[gentoo-dev] GLEP 83 update: Support for EAPIs by package managers

["Ulrich Müller" <ulm@gentoo.org>]

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Please find below an updated version of GLEP 83, with a new section
"Support for EAPIs by package managers".

This will give some guidelines when package managers can drop support
for old EAPIs, with rather long transition times.

A separate message with the patch will follow.

Ulrich


---
GLEP: 83
Title: EAPI deprecation
Author: Ulrich Müller <ulm@gentoo.org>
Type: Informational
Status: Active
Version: 2
Created: 2022-06-30
Last-Modified: 2025-06-19
Post-History: 2022-07-11, 2022-07-31, 2024-08-30, 2024-09-01, 2025-06-19
Content-Type: text/x-rst
---


Abstract
========

Introduce standardized criteria for deprecation and banning of EAPIs.


Motivation
==========

So far, old EAPIs were deprecated by the Gentoo Council in an ad-hoc
manner.  No fixed criteria were used, resulting in unpredictable
deprecation times after approval of newer EAPIs.  Standardized
criteria for deprecation and banning will make the life cycle of EAPIs
more predictable.


Specification
=============

Use of EAPIs in the Gentoo repository
-------------------------------------

A *deprecated EAPI* is no longer required for the upgrade path of
users' systems.  Its use is discouraged, and tools like pkgcheck will
warn about this [#COUNCIL-20130409]_.

A *banned EAPI* must no longer be used, neither for new ebuilds, nor
for updating of existing ebuilds [#COUNCIL-20140311]_.

The Gentoo Council will deprecate an EAPI when one or more newer
Council-approved EAPIs are supported by the stable version of Portage,
namely

* two newer EAPIs, one of them supported for at least 24 months, or
* one newer EAPI, supported for at least 48 months.

The Gentoo Council will ban a deprecated EAPI when

* 24 months have passed since its deprecation, and
* it is used by fewer than 5 % of ebuilds in the Gentoo repository.

EAPIs used in profiles are outside the scope of this section.


Support for EAPIs by package managers
-------------------------------------

Package managers may drop (or omit) support for an EAPI only when all
of the following conditions apply:

* The EAPI was deprecated at least 10 years ago,
* it has not been used by any ebuild in the Gentoo repository
  for the past 5 years, and
* it has not been used by any profile in the Gentoo repository
  for the past 2 years.

It is recommended that unmerging of old packages be supported
indefinitely.


Rationale
=========

Timing of EAPI deprecation is a trade-off between different factors.
On the one hand, the total number of EAPIs in active use should be
limited; this will prevent the learning curve for new developers and
contributors from becoming too steep and will help to reduce code
complexity, e.g. in eclasses.

On the other hand, an upgrade path to a stable system is guaranteed
for one year, plus limited support for systems that are outdated more
than a year [#COUNCIL-20091109]_.  Therefore, previous EAPIs are still
required during that time.  A period of 24 months before deprecation
has been chosen, which is more than the required minimum and will
allow projects to support a longer upgrade path.

Requiring two newer EAPIs before deprecation will allow ebuilds that
are otherwise seldom updated to be bumped to the next but one EAPI
immediately.  However, deprecation of an EAPI should not be deferred
forever, so it can be effected after a longer waiting period of 48
months even if only one newer EAPI exists at that point.

A delay of 24 months between deprecation and ban will give ebuild
authors enough time to update.  This is especially relevant for
overlays and downstream distributions.  An additional requirement for
banning an EAPI is that fewer than 5 % of ebuilds are using the EAPI
in question.  This requirement is defined to help keep the number of
ebuild updates (and bug reports requesting them) manageable, as a
banned EAPI is sufficient reason for updating an ebuild.

Similar considerations apply to support of EAPIs by package managers.
Supporting legacy EAPIs imposes ongoing maintenance costs;
accumulation of EAPI-specific conditionals makes the code harder to
read and maintain.  Also, unused code paths tend to "bit rot" and see
less testing over time.  Notably, at the time of writing, EAPIs 0 to 2
are broken in Portage [#BUG-875353]_.

Conversely, removing support for an EAPI from the package manager can
be disruptive for users.  Unofficial overlays and private repositories
often continue using older EAPIs long after their removal from the
main tree.  Therefore, the timeline for dropping package-manager
support is more generous than that for use of EAPIs in repositories.

Finally, dropping unmerge support could block upgrades of outdated
systems.  Therefore, unmerging of packages with legacy EAPIs should
stay supported indefinitely unless there is a compelling technical
reason for its removal.


Example
=======

Under this policy, EAPI 7 will be deprecated when either

* Portage has supported EAPI 8 for 24 months, and supports another
  later EAPI (e.g. EAPI 9), or
* Portage has supported EAPI 8 for 48 months.

Portage has supported EAPI 8 since 2021-07-05.  The first condition
would be fulfilled after 2023-07-05, as soon as an EAPI 9 is also
supported.  The second condition would be fulfilled after 2025-07-05.


Backwards Compatibility
=======================

The following table compares the actual dates of deprecations and bans
[#PMS-PROJECT]_ with the dates that would have resulted from the
criteria proposed in this GLEP ("new date").

====  ==========  ===========  ===========  ==========  ======  ===========  ==========  ======
EAPI  Portage     Gentoo repo  deprecated               diff.   banned                   diff.
----  ----------  -----------  -----------------------  ------  -----------------------  ------
\     stable      usage < 5 %  actual date  new date    months  actual date  new date    months
====  ==========  ===========  ===========  ==========  ======  ===========  ==========  ======
0     2005-12-26  2017-02-28   2014-02-25   2009-12-11  -50     2016-01-10   2017-02-28  +14
1     2007-12-11  2009-10-25   2013-04-09   2011-01-08  -27     2014-03-11   2013-01-08  -14
2     2009-01-08  2015-03-27   2013-04-09   2012-03-08  -13     2014-03-11   2015-03-27  +12
3     2010-03-08  2015-01-16   2014-02-25   2013-03-17  -11     2016-01-10   2015-03-17  -10
4     2011-03-17  2018-01-11   2015-10-11   2016-01-17   +3     2018-04-08   2018-01-17   -3
5     2012-12-11  2021-06-15   2018-05-13   2018-06-27   +1     2021-08-08   2021-06-15   -2
6     2016-01-17  2022-11-06   2021-07-11   2021-07-05    0                  2023-07-05
                  [*]_
7     2018-06-27
8     2021-07-05
====  ==========  ===========  ===========  ==========  ======  ===========  ==========  ======

.. [*] Extrapolated date, obtained by fitting data between 2021-01-01
   and 2022-07-31 with an exponential function.


References
==========

.. [#COUNCIL-20130409] "EAPI deprecation",
   Gentoo Council meeting summary 2013-04-09
   (https://projects.gentoo.org/council/meeting-logs/20130409-summary.txt).
   Note: The original quote says "Repoman" instead of "pkgcheck".

.. [#COUNCIL-20140311] "Ban on EAPI 1 and 2 should extend to updating
   EAPI in existing ebuilds", Gentoo Council meeting summary 2014-03-11
   (https://projects.gentoo.org/council/meeting-logs/20140311-summary.txt)

.. [#COUNCIL-20091109] "Upgrade path for old systems",
   Gentoo Council meeting summary 2009-11-09
   (https://projects.gentoo.org/council/meeting-logs/20091109-summary.txt)

.. [#BUG-875353] Bug 875353 - EAPI 0 ebuilds won't pass QA because ${ED}
   variable is empty and read only (https://bugs.gentoo.org/875353)

.. [#PMS-PROJECT] Gentoo Package Manager Specification project
   (https://wiki.gentoo.org/wiki/Project:Package_Manager_Specification#EAPI_life_cycle)


Copyright
=========

This work is licensed under the Creative Commons Attribution-ShareAlike 4.0
International License.  To view a copy of this license, visit
https://creativecommons.org/licenses/by-sa/4.0/.

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