Latest packaging (23.2) release breaks pipx detection of local path installation

[potiuk]

Describe the bug

Latest packaging release (23.2) breaks pipx detection of local path installation.

When you install pipx from the scratch and you are trying to run:

pipx install --editable  ./<path_to_package_spec>

You get this warning:

⚠️ Ignoring --editable install option. pipx disallows it for anything but a local path, to avoid having to create a new src/ directory.

This is clearly wrong, as we are trying to install package from local path, so --editable flag should be still OK.

How to reproduce

• Prepare clean installation of pipx from the scratch. Make sure packaging version is 23.2

> pip freeze | grep packaging
packaging==23.2

• Check out any Python source project to a local directory (for example you can check out git@github.com:apache/airflow.git and and look at ./dev/breeze project which is part of the repository)
• Run pipx install --editable <path_to_the project> (for example pipx install --editable ./dev/breeze in checked out airflow repository
• See the warning message produced:

⚠️ Ignoring --editable install option. pipx disallows it for anything but a local path, to avoid having to create a new src/ directory.

This change is caused by change in behaviour of the packaging (23.2) project, specifically pypa/packaging#120 . You can also go back t correct behaviour by downgrading the packaging to version 23.1)

pip install "packaging==23.1"
pipx install --editable ./dev/breeze

This works fine without the warning.

The root cause of it is this code from pipx/package_specifier.py:

 if not valid_pep508:
        try:
            package_req = Requirement("notapackagename @ " + package_spec)
        except InvalidRequirement:  # !!! <- this exception not thrown any more
            # not a valid url 
            pass
        else:
            valid_url = package_spec

    if not valid_pep508 and not valid_url:  #!!! <- valid_url is set, so we no longer determine if package_path_str exist
        (package_path_str, package_extras_str) = _split_path_extras(package_spec)

        (package_path, package_path_exists) = _check_package_path(package_path_str)

        if package_path_exists:
            valid_local_path = str(package_path.resolve()) + package_extras_str

The code relies implicitly on Requirement throwing an exception in case package specification is a local path. Since the exception is not thrown any more, valid_url is set and the check for existence of the path is not done.

Expected behavior

The local path should be detected as local path and editable install should be allowed.

[hussein-awala]

I wonder if this issue duplicates #1070, which was fixed by #1071 🤔

[potiuk]

Ah yes. I was on holidays when it happened... Closing as duplicate then.

[potiuk]

I did not even remember I commented it then.