[gentoo-dev] [RFC] Splitting dev-lang/python into per-slot packages, starting with 3.14

["Michał Górny" <mgorny@gentoo.org>]

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Hello,

Historically, all versions of CPython were slotted in a single package,
i.e.:

  dev-lang/python:3.N

This approach has been causing a major annoyance for users -- due to
Portage "greedy" upgrade behavior, any time a new Python version was
keyworded, Portage insisted on installing it, even though user's
selected targets did not request the specific version.  The potentially
worst consequence of that would be random user scripts stopping to work,
as they suddenly start using new Python, while all their dependencies
are still installed per PYTHON_TARGETS.

Upstream has recently added freethreading support to CPython.  Since
this support is not ABI compatible with the regular build, we need to
introduce a separate target for it, and to package it separately.
In the planned patchset, I've already put it as a separate package (dev-
lang/python-freethreading), because otherwise Portage would insist
on upgrading to it!

However, I think the cleanest way forward would be to stop slotting
CPython like this, and instead have a separate package for each version,
just like the vast majority of distributions do, i.e.:

  dev-lang/python3_N

This naturally means that only the specific version requested (e.g. via
targets) would be installed, and no cross-slot autoupgrades would
happen.  Ideally, I'd like to start doing that with Python 3.14 whose
first alpha is expected next week.  Depending on how they handle
freethreading, we'd end up having the first or both of:

  dev-lang/python3_14
  dev-lang/python3_14t

(Alternatives: python-3_14, python-freethreading-3_14? Though I think
following PYTHON_TARGETS is cleaner here.)

As a side notice, the existing versions would probably remain as-is
until removal, since there's really no gain in splitting them, given
we'd have to retain compatibility with existing depstrings.

Comments?

-- 
Best regards,
Michał Górny


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