[BUG] Tox doesn't respect `--discover`

[webknjaz]

$sbj. Dunno why but passing a full absolute path to a Python executable seems to be ignored. It's not even mentioned in the log. Not sure where it gets lost:

$ echo $PATH
~/bin:~/.nvm/versions/node/v22.9.0/bin:~/.pyenv/plugins/pyenv-virtualenv/shims:~/.pyenv/shims:~/.pyenv/bin:/usr/local/sbin:/usr/local/bin:/usr/bin:/opt/bin:/usr/lib/llvm/20/bin:/usr/lib/llvm/19/bin:/usr/lib64/opencascade/bin:~/.local/bin

$ tox --version
4.31.0 from ~/.local/share/pipx/venvs/tox/lib/python3.12/site-packages/tox/__init__.py

$ tox r --discover=~/.pyenv/versions/3.11.10/bin/python3.11 -e pre-commit -vv --notest
ROOT: 292 D setup logging to DEBUG on pid 369825 [tox/report.py:225]
.pkg: 332 I find interpreter for spec PythonSpec(path=~/.local/share/pipx/venvs/tox/bin/python) [virtualenv/discovery/builtin.py:77]
.pkg: 333 D filesystem is case-sensitive [virtualenv/discovery/info.py:20]
.pkg: 334 D got python info of /usr/bin/python3.12 from ~/.local/share/virtualenv/py_info/2/f0d7a494a3f776233427cb85a7e198c7cf4913b50a203c6febc678cc4f5bf265.json [virtualenv/app_data/via_disk_folder.py:132]
.pkg: 334 I proposed PythonInfo(spec=CPython3.12.11.final.0-64, system=/usr/bin/python3.12, exe=~/.local/share/pipx/venvs/tox/bin/python, platform=linux, version='3.12.11 (main, Jul 31 2025, 11:37:14) [GCC 14.3.0]', encoding_fs_io=utf-8-utf-8) [virtualenv/discovery/builtin.py:84]
.pkg: 334 D accepted PythonInfo(spec=CPython3.12.11.final.0-64, system=/usr/bin/python3.12, exe=~/.local/share/pipx/venvs/tox/bin/python, platform=linux, version='3.12.11 (main, Jul 31 2025, 11:37:14) [GCC 14.3.0]', encoding_fs_io=utf-8-utf-8) [virtualenv/discovery/builtin.py:86]
.pkg: 336 D symlink on filesystem does work [virtualenv/info.py:50]
.pkg: 336 D filesystem is case-sensitive [virtualenv/info.py:27]
.pkg: 375 I find interpreter for spec PythonSpec(path=~/.local/share/pipx/venvs/tox/bin/python) [virtualenv/discovery/builtin.py:77]
.pkg: 375 I proposed PythonInfo(spec=CPython3.12.11.final.0-64, system=/usr/bin/python3.12, exe=~/.local/share/pipx/venvs/tox/bin/python, platform=linux, version='3.12.11 (main, Jul 31 2025, 11:37:14) [GCC 14.3.0]', encoding_fs_io=utf-8-utf-8) [virtualenv/discovery/builtin.py:84]
.pkg: 376 D accepted PythonInfo(spec=CPython3.12.11.final.0-64, system=/usr/bin/python3.12, exe=~/.local/share/pipx/venvs/tox/bin/python, platform=linux, version='3.12.11 (main, Jul 31 2025, 11:37:14) [GCC 14.3.0]', encoding_fs_io=utf-8-utf-8) [virtualenv/discovery/builtin.py:86]
.pkg: 382 I find interpreter for spec PythonSpec(path=~/.local/share/pipx/venvs/tox/bin/python) [virtualenv/discovery/builtin.py:77]
.pkg: 382 I proposed PythonInfo(spec=CPython3.12.11.final.0-64, system=/usr/bin/python3.12, exe=~/.local/share/pipx/venvs/tox/bin/python, platform=linux, version='3.12.11 (main, Jul 31 2025, 11:37:14) [GCC 14.3.0]', encoding_fs_io=utf-8-utf-8) [virtualenv/discovery/builtin.py:84]
.pkg: 382 D accepted PythonInfo(spec=CPython3.12.11.final.0-64, system=/usr/bin/python3.12, exe=~/.local/share/pipx/venvs/tox/bin/python, platform=linux, version='3.12.11 (main, Jul 31 2025, 11:37:14) [GCC 14.3.0]', encoding_fs_io=utf-8-utf-8) [virtualenv/discovery/builtin.py:86]
.pkg: 389 I find interpreter for spec PythonSpec(path=~/.local/share/pipx/venvs/tox/bin/python) [virtualenv/discovery/builtin.py:77]
.pkg: 389 I proposed PythonInfo(spec=CPython3.12.11.final.0-64, system=/usr/bin/python3.12, exe=~/.local/share/pipx/venvs/tox/bin/python, platform=linux, version='3.12.11 (main, Jul 31 2025, 11:37:14) [GCC 14.3.0]', encoding_fs_io=utf-8-utf-8) [virtualenv/discovery/builtin.py:84]
.pkg: 390 D accepted PythonInfo(spec=CPython3.12.11.final.0-64, system=/usr/bin/python3.12, exe=~/.local/share/pipx/venvs/tox/bin/python, platform=linux, version='3.12.11 (main, Jul 31 2025, 11:37:14) [GCC 14.3.0]', encoding_fs_io=utf-8-utf-8) [virtualenv/discovery/builtin.py:86]
.pkg: 396 I find interpreter for spec PythonSpec(path=~/.local/share/pipx/venvs/tox/bin/python) [virtualenv/discovery/builtin.py:77]
.pkg: 396 I proposed PythonInfo(spec=CPython3.12.11.final.0-64, system=/usr/bin/python3.12, exe=~/.local/share/pipx/venvs/tox/bin/python, platform=linux, version='3.12.11 (main, Jul 31 2025, 11:37:14) [GCC 14.3.0]', encoding_fs_io=utf-8-utf-8) [virtualenv/discovery/builtin.py:84]
.pkg: 396 D accepted PythonInfo(spec=CPython3.12.11.final.0-64, system=/usr/bin/python3.12, exe=~/.local/share/pipx/venvs/tox/bin/python, platform=linux, version='3.12.11 (main, Jul 31 2025, 11:37:14) [GCC 14.3.0]', encoding_fs_io=utf-8-utf-8) [virtualenv/discovery/builtin.py:86]
.pkg: 400 I find interpreter for spec PythonSpec(path=~/.local/share/pipx/venvs/tox/bin/python) [virtualenv/discovery/builtin.py:77]
.pkg: 400 I proposed PythonInfo(spec=CPython3.12.11.final.0-64, system=/usr/bin/python3.12, exe=~/.local/share/pipx/venvs/tox/bin/python, platform=linux, version='3.12.11 (main, Jul 31 2025, 11:37:14) [GCC 14.3.0]', encoding_fs_io=utf-8-utf-8) [virtualenv/discovery/builtin.py:84]
.pkg: 400 D accepted PythonInfo(spec=CPython3.12.11.final.0-64, system=/usr/bin/python3.12, exe=~/.local/share/pipx/venvs/tox/bin/python, platform=linux, version='3.12.11 (main, Jul 31 2025, 11:37:14) [GCC 14.3.0]', encoding_fs_io=utf-8-utf-8) [virtualenv/discovery/builtin.py:86]
.pkg: 405 I find interpreter for spec PythonSpec(path=~/.local/share/pipx/venvs/tox/bin/python) [virtualenv/discovery/builtin.py:77]
.pkg: 405 I proposed PythonInfo(spec=CPython3.12.11.final.0-64, system=/usr/bin/python3.12, exe=~/.local/share/pipx/venvs/tox/bin/python, platform=linux, version='3.12.11 (main, Jul 31 2025, 11:37:14) [GCC 14.3.0]', encoding_fs_io=utf-8-utf-8) [virtualenv/discovery/builtin.py:84]
.pkg: 405 D accepted PythonInfo(spec=CPython3.12.11.final.0-64, system=/usr/bin/python3.12, exe=~/.local/share/pipx/venvs/tox/bin/python, platform=linux, version='3.12.11 (main, Jul 31 2025, 11:37:14) [GCC 14.3.0]', encoding_fs_io=utf-8-utf-8) [virtualenv/discovery/builtin.py:86]
.pkg: 410 I find interpreter for spec PythonSpec(path=~/.local/share/pipx/venvs/tox/bin/python) [virtualenv/discovery/builtin.py:77]
.pkg: 411 I proposed PythonInfo(spec=CPython3.12.11.final.0-64, system=/usr/bin/python3.12, exe=~/.local/share/pipx/venvs/tox/bin/python, platform=linux, version='3.12.11 (main, Jul 31 2025, 11:37:14) [GCC 14.3.0]', encoding_fs_io=utf-8-utf-8) [virtualenv/discovery/builtin.py:84]
.pkg: 411 D accepted PythonInfo(spec=CPython3.12.11.final.0-64, system=/usr/bin/python3.12, exe=~/.local/share/pipx/venvs/tox/bin/python, platform=linux, version='3.12.11 (main, Jul 31 2025, 11:37:14) [GCC 14.3.0]', encoding_fs_io=utf-8-utf-8) [virtualenv/discovery/builtin.py:86]
.pkg: 427 W _optional_hooks> python ~/.local/share/pipx/venvs/tox/lib/python3.12/site-packages/pyproject_api/_backend.py True setuptools.build_meta [tox/tox_env/api.py:464]
[...]
  pre-commit: OK (2.91 seconds)
  congratulations :) (3.03 seconds)

[webknjaz]

FTR, I've found this bug while trying to make sense of #3403 (comment) that feels related.