How can I specify which positional argument to use in tox?

Question

I have the following tox.ini:

[tox]
envlist = py37-{lint, test}

[testenv:py37-{lint, test}]
envdir = {toxworkdir}/lint_and_test_env
deps = 
    pylint
    pytest
    pytest-xdist
commands =
    lint: pylint src {posargs}
    test: pytest tests {posargs}

I want to run both environments in parallel and specify --jobs=4 for pylint and -n auto for pytest. Executing tox -p -- --jobs=4 -n auto fails because pylint does not recognize the -n argument and vice versa.

Is there a way to achieve my goal?

Answer 1

I see no way to do what you want.

That said, I would strongly recommend that you split your environments and use one for testing and one for linting.

[tox]
envlist = py37, lint

[testenv]
deps =
    pytest
    pytest-xdist
commands =
    pytest tests {posargs}

[testenv:lint]
deps = pylint
commands = pylint src {posargs}

Then you can pass in different arguments to the commands, or run all envs via tox.

Also you could set defaults in case you do not specify {posargs}.

e.g.

[testenv:lint]
deps = pylint
commands = pylint src {--jobs=4:posargs}

If you want to run all tox envs in parallel you could run...

tox -p

P.S.: I am one of the tox maintainers, and I have contributed to hundreds of open source projects, and basically 99% use separate envs for testing and linting.

P.P.S.: If you want to run more than one linter, you should have a look at pre-commit.