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Revision 1.2 Revision 1.4
1GLEP: 33 1GLEP: 33
2Title: Eclass Restructure/Redesign 2Title: Eclass Restructure/Redesign
3Version: $Revision: 1.2 $ 3Version: $Revision: 1.4 $
4Last-Modified: $Date: 2005/03/06 20:33:20 $ 4Last-Modified: $Date: 2005/09/15 02:37:38 $
5Author: Brian Harring <ferringb@gentoo.org>, John Mylchreest <johnm@gentoo.org> 5Author: Brian Harring <ferringb@gentoo.org>, John Mylchreest <johnm@gentoo.org>
6Status: Draft 6Status: Draft
7Type: Standards Track 7Type: Standards Track
8Content-Type: text/x-rst 8Content-Type: text/x-rst
9Created: 29-Jan-2005 9Created: 29-Jan-2005
10Post-History: 29-Jan-2005 10Post-History: 29-Jan-2005 6-Mar-2005
11 11
12 12
13Abstract 13Abstract
14======== 14========
15 15
36======================== 36========================
37 37
38Eclasses within the tree currently are a bit of a mess- they're forced to 38Eclasses within the tree currently are a bit of a mess- they're forced to
39maintain backwards compatibility w/ all previous functionality. In effect, 39maintain backwards compatibility w/ all previous functionality. In effect,
40their api is constant, and can only be added to- never changing the existing 40their api is constant, and can only be added to- never changing the existing
41functionality. This obviously is quite limiting, and leads to cruft accruing in 41functionality. This obviously is quite limiting, and leads to cruft accruing in
42eclasses as a eclasses design is refined. This needs to be dealt with prior to 42eclasses as a eclasses design is refined. This needs to be dealt with prior to
43eclass code reaching a critical mass where they become unmanageable/fragile 43eclass code reaching a critical mass where they become unmanageable/fragile
44(recent pushes for eclass versioning could be interpreted as proof of this). 44(recent pushes for eclass versioning could be interpreted as proof of this).
45 45
46Beyond that, eclasses were originally intended as a method to allow for ebuilds 46Beyond that, eclasses were originally intended as a method to allow for ebuilds
47to use a pre-existing block of code, rather then having to duplicate the code in 47to use a pre-existing block of code, rather then having to duplicate the code in
48each ebuild. This is a good thing, but there are ill effects that result from 48each ebuild. This is a good thing, but there are ill effects that result from
49the current design. Eclasses inherit other eclasses to get a single function- in 49the current design. Eclasses inherit other eclasses to get a single function- in
50doing so, modifying the the exported 'template' (default src_compile, default 50doing so, modifying the the exported 'template' (default src_compile, default
51src_unpack, various vars, etc). All the eclass designer was after was reusing a 51src_unpack, various vars, etc). All the eclass designer was after was reusing a
52function, not making their eclass sensitive to changes in the template of the 52function, not making their eclass sensitive to changes in the template of the
53eclass it's inheriting. The eclass designer -should- be aware of changes in the 53eclass it's inheriting. The eclass designer -should- be aware of changes in the
54function they're using, but shouldn't have to worry about their default src_* 54function they're using, but shouldn't have to worry about their default src_*
55and pkg_* functions being overwritten, let alone the env changes. 55and pkg_* functions being overwritten, let alone the env changes.
56 56
61rather then requiring them to be aware of what phase of eclass changes is in 61rather then requiring them to be aware of what phase of eclass changes is in
62progress. 62progress.
63 63
64By rolling all changes into one large change, a line is intentionally drawn in 64By rolling all changes into one large change, a line is intentionally drawn in
65the sand. Old eclasses allowed for this, behaved this way. New eclasses allow 65the sand. Old eclasses allowed for this, behaved this way. New eclasses allow
66for that, and behave this way. This should reduce misconceptions about what is 66for that, and behave this way. This should reduce misconceptions about what is
67allowed/possible with eclasses, thus reducing bugs that result from said 67allowed/possible with eclasses, thus reducing bugs that result from said
68misconceptions. 68misconceptions.
69 69
70A few words on elibs- think of them as a clear definition between behavioral 70A few words on elibs- think of them as a clear definition between behavioral
71functionality of an eclass, and the library functionality. Eclass's modify 71functionality of an eclass, and the library functionality. Eclass's modify
74 74
75Consider the majority of the portage bin/* scripts- these all are candidates for 75Consider the majority of the portage bin/* scripts- these all are candidates for
76being added to the tree as elibs, as is the bulk of eutils. 76being added to the tree as elibs, as is the bulk of eutils.
77 77
78 78
79Specification. 79Specification
80============== 80=============
81 81
82The various parts of this proposal are broken down into a set of changes and 82The various parts of this proposal are broken down into a set of changes and
83elaborations on why a proposed change is preferable. It's advisable to the 83elaborations on why a proposed change is preferable. It's advisable to the
84reader that this be read serially, rather then jumping around. 84reader that this be read serially, rather then jumping around.
85 85
108initialization of the library that is absolutely needed. Additionally, they 108initialization of the library that is absolutely needed. Additionally, they
109cannot modify any ebuild template functions- src_compile, src_unpack. Since they are 109cannot modify any ebuild template functions- src_compile, src_unpack. Since they are
110required to not modify the metadata keys, nor in any way affect the ebuild aside 110required to not modify the metadata keys, nor in any way affect the ebuild aside
111from providing functionality, they can be conditionally pulled in. They also 111from providing functionality, they can be conditionally pulled in. They also
112are allowed to pull in other elibs, but strictly just elibs- no eclasses, just 112are allowed to pull in other elibs, but strictly just elibs- no eclasses, just
113other elibs. A real world example would be the eutils eclass. 113other elibs. A real world example would be the eutils eclass.
114 114
115Portage, since the elib's don't modify metadata, isn't required to track elibs 115Portage, since the elib's don't modify metadata, isn't required to track elibs
116as it tracks eclasses. Thus a change in an elib doesn't result in half the tree 116as it tracks eclasses. Thus a change in an elib doesn't result in half the tree
117forced to be regenerated/marked stale when changed (this is more of an infra 117forced to be regenerated/marked stale when changed (this is more of an infra
118benefit, although regen's that take too long due to eclass changes have been 118benefit, although regen's that take too long due to eclass changes have been
119known to cause rsync issues due to missing timestamps). 119known to cause rsync issues due to missing timestamps).
120 120
121Elibs will not be available in the global scope of an eclass, or ebuild- nor during the 121Elibs will not be available in the global scope of an eclass, or ebuild- nor during the
122depends phase (basically a phase that sources the ebuild, to get it's metadata). Elib 122depends phase (basically a phase that sources the ebuild, to get its metadata). Elib
123calls in the global scope will be tracked, but the elib will not be loaded till just before 123calls in the global scope will be tracked, but the elib will not be loaded till just before
124the setup phase (pkg_setup). There are two reasons for this- first, it ensures elibs are 124the setup phase (pkg_setup). There are two reasons for this- first, it ensures elibs are
125completely incapable of modifying metadata. There is no room for confusion, late loading 125completely incapable of modifying metadata. There is no room for confusion, late loading
126of elibs gives you the functionality for all phases, except for depends- depends being the 126of elibs gives you the functionality for all phases, except for depends- depends being the
127only phase that is capable of specifying metadata. Second, as an added bonus, late 127only phase that is capable of specifying metadata. Second, as an added bonus, late
128loading reduces the amount of bash sourced for a regen- faster regens. This however is minor, 128loading reduces the amount of bash sourced for a regen- faster regens. This however is minor,
129and is an ancillary benefit of the first reason. 129and is an ancillary benefit of the first reason.
130 130
131There are a few further restrictions with elibs- mainly, elibs to load can only be specified 131There are a few further restrictions with elibs--mainly, elibs to load can only be specified
132in either global scope, or in the setup, unpack, compile, test, and install phases. You can 132in either global scope, or in the setup, unpack, compile, test, and install phases. You can
133not load elibs in prerm, postrm, preinst, and postinst. The reason being, for *rm phases, 133not load elibs in prerm, postrm, preinst, and postinst. The reason being, for \*rm phases,
134installed pkgs will have to look to the tree for the elib, which allows for api drift to cause 134installed pkgs will have to look to the tree for the elib, which allows for api drift to cause
135breakage. For *inst phases, same thing, except the culprit is binpkgs. 135breakage. For \*inst phases, same thing, except the culprit is binpkgs.
136 136
137There is a final restriction- elibs cannot change their exported api dependent on the api 137There is a final restriction--elibs cannot change their exported api dependent on the api
138(as some eclass do for example). The reason mainly being that elibs are loaded once- not 138(as some eclass do for example). The reason mainly being that elibs are loaded once--not
139multiple times, as eclasses are. 139multiple times, as eclasses are.
140 140
141To clarify, for example this is invalid. 141To clarify, for example this is invalid.
142:: 142::
143
143 if [[ -n ${SOME_VAR} ]]; then 144 if [[ -n ${SOME_VAR} ]]; then
144 func x() { echo "I'm accessible only via tweaking some var";} 145 func x() { echo "I'm accessible only via tweaking some var";}
145 else 146 else
146 func x() { echo "this is invalid, do not do it."; } 147 func x() { echo "this is invalid, do not do it."; }
147 fi 148 fi
148 149
149 150
150Regarding maintainability of elibs, it should be a less of a load then old 151Regarding maintainability of elibs, it should be a less of a load then old
151eclasses. One of the major issues with old eclasses is that their functions are 152eclasses. One of the major issues with old eclasses is that their functions are
152quite incestuous- they're bound tightly to the env they're defined in. This 153quite incestuous- they're bound tightly to the env they're defined in. This
153makes eclass functions a bit fragile- the restrictions on what can, and cannot 154makes eclass functions a bit fragile- the restrictions on what can, and cannot
154be done in elibs will address this, making functionality less fragile (thus a 155be done in elibs will address this, making functionality less fragile (thus a
155bit more maintainable). 156bit more maintainable).
156 157
157There is no need for backwards compatibility with elibs- they just must work 158There is no need for backwards compatibility with elibs- they just must work
168 169
169The reduced role of Eclasses, and a clarification of existing Eclass requirements 170The reduced role of Eclasses, and a clarification of existing Eclass requirements
170--------------------------------------------------------------------------------- 171---------------------------------------------------------------------------------
171 172
172Since elibs are now intended on holding common bash functionality, the focus of 173Since elibs are now intended on holding common bash functionality, the focus of
173eclasses should be in defining an appropriate template for ebuilds. For example, 174eclasses should be in defining an appropriate template for ebuilds. For example,
174defining common DEPENDS, RDEPENDS, src_compile functions, src_unpack, etc. 175defining common DEPENDS, RDEPENDS, src_compile functions, src_unpack, etc.
175Additionally, eclasses should pull in any elibs they need for functionality. 176Additionally, eclasses should pull in any elibs they need for functionality.
176 177
177Eclass functionality that isn't directly related to the metadata, or src_* and 178Eclass functionality that isn't directly related to the metadata, or src_* and
178pkg_* funcs should be shifted into elibs to allow for maximal code reuse. This 179pkg_* funcs should be shifted into elibs to allow for maximal code reuse. This
215 216
216 217
217The end of backwards compatibility... 218The end of backwards compatibility...
218------------------------------------- 219-------------------------------------
219 220
220With current eclasses, once the eclass is in use, it's api can no longer be 221With current eclasses, once the eclass is in use, its api can no longer be
221changed, nor can the eclass ever be removed from the tree. This is why we still 222changed, nor can the eclass ever be removed from the tree. This is why we still
222have *ancient* eclasses that are completely unused sitting in the tree, for 223have *ancient* eclasses that are completely unused sitting in the tree, for
223example inherit.eclass . The reason for this, not surprisingly is a portage 224example inherit.eclass. The reason for this, not surprisingly, is a portage
224deficiency- on unmerging an installed ebuild, portage used the eclass from the 225deficiency: on unmerging an installed ebuild, portage used the eclass from the
225current tree. 226current tree.
226 227
227For a real world example of this, if you merged a glibc 2 years back, whatever 228For a real world example of this, if you merged a glibc 2 years back, whatever
228eclasses it used must still be compatible, or you may not be able to unmerge the 229eclasses it used must still be compatible, or you may not be able to unmerge the
229older glibc version during an upgrade to a newer version. So either the glibc 230older glibc version during an upgrade to a newer version. So either the glibc
265 266
266In other words, these new eclasses would in effect, be old eclasses since older 267In other words, these new eclasses would in effect, be old eclasses since older
267portage versions could still access them. 268portage versions could still access them.
268 269
269 270
270Tree restructuring. 271Tree restructuring
271------------------- 272------------------
272 273
273There are only two way to block the existing (as of this writing) inherit 274There are only two way to block the existing (as of this writing) inherit
274functionality from accessing the new eclasses- either change the extension of 275functionality from accessing the new eclasses- either change the extension of
275eclasses to something other then 'eclass', or to have them stored in a separate 276eclasses to something other then 'eclass', or to have them stored in a separate
276subdirectory of the tree then eclass. 277subdirectory of the tree then eclass.
286eclasses, please reread the previous section. It's unfortunately a requirement 287eclasses, please reread the previous section. It's unfortunately a requirement
287to take advantage of all that the next major portage release will allow. 288to take advantage of all that the next major portage release will allow.
288 289
289The proposed directory structure is ${PORTDIR}/include/{eclass,elib}. 290The proposed directory structure is ${PORTDIR}/include/{eclass,elib}.
290Something like ${PORTDIR}/new-eclass, or ${PORTDIR}/eclass-ng could be used 291Something like ${PORTDIR}/new-eclass, or ${PORTDIR}/eclass-ng could be used
291(although many would cringe at the -ng), but such a name is unwise. Consider the 292(although many would cringe at the -ng), but such a name is unwise. Consider the
292possibility (likely a fact) that new eclasses someday may be found lacking, and 293possibility (likely a fact) that new eclasses someday may be found lacking, and
293refined further (version three as it were). Or perhaps we want to add yet more 294refined further (version three as it were). Or perhaps we want to add yet more
294functionality with direct relation to sourcing new files, and we would then need 295functionality with direct relation to sourcing new files, and we would then need
295to further populate ${PORTDIR}. 296to further populate ${PORTDIR}.
296 297
297The new-eclass directory will be (at least) 2 levels deep- for example: 298The new-eclass directory will be (at least) 2 levels deep- for example:
298 299
314to ensure no files are missing, and that nothing has been tainted. 315to ensure no files are missing, and that nothing has been tainted.
315 316
316The elib directory will be structured in the same way, for the same reasons. 317The elib directory will be structured in the same way, for the same reasons.
317 318
318Repoman will have to be extended to work within new eclass and elib groups, and 319Repoman will have to be extended to work within new eclass and elib groups, and
319to handle signing and committing. This is intentional, and a good thing. This 320to handle signing and committing. This is intentional, and a good thing. This
320gives repoman the possibility of doing sanity checks on elibs/new eclasses. 321gives repoman the possibility of doing sanity checks on elibs/new eclasses.
321 322
322Note these checks will not prevent developers from doing dumb things with eclass- 323Note these checks will not prevent developers from doing dumb things with eclass-
323these checks would only be capable of doing basic sanity checks, such as syntax checks. 324these checks would only be capable of doing basic sanity checks, such as syntax checks.
324There is no way to prevent people from doing dumb things (exempting perhaps repeated 325There is no way to prevent people from doing dumb things (exempting perhaps repeated
330--------------------------------------------------------- 331---------------------------------------------------------
331 332
332As clarified above, new eclasses will exist in a separate directory that will be 333As clarified above, new eclasses will exist in a separate directory that will be
333intentionally inaccessible to the inherit function. As such, users of older 334intentionally inaccessible to the inherit function. As such, users of older
334portage versions *will* have to upgrade to merge any ebuild that uses elibs/new 335portage versions *will* have to upgrade to merge any ebuild that uses elibs/new
335eclasses. A depend on the next major portage version would transparently handle 336eclasses. A depend on the next major portage version would transparently handle
336this for rsync users. 337this for rsync users.
337 338
338There still is the issue of users who haven't upgraded to the required portage 339There still is the issue of users who haven't upgraded to the required portage
339version. This is a minor concern frankly- portage releases include new 340version. This is a minor concern frankly- portage releases include new
340functionality, and bug fixes. If they won't upgrade, it's assumed they have 341functionality, and bug fixes. If they won't upgrade, it's assumed they have
341their reasons and are big boys, thus able to handle the complications themselves. 342their reasons and are big boys, thus able to handle the complications themselves.
342 343
343The real issue is broken envs, whether in binpkgs, or for installed packages. 344The real issue is broken envs, whether in binpkgs, or for installed packages.
344Two options exist- either the old eclasses are left in the tree indefinitely, or 345Two options exist- either the old eclasses are left in the tree indefinitely, or
380 381
381Note for this to happen requires either rather... unwise uses of root, or significant 382Note for this to happen requires either rather... unwise uses of root, or significant
382fs corruption. Regardless of the cause, it's quite likely for this to even become an 383fs corruption. Regardless of the cause, it's quite likely for this to even become an
383issue, the system's vdb is completely unusable. It's a moot issue at that point. 384issue, the system's vdb is completely unusable. It's a moot issue at that point.
384If you lose your vdb, or it gets seriously damaged, it's akin to lobotomizing portage- 385If you lose your vdb, or it gets seriously damaged, it's akin to lobotomizing portage-
385it doesn't know what's installed, it doesn't know of it's own files, and in general, 386it doesn't know what's installed, it doesn't know of its own files, and in general,
386a rebuilding of the system is about the only sane course of action. The missing env is 387a rebuilding of the system is about the only sane course of action. The missing env is
387truly the least of the users concern in such a case. 388truly the least of the users concern in such a case.
388 389
389Continuing with the more likely scenario, users unwilling to upgrade portage will 390Continuing with the more likely scenario, users unwilling to upgrade portage will
390*not* be left out in the rain. Merging the old eclass compat ebuild will provide 391*not* be left out in the rain. Merging the old eclass compat ebuild will provide
391the missing eclasses, thus providing that lost functionality . 392the missing eclasses, thus providing that lost functionality.
392 393
393Note the intention isn't to force them to upgrade, hence the ability to restore the 394Note the intention isn't to force them to upgrade, hence the ability to restore the
394lost functionality. The intention is to clean up the existing mess, and allow us 395lost functionality. The intention is to clean up the existing mess, and allow us
395to move forward. The saying "you've got to break a few eggs to make an omelet" 396to move forward. The saying "you've got to break a few eggs to make an omelet"
396is akin, exempting the fact we're providing a way to make the eggs whole again 397is akin, exempting the fact we're providing a way to make the eggs whole again
397(the king's men would've loved such an option). 398(the king's men would've loved such an option).
398 399
399 400
400Migrating to the new setup 401Migrating to the new setup
416infrastructure server that generates the cache for rsync users will have to 417infrastructure server that generates the cache for rsync users will have to
417either be upgraded to a version of portage supporting new eclasses, or patched. 418either be upgraded to a version of portage supporting new eclasses, or patched.
418The former being much more preferable then the latter for the portage devs. 419The former being much more preferable then the latter for the portage devs.
419 420
420Beyond that, an appropriate window for old eclasses to exist in the tree must be 421Beyond that, an appropriate window for old eclasses to exist in the tree must be
421determined, and prior to that window passing an ebuild must be added to the tree 422determined, and prior to that window passing, an ebuild must be added to the tree
422so users can get the old eclasses if needed. 423so users can get the old eclasses if needed.
423 424
424For eclass devs to migrate from old to new, it is possible for them to just 425For eclass devs to migrate from old to new, it is possible for them to just
425transfer the old eclass into an appropriate grouping in the new eclass directory, 426transfer the old eclass into an appropriate grouping in the new eclass directory,
426although it's advisable they cleanse all cruft out of the eclass. You can 427although it's advisable they cleanse all cruft out of the eclass. You can
427migrate ebuilds gradually over to the new eclass, and don't have to worry about 428migrate ebuilds gradually over to the new eclass, and don't have to worry about
428having to support ebuilds from X years back. 429having to support ebuilds from X years back.
429 430
430Essentially, you have a chance to nail the design perfectly/cleanly, and have a 431Essentially, you have a chance to nail the design perfectly/cleanly, and have a
431window in which to redesign it. It's humbly suggested eclass devs take 432window in which to redesign it. It's humbly suggested eclass devs take
441a more in depth discussion of the issue, along with a more extensive explanation 442a more in depth discussion of the issue, along with a more extensive explanation
442of the potential solutions, and reasons for the chosen solution. 443of the potential solutions, and reasons for the chosen solution.
443 444
444To recap: 445To recap:
445:: 446::
447
446 New eclasses and elib functionality will be tied to a specific portage 448 New eclasses and elib functionality will be tied to a specific portage
447 version. A DEPENDs on said portage version should address this for rsync 449 version. A DEPENDs on said portage version should address this for rsync
448 users who refuse to upgrade to a portage version that supports the new 450 users who refuse to upgrade to a portage version that supports the new
449 eclasses/elibs and will gradually be unable to merge ebuilds that use said 451 eclasses/elibs and will gradually be unable to merge ebuilds that use said
450 functionality. It is their choice to upgrade, as such, the gradual 452 functionality. It is their choice to upgrade, as such, the gradual
451 'thinning' of available ebuilds should they block the portage upgrade is 453 'thinning' of available ebuilds should they block the portage upgrade is
452 their responsibility. 454 their responsibility.
453 455
454 Old eclasses at some point in the future should be removed from the tree, 456 Old eclasses at some point in the future should be removed from the tree,
455 and released in a tarball/ebuild. This will cause installed ebuilds that 457 and released in a tarball/ebuild. This will cause installed ebuilds that
456 rely on the old eclass to be unable to unmerge, with the same applying for 458 rely on the old eclass to be unable to unmerge, with the same applying for
457 merging of binpkgs dependent on the following paragraph. 459 merging of binpkgs dependent on the following paragraph.
458 460
459 The old eclass-compat is only required for users who do not upgrade their 461 The old eclass-compat is only required for users who do not upgrade their
460 portage installation, and one further exemption- if the user has somehow 462 portage installation, and one further exemption- if the user has somehow

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