Use fallback_version if SCM isn't found

[CharlesB2]

I'm in some situation (testing my package in Docker) where git isn't available, and thought I could just use fallback_version argument, but it turns out I still get an exception OSError: 'git' was not found.

I found I can overcome this by defining the SETUPTOOLS_SCM_PRETEND_VERSION environment variable, but I thought it would be easier to use fallback_version in this case as well?

I'm not sure I understood the different cases where one should use SETUPTOOLS_SCM_PRETEND_VERSION or fallback_version?

[RonnyPfannschmidt]

please post the full output of the build process when export SETUPTOOLS_SCM_DEBUG=1 is used
also what version is being used
there should not be a error on missing git commands

fallback is supposed to be used when all else fails, so when git fails it should be used
pretend is supposed to be used instead of figuring it, so distros can manage their envs

[CharlesB2]

Sorry I wasn't clear, I didn't want to report any error as using SETUPTOOLS_SCM_PRETEND_VERSION works when git isn't available.

It was more a suggestion to simplify things from a usage point of view, as for me after reading the docs I was thinking that fallback_version would work. It can be also completing the docs, e.g. to document the different cases where both SETUPTOOLS_SCM_PRETEND_VERSION and fallback_version apply

[RonnyPfannschmidt]

let me be clear, if setuptools_scm fails with fallback set, it is a bug and needs to be fixed

fallback is something you use more as a author
pretend is something you use as a packager

[CharlesB2]

OK then, here's the trace for the error I get when fallback_version is defined, and git not installed:

>>> import setuptools_scm
>>> setuptools_scm.get_version(fallback_version="TEST")
l {'root': '.', 'relative_to': None}
root '/work'
relative_to None
dist name: None
looking for ep setuptools_scm.parse_scm /work
found ep .git = setuptools_scm.git:parse
<class 'FileNotFoundError'> [Errno 2] No such file or directory: 'git' <traceback object at 0x7f15e2a4c5c0>
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/local/lib/python3.9/site-packages/setuptools_scm/__init__.py", line 169, in get_version
    return _get_version(config)
  File "/usr/local/lib/python3.9/site-packages/setuptools_scm/__init__.py", line 173, in _get_version
    parsed_version = _do_parse(config)
  File "/usr/local/lib/python3.9/site-packages/setuptools_scm/__init__.py", line 127, in _do_parse
    version = _version_from_entrypoints(config) or _version_from_entrypoints(
  File "/usr/local/lib/python3.9/site-packages/setuptools_scm/__init__.py", line 65, in _version_from_entrypoints
    version = _call_entrypoint_fn(root, config, ep.load())
  File "/usr/local/lib/python3.9/site-packages/setuptools_scm/__init__.py", line 46, in _call_entrypoint_fn
    return fn(root, config=config)
  File "/usr/local/lib/python3.9/site-packages/setuptools_scm/git.py", line 115, in parse
    require_command("git")
  File "/usr/local/lib/python3.9/site-packages/setuptools_scm/utils.py", line 142, in require_command
    raise OSError("%r was not found" % name)
OSError: 'git' was not found

Version used is 6.0.1, installed from pip.

[RonnyPfannschmidt]

thanks, the controll flow is indeed incorrect, i'll need to add a test that validates this so i dont introduce it by accident

[P403n1x87]

I'm also trying to use fallback_version from setup.py inside a git submodle and it seems that the configuration argument is completely ignored as I still get a LookupError as if I didn't set fallback_version at all.

My setup.py has

use_scm_version={"fallback_version": "0.0.0"},

and the debug logs give

    l {'root': '.', 'relative_to': None}
    root '/private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-req-build-nc68aatt'
    relative_to None
    dist name: ddtrace
    looking for ep setuptools_scm.parse_scm /private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-req-build-nc68aatt
    found ep EntryPoint(name='.git', value='setuptools_scm.git:parse', group='setuptools_scm.parse_scm') in /private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-req-build-nc68aatt
    GIT_ASKPASS /Applications/Visual Studio Code.app/Contents/Resources/app/extensions/git/dist/askpass.sh
    cmd 'git rev-parse --show-prefix'
     in /private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-req-build-nc68aatt
    GIT_ASKPASS /Applications/Visual Studio Code.app/Contents/Resources/app/extensions/git/dist/askpass.sh
    err b'fatal: not a git repository: /private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-req-build-nc68aatt/../../.git/modules/prof-probe/slydog-dd-trace-py\n'
    ret 128
    EntryPoint(name='.git', value='setuptools_scm.git:parse', group='setuptools_scm.parse_scm') None
    looking for ep setuptools_scm.parse_scm_fallback /private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-req-build-nc68aatt
    found ep EntryPoint(name='setup.py', value='setuptools_scm.hacks:fallback_version', group='setuptools_scm.parse_scm_fallback') in /private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-req-build-nc68aatt
    version 0.0.0 -> 0.0.0
    EntryPoint(name='setup.py', value='setuptools_scm.hacks:fallback_version', group='setuptools_scm.parse_scm_fallback') <ScmVersion 0.0.0 d=None n=None d=False b=None>
    scm version <ScmVersion 0.0.0 d=None n=None d=False b=None>
    config {'version_scheme': 'guess-next-dev', 'local_scheme': 'node-and-date'}
    l {'root': '.', 'relative_to': None}
    root '/private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-req-build-nc68aatt'
    relative_to None
    dist name: ddtrace
    looking for ep setuptools_scm.parse_scm /private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-req-build-nc68aatt
    found ep EntryPoint(name='.git', value='setuptools_scm.git:parse', group='setuptools_scm.parse_scm') in /private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-req-build-nc68aatt
    GIT_ASKPASS /Applications/Visual Studio Code.app/Contents/Resources/app/extensions/git/dist/askpass.sh
    cmd 'git rev-parse --show-prefix'
     in /private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-req-build-nc68aatt
    GIT_ASKPASS /Applications/Visual Studio Code.app/Contents/Resources/app/extensions/git/dist/askpass.sh
    err b'fatal: not a git repository: /private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-req-build-nc68aatt/../../.git/modules/prof-probe/slydog-dd-trace-py\n'
    ret 128
    EntryPoint(name='.git', value='setuptools_scm.git:parse', group='setuptools_scm.parse_scm') None
    looking for ep setuptools_scm.parse_scm_fallback /private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-req-build-nc68aatt
    found ep EntryPoint(name='setup.py', value='setuptools_scm.hacks:fallback_version', group='setuptools_scm.parse_scm_fallback') in /private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-req-build-nc68aatt
    EntryPoint(name='setup.py', value='setuptools_scm.hacks:fallback_version', group='setuptools_scm.parse_scm_fallback') None
    Traceback (most recent call last):
      File "/private/tmp/foo/lib/python3.9/site-packages/pip/_vendor/pep517/in_process/_in_process.py", line 349, in <module>
        main()
      File "/private/tmp/foo/lib/python3.9/site-packages/pip/_vendor/pep517/in_process/_in_process.py", line 331, in main
        json_out['return_val'] = hook(**hook_input['kwargs'])
      File "/private/tmp/foo/lib/python3.9/site-packages/pip/_vendor/pep517/in_process/_in_process.py", line 151, in prepare_metadata_for_build_wheel
        return hook(metadata_directory, config_settings)
      File "/private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-build-env-99xv5rim/overlay/lib/python3.9/site-packages/setuptools/build_meta.py", line 174, in prepare_metadata_for_build_wheel
        self.run_setup()
      File "/private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-build-env-99xv5rim/overlay/lib/python3.9/site-packages/setuptools/build_meta.py", line 158, in run_setup
        exec(compile(code, __file__, 'exec'), locals())
      File "setup.py", line 150, in <module>
        setup(
      File "/private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-build-env-99xv5rim/overlay/lib/python3.9/site-packages/setuptools/__init__.py", line 153, in setup
        return distutils.core.setup(**attrs)
      File "/usr/local/Cellar/python@3.9/3.9.7/Frameworks/Python.framework/Versions/3.9/lib/python3.9/distutils/core.py", line 108, in setup
        _setup_distribution = dist = klass(attrs)
      File "/private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-build-env-99xv5rim/overlay/lib/python3.9/site-packages/setuptools/dist.py", line 453, in __init__
        _Distribution.__init__(
      File "/usr/local/Cellar/python@3.9/3.9.7/Frameworks/Python.framework/Versions/3.9/lib/python3.9/distutils/dist.py", line 292, in __init__
        self.finalize_options()
      File "/private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-build-env-99xv5rim/overlay/lib/python3.9/site-packages/setuptools/dist.py", line 831, in finalize_options
        ep(self)
      File "/private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-build-env-99xv5rim/overlay/lib/python3.9/site-packages/setuptools_scm/integration.py", line 94, in infer_version
        dist.metadata.version = _get_version(config)
      File "/private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-build-env-99xv5rim/overlay/lib/python3.9/site-packages/setuptools_scm/__init__.py", line 177, in _get_version
        parsed_version = _do_parse(config)
      File "/private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-build-env-99xv5rim/overlay/lib/python3.9/site-packages/setuptools_scm/__init__.py", line 135, in _do_parse
        raise LookupError(
    LookupError: setuptools-scm was unable to detect version for '/private/var/folders/zm/3z1wy1b135721pl0l6n61yt00000gn/T/pip-req-build-nc68aatt'.

This seems to be caused by the presence of a pyproject.toml file. The first fallback version (from the setup.py) is overridden by the pyproject.toml, which in my case had no fallback version specified.