Re: [gentoo-dev] Re: useflag policies

[Ian Stakenvicius]

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On 12/08/15 01:50 PM, Ciaran McCreesh wrote:
> On Wed, 12 Aug 2015 19:43:55 +0200 Ulrich Mueller
> <ulm@g.o> wrote:
>>>>>>> On Wed, 12 Aug 2015, Ulrich Mueller wrote:
>>> Hm, how about adding a new PM command like "required_use foo
>>> -bar"? It would be used exclusively in pkg_pretend, and tell
>>> the PM to suggest the necessary package.use changes to the
>>> user (or even update them automatically with the appropriate
>>> --autounmask-* option).
>>
>> To clarify, I'm thinking about something like this:
>>
>> pkg_pretend() { if use qt4; then required_use -qt5 else
>> required_use qt5 fi }
>>
>> The advantage would be that any number of elog messages could
>> be added which would further explain things to the user.
>
> And how would the PM understand that -qt5 is conditional upon
> qt4? Such knowledge is required if it's supposed to auto-resolve
> stuff...
>

I don't think required_use could auto-resolve here, without some
other rather large changes to PMs -- for instance, the spec
pkg_pretend likely needs to be assured to be taken into account
before dependency resolution of that package somehow.

Also, the required_use function needs to be permitted to modify
effective-use and/or do whatever else it does, meaning that for what
I believe is the first time we will have function calls in ebuilds
modifying the precursors to dependency resolution dynamically rather
than it being deterministic based on state and pre-defined static
logic.  (i hope that makes sense, unsure if i'm using anything even
close to the correct terminology)


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