Use venv API to get venv paths

[dukecat0]

• I have added an entry to docs/changelog.md

Summary of changes

Use venv API to get venv paths.

Closes #701

Test plan

Tested by running

pipx install black --verbose

[dukecat0]

However, some users might not have venv installed (see #853). Maybe we should also support virtualenv?

[uranusjr]

I have a gut feeling this may be problematic if the environment path contains non-ASCII characters, since not all terminals can output those characters (say if the encoding is not configured to UTF-8).

It’s probably more reliable to write the path to a temp file instead.

[uranusjr]

Suggested change

	root_paths = venv.EnvBuilder().ensure_directories(r"{str(root)}")
	root_paths = venv.EnvBuilder().ensure_directories({root})

[dukecat0]

Probably raw string should be used? (For handling paths on Windows)

[uranusjr]

Maybe we should also support virtualenv?

Does virtualenv provide an interface to introspect an environment outside of it? Because an environment created by virtualenv does not have access to the virtualenv module.

[dukecat0]

I have a gut feeling this may be problematic if the environment path contains non-ASCII characters, since not all terminals > can output those characters (say if the encoding is not configured to UTF-8).

It’s probably more reliable to write the path to a temp file instead.

pipx/src/pipx/util.py

Lines 130 to 137 in 4c0f289

	def get_site_packages(python: Path) -> Path:
	output = run_subprocess(
	[python, "-c", "import sysconfig; print(sysconfig.get_path('purelib'))"],
	capture_stderr=False,
	).stdout
	path = Path(output.strip())
	path.mkdir(parents=True, exist_ok=True)
	return path

The output is just printed to the terminal in this function and it seems fine?

[dukecat0]

Does virtualenv provide an interface to introspect an environment outside of it?

I think no. Or probably we can keep this for virtualenv users?

if WINDOWS:

    def get_venv_paths(root: Path) -> Tuple[Path, Path]:
        bin_path = root / "Scripts"
        python_path = bin_path / "python.exe"
        return bin_path, python_path

else:

    def get_venv_paths(root: Path) -> Tuple[Path, Path]:
        bin_path = root / "bin"
        python_path = bin_path / "python"
        return bin_path, python_path

[uranusjr]

If we need to keep the bin/Script guess logic I’d rather keep it and improve the detection logic to account for MSYS. I think there’s established logic out there somewhere that can reliably detect this.

[dukecat0]

I think there’s established logic out there somewhere that can reliably detect this.

Yes, for example python-poetry/poetry#4467 and python-poetry/poetry#3713.

[dukecat0]

If we need to keep the bin/Script guess logic I’d rather keep it and improve the detection logic to account for MSYS.

I will open another PR for this. (#908)