Run commands before extras/package installation

[yannikschaelte]

Is there a way of executing commands prior to package/extras installation?

Reason: Some dependencies may require the installation of further dependencies before pip installing them. For this, being able to define commands to run before that would be good. "commands_pre" does not seem to do that, as far as I see.

[gaborbernat]

You can enlist these in the https://tox.readthedocs.io/en/latest/config.html#conf-deps. though for modern packaging best practices all you need is pyproject.toml with isolated builds.

[yannikschaelte]

Thanks @gaborbernat , totally makes sense. I missed the "prior to" in the deps documentation. install_requires would indeed be preferable, here just not directly applicable as it concerns an optional dependency which must be set up more properly.

[ssbarnea]

@gaborbernat I am inclined to say that the issue is still valid. For example I want to run a command before installing dependencies, to check if system packages were installed, system packages that in case of missing would prevent installation of the dependencies.