An underscore in a package name appears as a hyphen on PyPI

[Kodiologist]

Describe the bug
I have a package named geocode_sparcs, but it appears at https://pypi.org/project/geocode-sparcs . In fact, https://pypi.org/project/geocode_sparcs redirects there. Evidently it's not just a matter of PyPI not supporting underscores in package names, because e.g. https://pypi.org/project/ls_json exists, and https://pypi.org/project/ls-json redirects to it.

In general, I don't understand what the deal is with hyphens or underscores in package names it comes to PyPI.

To Reproduce
Upload geocode_sparcs-0.2.0.tar.gz with twine upload.

My Platform
twine version 4.0.1 (importlib-metadata: 4.6.4, keyring: 23.8.2, pkginfo: 1.8.3, requests: 2.27.1, requests-toolbelt: 0.9.1, urllib3: 1.26.9)

[di]

This is pypa/twine#920: twine is normalizing the package name to something that is functionally equivalent when uploading to PyPI, but not exactly the same as what you originally specified.

PyPI is just using whatever is provided at upload-time, so I don't think there's anything to do here.

[Kodiologist]

Yep, sounds like a Twine thing. I should've guessed. Thanks.