Fail to resolve env var default in git packages

[ltrojan-ths]

Description

Trying to add a default value to the git ref specified as an env var fails to parse the value correctly:

my-package @ git+ssh://git@github.com/my-repo.git@${PACKAGE_REF:-main}#subdirectory=package

will produce the following error:

(...)

Running command git clone --filter=blob:none --quiet 'ssh://****@github.com/my-repo.git /tmp/pip-install-7fi75vp9/my-package_12345


  WARNING: Did not find branch or tag '${PACKAGE_REF:-main}', assuming revision or ref.
  Running command git checkout -q '${PACKAGE_REF:-main}'
  error: pathspec '${PACKAGE_REF:-main}' did not match any file(s) known to git
  error: subprocess-exited-with-error
  
  × git checkout -q '${PACKAGE_REF:-main}' did not run successfully.
  │ exit code: 1
  ╰─> See above for output.

the same happens regardless of whether the PACKAGE_REF is defined or not...

Expected behavior

the correct branch is checked out: master if PACKAGE_REF is not defined and $PACKAGE_REF if it is defined

pip version

24.0

Python version

Python 3.10.9 (pyenv/venv)

OS

Linux ltrojan-laptop 5.15.0-101-generic #111~20.04.1-Ubuntu SMP Mon Mar 11 15:44:43 UTC 2024 x86_64 x86_64 x86_64 GNU/Linux

How to Reproduce

1. create and setup a repo (with a pyproject.toml and a source folder containing some basic python code)
2. create a feature branch and adit the python code
3. in a separate folder, create a requirements.txt
4. add `py-package @ git+ssh://git@github.com/my-repo.git@${PACKAGE_REF:-main}#subdirectory=package
5. ensure git can clone the repo (ssh keys are setup properly)
6. run pip install -r requirements.txt
7. run PACKAGE_REF=my-feature-branch pip install -r requirements.txt

Output

see above

Code of Conduct

• I agree to follow the PSF Code of Conduct.

[pfmoore]

The ${PACKAGE_REF:-main} syntax is specific to bash (and maybe some other shells?) It's not supported by pip, so it won't get interpreted correctly in a requirements file.

[ltrojan-ths]

@pfmoore thanks for the reply!

ok... i miss-read another issue from a couple of years ago'.. i thought the : and the :- notation were not bash specific...

is there another way to provide a default to an env var? the idea is that the env var should be set only in "special" occasions, in this particular case if one wants to try a new feature only being developed as a new feature branch...

[pfmoore]

Docs are here. No, there's no way to provide a default.