Custom local_scheme not used when building

[andy-maier]

When specifying a local_scheme in pyproject.toml using entrypoints, it is used correctly in python -m setuptools_scm but not used in the generated version file, and not used in the file names of the distribution archives when building them.

The pyroject.toml file has these relevant sections:

[build-system]
requires = [
    "setuptools>=70.0.0",
    "setuptools-scm[toml]>=8.1.0",
    "wheel>=0.41.3"
]
build-backend = "setuptools.build_meta"

. . .

[tool.setuptools_scm]
version_file = "myproject/_version_scm.py"
version_scheme = "no-guess-dev"
local_scheme = "myproject._local_scheme:main"

The myproject/_local_scheme.py file has this content:

from setuptools_scm.version import ScmVersion

def main(version: ScmVersion) -> str:
    return version.format_choice("", "+dirty")

Here is the difference between the python -m setuptools_scm output and the version in the (freshly) generated _version_scm.py file:

Commit state   Latest tag                  python -m setuptools_scm   _version_scm.py
------------------------------------------------------------------------------------------------
Clean          1.23.0 on latest commit     1.23.0                     1.23.0+unknown
Dirty          1.23.0 on latest commit     1.23.0.post1.dev0+dirty    1.23.0.post1.dev0+unknown
Clean          1.22.2 on 13 commits back   1.22.2.post1.dev13         1.22.2.post1.dev13+unknown
Dirty          1.22.2 on 13 commits back   1.22.2.post1.dev13+dirty   1.22.2.post1.dev13+unknown

[andy-maier]

After some more investigation, it turns out that the result depends on whether "build" is run in an isolated environment or not:

• The above results were for an isolated environment (default of "build").
• When running "build" in a non-isolated environment (i.e. specify its --no-isolation option), the generated _version_scm.py file shows the same version that python -m setuptools_scm shows.

So my circumvention for now is to run "build" in a non-isolated environment. That's more transparent anyway.

[RonnyPfannschmidt]

whats the logging output when `SETUPTOOLS_SCM_DEBUG=1" in the environment

there should be a error when the version scheme is not found - if that error gets accidentally hidden we are missing a bug