Re: [gentoo-dev] Dependencies that're available at pkg_*inst

[Ciaran McCreesh <ciaran.mccreesh@googlemail.com>]

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On Mon, 21 Apr 2008 10:52:57 +0200
"Marijn Schouten (hkBst)" <hkBst@gentoo.org> wrote:
> | cat/a-1 is installed and has RDEPEND cat/b
> | cat/a-2 is to be installed and has DEPEND cat/b and RDEPEND =cat/b-2
> | cat/b-1 is installed and has RDEPEND cat/a
> | cat/b-2 is to be installed and has DEPEND cat/a and RDEPEND =cat/a-2
> |
> | Solve this and enlightenment shall be yours!
> |
> | Or a headache.
> 
> This problem has the two obvious solutions: either install a-2 and
> then b-2 or the other way around.

Bzzt, wrong! Once you've installed a-2, you can't install b-2 since it
DEPENDs upon cat/a, but cat/a's run dependencies aren't satisfied, so
the dependency isn't met. And likewise for the other way around.

This problem is nowhere near as simple as you think it is.

> But to be relevant to the current discussion you need to specify
> whether or not there are any pkg_{pre,post}inst functions. If there
> are too many then it becomes unsolvable and is probably a bug, as I
> already explained:

The package manager can't sanely know whether such functions exist. (It
could, theoretically, insanely know, but forcing package managers to
be able to work that out really isn't something we want to do.)

> | Labels are a cleaner solution to this. But again, we're discussing
> | current EAPIs here.
> 
> Labels seems to be another syntax for providing the same information
> as I proposed AIUI, i.e. finer-grained deps.

Labels do that and a lot more, and without the explosion in number of
metadata keys. But they're a different discussion.

-- 
Ciaran McCreesh

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