Re: [gentoo-dev] Pre-GLEP RFC: Automated enforcing of REQUIRED_USE constraints

[Michał Górny]

On nie, 2017-07-09 at 10:29 +0200, Ulrich Mueller wrote:
> > > > > > On Sun, 09 Jul 2017, Michał Górny wrote:
> > On nie, 2017-07-09 at 09:22 +0200, Ulrich Mueller wrote:
> > > Second, and more important, introduction of an automatic solver
> > > would inevitably lead to proliferation of REQUIRED_USE in the tree.
> > > However, nothing would guarantee that the package manager on the
> > > user's side is capable of solving the constraints automatically.
> > > The result would be more emerge failures and asking for more
> > > micro-management of flags by users.
> > Think of dynamic deps. We were able to eventually contain them, and
> > teach developers not to account for them even though they are still
> > enabled by default, I think.
> > I don't see why optional autosolving of REQUIRED_USE could not be
> > contained by a policy as well.
>
> Then can you please confirm that the policy outlined in
> https://devmanual.gentoo.org/general-concepts/use-flags/index.html#conflicting-use-flags
> can stay in place indefinitely, and that your GLEP doesn't intend to
> change it?

The GLEP does not mention that policy at all, so it's not affected.
If we decide to change it, it will be done independently of the GLEP.

> > Of course, there will be some people who will violate it but it's
> > not something that doesn't happen anyway right now.
>
> A policy that isn't enforced is useless.

Say that to the people who invented USE=gtk2,gtk3 instead of USE=gtk. Oh
wait...

> > Are you suggesting that we introduce half-tested feature in EAPI 7,
> > then spend a few years figuring out that it doesn't work as
> > expected?
>
> No, I am suggesting that we introduce a new package manager feature in
> a well defined way, so that ebuild authors can rely on it. We have a
> mechanism for that, and I don't see a good reason not to follow it.
>
> > Because I don't see how we get it tested properly without having
> > users actually test it and report the results.
>
> It shouldn't be necessary for the spec to specify all details of the
> algorithm. It should catch the basics though in the next EAPI, like
> leftmost preferred, banning empty groups, and banning USE conditionals
> inside groups.
>

Works for me. However, the problem is whether i'll live to see the day
when I can realistically use it.

python-single-r1 needs this urgently. Today. Not 15 years from now when
we can drop support for EAPI <=6. Presuming Gentoo will be anything but 
a huge pile of defunct policies and bureaucracy 15 years from now.

-- 
Best regards,
Michał Górny