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List:       gentoo-dev
Subject:    Re: [gentoo-dev] perl eclass review - EAPI=3 + new helper eclass
From:       Zac Medico <zmedico () gentoo ! org>
Date:       2010-04-25 6:16:40
Message-ID: 4BD3DE48.1050306 () gentoo ! org
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On 04/23/2010 08:14 AM, James Cloos wrote:
>>>>>> "HvD" == Harald van Dijk <truedfx@gentoo.org> writes:
> 
> HvD> Let's say this is in the tree:
> 
> HvD> foo.eclass:
> HvD> DEPEND="dev-lang/python:2.6"
> 
> HvD> bar-1.ebuild:
> HvD> inherit foo
> 
> HvD> Let's say this is in your overlay:
> 
> HvD> foo.eclass:
> HvD> DEPEND="|| ( dev-lang/python:3.1 dev-lang/python:2.6 )"
> 
> HvD> Now you install bar. How should portage know that it must regenerate the
> HvD> metadata cache, to see that it doesn't need to install python 2.6 if you
> HvD> already have 3.1?
> 
> It shouldn't bother. :)
> 
> Really, that isn't the kind of change that I find I need to make.

Different users have different needs. The user who reported this bug
needed the opposite behavior:

  http://bugs.gentoo.org/show_bug.cgi?id=276264

> And it should never regenerate the metadata cache (ie portage/metadata/cache).

Again, different users have different needs and the user in bug
#276264 really needed to regenerate the cache.

> The docs used to -- and probably still do -- recommend regenerating that
> cache after certain changes.  Which is a drasticly bogus suggestion unless
> you have a *very* fast system.

It's a somewhat bogus suggestion if you are not modifying eclasses
in the same way as the user from bug #276264. Note that it's
possible to enable eclass-overrides without discarding
$PORTDIR/metadata/cache. It seems like that might work for your use
case (don't forget that this won't necessarily be appropriate for
every user).

For the user in bug #276264, it's more appropriate to discard
$PORTDIR/metadata/cache and run emerge --regen (with --jobs if he
wants to use multiple cpu cores in parallel).

> Even across a dialup straw, an emerge --sync
> is orders of magnitude faster.

Different things give different results. It may work for your use
case but not for others.

> If the ebuild calls a class which has been overridden by a local class, and
> the original class set DEPENDs or the like, then as it reads in the new class
> file it should just use those values in place of the ones in the cache.

And that's the behavior that you'll get if you don't discard
$PORTDIR/metadata/cache (which would be inappropriate for the user
in bug #276264).

> 
> -JimC


-- 
Thanks,
Zac

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