[MacPorts] #30328: Enable variants for specific ports in variants.conf

[MacPorts]

#30328: Enable variants for specific ports in variants.conf
----------------------------+-----------------------------------------------
 Reporter:  ionic@…         |       Owner:  macports-tickets@…                   
     Type:  enhancement     |      Status:  new                                  
 Priority:  Low             |   Milestone:                                       
Component:  base            |     Version:                                       
 Keywords:                  |        Port:                                       
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 Currently, variants.conf only provides the possibility to globally enable
 or disable variants.

 I'm proposing a feature letting users define port specific variants in
 this file too, similar to Gentoo's package.use or use.conf file(s), though
 not necessarily as sophisticated.

 Basically it would be really nice to turn variants on and off in the
 variants.conf file for specific ports and globally, without fiddling with
 them on the command line.

 Thus, I propose following syntax:

 {{{
 portname +variant1 -variant2 +variant3 +variant4 -variant5
 }}}

 Or, if that's more convenient,

 {{{
 portname variant1 -variant2 variant3 variant4 -variant5
 }}}


 We can retain the global variants definition by using the virtual portname
 "all", as in

 {{{
 all +universal
 }}}

 or

 {{{
 all universal
 }}}


 The upgrade option --enforce-variants SHOULD check for changed variants
 definitions and rebuild packages accordingly.
 Without specifying it, upgrade SHOULD NOT rebuild packages because of
 variants changes only.

 However, is a port is already outdated, the upgrade command SHOULD update
 the specific port using the variants defined in there, but MUST NOT use
 the variants defined when previously installed.

 Once this is in place, we COULD drop specifying variants on the command
 line. Retaining the functionality is fine too, but if so, global variants,
 package specific variants and variants defined on the command line SHOULD
 be merged and "variant conflicts" "resolved", with this priority:

 cmdline >> specific >> global

 I guess the current behavior is cmdline >> global, so specific variants
 would come between this and override any globally set variants.

-- 
Ticket URL: <https://trac.macports.org/ticket/30328>
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