Re: [gentoo-dev] [rfc] Sane defaults for USE_PYTHON, patch to python eclass

[Thomas Sachau]

Am 04.12.2010 21:23, schrieb Sebastian Pipping:
> On 12/04/10 16:38, Thomas Sachau wrote:
>>> Proposed new situation
>>> ======================
>>> If I have a version of Python installed, it should be usable well.
>>> So USE_PYTHON is derived from the list of all available Python slots.
>>> Excluded are ABIs restricted by an ebuild, say by a line like
>>>
>>>   RESTRICT_PYTHON_ABIS="3.*"
>>>
>>> for software that does not build with Python 3.x.
>>
>> I am against this proposal. I already masked python-3* on my system, because no package actually
>> needs it, but the current behaviour installs completly useless code for those versions.
>
> Does it?  I assume when you say you masked it you also mean that you
> don't have Python 3.x installed?

Exactly.

>
> Packages are installed against an ABI iff:
> 1) The ABI is know to the python eclass - granted
> 2) The build is not restricting the ABI
> 3) The related version of python is actually installed
>
> Let's do this check: Please run this command:
>
>   # equery f dev-python/pyinotify | fgrep site-packages
>
> If you don't have any Python 3.x installed you should see no files for it.
>
>
>> Same would
>> happen for all other, not active versions of python.
>
> See above, please re-check if that happens for you.
>
>
>> One default active version should be enough, if
>> i want more, i can select and set it.
>
> Please elaborate in more detail on that so I'm sure I reply to the
> comment you actually had in mind.

You only need one active python around, in this case, python-2.6.

But you also get newer versions, like python-2.7 and python-3.1. While there is no big issue with
python-2.7 (it is masked, until most packages depending on it are fixed), since when it gets stable,
you can select it, update your depending packages, remove python-2.6 and be done with it. And as
long, as you dont select python-2.7, you wont get anything into the site-packages dir of python-2.7.

But with python-3*, it is different. You dont select it, it cannot even be the main or only python
version around. But by default, all packages working with it additionally install their files for
python-3*. This is some black magic behind the scene and invisible to the user. Imho nothing should
be installed for anything else except the main selected version, unless you request it. So while you
want to enable the installation for all versions currently installed, i request the other way round:
Only install for the current main active version and nothing else by default.

-- 
Thomas Sachau

Gentoo Linux Developer