tox-extras

A tox plugin to install extras directly from pyproject.toml into a testenv

Quick start

Install it with

pip install tox-extras

Add it to requires in the [tox] section of your tox.ini

[tox]
min_version = 4.0
requires = tox-extras

Say you have a lint extra in pyproject.toml which you want to use in a testenv:

[project.optional-dependencies]
lint = ["black==23.3.0"]

In your tox.ini testenv sections you can write

[testenv:lintonly]
skip_sdist = true
skip_install = true
tox_extras = lint
commands = black --check example.py

and this will install all deps from the "lint" extra into the testenv without installing your package or any of its deps.

Motivation

Tox has built-in support for installing extras using the extras testenv config option, but this does not work when combined with skip_install.

This plugin adds a tox_extras option to the tox EnvConfigSet and installs the extras named in this option into the testenv directly from pyproject.toml without installing the package.

This would be especially valuable when we want to use pyproject.toml as a single source of truth for our build, install, and dev dependencies (so putting deps in tox.ini is out of the question), but at the same time we don't want to "waste time" building and installing our package (and maybe its deps in a first-time tox run, e.g., in CI) into a testenv that only runs a linter (and therefore does not depend at all on the package or any deps being installed).

See https://github.com/tox-dev/tox/issues/2301 for the corresponding feature request in tox.

See https://github.com/pypa/pip/issues/4783#issuecomment-343771222 for commentary about the possible advantages of keeping all dependencies in one place.

Limitations

This plugin explicitly parses pyproject.toml, so it will not work with projects that define extras in setup.py.