Plugin for modifying install_requirements

[StefanUlbrich]

Similar to writing plugins that add custom python_artifact() keywords, I want to modify the generated install_requires post inference (e.g., relax the version of an internal dependency).

I think this can be achieved by adding the @union decorator to GenerateSetupPyRequest (and maybe add an is_applicable classmethod?). Then I could write a rule that calls determine_finalized_setup_kwargs and modify the requires.

This seems to me to be the only way to achieve my goal. I wonder, however, if it is too"hacky". Is it worth opening a pull request for this idea?

[benjyw]

Hmmm. This whole area of how to use a generated setup.py but influence its arguments needs a bunch of work. Related issues:

#12487
#16360

[benjyw]

It's a common enough use case that we should have a proper API for it. I think I'd prefer that to hacking something in.

[benjyw]

But your general idea is in the right direction, I think. We need a hook to let you modify the generated kwargs, and we can make that clunky at first.

So a proof-of-concept would be welcome!