Dropping black formatter for ruff

[john-science]

What is the change?

Here I dropped the black linter from the project entirely, and switched to using ruff. This meant I had to:

• Remove black from pyproject.toml and the CI
• Update ruff to 0.9.7.
• Changed the ruff target-version from Python 3.9 to Python 3.13
• Format ARMI with ruff (notice this make a TON of small changes for line length).
• Added ruff format to CI.
• Updated the docs to remove black and add ruff format.

Why is the change being made?

1. ruff format is ~30 times faster than black
2. This will make reduce the number of dependencies we have.

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Checklist

• This PR has only one purpose or idea.
• Tests have been added/updated to verify any new/changed code.
• The code style follows good practices.
• The release notes have been updated if necessary.
• The documentation is still up-to-date in the doc folder.
• The dependencies are still up-to-date in pyproject.toml.

[keckler]

Question -- Is this going to cause issues for people that currently have the black formatter automatically triggered by their IDE? Or are the two formatters supposedly totally compatible in terms of their formatting rules?

[john-science]

Question -- Is this going to cause issues for people that currently have the black formatter automatically triggered by their IDE? Or are the two formatters supposedly totally compatible in terms of their formatting rules?

ruff says they copied the black formatting one-for-one, and this is a drop-in replacement:

https://docs.astral.sh/ruff/faq/#how-does-ruffs-formatter-compare-to-black

But, certainly, the entire idea here is that users just stop using black, and go with ruff. (Your internal code bases will follow suit, in in a month or so, by the way.)

Part of the impetus here is people complain to me that black is too slow kind of a lot. Well ruff format is 30 times faster: https://astral.sh/blog/the-ruff-formatter

Thoughts?

[ntouran]

Question -- Is this going to cause issues for people that currently have the black formatter automatically triggered by their IDE?

yes! they will fight to a degree.

[ntouran]

you sure you don't want to take this opportunity to go to the ruff and black default of 88? 88 is great! https://docs.astral.sh/ruff/settings/#line-length https://stackoverflow.com/a/578318/1279313

otherwise this looks great.

[john-science]

I tried. Even going down to 100 meant I had over 400 files that required manual changes. (Things like docstrings couldn't be automatically reformatted.)

And I do not have time for manually touching >1,000 lines to make them shorter.

(Also, as a personal preference, I might go 100, but 88 feels a bit too narrow when you have a lot of math on the same line.)

[opotowsky]

Question -- Is this going to cause issues for people that currently have the black formatter automatically triggered by their IDE? Or are the two formatters supposedly totally compatible in terms of their formatting rules?

Since ppl are fond of VSCode and this will cause problems for folks while we convert to this, John has graciously agreed to delay this PR. So I marked it as draft. There will be an adjustment period, but we will plan to get everything downstream converted. Only folks who work on ARMI will have to battle the conflicting formatters. ruff on the command line will fix that easily though.