
So we will have to wait until ruff has autoformat support before we can switch. I'll open an issue for this to keep track on it. Merging this, thanks for the review!

[charliermarsh]

Sorry for the drive-by comment but I just saw this is in Ruff's dependency graph and as a long-time Altair user I can't help but mention how cool it is to be able to support the project. Let me know if you ever run into issues with Ruff or have questions on usage etc.

[joelostblom]

That's great, thank you for taking the time to comment and offering your support @charliermarsh !