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Spelling updates, 21 is Final, but keeping Genons status message to inform people that implementation does not match GLEP.

1 GLEP: 21
2 Title: User-defined Package Sets
3 Version: $Revision: 1.5 $
4 Last-Modified: $Date: 2007/10/21 11:42:57 $
5 Author: Tal Peer <coredumb@gentoo.org>,
6 Alec Warner <antarus@gentoo.org>
7 Status: Final
8 Type: Standards Track
9 Discussed-To: gentoo-portage-dev@lists.gentoo.org
10 Content-Type: text/x-rst
11 Created: 22-Feb-2004
12 Post-History: 6-Mar-2004, 3-Sep-2006
13
14 Status
15 ======
16
17 Abandoned. Package set support has been added in portage-2.2, but it
18 doesn't match the description in this document in many cases, and the
19 document has several major gaps regarding the behavior and restrictions
20 of package sets.
21
22 Abstract
23 ========
24
25 In Portage, package sets (formerly known as 'classes' or 'targets')
26 are mere groups of packages, grouped together to allow easier updating
27 and handling of them. Currently it is impossible to define sets further
28 than the two default ones: "system" and "world".
29
30 Motivation
31 ==========
32
33 Over the months, quite a few requests for user-defined sets were
34 made by users and developers, either by posting bugs, messages to
35 mailing lists or on IRC. Usually the response is that this is an
36 awesome idea, but no one ever took the time to actually define it
37 properly and implement it.
38
39 This document offers a specification for the implementation of
40 user-defined sets using configuration files similar to the current
41 world/system sets use.
42
43 Specification
44 =============
45
46 The proposed implementation uses a one file per set approach, meaning
47 each package set is defined in a single file. All set definition files
48 will reside in a directory ``/etc/portage/sets/`` and each set's name
49 will be its file name. Therefore, if one defines a set in
50 /etc/portage/sets/foo-set, the set name will be 'foo-set'. Usual
51 package naming rules [#NAME-RULES]_ also apply to sets.
52
53 As it is impossible to create two or more files with identical names
54 in the same directory, a theoretic conflict between two different sets
55 sharing the same name is impossible. However, users may define a
56 package set whose name conflicts with one more or packages (for ambiguity
57 resolution, see below).
58
59 Syntax for the package list file is the same as the world file syntax,
60 as described in the Portage manpage [#PORTAGE-MANPAGE]_, with one
61 addition: sets may not be 'inherited' by other sets, only packages may
62 be listed. There is no limitation to the number of packages in a set
63 or to the number of sets a package may belong to.
64
65 Using User-defined Sets With Emerge
66 --------------------------------------
67
68 The user-defined sets will be available either directly or using
69 the --package-set option, As in::
70
71 # Basically the same:
72 emerge foo-set
73 emerge --package-set foo-set
74
75 The --package-set option is introduced to bypass ambiguities, as
76 illustrated in the next example::
77
78 emerge foo # Where foo is both a set and a one or more
79 # existing packages. This will cause emerge to show
80 # the ambiguity, ask us to be more
81 # specific, and stop.
82
83 emerge --package-set foo # So we specify that what we actually
84 # meant was the package set.
85
86 emerge cat-bar/foo # Or we specify the exact package name.
87
88 When running emerge with the --pretend option, sets will be
89 expanded to the packages they are comprised off in the output, as with
90 the current system-defined sets.
91
92 Only one set may be passed to portage at time, and sets can not
93 be mixed with ordinary packages. Thus, the following snippets are
94 all invalid and will result in an error (assuming ``foo-set`` and
95 ``bar-set`` are defined as sets)::
96
97 emerge foo-set glibc
98 emerge bar-set system
99 emerge world foo-set gcc
100
101 Compatibility With Other Portage Features
102 -----------------------------------------
103
104 * Dependencies:
105 Package sets (both system-defined and user-defined) may not be
106 depended on by ordinary packages and eclasses.
107
108 * package.mask:
109 Masking a package set through the ``package.mask`` file is forbidden.
110 In order to 'mask' a package set, one should move it away from the
111 sets directory.
112
113 * package.use:
114 USE flags may not be defined for sets in the ``package.use`` file.
115
116 Implementation
117 ==============
118
119 The implementation of the package sets concept in Portage should be
120 mostly done in portage.py, and only the interface parts should be
121 added to emerge itself, to keep the separation between interface and
122 logic.
123
124 The amount of work needed for implementation is not trivial, but not
125 huge either.
126
127 Rationale
128 =========
129
130 The one file per set approach makes it easy to list the sets which are
131 defined on a system by just listing the ``/etc/portage/sets``
132 directory contents. Additionally, it makes the set lookup process more
133 efficient as it only requires to check if a file exists.
134
135 I chose the --package-set option over the --set option for explicitly
136 telling portage to emerge a set mostly because --set implies setting
137 an environment variable, or such.
138
139 Allowing sets' USE flags to be manipulated through the ``package.use``
140 file would have done more harm than good, for several reasons:
141
142 - If a USE flag is turned on (i.e. 'foo') for a set and the same USE
143 flag is turned off (i.e. '-foo'), for a package which is part of
144 the set, it is unclear which setting should take precedence.
145
146 - Similarly, if a USE flag is turned on for a set and the same USE flag
147 is turned off for a set that is a subset of the original set, it is
148 unclear which setting should take precedence.
149
150 - If a USE flag is defined (either off or on) for a set and a package
151 that belongs in the set is to be emerged, it is unclear whether the
152 USE flag should be defined when emerging the package in question.
153
154 Therefore, I have decided it would be better to disallow setting USE
155 flags for sets.
156
157 Backwards Compatibility
158 =======================
159
160 Backwards compatibility with the current situation, in which only two
161 system-defined sets exist can be kept in one of two ways:
162
163 1. Leaving the situation as is - the 'world' and 'system' sets are
164 hard-coded in Portage.
165 2. Distributing default 'system' and 'world' files under the
166 ``/etc/portage/sets/`` directory.
167
168 Other than that, there are no other backwards compatibility concerns
169 involved.
170
171 References
172 ==========
173
174 .. [#NAME-RULES] Gentoo Linux Development Policy - Ebuild Policy
175 (http://www.gentoo.org/doc/en/policy.xml#doc_chap3)
176
177 .. [#PORTAGE-MANPAGE]
178 http://www.gentoo.org/cgi-bin/viewcvs.cgi/portage/man/portage.5?root=gentoo-src
179
180 Copyright
181 =========
182
183 This document has been placed in the public domain.

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