Re: [gentoo-dev] don't rely on dynamic deps

[Michał Górny]

Dnia 2014-07-21, o godz. 21:34:10
Alexandre Rostovtsev <tetromino@g.o> napisał(a):

> On Mon, 2014-07-21 at 22:56 +0200, Michał Górny wrote:
> > Yes, it does. I'm not sure if it leads anywhere, though. Dynamic deps
> > are a pipe dream. You can't implement them properly, so we're using
> > half-working implementation as an excuse to be lazy.
>
> Why not adapt the updates mechanism for modifying rdepends? Perhaps
> something like
>
> rdepends-add foo-bar/blah-3.14 "wombat? ( >=dev-libs/wombat-1.0 )"
>
> This would give the package manager all the benefits of static dep
> resolution while allowing us to dynamically make simple changes (like
> adding a missing dependency to an ebuild) without forcing users to
> rebuild the package.

At the moment updates are stateless. In other words, PM has no idea if
the update has been applied or not, and the update should be defined so
that it can't be applied multiple times.

IOW, if you do a pkgmove via updates, the originating package ebuild
must no longer exist so that the update can be only applied once. If
you do a slotmove, the originating slot must no longer be used
in affected ebuilds.

Now, with dependency updates you lack this guarantee. Package manager
can add the dependency... and then add it again... and again...
and again. It could supposedly try to match dependencies and find out
whether a particular dependency has been added already but that sounds
like something that could easily cause issues in the future.

-- 
Best regards,
Michał Górny