MNT: Set up a linter for Cython code

[leofang]

We should run cython-lint on hand-crafted Cython code (and skip the auto-generated ones).

[kkraus14]

It would be nice to lint the generated code as well. We control the codegen as well where in theory we should be able to handle any issues?

[leofang]

My argument every time this comes up is: No one should read the generated code. No one should modify the generated code by hand. The generated code is not something that we should touch on a daily basis. Plus, the same codegen is used by multiple teams. I don't want to get into the business of dictating and arguing about the style choice. Take the code and do whatever you like. Finally, it actually requires a lot of (unnecessary, IMHO) work to make codegen emit perfectly formatted code. The level of efforts is too high to justify when the sole purpose is aesthetics.

[rwgk]

I agree that in the first iteration we definitely shouldn't try to cover generated code, but...

sole purpose is aesthetics.

I've seen linters being extremely useful for discovering real (often suble) bugs. This can be a big time saver.

[mdboom]

I've seen linters being extremely useful for discovering real (often suble) bugs. This can be a big time saver.

I was going to say this same thing. I think with judicious ignoring of certain specific lints that would be hard to handle with generated code, we would still get some benefit from running most of them.

[leofang]

As far as Cython code is concerned, what would be the bugs that would have been caught if a Cython linter were used and are not capturable by our test suite?

[kkraus14]

As far as Cython code is concerned, what would be the bugs that would have been caught if a Cython linter were used and are not capturable by our test suite?

https://github.com/MarcoGorelli/cython-lint?tab=readme-ov-file#which-checks-are-implemented

Many of these are things that the compiler / tests would not cover because they either will always return True or are subtle inefficiencies that it would be nice to have something giving us feedback "for free" on.

[rwgk]

https://github.com/MarcoGorelli/cython-lint?tab=readme-ov-file#which-checks-are-implemented

"Used by CuPy, pandas, RAPIDS, scipy"

Not a bad company to be with :-)