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<tr class="field"><th class="field-name">GLEP:</th><td class="field-body">55</td>
</tr>
<tr class="field"><th class="field-name">Title:</th><td class="field-body">Use EAPI-suffixed ebuilds (.ebuild-EAPI)</td>
</tr>
<tr class="field"><th class="field-name">Version:</th><td class="field-body">1.5</td>
</tr>
<tr class="field"><th class="field-name">Last-Modified:</th><td class="field-body"><a class="reference external" href="http://www.gentoo.org/cgi-bin/viewcvs.cgi/xml/htdocs/proj/en/glep/glep-0055.txt?cvsroot=gentoo">2009/05/17 20:56:53</a></td>
</tr>
<tr class="field"><th class="field-name">Author:</th><td class="field-body">Piotr Jaroszyński &lt;peper&#32;&#97;t&#32;gentoo.org&gt;</td>
</tr>
<tr class="field"><th class="field-name">Status:</th><td class="field-body">Draft</td>
</tr>
<tr class="field"><th class="field-name">Type:</th><td class="field-body">Standards Track</td>
</tr>
<tr class="field"><th class="field-name">Content-Type:</th><td class="field-body"><a class="reference external" href="glep-0002.html">text/x-rst</a></td>
</tr>
<tr class="field"><th class="field-name">Created:</th><td class="field-body">17-Dec-2007</td>
</tr>
<tr class="field"><th class="field-name">Post-History:</th><td class="field-body">17-Dec-2007, 22-Dec-2007, 17-May-2009</td>
</tr>
</tbody>
</table>
<hr />
<div class="contents topic" id="contents">
<p class="topic-title first">Contents</p>
<ul class="simple">
<li><a class="reference internal" href="#abstract" id="id3">Abstract</a></li>
<li><a class="reference internal" href="#problem" id="id4">Problem</a></li>
<li><a class="reference internal" href="#current-behaviour" id="id5">Current behaviour</a><ul>
<li><a class="reference internal" href="#incompatible-change-of-inherit-e-g-make-it-look-in-the-package-dir-too" id="id6">Incompatible change of inherit (e.g. make it look in the package dir too)</a></li>
<li><a class="reference internal" href="#new-global-scope-function" id="id7">New global scope function</a></li>
<li><a class="reference internal" href="#new-version-format" id="id8">New version format</a></li>
<li><a class="reference internal" href="#use-newer-bash-features" id="id9">Use newer bash features</a></li>
</ul>
</li>
<li><a class="reference internal" href="#abstract-solution" id="id10">Abstract solution</a></li>
<li><a class="reference internal" href="#proposed-solution" id="id11">Proposed solution</a></li>
<li><a class="reference internal" href="#specification" id="id12">Specification</a></li>
<li><a class="reference internal" href="#summary-of-ideas" id="id13">Summary of ideas</a><ul>
<li><a class="reference internal" href="#eapi-suffixed-ebuilds-proposed-solution" id="id14">EAPI-suffixed ebuilds (proposed solution)</a></li>
<li><a class="reference internal" href="#eapi-in-the-filename-with-one-time-extension-change" id="id15">EAPI in the filename with one-time extension change</a></li>
<li><a class="reference internal" href="#easily-fetchable-eapi-inside-the-ebuild" id="id16">Easily fetchable EAPI inside the ebuild</a></li>
<li><a class="reference internal" href="#easily-fetchable-eapi-inside-the-ebuild-and-one-time-extension-change" id="id17">Easily fetchable EAPI inside the ebuild and one-time extension change</a></li>
<li><a class="reference internal" href="#use-different-subdirectories-for-different-eapis-i-e-cat-pkg-eapix" id="id18">Use different subdirectories for different EAPIs, i.e. cat/pkg/eapiX/</a></li>
</ul>
</li>
<li><a class="reference internal" href="#references" id="id19">References</a></li>
<li><a class="reference internal" href="#copyright" id="id20">Copyright</a></li>
</ul>
</div>
<blockquote>
<p>&quot;A little learning is a dangerous thing; drink deep, or taste not the Pierian
spring: there shallow draughts intoxicate the brain, and drinking largely
sobers us again.&quot;</p>
<p class="attribution">&mdash;Alexander Pope, An Essay on Criticism</p>
</blockquote>
<div class="section" id="abstract">
<h1><a class="toc-backref" href="#id3">Abstract</a></h1>
<p>This GLEP proposes usage of EAPI-suffixed file extensions for ebuilds (for
example, foo-1.2.3.ebuild-1).</p>
</div>
<div class="section" id="problem">
<h1><a class="toc-backref" href="#id4">Problem</a></h1>
<p>The current way of specifying the EAPI in ebuilds is flawed. In order to get the
EAPI the package manager needs to source the ebuild, which itself needs the EAPI
in the first place. Otherwise it imposes a serious limitation, namely every ebuild,
using any of the future EAPIs, will have to be source'able by old package
managers and hence there is no way to do any of the following:</p>
<blockquote>
<ul class="simple">
<li>Change the behaviour of inherit in any way (for example, to extend or change
eclass functionality).</li>
<li>Add new global scope functions in any sane way.</li>
<li>Extend versioning rules in an EAPI - for example, addition of the scm
suffix - GLEP54 <a class="footnote-reference" href="#glep54" id="id1">[1]</a> or allowing more sensible version formats like
<tt class="docutils literal"><span class="pre">1-rc1</span></tt>, <tt class="docutils literal"><span class="pre">1-alpha</span></tt> etc. to match upstream more closely.</li>
<li>Use newer bash features.</li>
</ul>
</blockquote>
</div>
<div class="section" id="current-behaviour">
<h1><a class="toc-backref" href="#id5">Current behaviour</a></h1>
<p>Following subsections show what happens if you introduce any of the mentioned
changes in an ebuild and try to install it with portage 2.1.6.13.</p>
<div class="section" id="incompatible-change-of-inherit-e-g-make-it-look-in-the-package-dir-too">
<h2><a class="toc-backref" href="#id6">Incompatible change of inherit (e.g. make it look in the package dir too)</a></h2>
<p><tt class="docutils literal"><span class="pre">sys-apps/foo-1.ebuild</span></tt>:</p>
<pre class="literal-block">
EAPI=&quot;5&quot;
inherit &quot;foo&quot;

DESCRIPTION=&quot;&quot;
HOMEPAGE=&quot;&quot;
SRC_URI=&quot;&quot;
...
</pre>
<p>Result:</p>
<pre class="literal-block">
*
* ERROR: sys-apps/foo-1 failed.
* Call stack:
*               ebuild.sh, line 1879:  Called _source_ebuild
*               ebuild.sh, line 1818:  Called source '/var/lib/gentoo/repositories/peper/sys-apps/foo/foo-1.ebuild'
*            foo-1.ebuild, line    6:  Called inherit 'foo'
*               ebuild.sh, line 1218:  Called die
* The specific snippet of code:
*              [ ! -e &quot;$location&quot; ] &amp;&amp; die &quot;${1}.eclass could not be found by inherit()&quot;
*  The die message:
*   foo.eclass could not be found by inherit()
*
* If you need support, post the topmost build error, and the call stack if relevant.
* This ebuild is from an overlay: '/var/lib/gentoo/repositories/peper/'
*

!!! All ebuilds that could satisfy &quot;sys-apps/foo&quot; have been masked.
!!! One of the following masked packages is required to complete your request:
- sys-apps/foo-1 (masked by: corruption)
</pre>
<p>Current portage looks for eclasses only in the <tt class="docutils literal">eclass</tt> directory of a
repository. This results in a fatal error and ebuild being masked by corruption
- might be pretty confusing to users.</p>
</div>
<div class="section" id="new-global-scope-function">
<h2><a class="toc-backref" href="#id7">New global scope function</a></h2>
<p><tt class="docutils literal"><span class="pre">sys-apps/foo-1.ebuild</span></tt>:</p>
<pre class="literal-block">
EAPI=&quot;5&quot;
new_global_scope_function &quot;foo&quot;

DESCRIPTION=&quot;&quot;
HOMEPAGE=&quot;&quot;
SRC_URI=&quot;&quot;
...
</pre>
<p>Result:</p>
<pre class="literal-block">
/var/lib/gentoo/repositories/peper/sys-apps/foo/foo-1.ebuild: line 7: new_global_scope_function: command not found

!!! All ebuilds that could satisfy &quot;sys-apps/foo&quot; have been masked.
!!! One of the following masked packages is required to complete your request:
- sys-apps/foo-1 (masked by: EAPI 5)

The current version of portage supports EAPI '2'. You must upgrade to a
newer version of portage before EAPI masked packages can be installed.
</pre>
<p>Not that bad as user is advised to upgrade portage.</p>
</div>
<div class="section" id="new-version-format">
<h2><a class="toc-backref" href="#id8">New version format</a></h2>
<p><tt class="docutils literal"><span class="pre">sys-apps/foo-2-rc1.ebuild</span></tt>:</p>
<pre class="literal-block">
Invalid ebuild name: /var/lib/gentoo/repositories/peper/sys-apps/foo/foo-2-rc1.ebuild

emerge: there are no ebuilds to satisfy &quot;sys-apps/foo&quot;
</pre>
<p>Not the best error message, especially if there are lots of them.</p>
</div>
<div class="section" id="use-newer-bash-features">
<h2><a class="toc-backref" href="#id9">Use newer bash features</a></h2>
<p><tt class="docutils literal">|&amp;</tt> is a new type of redirection added in bash-4. It cannot be used even in
local scope as bash still parses the whole ebuild.</p>
<p><tt class="docutils literal"><span class="pre">sys-apps/foo-1.ebuild</span></tt>:</p>
<pre class="literal-block">
EAPI=&quot;5&quot;

foo() {
   echo &quot;foo&quot; |&amp; cat
}
</pre>
<p>Result:</p>
<pre class="literal-block">
/var/lib/gentoo/repositories/peper/sys-apps/foo/foo-1.ebuild: line 8: syntax error near unexpected token `&amp;'
/var/lib/gentoo/repositories/peper/sys-apps/foo/foo-1.ebuild: line 8: ` echo &quot;foo&quot; |&amp; cat'
*
* ERROR: sys-apps/foo-1 failed.
* Call stack:
*               ebuild.sh, line 1879:  Called _source_ebuild
*               ebuild.sh, line 1818:  Called die
* The specific snippet of code:
*      source &quot;${EBUILD}&quot; || die &quot;error sourcing ebuild&quot;
*  The die message:
*   error sourcing ebuild
*
* If you need support, post the topmost build error, and the call stack if relevant.
* This ebuild is from an overlay: '/var/lib/gentoo/repositories/peper/'
*                                                                                                                                                                                                       ... done!

!!! All ebuilds that could satisfy &quot;sys-apps/foo&quot; have been masked.
!!! One of the following masked packages is required to complete your request:
- sys-apps/foo-1 (masked by: corruption)
</pre>
<p>Again, not the best error.</p>
</div>
</div>
<div class="section" id="abstract-solution">
<h1><a class="toc-backref" href="#id10">Abstract solution</a></h1>
<p>A solution to this problem has to lift those limitations and the only way to do
it is to make the EAPI of an ebuild available to the package managers in a way
that doesn't require them to source the ebuild. Another important requirement is
for the solution to be backward compatible, which has the pleasant side-effect
of making the solution applicable in the Gentoo tree right away. Opposed to
waiting an arbitrary amount of time, which is never long enough anyway, as the
issues listed on the common portage problems page - <a class="footnote-reference" href="#portageproblems" id="id2">[2]</a> - show.</p>
</div>
<div class="section" id="proposed-solution">
<h1><a class="toc-backref" href="#id11">Proposed solution</a></h1>
<p>The proposed solution is to use EAPI-suffixed file extensions for ebuilds. This
allows package managers to trivially read the EAPI from the ebuild filename. It
is also backwards compatible, because currently ebuilds are recognised by the
<tt class="docutils literal">.ebuild</tt> file extension and hence EAPI-suffixed ebuilds are simply ignored by
the package managers.</p>
</div>
<div class="section" id="specification">
<h1><a class="toc-backref" href="#id12">Specification</a></h1>
<p>Ebuild filename extension syntax: <tt class="docutils literal"><span class="pre">ebuild[-&lt;EAPI&gt;]</span></tt>, where <tt class="docutils literal">[]</tt> denotes an
optional part, and <tt class="docutils literal">&lt;EAPI&gt;</tt> is the EAPI of the ebuild.</p>
<p>The EAPI used by the ebuild is the EAPI included in the filename if it is set.
Otherwise the EAPI set inside the ebuild is used, which defaults to 0 (this is
the current behaviour).</p>
<p>Ebuilds with unsupported EAPIs are masked.</p>
<p>It should be considered an error to set the EAPI both in the filename and in the
ebuild.</p>
<p>Examples:</p>
<blockquote>
<ul>
<li><dl class="first docutils">
<dt><tt class="docutils literal"><span class="pre">pkg-1.ebuild</span></tt>, no EAPI set inside the ebuild</dt>
<dd><p class="first last">EAPI defaults to 0.</p>
</dd>
</dl>
</li>
<li><dl class="first docutils">
<dt><tt class="docutils literal"><span class="pre">pkg-2.ebuild-1</span></tt>, no EAPI set inside the ebuild</dt>
<dd><p class="first last">EAPI 1 is used.</p>
</dd>
</dl>
</li>
<li><dl class="first docutils">
<dt><tt class="docutils literal"><span class="pre">pkg-3.ebuild-1</span></tt>, <tt class="docutils literal"><span class="pre">EAPI=&quot;1&quot;</span></tt></dt>
<dd><p class="first last">EAPI set in both places - error.</p>
</dd>
</dl>
</li>
</ul>
</blockquote>
<p>Note that it is still not permitted to have more than one ebuild with equal
category, package name, and version. Although it would have the advantage of
allowing authors to provide backwards compatible ebuilds, it would introduce
problems too. The first is the requirement to have strict EAPI ordering, the
second is ensuring that all the ebuilds for a single category/package-version
are equivalent, i.e. installing any of them has exactly the same effect on a
given system.</p>
<p>Also note that it is not a new restriction. It is already possible to illegally
have multiple versions with different EAPIs as e.g. <tt class="docutils literal">1.0 == 1.00 == <span class="pre">1.00-r0</span></tt>
and hence you could have <tt class="docutils literal"><span class="pre">foo-1.0.ebuild</span></tt> with EAPI X and <tt class="docutils literal"><span class="pre">foo-1.00.ebuild</span></tt>
with EAPI Y.</p>
</div>
<div class="section" id="summary-of-ideas">
<h1><a class="toc-backref" href="#id13">Summary of ideas</a></h1>
<div class="section" id="eapi-suffixed-ebuilds-proposed-solution">
<h2><a class="toc-backref" href="#id14">EAPI-suffixed ebuilds (proposed solution)</a></h2>
<dl class="docutils">
<dt>Properties:</dt>
<dd><ul class="first last simple">
<li>Can be used right away: yes</li>
<li>Hurts performance: no</li>
</ul>
</dd>
</dl>
<p>Some say it is clear and simple, others that it is ugly and unintuitive.</p>
</div>
<div class="section" id="eapi-in-the-filename-with-one-time-extension-change">
<h2><a class="toc-backref" href="#id15">EAPI in the filename with one-time extension change</a></h2>
<p>One of the proposed filename formats:
<tt class="docutils literal"><span class="pre">&lt;PKG&gt;-&lt;VER&gt;.eapi-&lt;EAPI&gt;.eb</span></tt></p>
<dl class="docutils">
<dt>Properties:</dt>
<dd><ul class="first last simple">
<li>Can be used right away: yes</li>
<li>Hurts performance: no</li>
</ul>
</dd>
</dl>
<p>This is equivalent to the proposed solution.</p>
<p>Some say it is better because the extension is static.</p>
</div>
<div class="section" id="easily-fetchable-eapi-inside-the-ebuild">
<h2><a class="toc-backref" href="#id16">Easily fetchable EAPI inside the ebuild</a></h2>
<dl class="docutils">
<dt>Properties:</dt>
<dd><ul class="first last simple">
<li>Can be used right away: no</li>
<li>Hurts performance: yes</li>
</ul>
</dd>
</dl>
<p>Cannot be used right away as it would trigger the errors shown in Current
behaviour section for old package managers.</p>
<p>Performance decrease comes from the fact that with version format changes in the
picture package managers need EAPI to parse the ebuild's version. That means that merely
picking the best version of a package requires loading EAPI (from cache or the
ebuild) for each available ebuild.</p>
<p>Here is more or less how the package manager figures out the best available
version for a package with N versions available.</p>
<blockquote>
<ul class="simple">
<li>EAPI in the filename<ul>
<li>Read the directory containing the package - readdir()</li>
<li>For each ebuild, read its EAPI and using that parse its version - no I/O</li>
<li>Sort the versions - no I/O</li>
<li>Going down from the highest to the lowest version<ul>
<li>Get the metadata from cache - 2 x stat() + read()</li>
<li>break if the version is visible</li>
</ul>
</li>
</ul>
</li>
<li>EAPI in the ebuild<ul>
<li>Read the directory containing the package - readdir()</li>
<li>For each ebuild load its metadata from cache to get its EAPI - N x (2 x stat() + read())</li>
<li>Sort the versions - no I/O</li>
<li>Going down from the highest to the lowest version<ul>
<li>(metadata is already loaded) - no I/O</li>
<li>break if the version is visible - no I/O</li>
</ul>
</li>
</ul>
</li>
</ul>
</blockquote>
<p>The difference is in for how many versions the package manager needs to hit
cache. With EAPI in the ebuild it needs to do that for all versions, with EAPI
in the filename it depends on versions visibility.
For example, package foo has versions 1, 2, 3, 4, 5 and 6. 6 is masked, 5 is
~arch and 1,2,3 and 4 are arch. Say, the user accepts only arch for this
package. With EAPI in the filename it will read metadata only for versions
6, 5 and 4. With EAPI in the ebuild it needs to load metadata for all versions.</p>
<p>It's hard to say what's the avarage case, but surely the worst case scenario
(when only the lowest version is visible) is uncommon.</p>
</div>
<div class="section" id="easily-fetchable-eapi-inside-the-ebuild-and-one-time-extension-change">
<h2><a class="toc-backref" href="#id17">Easily fetchable EAPI inside the ebuild and one-time extension change</a></h2>
<dl class="docutils">
<dt>Properties:</dt>
<dd><ul class="first last simple">
<li>Can be used right away: yes</li>
<li>Hurts performance: yes</li>
</ul>
</dd>
</dl>
<p>Performance decrease as described in the previous section.</p>
<p>Some say it is clear and simple, others that it is confusing and unintuitive,
because of the arbitrary format restrictions in what is a bash script otherwise.</p>
</div>
<div class="section" id="use-different-subdirectories-for-different-eapis-i-e-cat-pkg-eapix">
<h2><a class="toc-backref" href="#id18">Use different subdirectories for different EAPIs, i.e. cat/pkg/eapiX/</a></h2>
<dl class="docutils">
<dt>Properties:</dt>
<dd><ul class="first last simple">
<li>Can be used right away: yes</li>
<li>Hurts performance: yes</li>
</ul>
</dd>
</dl>
<p>Performance decrease comes from the fact that it adds several more directory
reads.</p>
<p>Some say that it makes it much harder for maintainers to see what they have.</p>
</div>
</div>
<div class="section" id="references">
<h1><a class="toc-backref" href="#id19">References</a></h1>
<table class="docutils footnote" frame="void" id="glep54" rules="none">
<colgroup><col class="label" /><col /></colgroup>
<tbody valign="top">
<tr><td class="label"><a class="fn-backref" href="#id1">[1]</a></td><td>GLEP 54, scm package version suffix
(<a class="reference external" href="http://glep.gentoo.org/glep-0054.html">http://glep.gentoo.org/glep-0054.html</a>)</td></tr>
</tbody>
</table>
<table class="docutils footnote" frame="void" id="portageproblems" rules="none">
<colgroup><col class="label" /><col /></colgroup>
<tbody valign="top">
<tr><td class="label"><a class="fn-backref" href="#id2">[2]</a></td><td>Common portage problems
(<a class="reference external" href="http://www.gentoo.org/proj/en/portage/doc/common-problems.xml">http://www.gentoo.org/proj/en/portage/doc/common-problems.xml</a>)</td></tr>
</tbody>
</table>
</div>
<div class="section" id="copyright">
<h1><a class="toc-backref" href="#id20">Copyright</a></h1>
<p>This document has been placed in the public domain.</p>
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