use setuptools_scm for python version management

[luizirber]

Hello,

I noticed https://pypi.org/project/wasmtime/ is still stuck in 0.2, and releases like 0.8.0 still generate version 0.0.1 for the Python wheels.

This PR uses setuptools_scm to read version information from the git tags, so the right version will be picked up (and no manual update is needed in setup.py).

TODO: check what happens with the dev tag...

[alexcrichton]

Thanks for the PR! You can check out the "tarballs" artifact of this PR and see that there's names like:

• wasmtime-0.1.dev2088+gf15450b-cp37-cp37m-win_amd64.whl

I think that's probably not quite what we want? Would it be possible to just use dev for the branch builds?

Also can you try making a tag in your local repository to make sure that the name generation works for tagged builds as expected?

[luizirber]

Thanks for the PR! You can check out the "tarballs" artifact of this PR and see that there's names like:

* `wasmtime-0.1.dev2088+gf15450b-cp37-cp37m-win_amd64.whl`

Also can you try making a tag in your local repository to make sure that the name generation works for tagged builds as expected?

I merged this PR into my fork, and tagged 0.8.1 to see what happened. Turns out that calculating versions from git describe is not working for deriving versions from untagged commits, but it does work for tagged ones. Here's an example:

https://github.com/luizirber/wasmtime/runs/319963416
generating wasmtime-0.8.1-cp37-cp37m-macosx_10_13_x86_64.whl

I think that's probably not quite what we want? Would it be possible to just use dev for the branch builds?

I can try to figure out this, or is it good enough that the proper version is being generated for tags/releases for github? This is the generated release for 0.8.1: https://github.com/luizirber/wasmtime/releases/tag/v0.8.1

I'll also create a new dev tag and see what happens.

[alexcrichton]

Nice!

For the dev/master releases we largely just want a constant filename there, that allows us to have a stable download link.

[luizirber]

For the dev/master releases we largely just want a constant filename there, that allows us to have a stable download link.

I just found about the version_scheme and local_scheme configs, and it's easy to define a new function to do what we want (if there is a tag, use the tag; else default to dev).

The issue is that auditwheel can't parse the dev version (it's not valid according to PEP 440 - see log). Should I default the dev version to 0.0.1 to match current dev releases?

[alexcrichton]

Seems reasonable to me, and we can always continue to tweak as necessary. Thanks @luizirber!