Re: [gentoo-soc] Multiple Repository Support in Portage - Week 3

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

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On Sat, 19 Jun 2010 13:18:21 -0700
Brian Harring <ferringb@gmail.com> wrote:
> From pkgcore's view, the 1st ':' is required- if there is no slot
> dep, leave it empty.  The second demarks the start of a repository
> dep.

I prefer the "always ::" form, simply because it's easier to go "if
repo, then add ::repo" than it is to go "if repo, then add :repo, but
also stick another : in there if we've not done a slot". What a repo
dep looks like shouldn't change based upon whether there's also a slot
dep there.

> > Also note that that specifically only covers packages that are *in*
> > the ::gentoo repository. The package you have installed *from* the
> > gentoo repository is ::gentoo->/ or ::gentoo->installed .
> 
> '->' doesn't work very well though; specifically, the '-' is allowed 
> as part of a repository name.  Backtracking parsers can handle that 
> fine, it's just nonoptimal to have one of the splitter char's be part 
> of the allowed character set for a name.

Eh, I'd hardly take "your parser must support a single character
lookahead" to be a defining argument, especially when you consider the
mess that's needed to split pkg-ver up.

> @, or some other char that is explicitly disallow seems a better 
> choice.

The rationale behind -> is that it reads clearly. ::from->to reads like
what it does. Experience has shown that users do need and make use of
both forms (although unfortunately they're less inclined to appreciate
the difference between ::installed and ::/ ), so it's best to pick
something they can eventually understand.

On a semi-related note: real world experience has also shown that every
time we've thought about using ::repo deps of any kind in a repository
rather than a user context, it's been the wrong thing to do, and the
right thing to do is almost always [feature(-)].

-- 
Ciaran McCreesh

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