Substitution of a command marked with - (ignore exit code)

[mportesdev]

I noticed that tox 4.x does not observe the - mark to ignore a command's exit code when using a {[testenv:x]commands} substitution from another section. This behavior is different from tox 3.x.

I don't know if this is expected, but I think it should at least be documented somewhere. I haven't found this mentioned in any of these docs sections:
Upgrading to tox v4
Substitution for values from other sections
Ignoring the exit code of a given command

[mportesdev]

For example:

[tox]
skipsdist = true

[testenv:x]
commands = - python -c 'raise SystemExit(1)'

[testenv:y]
commands = {[testenv:x]commands}

Running tox 3, both jobs succeed:

$ venv-tox3/bin/tox --version
3.28.0 imported from /home/michal/python/toxrepro/venv-tox3/lib/python3.11/site-packages/tox/__init__.py
$ venv-tox3/bin/tox -e x,y
x create: /home/michal/python/toxrepro/.tox/x
x run-test-pre: PYTHONHASHSEED='1995657920'
x run-test: commands[0] | - python -c 'raise SystemExit(1)'
y create: /home/michal/python/toxrepro/.tox/y
y run-test-pre: PYTHONHASHSEED='1995657920'
y run-test: commands[0] | - python -c 'raise SystemExit(1)'
___________________________________________________________________________________________________________ summary ____________________________________________________________________________________________________________
  x: commands succeeded
  y: commands succeeded
  congratulations :)

Running tox 4, the y job fails:

$ rm -rf .tox/
$ venv-tox4/bin/tox --version
4.4.11 from /home/michal/python/toxrepro/venv-tox4/lib/python3.11/site-packages/tox/__init__.py
$ venv-tox4/bin/tox run -e x,y
x: commands[0]> python -c 'raise SystemExit(1)'
x: exit 1 (0.08 seconds) /home/michal/python/toxrepro> python -c 'raise SystemExit(1)' pid=145788
x: command failed but is marked ignore outcome so handling it as success
x: OK ✔ in 0.42 seconds
y: commands[0]> python -c 'raise SystemExit(1)'
y: exit 1 (0.06 seconds) /home/michal/python/toxrepro> python -c 'raise SystemExit(1)' pid=145799
  x: OK (0.42=setup[0.35]+cmd[0.08] seconds)
  y: FAIL code 1 (0.31=setup[0.25]+cmd[0.06] seconds)
  evaluation failed :( (0.84 seconds)

[gaborbernat]

PR to fix it is welcome.