Re: [gentoo-dev] RFC: USE flags in virtuals, to allow a specific provider to be determined

[Michał Górny]

Dnia 2014-07-25, o godz. 14:49:44
Ian Stakenvicius <axs@g.o> napisał(a):

> Hey all..  So, putting aside for now how much of a mess this would be
> to implement in the virtuals' ebuilds themselves, what do people think
> of changing the virtuals so that they contain an entry in IUSE for
> each provider that can satisfy it?
>
> The idea here is that the package satisfying a virtual could be
> optionally explicitly-chosen through package.use (or USE= in
> make.conf, perhaps) instead of having an entry in @world, that way if
> nothing depends on the virtual then it and the provider can be
> - --depclean'ed from the system.  The idea is specifically NOT to have
> rdeps depend on these flags, that would undermine the whole purpose of
> the virtual; it would just be for end-users to set if they so chose.

I think I don't get this argument.

If you really want to have a particular provider for the virtual for
external purposes, it's fully purposeful to put it in @world or
otherwise in a custom set. In this case, USE flags aren't helpful.

If you only prefer a particular provider, you can tip portage easily to
use it without resorting to USE flags. This also allows portage to
semi-transparently switch to other provider if dependencies need it.
In this case, USE flags only make this auto-switching harder.

> This may also help with getting portage to peg a virtual's provider to
> a specific package instead of constantly trying to switch from one to
> another, ie, how systemd kept getting pulled in, in relation to the
> upower virtual.  Note - I haven't done any tests to determine if this
> actually helps with such issues tho (or even attempted to reproduce
> them, as i was apparently one of the lucky ones that it didn't happen to).

While I agree that finding some solution is a good step forward, I'm
afraid this doesn't really lead us anywhere. Even if it allows to
workaround the actual portage issue, I'm afraid we will hit it again
somewhere else. Shortly, Gentoo would be full of workarounds... oh
wait, it already is.

By the way, proper virtuals for krb5 would involve much more crazy
stuff to get slot operator right. And then Ciaran would yell at us for
abusing slots.

-- 
Best regards,
Michał Górny