Thanks for the PR! Should this go into the v1.3 branch?

Tl;dr: version bumping should now work correctly and installing from an sdist should work again when this lands.

Background

If we don't pass in a parse function then setuptools_scm has the following precedence order:

• The SETUPTOOLS_SCM_PRETEND_VERSION[_FOR_X] env var. Will not bump the version, returns the version string directly. This is not what we want: That is, we want to use OVERRIDE_GIT_DESCRIBE to manually set the <version>-<distance>-g<commit> string.
• Git repository (with git describe) Used if .git/ exists and git describe succeeds. Builds a full ScmVersion object and will bump the version (either with a built-in scheme or whatever we pass in version_scheme. This is what we want
• PKG-INFO. Used only if no Git repository is found, or git describe fails, and PKG-INFO file exists and contains a valid Version field. No ScmVersion is created and will not bump the version. This is what we want (this only happens when we're building from an sdist and when we do that, the version was already bumped)
• fallback_version Used only if: no Git repo, no PKG-INFO, no SETUPTOOLS_SCM_PRETEND_VERSION[_FOR_X] Passed directly through as the final version string, i.e. will not bump the version. We don't care about this

If we do pass in a parse function, then none of the above will happen (no overrides, no git describe, no PKG-INFO, no fallback version). The version bumping logic will be called every time. This is what we did and so we had to replicate the git describe, override and PKG-INFO logic, and carefully choose in which cases we want to bump the version.

Since setuptools_scm does only one thing different from how we want it, I just fixed that. In this pr:

• we disallow passing in SETUPTOOLS_SCM_PRETEND_VERSION and SETUPTOOLS_SCM_PRETEND_VERSION_FOR_DUCKDB manually
• we allow passing OVERRIDE_GIT_DESCRIBE, parse and bump it, and pass it to setuptools_scm in SETUPTOOLS_SCM_PRETEND_VERSION_FOR_DUCKDB.
• we make sure the version gets bumped correctly when git describe is used by setuptools_scm.

Thanks, this makes sense to me 👍 As far as I can tell the biggest changes are:

• That we don't allow SETUPTOOLS_SCM_PRETEND_VERSION[_FOR_DUCKDB]
• We use a generated SETUPTOOLS_SCM_PRETEND_VERSION_FOR_DUCKDB to forward the intention of the OVERRIDE_GIT_DESCRIBE functionality.

Removing the hacky (and problematic) parse method override in the process 🎉

One question popped up though, about SETUPTOOLS_SCM_PRETEND_VERSION, is it not possible that this is set for a different package, where duckdb is somehow part of the build process? If we delete the env, it might cause a problem for that package (if this scenario even exists) Perhaps we can save it and restore it after we're done?

That's a good point, i'll add that!

Edit: When building a package pip spawns off a child process for each package, so changing the environment in one building process won't affect the environment for another process. This also happens when you use --no-build-isolation. So no need to re-set SETUPTOOLS_SCM_PRETEND_VERSION.

This looks ready to me, should this also go in?

Thanks!