Michał Górny

The ultimate guide to EAPI 8

Three years ago, I had the pleasure of announcing EAPI 7 as a major step forward in our ebuild language. It introduced preliminary support for cross-compilation, it finally provided good replacements for the last Portagisms in ebuilds and it included many small changes that made ebuilds simpler.

Only a year and a half later, I have started working on the initial EAPI 8 feature set. Similarly to EAPI 6, EAPI 8 was supposed to focus on small changes and improvements. The two killer features listed below were already proposed at the time. I have prepared a few patches to the specification, as well as the initial implementation of the respective features for Portage. Unfortunately, the work stalled at the time.

Finally, as a result of surplus of free time last month, I was able to resume the work. Along with Ulrich Müller, we have quickly prepared the EAPI 8 feature set, got it pre-approved, prepared the specification and implemented all the features in Portage and pkgcore. Last Sunday, the Council has approved EAPI 8 and it’s now ready for ~arch use.

What’s there in EAPI 8? Well, for a start we have install-time dependencies (IDEPEND) that fill a gap in our cross-compilation design. Then, selective fetch/mirror restriction make it easier to combine proprietary and free distfiles in a single package. PROPERTIES and RESTRICT are now accumulated across eclasses reducing confusion for eclass writers. There’s dosym -r to create relative symlinks conveniently from dynamic paths. Plus bunch of other improvements, updates and cleanups.

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Retiring the multilib project

I created the Multilib project back in November 2013 (though the effort itself started roughly a year earlier) with the goal of maintaining the multilib eclasses and porting Gentoo packages to them. Back in the day, we were even requested to co-maintain a few packages whose maintainers were opposed to multilib ports. In June 2015, last of the emul-linux-x86 packages were removed and our work has concluded.

The project continued to exist for the purpose of maintaining the eclasses and providing advice. Today, I can say that the project has served its purpose and it is time to retire it. Most of the team members have already left, the multilib knowledge that we advised on before is now common developer knowledge. I am planning to take care of the project-maintained eclasses personally, and move the relevant documentation to the general wiki space.

At the same time, I would like to take this opportunity to tell the history of our little multilib project.

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From build-dir to venv — testing Python packages in Gentoo

A lot of Python packages assume that their tests will be run after installing the package. This is quite a reasonable assumption if you take that the tests are primarily run in dedicated testing environments such as CI deployments or test runners such as tox. However, this does not necessarily fit the Gentoo packaging model where packages are installed system-wide, and the tests are run between compile and install phases.

In great many cases, things work out of the box (because the modules are found relatively to the current directory), or require only minimal PYTHONPATH adjustments. In others, we found it necessary to put a varying amount of effort to create a local installation of the package that is suitable for testing.

In this post, I would like to shortly explore the various solutions to the problem we’ve used over the years, from simple uses of build directory to the newest ideas based on virtual environments.
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10 Years’ Perspective on Python in Gentoo

I’m a Gentoo developer for over 10 years already. I’ve been doing a lot of different things throughout that period. However, Python was pretty much always somewhere within my area of interest. I don’t really recall how it all started. Maybe it had something to do with Portage being written in Python. Maybe it was the natural next step after programming in Perl.

I feel like the upcoming switch to Python 3.9 is the last step in the prolonged effort of catching up with Python. Over the last years, we’ve been working real hard to move Python support forward, to bump neglected packages, to enable testing where tests are available, to test packages on new targets and unmask new targets as soon as possible. We have improved the processes a lot. Back when we were switching to Python 3.4, it took almost a year from the first false start attempt to the actual change. We started using Python 3.5 by default after upstream dropped bugfix support for it. In a month from now, we are going to start using Python 3.9 even before 3.10 final is released.

I think this is a great opportunity to look back and see what changed in the Gentoo Python ecosystem, in the last 10 years.
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Moving commits between independent git histories

PyPy is an alternative Python implementation. While it does replace a large part of the interpreter, a large part of the standard library is shared with CPython. As a result, PyPy is frequently affected by the same vulnerabilities as CPython, and we have to backport security fixes to it.

Backporting security fixes inside CPython is relatively easy. All main Python branches are in a single repository, so it’s just a matter of cherry-picking the commits. Normally, you can easily move patches between two related git repositories using git-style patches but this isn’t going to work for two repositories with unrelated histories.

Does this mean manually patching PyPy and rewriting commit messages by hand? Luckily, there’s a relatively simple git am trick that can help you avoid that.
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