/[gentoo]/xml/htdocs/proj/en/glep/glep-0055.txt
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1GLEP: 55 1GLEP: 55
2Title: Use EAPI-suffixed ebuilds (.ebuild-EAPI) 2Title: Use EAPI-suffixed ebuilds (.ebuild-EAPI)
3Version: $Revision: 1.2 $ 3Version: $Revision: 1.3 $
4Last-Modified: $Date: 2008/01/06 02:39:42 $ 4Last-Modified: $Date: 2009/05/17 15:50:27 $
5Author: Piotr Jaroszyński <peper@gentoo.org> 5Author: Piotr Jaroszyński <peper@gentoo.org>
6Status: Draft 6Status: Draft
7Type: Standards Track 7Type: Standards Track
8Content-Type: text/x-rst 8Content-Type: text/x-rst
9Created: 17-Dec-2007 9Created: 17-Dec-2007
10Post-History: 17-Dec-2007, 22-Dec-2007 10Post-History: 17-Dec-2007, 22-Dec-2007, 17-May-2009
11 11
12 "A little learning is a dangerous thing; drink deep, or taste not the Pierian 12 "A little learning is a dangerous thing; drink deep, or taste not the Pierian
13 spring: there shallow draughts intoxicate the brain, and drinking largely 13 spring: there shallow draughts intoxicate the brain, and drinking largely
14 sobers us again." 14 sobers us again."
15 15
34 eclass functionality). 34 eclass functionality).
35 35
36 * Add new global scope functions in any sane way. 36 * Add new global scope functions in any sane way.
37 37
38 * Extend versioning rules in an EAPI - for example, addition of the scm 38 * Extend versioning rules in an EAPI - for example, addition of the scm
39 suffix - GLEP54 [#GLEP54]_. 39 suffix - GLEP54 [#GLEP54]_ or allowing more sensible version formats like
40 ``1-rc1``, ``1-alpha`` etc. to match upstream more closely.
40 41
42
43Current behaviour
44=================
45
46Following subsections show what happens if you introduce any of the mentioned
47changes in an ebuild and try to install it with portage 2.1.6.13.
48
49Incompatible change of inherit (e.g. make it look in the package dir too)
50-------------------------------------------------------------------------
51
52``sys-apps/foo-1.ebuild``::
53
54 EAPI="5"
55 inherit "foo"
56
57 DESCRIPTION=""
58 HOMEPAGE=""
59 SRC_URI=""
60 ...
61
62Result::
63
64 *
65 * ERROR: sys-apps/foo-1 failed.
66 * Call stack:
67 * ebuild.sh, line 1879: Called _source_ebuild
68 * ebuild.sh, line 1818: Called source '/var/lib/gentoo/repositories/peper/sys-apps/foo/foo-1.ebuild'
69 * foo-1.ebuild, line 6: Called inherit 'foo'
70 * ebuild.sh, line 1218: Called die
71 * The specific snippet of code:
72 * [ ! -e "$location" ] && die "${1}.eclass could not be found by inherit()"
73 * The die message:
74 * foo.eclass could not be found by inherit()
75 *
76 * If you need support, post the topmost build error, and the call stack if relevant.
77 * This ebuild is from an overlay: '/var/lib/gentoo/repositories/peper/'
78 *
79
80 !!! All ebuilds that could satisfy "sys-apps/foo" have been masked.
81 !!! One of the following masked packages is required to complete your request:
82 - sys-apps/foo-1 (masked by: corruption)
83
84Current portage looks for eclasses only in the ``eclass`` directory of a
85repository. This results in a fatal error and ebuild being masked by corruption
86- might be pretty confusing to users.
87
88New global scope function
89-------------------------
90
91``sys-apps/foo-1.ebuild``::
92
93 EAPI="5"
94 new_global_scope_function "foo"
95
96 DESCRIPTION=""
97 HOMEPAGE=""
98 SRC_URI=""
99 ...
100
101Result::
102
103 /var/lib/gentoo/repositories/peper/sys-apps/foo/foo-1.ebuild: line 7: new_global_scope_function: command not found
104
105 !!! All ebuilds that could satisfy "sys-apps/foo" have been masked.
106 !!! One of the following masked packages is required to complete your request:
107 - sys-apps/foo-1 (masked by: EAPI 5)
108
109 The current version of portage supports EAPI '2'. You must upgrade to a
110 newer version of portage before EAPI masked packages can be installed.
111
112Not that bad as user is advised to upgrade portage.
113
114New version format
115------------------
116
117``sys-apps/foo-2-rc1.ebuild``::
118
119 Invalid ebuild name: /var/lib/gentoo/repositories/peper/sys-apps/foo/foo-2-rc1.ebuild
120
121 emerge: there are no ebuilds to satisfy "sys-apps/foo"
122
123Not the best error message, especially if there are lots of them.
41 124
42Abstract solution 125Abstract solution
43================= 126=================
44 127
45A solution to this problem has to lift those limitations and the only way to do 128A solution to this problem has to lift those limitations and the only way to do
64============= 147=============
65 148
66Ebuild filename extension syntax: ``ebuild[-<EAPI>]``, where ``[]`` denotes an 149Ebuild filename extension syntax: ``ebuild[-<EAPI>]``, where ``[]`` denotes an
67optional part, and ``<EAPI>`` is the EAPI of the ebuild. 150optional part, and ``<EAPI>`` is the EAPI of the ebuild.
68 151
69Let's call the EAPI included in the ebuild filename the pre-source EAPI, and the 152The EAPI used by the ebuild is the EAPI included in the filename if it is set.
70EAPI set inside the ebuild the post-source EAPI. Given these two, the final EAPI 153Otherwise the EAPI set inside the ebuild is used, which defaults to 0 (this is
71used by the ebuild can be established by following these steps: 154the current behaviour).
72
73 * If the pre-source EAPI is not set it defaults to 0.
74 * If the pre-source EAPI is not recognised it is returned immediately.
75 * If the post-source EAPI is not set, it defaults to the pre-source EAPI.
76 * post-source EAPI is returned.
77
78The above process should be only used to generate the metadata cache. Should the
79pre-source EAPI be unsupported the cache entry cannot be generated.
80 155
81Ebuilds with unsupported EAPIs are masked. 156Ebuilds with unsupported EAPIs are masked.
82 157
83QA tools should consider it an error for both EAPIs to be set explicitly to 158It should be considered an error to set the EAPI both in the filename and in the
84different values. Package managers may warn, but must use the post-source EAPI 159ebuild.
85in such cases.
86 160
87Examples: 161Examples:
88 162
89 * ``pkg-1.ebuild``, no EAPI set inside the ebuild 163 * ``pkg-1.ebuild``, no EAPI set inside the ebuild
90 pre-source EAPI defaults to 0, post-source EAPI defaults to pre-source EAPI. 164 EAPI defaults to 0.
91 EAPI 0 is used.
92 165
93 * ``pkg-2.ebuild-1``, no EAPI set inside the ebuild 166 * ``pkg-2.ebuild-1``, no EAPI set inside the ebuild
94 pre-source EAPI is 1, post-source EAPI defaults to pre-source EAPI.
95 EAPI 1 is used. 167 EAPI 1 is used.
96 168
97 * ``pkg-3.ebuild``, ``EAPI="1"`` 169 * ``pkg-3.ebuild-1``, ``EAPI="1"``
98 pre-source EAPI defaults to 0, post-source EAPI is 1. 170 EAPI set in both places - error.
99 EAPI 1 is used.
100
101 * ``pkg-4.ebuild-2``, ``EAPI="1"``
102 pre-source EAPI is 2, post-source EAPI is 1.
103 EAPI 1 is used, but note that one should **never** explicitly set both
104 EAPIs to different values.
105
106 * ``pkg-5.ebuild-2``, no EAPI set inside the ebuild, package manager not supporting EAPI 2
107 pre-source EAPI is 2, post-source EAPI is never checked.
108 ebuild is masked because of the unsupported pre-source EAPI.
109
110 * ``pkg-6.ebuild``, ``EAPI="2"``, package manager not supporting EAPI 2
111 pre-source EAPI defaults to 0, post-source EAPI is 2 (assuming the
112 package manager didn't die when sourcing the ebuild thinking that EAPI 0
113 is used).
114 ebuild is masked because of the unsupported post-source EAPI.
115 171
116Note that it is still not permitted to have more than one ebuild with equal 172Note that it is still not permitted to have more than one ebuild with equal
117category, package name, and version. Although it would have the advantage of 173category, package name, and version. Although it would have the advantage of
118allowing authors to provide backwards compatible ebuilds, it would introduce 174allowing authors to provide backwards compatible ebuilds, it would introduce
119problems too. The first is the requirement to have strict EAPI ordering, the 175problems too. The first is the requirement to have strict EAPI ordering, the
120second is ensuring that all the ebuilds for a single category/package-version 176second is ensuring that all the ebuilds for a single category/package-version
121are equivalent, i.e. installing any of them has exactly the same effect on a 177are equivalent, i.e. installing any of them has exactly the same effect on a
122given system. 178given system.
123 179
124Application 180Summary of ideas
125=========== 181================
126 182
127Note that the developers should only set the pre-source EAPI. The process 183EAPI-suffixed ebuilds (proposed solution)
128described above is only necessary to avoid undefined behaviour in corner cases 184-----------------------------------------
129and to retain backwards compatibility.
130 185
131QA tools may warn if the post-source EAPI is set at all, thus helping with the 186Properties:
132transition to the new format. 187 * Can be used right away: yes
188 * Hurts performance: no
133 189
134Other ideas 190Some say it is clear and simple, others that it is ugly and unintuitive.
135===========
136 191
137There were some other solutions proposed on the mailing list: 192EAPI in the filename with one-time extension change
193---------------------------------------------------
138 194
139 * Set the EAPI inside the ebuild in a way that makes it easy to fetch it 195One of the proposed filename formats:
140 * Doesn't meet the backward compatibility requirement. 196``<PKG>-<VER>.eapi-<EAPI>.eb``
141 * Isn't forward compatible either.
142 * Could be confusing as ebuilds are considered bash scripts and this
143 would impose additional restrictions on the ebuild format.
144 197
145 * Do the above and change the ebuild extension to ``.ebuild-ng`` 198Properties:
146 * Meets the backward compatibility requirement. 199 * Can be used right away: yes
147 * Still can be confusing. 200 * Hurts performance: no
148 * Isn't really forward compatible. What would be after ``.ebuild-ng``?
149 ``.ebuild-ng-ng``?
150 201
202This is equivalent to the proposed solution.
203
204Some say it is better because the extension is static.
205
206Easily fetchable EAPI inside the ebuild
207---------------------------------------
208
209Properties:
210 * Can be used right away: no
211 * Hurts performance: yes
212
213Cannot be used right away as it would trigger the errors shown in Current
214behaviour section for old package managers.
215
216Performance decrease comes from the fact that with version format changes in the
217picture package managers need EAPI to parse the ebuild's version. That means that merely
218picking the best version of a package requires loading EAPI (from cache or the
219ebuild) for each available ebuild.
220
221
222Easily fetchable EAPI inside the ebuild and one-time extension change
223---------------------------------------------------------------------
224
225Properties:
226 * Can be used right away: yes
227 * Hurts performance: yes
228
229Performance decrease as described in the previous section.
230
231Some say it is clear and simple, others that it is confusing and unintuitive,
232because of the arbitrary format restrictions in what is a bash script otherwise.
233
151 * Use different subdirectories for different EAPIs, i.e. cat/pkg/eapiX/ 234Use different subdirectories for different EAPIs, i.e. cat/pkg/eapiX/
152 * Meets both requirements. 235---------------------------------------------------------------------
153 * Introduces a noticeable performance hit (several more directory reads 236
154 in an I/O bound operation). 237Properties:
238 * Can be used right away: yes
239 * Hurts performance: yes
240
241Performance decrease comes from the fact that it adds several more directory
242reads.
243
155 * Makes it much harder for maintainers to see what they have. 244Some say that it makes it much harder for maintainers to see what they have.
156
157 245
158References 246References
159========== 247==========
160 248
161.. [#GLEP54] GLEP 54, scm package version suffix 249.. [#GLEP54] GLEP 54, scm package version suffix

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