IndexError with empty command via env

[blueyed]

Given this tox.ini:

[tox]
skipsdist = True
[testenv]
commands =
  {env:EMPTY_COMMAND:}
  true

tox fails:

% tox
python run-test-pre: PYTHONHASHSEED='215393528'
python run-test: commands[0] | 
___________________________________ summary ____________________________________
  python: commands succeeded
  congratulations :)
Traceback (most recent call last):
  File "…/Vcs/tox/.venv/bin/tox", line 11, in <module>
    load_entry_point('tox', 'console_scripts', 'tox')()
  File "…/Vcs/tox/src/tox/session/__init__.py", line 44, in cmdline
    main(args)
  File "…/Vcs/tox/src/tox/session/__init__.py", line 68, in main
    exit_code = session.runcommand()
  File "…/Vcs/tox/src/tox/session/__init__.py", line 192, in runcommand
    return self.subcommand_test()
  File "…/Vcs/tox/src/tox/session/__init__.py", line 220, in subcommand_test
    run_sequential(self.config, self.venv_dict)
  File "…/Vcs/tox/src/tox/session/commands/run/sequential.py", line 22, in run_sequential
    runtestenv(venv, config)
  File "…/Vcs/tox/src/tox/session/commands/run/sequential.py", line 75, in runtestenv
    config.pluginmanager.hook.tox_runtest(venv=venv, redirect=redirect)
  File "…/Vcs/tox/.venv/lib/python3.7/site-packages/pluggy/hooks.py", line 289, in __call__
    return self._hookexec(self, self.get_hookimpls(), kwargs)
  File "…/Vcs/tox/.venv/lib/python3.7/site-packages/pluggy/manager.py", line 87, in _hookexec
    return self._inner_hookexec(hook, methods, kwargs)
  File "…/Vcs/tox/.venv/lib/python3.7/site-packages/pluggy/manager.py", line 81, in <lambda>
    firstresult=hook.spec.opts.get("firstresult") if hook.spec else False,
  File "…/Vcs/tox/.venv/lib/python3.7/site-packages/pluggy/callers.py", line 208, in _multicall
    return outcome.get_result()
  File "…/Vcs/tox/.venv/lib/python3.7/site-packages/pluggy/callers.py", line 80, in get_result
    raise ex[1].with_traceback(ex[2])
  File "…/Vcs/tox/.venv/lib/python3.7/site-packages/pluggy/callers.py", line 187, in _multicall
    res = hook_impl.function(*args)
  File "…/Vcs/tox/src/tox/venv.py", line 748, in tox_runtest
    venv.test(redirect=redirect)
  File "…/Vcs/tox/src/tox/venv.py", line 507, in test
    if argv[0].startswith("-"):
IndexError: list index out of range

Empty commands should be either filtered out before, or skipped when being run - which makes a difference for the counter/index.
It is probably good to see that a command turned out to be empty.

My use case here is injecting a command to uninstall "colorama" for when the "colorama" factor is not used (but pytest installs it as a dependency).

tox 3.13.3.dev16+g0bd5198

[blueyed]

As for my use case: using nocolorama: pip uninstall --yes colorama as a separate command, without redirection via env works.
But this is still a bug I would say - or would need a clearer error, i.e. "empty commands are not allowed".

[wisepotato]

Running into the same error. using echo as a placeholder, but removing the commands from a base environment would seem logical.

[gaborbernat]

Feel free to open a PR against master and fix it. My available efforts at the moment are aimed at fixing this as part of #1394, but that probably will take a while (ETA September).

[gaborbernat]

❯ tox4 c -e py -k commands
[testenv:py]
commands = true
/tmp/magic

This now has been fixed with tox 4.