Feels definitely snappier. Is hatchling commonly enough used so that this doesn't create problems for downstream packagers?

Yes, hatchling is pretty popular these days. It's also used by some important projects like Jupyter, attrs and Black.

Good to go then!

Ok, I just tried this and python -m build uses hatchling now (apparently without having to install anything manually), so that's good. Does this impact the build itself in any way? For me at the very least it changed the capitalization of the output files -- i.e. it produced lower-case pygments now. If you look at the release checklist, that breaks the command line there. I can obviously rename it manually, but is there a way to teach hatchling about this?

Ok, I just tried this and python -m build uses hatchling now (apparently without having to install anything manually), so that's good.

Yes, this is the “build isolation” feature — by default, build (and pip) create a fresh virtual environment and install the build dependencies (from build-system.requires) into it.

For me at the very least it changed the capitalization of the output files -- i.e. it produced lower-case pygments now.

Oh, that's right, good point. However, after looking into it, it seems that the consensus among packaging people is that normalizing the project name in sdist/wheel file names is better and setuptools should change to do it. See pypa/setuptools#3777

So let's just update the release procedure?

This PR apparently broke the WASM build of Pygments with Pyodide in the CI, but I don't understand why.

The error says

#9 71.01 OSError: Readme file does not exist: description.rst

Lower-case is totally fine for me, it's just something that needs to be mentioned in the changelog because there must be someone out there using a script which expects it upper-case.

I don't know what's up with WASM. @birkenfeld ?

I'm looking into the Pyodide problem now.

(I've added a note to the CHANGES file about distribution file names.)

#2580 should hopefully fix the CI.

Indeed it does :)