Regular expression for version validation includes non-period delimiters

[towo]

Issue Description

The VERSION_PATTERN regular expression in Appendix B of the PyPA version specifiers spec allows for dashes and underscores instead of a period to separate pre/post/dev releases, an also allows those characters in the local version string.

From my understanding of the spec, this is not allowed, and I'm willing to correct the RE in that regard, but would want some further guidance if this is a legacy compatibility issue or just an oversight.

Code of Conduct

• I am aware that participants in this repository must follow the PSF Code of Conduct.

[webknjaz]

I think that one place might refer to the normalized version and the other to the user input. But it'd be helpful if you included links to parts of the documents you're talking about. Attaching quotes from there would also be useful for the context.

[webknjaz]

P.S. https://github.com/pypa/packaging is a library that is used in the ecosystem. Sometimes, it's a dependency and sometimes (like in the case of pip), it's vendored. It's considered to be the source of truth for the respective behaviors. You can check how it's implemented there. And if you think that the spec says something else, that would be the first place to submit a fix to (if the spec itself doesn't need clarification, that is).

[notatallshaw]

The regex is correct because it is handling unnormalized versions, it is only the normalized versions that do not allow the things you say.

https://packaging.python.org/en/latest/specifications/version-specifiers/#normalization

[webknjaz]

That's my impression too..

[towo]

Okay, I totally misread that, then. My bad!