tox ignores package data from setuptools_scm with Mercurial (hg)

[schlamar]

Issue

tox does not include package data from setuptools_scm if there is a Mercurial (hg) repository.

I attached a reproducible example: tox_scm.zip

Running

> hg init
> hg add *
> hg commit -m "init"
> tox

fails with FileNotFoundError: [Errno 2] No such file or directory: '.tox\py\lib\site-packages\mypkg\data.txt'

In src\mypkg.egg-info\SOURCES.txt you can see that data.txt is missing in the build.

Running the build frontend (py -m build) updates SOURCES.txt to include src/mypkg/data.txt and includes data.txt in dist/*.tar.gz and dist/*.whl. So this is probably an issue with the tox build frontend itself.

Running the same steps above with git works. In this case data.txt is installed to .tox\py\lib\site-packages\mypkg

Environment

Platform: Windows 10
tox version: 4.2.3
Python version running tox: 3.9.13 32bit

[gaborbernat]

This means the build backend requires some env-vars that tox doesn't pass through. You should set this and everything should work. It's a bit of trial and error to figure out which env-vars are needed.