Following a comment in #3420 review, I've collected a range of ruff rules, to propose adopting in altair.

This is an opinionated list, with a focus on rules providing an autofix (ruff check . --fix) - to limit any extra work removing warnings.

I think the ruff docs do a great job explaining each rule, so I've kept my additional notes brief. Strongly recommend checking out rules marked with a 🛠️ for examples of the change they would make.

Also, if accepted, I would suggest introducing any new rules close to a new release - since this would very likely create a large diff, especially if all of these were added at once.

flake8-simplify (SIM)

• Majority have autofixes
• First mentioned in #3420 review

pydocstyle (D)

• Majority have autofixes
• I haven't come across any altair specific doc conventions
• A starting point could be the config below and then tweaking DXXX rules from there
• See docstring-formatting for sample output

[tool.ruff.format]
docstring-code-format=true
docstring-code-line-length=72

[tool.ruff.lint]
pycodestyle={ max-doc-length=88 }
pydocstyle={ convention="numpy" }

pyupgrade (UP)

• All have autofixes and respect tool.ruff.target-version
• Really helpful considering altair 1.0.0 targeted python>=2.7,<3.6
• When paired with FA100, the autofixes can help improve readability of annotations - some of which are particularly verbose on python<3.9.

flake8-type-checking (TCH)

• Majority have autofixes
• Related to #3405 @binste
• Also relates to UP, FA100

flake8-errmsg (EM)

• All have autofixes

flake8-pie (PIE)

• All have autofixes, except PIE796
• Found only a single use of enum anyway

flake-8-use-pathlib (PTH)

• No autofixes, but most do improve readability
• First mentioned in #3426 commit

Misc

• static-join-to-f-string (FLY002)
• Ruff-specific rules (RUF)

Library-specific

These seem like a good fit, based on the current dependencies however I haven't used them before - unlike all other suggestions:

• NumPy-specific rules (NPY)
• pandas-vet (PD)
• flake8-pytest-style (PT)

Preview

These mostly require the opt-in preview mode, with varying degrees of autofixes.

• pylint (PLC, E, R, W)
• refurb (FURB)