test.tar.gz does not appear to be a Python project: neither 'setup.py' nor 'pyproject.toml' found.

Description

I’m writing a small build-backend, essentiall a wrapper around setuptools. In a test project, the pyproject.toml is

[build-system]
requires = [
  "setuptools",
  "mybuildbackend",
  "wheel"
]
# build-backend = "setuptools.build_meta"
build-backend = "mybuildbackend.build_meta"

Upon

python -m build --sdist

this spits out a nice-looking dist/test-project.tar.gz. When trying to

pip install dist/test-project.tar.gz

however, I’m getting

ERROR: file:///path/to/dist/test-project-0.0.1.tar.gz does not appear to be a Python project: neither 'setup.py' nor 'pyproject.toml' found.

It works fine when pip-installing the untarred folder. It also works when changing just one line in tar, namely adding

build-backend = "setuptools.build_meta"

instead of the custom one.

I have no clue why that could be. The error message is misleadiing since there is a pyproject.toml.

Any idea what may be going wrong?

Expected behavior

No response

pip version

22.0.4

Python version

3.9.10

OS

Ubuntu 22.04

How to Reproduce

See above.

Output

No response

Code of Conduct

• I agree to follow the PSF Code of Conduct.

[nschloe]

Thanks everyone for the input. I’ve found the bug, and it was a subtle one in the backend. When recreating the tar.gz-file, a leading / was accidentally added in the file. That’s why pip was not able to find the pyproject.toml file.

I would have been happy about a clearer error message (found the file here but it should be there), but I think this is so niche that it doesn’t warrant anyone spending more time on this. Thanks again!

[pradyunsg]

(found the file here but it should be there)

There’s no “found file here” – it basically looks if there’s a file pyproject.toml or setup.py file in the tarball. It doesn’t go around searching or recursing to look for it – it’s a one-time lookup of a specific filename.

It didn’t find any file with that filename where it looked (the root of the source tarball) and presented that as an error.

I agree that working to add a clearer error message is not worth the effort here.