Providing base version without git tags

[AbdealiLoKo]

Hi, We use a monorepo in my organization and so we do not use git tags for each project release. Instead, we are expected to note the version number within the respective project folder in the pyproject.toml

We are trying to add nightly releases, and use setuptools-scm to add the git commit to the version number for a specific project.

So, I have gotten setuptools-scm to work by adding it to the setuptools build system that we have, but I am not able to figure out how to get setuptools-scm to create the version number correctly.

Specifically, I have this in my pyproject.toml:

[build-system]
requires = [
    "setuptools>=62.3", # Need recursive package-data glob support
    "setuptools-scm",
]
build-backend = "setuptools.build_meta"

[project]
name = "myapp"
version = "1.34.0"

When I change the version = "1.34.0" to dynamic = ["version"] - setuptools-scm does give me a lot of nice stuff (it adds the git and diff/dirty parts to the version) - i.e. +g1a1a1a1a.d20251023 is appended - the "pseudo unique versions per commmit" feature

Things i found:

• I found the tag_regex config - But that still needs a git tag to be present
• I found the SETUPTOOLS_SCM_PRETEND_VERSION env var - But that doesn't add the +g... part to the version as it is taken as the final version
• I saw some version_scheme options - But couldn't find one that would fit my need

Wanted to check if I was missing any documentation or suggestions on how we coud use setuptools-scm to add the pseudo unique part to a base version we could provide in the pyproject.toml or another file in the monorepo (but not from git tags)?

PS: We also really liked the auto add items added to git into the package-data feature

[RonnyPfannschmidt]

thats what fallback version is for

im using it in #1228 where this repo turns into a monorepo

[RonnyPfannschmidt]

as for more detailed version schemes for monorepos - i don't have tag distance calculation for subtrees in yet - that needs some brainstorming on the features

[AbdealiLoKo]

Ah, thanks - looks like I missed the fallback_version in the docs !

So, I tried fallback_version and it seems like from 5 years ago there are some git tags present in the git repo and those seem to be getting used instead of the fallback version :(
I did try to set tag_regex = "invalid-no-tag-(.*)" - i.e. try to tell setuptools-scm to use a tag pattern that doesn't exist.
But then I get the error:

  File "venv/lib/python3.10/site-packages/setuptools_scm/git.py", line 347, in parse_describe
    return meta(tag=tag, distance=distance, dirty=dirty, node=node, config=config)
  File "venv/lib/python3.10/site-packages/setuptools_scm/version.py", line 264, in meta
    parsed_version = _parse_tag(tag, preformatted, config)
  File "venv/lib/python3.10/site-packages/setuptools_scm/version.py", line 238, in _parse_tag
    assert version is not None
AssertionError

[RonnyPfannschmidt]

You also need to set a custom descibr command

[AbdealiLoKo]

THanks @RonnyPfannschmidt looks like I got something working after some trial and error:

[build-system]
requires = ["setuptools>=80", "setuptools-scm"]
build-backend = "setuptools.build_meta"

[project]
name = "myapp"
dynamic = ["version"]

[tool.setuptools_scm]
root = "../.."
version_scheme = "only-version"
scm.git.describe_command = 'sh -c "echo v1.34.0-1-g$(git describe --always --long --dirty --abbrev=40)"'

Is this what you had in mind ? I couldn't figure out how to use fallback_version though

I guess there are a bunch of issues here though - had to remove the distance because there is no git tag to find the distance.
I am not sure why - but removing the --dirty in this command causes setuptools-scm to stop working

I wonder if there is a nice way to track versions from a file. That way using git history there could be some way to track when that file version number was set. And have a distance calculation based on that ...

[RonnyPfannschmidt]

Yikes no

I may need more details but never use the sh hack you used there

[RonnyPfannschmidt]

again - i strongly recommend the branch i linked as example that works

[AbdealiLoKo]

Aha, I see - I got a bit confused by the monorepo-branch cause I saw it using hatchling - but diving deeper I see the relevant configs.

Got it working with this now:

version_scheme = "only-version"
scm.git.describe_command = ["git", "describe", "--dirty", "--tags", "--long", "--match", "myapp-*"]
fallback_version = "2025.10.17"

I also realized that scm.git.describe_command can also be ["git", "invalidcmd"] - basically in this case the describe_command should have a non-zero exitcode and fallback it used :D

Much simpler. I still wonder if a version.txt file based approach might simplify this a lot more (as the distance is not really correct).
But the current fallback_version based thing is good for me.

[RonnyPfannschmidt]

a key intent of this toolset is to ensure a single source of truth for the version metadata

so no to files with version text - the scm is the source

[RonnyPfannschmidt]

additional detail - only version is more of a workaround for broken ci pipelines - its recommended to have every commit geta own .dev version isntead of forcing a preexisting version

if you want a static version anyway - just put it directly into pyproject.toml