Projects that aren't meant to generate a wheel and `pyproject.toml`

I’m okay with splitting this to a new thread, but it was my intent to contribute to the discussion of the run table – which seems like an important sub-topic.

You’re saying it’s wrong to try to put everything in a single file is wrong. I agree with this.
But what about just the dependency specifications?

It’s common with tox to have a number of extras defined in package metadata, and then for tox to define a matrix over those extras to test. That’s the separation I’d like to see – only, I don’t want to use extras for it because

  • extras require installing the package, which is often not correct
  • extras are published as metadata, which produces undesirable pressure to hide or remove them, or keep them small in number

Is the run table not a good place to tackle this? It seems like it to me, so if not, I have missed something important.