Allow extras to specify different versions of dependencies

[Gattocrucco]

Issue Kind

Brand new capability

Description

I want to define an extra for my package that pins specific versions of some dependencies, without affecting dependency resolution when it is not used.

My use case: I'm writing a library that depends on jax. I want to define an extras metal that installs jax-metal to support Apple GPUs. However, jax-metal requires a specific version of jaxlib. Since jax updates frequently, it is limiting to force a certain version of jax even when the extra is not used.

Possible way the thing could look like:

[tool.poetry.dependencies]
jax = "^0.4.22"
jaxlib = "^0.4.22"
jax-metal = { version = "0.0.6", optional = true }

[tool.poetry.extras]
metal = [
    "jax-metal",
    { change-dependency = "jaxlib", version = "0.4.22" },
]

Would it be possible at all to do this? Or is it blocked by the way pip itself handles extras in packages it installs?

Impact

I've found someone having a similar problem on this stackoverflow thread. They made a plugin, but 1) it seems unmaintained and a bit messy, so I don't trust depending on it, 2) it works at the level of installing groups, so not for the extras in my final released package.

I guess there are other people with similar needs, but I don't know how many.

Workarounds

Workarounds I know of:

• Create a separate package for my library with different dependencies
  • Time-consuming for me
• Ask users to install jax-metal themselves following instructions
  • Time-consuming for users
  • Annoying for me because I can't use poetry to install things on my development copy

[dimbleby]

basically a special case of #6419

[Gattocrucco]

Ah thanks! I missed that. Closing this.

[github-actions]

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