Exposing a dependency's extra as main packages extra

[ena-cradle]

I'm developing a package, that depends on package A. Package A provides an extra: a that I would like to expose as my own extra. How would I go about it?

---

Here are some options I explored:

Option 1: Using [] in extra specification

[tool.poetry.dependencies]
A = {version = ... }

[tool.poetry.extras]
with_a = [ "A[a]" ]

Apart from being a bit confusing and not explicit/expressive enough in my opinion (what if I want a different version of A[a], etc.), this
gives me:

[extras.with_a.0] 'A[a]' does not match '^[a-zA-Z-_.0-9]+$'

Option 2: Naming the A dependency different based on whether it includes the extra

[tool.poetry.dependencies]
A = {version = ...}
A_with_a = {version = ..., extras = ["a"], optional = true}

[tool.poetry.extras]
with_a = [ "A_with_a" ]

gives me

The dependency name for A-with-a does not match the actual package's name: A

Option 3: Using groups

[tool.poetry.dependencies]
A = {version = ...}

[tool.poetry.group.extra_a]
optional = true

[tool.poetry.group.extra_a.dependencies]
A = {version=..., extras=[a]}

[tool.poetry.extras]
with_a = [ "extra_a" ]

This doesn't seem to be supported (see discussion here) but looks like what would solve the issue. Additionally, if I understand this comment, extras need to be specified in the main dependency group which in my case leads to naming issues.

---

Is there something I'm missing?