On Tue, Mar 24, 2020 at 8:40 AM Miro Hrončok wrote:
>
> Hello Pythonistas.
>
> (I've CC'ed the devel list for further exposure. But let's discuss this on
> python-devel list please to avoid noise.)
>
>
> We would like ro rename the "python3" component (SRPM) to "python39" to make
> maintaining various Python versions in various Fedora versions easier.
> The names of binary RPMs would be unchanged; you still do `dnf install
> python3`.
>
> The change should only affect packagers of Python itself; not users or
> packagers
> of software written in Python.
> The only user-visible or general-packager-visible change is a different
> component (SRPM) name.
>
> Details follow.
>
>
>
> Currently, we build the Python interpreters this way:
>
> - the "main" Python 3 interpreter component is called python3
> - it builds a couple of subpackages, like python3-libs or python3-devel
> - the "alternate" Python 3 versions components are called python3X
> (python37,
> python39...)
>
> For example, Fedora 31 has:
>
> - python36
> - python3 (the "main" Python, which is 3.7.x)
> - python38
> - python39
>
> (python37 is retired in f31, but present in Fedora versions where python3 !=
> 3.7)
>
> This makes updating the "main" Python fairly complicated. To upgrade from 3.7
> to
> 3.8 in f32, we had to:
>
> 1) retire python38
> 2) upgrade python3 from 3.7 to 3.8 (this makes python3 obsolete python38)
> 3) re-introduce (unretire) python37
>
> Such an update comes every few years:
> - https://fedoraproject.org/wiki/Changes/Python3.7 (f29)
> - https://fedoraproject.org/wiki/Changes/Python3.8 (f32)
> - https://fedoraproject.org/wiki/Changes/Python3.9 (f33)
>
> What's even more complicated is backporting patches across Fedora releases.
> Assume there is an important upgrade/fix for Python 3.7 we wish to apply for
> all
> Fedoras including stable. That currently means we need to apply the fix in:
>
> - master branch of python37
> - f32 branch of python37
> - f31 branch of python3 (!)
> - f30 branch of python3
>
> While cherry-picking or merging patches between branches of one git repo is
> quite straight-forward (the only major obstacle is the release and
> %chaneglog),
> doing this across multiple git repos (and spec filenames) is very tedious and
> error-prone (albeit possible).
>
> With the 3.9 update approaching in Fedora 33, we would end up with the
> following
> scheme when updating Python 3.8:
>
> - master branch of python38
> - f32 branch of python3 (!)
> - f31 branch of python38 (!)
> - f30 branch of python38
>
> Apart from technological obstacles, this causes nontrivial cognitive overhead.
> So far, I've been carrying that overhead myself, but others (who don't work on
> the Fedora Python packages daily) always need my assistance with this, because
> it's overly complicated and hard to understand without drawing pictures.
>
>
>
> For this to be easier for us, while keeping the change minimal for others, we
> have decided to retire the python3 component and only continue maintaining the
> interpreters in "python3X" components. The names of "binary" packages remain
> unchanged.
>
> Before:
>
> SRPM: python3
> builds:
> - python3
> - python-unversioned-command
> - python3-{libs,devel,tkinter,idle,test,debug}
> - python3-debug{info,source}
>
> After:
>
> SRPM: python39
> builds:
> - python3 (unchanged)
> - python-unversioned-command (unchanged)
> - python3-{libs,devel,tkinter,idle,test,debug} (unchanged)
> - python39-debug{info,source} (usually not installed by name)
>
> To avoid further confusion, the "python3-libs" etc. packages will provide
> "python39-libs" as well.
>
> We plan to do this together with the Python 3.9 upgrade. I'll update the
> change
> page after some feedback happens here.
>
> The initial implementation is in:
>https://src.fedoraproject.org/rpms/python39/pull-request/32
>
>
> Here are other approaches we have considered:
>
>
> Why not rename the packages to python39-libs etc. (and only provide
> python3-libs)?
>
>This would be inconsistent with the way other Python 3 packages are called
> (e.g. python39-setuptools). We consider that confusing.
>
>The goal here is to make our work easier while introducing minimal changes
> to
> our users and contributors.
>
>
> Why not rename all the Python packages to python39-setuptools etc.?
>
>This would create a mess upon distro boundary Python upgrades.
>All python39-foo packages would need to obsolete all python38-foo packages.
>Even if we add the obsoletes metadata to all the packages, it would prevent
> users from having the two parallel stacks of Python installed on the same OS.
> (We don't have such stacks in Fedora, but we intend to continue to make this
> possible in third party repos, downstreams of Fedora or other systems built on
> top or Fedora).
>
>See also the "minimal changes" point above.
>
>
> Why not package the alternate stacks as modular streams and keep every
