Opt-out optional dependencies/extras

[smheidrich]

Introduction

This has already been discussed in other places (see 2nd section) but I couldn't find an issue for it in this repo yet.

Summary

It would be nice if it was possible for package authors to mark an optional dependency as "opt-out", meaning that it gets installed by default, unless the consumer (dependent package or user installing directly via pip) explicitly opts out of it.

Discussions elsewhere

• Proposal - expanding optional dependencies to support opt-out of recommended/default installables (discuss.python.org, 2023)
  • Work-in-progress PEP: WIP: initial base draft for default extras RonnyPfannschmidt/python-peps#1
• Optional dependency groups omitting package requirements (discuss.python.org, 2022)

Other ecosystems

• Rust's Cargo has this, of course, in the form of the ability to disable default "features" (their equivalent of optional dependencies / extras).
  • A bit more cumbersome than the proposal from the WIP PEP linked above, because they can only be disabled all at once, with consumers then having to re-enable the ones they did want. See issue about this: Ability to disable individual default features rust-lang/cargo#3126

Related issues

• Add support for opportunistic dependencies #214
  • That issue is about implicit/automatic opt-out for packages that e.g. aren't available for the current Python version or platform, while this issue is about explicit opt-out configurable by library dependents.

[henryiii]

Would this make sense at https://github.com/wheel-next/ideas ?

(I'd be a huge fan of these, lots of places I'd use it, but IIRC from the packaging summit a couple of years ago it's pretty hard to add due to back-compat)

[smheidrich]

Not sure if the question is addressed to me or "the room" 😅 But in any case I don't know 🤷