Description

When using pyenv to manage Python versions, virtualenv's builtin discovery resolves pyenv shims to the system Python instead of the pyenv-managed version. For example, with pyenv providing Python 3.8.12 on $PATH, virtualenv resolves the shim to /usr/bin/python3.8 (system Python 3.8.6).

Originally reported as tox-dev/tox#3064, but the issue is in virtualenv's discovery logic, not tox.

Steps to Reproduce

1. Install a Python version via pyenv (e.g. pyenv install 3.8.12)
2. Set it as local version (pyenv local 3.8.12)
3. Confirm python3.8 --version returns 3.8.12
4. Have a different system Python 3.8 installed (e.g. /usr/bin/python3.8 = 3.8.6)
5. Create a virtualenv targeting python3.8

The virtualenv will use the system Python 3.8.6 instead of the pyenv-managed 3.8.12.

Verbose Discovery Log

From the original report, running tox -rvvve py38 shows virtualenv's discovery:

py38: discover exe for PythonInfo(spec=CPython3.10.6) in /usr
py38: discover PATH[0]=/home/user/.pyenv/plugins/pyenv-virtualenv/shims
py38: discover PATH[1]=/home/user/.pyenv/shims
py38: got python info of %s from (PosixPath('/home/user/.pyenv/shims/python3.8'), ...)
py38: got python info of %s from (PosixPath('/usr/bin/python3.8'), ...)
py38: proposed PathPythonInfo(spec=CPython3.8.6.final.0-64, system=/usr/bin/python3.8, exe=/home/user/.pyenv/shims/python3.8, ...)
py38: accepted PathPythonInfo(spec=CPython3.8.6.final.0-64, system=/usr/bin/python3.8, ...)

The shim at /home/user/.pyenv/shims/python3.8 is found first, but when resolving to get PythonInfo, it resolves system=/usr/bin/python3.8 (3.8.6) instead of the pyenv-managed /home/user/.pyenv/versions/3.8.12/bin/python3.8.

Expected Behavior

virtualenv should resolve pyenv shims to the actual Python they delegate to, respecting pyenv's version selection (.python-version, PYENV_VERSION, etc.), rather than resolving to the system Python.

Environment

• OS: Ubuntu (Linux)
• pyenv with pyenv-virtualenv plugin
• virtualenv 20.23.1 (at time of original report)
• Both system Python 3.8.6 and pyenv Python 3.8.12 installed