inject command uses wrong python interpreter for local packages

[lecardozo]

Describe the bug
While trying to pipx inject a local wheel with specific Python version constraints into a compatible environment (i.e. with a valid interpreter for those constraints), I keep getting the following error:

ERROR: Package 'my-local-package' requires a different Python: 3.11.1 not in '<3.11,>=3.8'

Here are the relevant versions and constraints 👇

• package (to be injected) interpreter constraints: <3.11, >=3.8
• environment interpreter: 3.8
• pipx interpreter: 3.11.1

After seeing the error, it became clear that somehow in the middle of the injection process, pipx was trying to install the package with a different interpreter for some reason. After some debugging, I noticed that when the package is a local distribution we need to install it (without its dependencies) into a temporary venv in order to extract its name. However, when we do it, we end up using a default Python interpreter, instead of the one associated with the venv here 👇

pipx/src/pipx/commands/inject.py

Lines 46 to 51 in 726eaf8

	# package_spec is anything pip-installable, including package_name, vcs spec,
	# zip file, or tar.gz file.
	if package_name is None:
	package_name = package_name_from_spec(
	package_spec, venv.python, pip_args=pip_args, verbose=verbose
	)

I locally replaced venv.python (which maps to a default interpreter in this case) with venv.python_path (which maps to venv-specific interpreter) and it worked 😃

How to reproduce

Verbose logs for the inject command

pipx >(_parsed_package_to_package_or_url:128): cleaned package spec: /path/to/my-local-package-1.0.0-py3-none-any.whl
creating virtual environment...
pipx >(run_subprocess:173): running /opt/homebrew/Cellar/pipx/1.1.0/libexec/bin/python3.11 -m venv --without-pip /var/folders/vj/chbx1tms2c93nmnnp2gw4wh80000gq/T/tmpe5g_foll
pipx >(run_subprocess:173): running /var/folders/vj/chbx1tms2c93nmnnp2gw4wh80000gq/T/tmpe5g_foll/bin/python -c import sysconfig; print(sysconfig.get_path('purelib'))
pipx >(run_subprocess:173): running /Users/me/.local/pipx/shared/bin/python -c import sysconfig; print(sysconfig.get_path('purelib'))
pipx >(run_subprocess:173): running /var/folders/vj/chbx1tms2c93nmnnp2gw4wh80000gq/T/tmpe5g_foll/bin/python --version
determining package name from '/path/to/my-local-package-1.0.0-py3-none-any.whl'...
pipx >(run_subprocess:173): running /var/folders/vj/chbx1tms2c93nmnnp2gw4wh80000gq/T/tmpe5g_foll/bin/python -m pip list --format=json
pipx >(run_subprocess:173): running /var/folders/vj/chbx1tms2c93nmnnp2gw4wh80000gq/T/tmpe5g_foll/bin/python -m pip install --no-dependencies /path/to/my-local-package-1.0.0-py3-none-any.whl
Looking in indexes: https://pypi.org/simple
Processing /path/to/my-local-package-1.0.0-py3-none-any.whl
ERROR: Package 'my-local-package' requires a different Python: 3.11.1 not in '<3.11,>=3.8'
pipx >(subprocess_post_check:207): '/var/folders/vj/chbx1tms2c93nmnnp2gw4wh80000gq/T/tmpe5g_foll/bin/python -m pip install --no-dependencies /path/to/my-local-package-1.0.0-py3-none-any.whl' failed
Cannot determine package name from spec '/path/to/my-local-package-1.0.0-py3-none-any.whl'. Check package spec for errors.

Expected behavior

pipx should be able to inject dependencies into existing environments if their interpreters are compatible.