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>>>>> On Wed, 12 Aug 2015, Ian Stakenvicius wrote: |
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> On 12/08/15 11:08 AM, Ulrich Mueller wrote: |
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>> I was thinking about some syntax like this: |
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>> |
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>> REQUIRED_USE="|| ( +foo bar ) ^^ ( +qt5 -qt4 )" |
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>> |
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>> The package manager would first evaluate each group in |
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>> REQUIRED_USE with the original set of USE flags. If that doesn't |
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>> evaluate to true, retry with flags changed as indicated by the + |
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>> and - signs. |
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> Having the ability for REQUIRED_USE to provide a default resolution |
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> path should definitely help with things; I assume this is meant to |
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> do its work via --autounmask-write or similar, ie to help users |
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> adjust their config files? Or was the thought to allow PMs to |
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> override USE immediately? |
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In fact, I was thinking about overriding it immediately. It is the |
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same as the ebuild explicitly picking a working default from |
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conflicting flags, where there is also no user interaction required. |
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(The PM should emit a warning, though.) |
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> Questions: |
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> 1 - how does +foo in REQUIRED_USE relate to use-defaults set in |
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> IUSE? |
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Apart from the similar syntax, they are not related. |
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> 2 - is there a particular reasoning for the - in front of qt4 here? |
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> I only ask because it would seem that a single default-enable |
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> should suffice in lists like this to indicate a resolution path, no? |
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> That is, '^^ ( +flag1 -flag2 -flag3 -flag4 )' to me seems like it |
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> would be the same as '^^ ( +flag1 flag2 flag3 flag4 )' |
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If the user has both "qt4 qt5", then enabling qt5 alone won't help to |
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resolve "^^ ( qt5 qt4 )". |
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> 3 - will having REQUIRED_USE be able to force flags on (and others |
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> off) likely result in abuse of profiles and other use defaults? |
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It wouldn't look for the origin of a USE flag setting in its input |
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data. So, yes. |
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> I forsee this being a way, for instance, for a dev to get around |
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> users setting USE="-*" in make.conf to ensure a default use flag |
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> setting is honoured. |
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> 4 - Will a change to which flag the '+' is on likely to require a |
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> revbump for VDB updates? |
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I don't think so. For Portage users, it would be handled by --newuse, |
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I guess. |
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> For something like '^^ ( +qt4 qt5 )' I could see maintainers wanting |
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> to switch which flag is default across a bunch of packages at once |
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> when, say, the qt team wants qt5 to become the de-facto default. |
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Ulrich |
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