Expand environment variables in path field

It would be nice if the injection of environment variables worked for the path variable too

@njgrisafi from #1688

It would be nice if we can have environment variables loaded throughout the entire Pipfile. E.g.

[dev-packages]
my-package = {path="${PATH_TO_REPO}", editable = true}

Is your feature request related to a problem? Please describe.

Environment expansion does not work for path or file as observed in #2317

Describe the solution you’d like

I’d like the variable expansion to work for the path/file fields. Unfortunately, this probably involves an expansion in the Pipfile.lock too, so that both can truly be portable with respect to the environment variable

Describe alternatives you’ve considered

I tried this in pipenv/project.py as a failed POC.

    def _parse_pipfile(self, contents):
        from pipfile.api import PipfileParser
           
        try: 
            d = tomlkit.parse(contents)
        except Exception:
            # We lose comments here, but it's for the best.)
            # Fallback to toml parser, for large files.
            d = toml.loads(contents)
        return PipfileParser().inject_environment_variables(d)

I will have to use symlinks in the meantime

[heronrs]

Would be nice to have this feature. Currently we need to install an #egg from a private gitlab repo and the ability to inject the user token would be nice, such as:

mypkg = {git = "https://oauth2:$[e-mail]/my-repo#egg=mypkg"}

[frostming]

@bkemmer Your Pipfile is not valid, [[source]] is for PyPI index, not VCS repo.