On Fri, 2012-07-20 at 18:54 +0100, Ciaran McCreesh wrote:
> On Fri, 20 Jul 2012 13:43:15 -0400
> Alexandre Rostovtsev <tetromino@gentoo.org> wrote:
> > > If you dep upon foo[linguas_en(+)] and linguas_en isn't in IUSE,
> > > what happens?
> > 
> > Fatal error. If a package installs its translations implicitly via
> > gettext's rules depending on the value of LINGUAS at configure time,
> > then obviously other packages must rely on that package having
> > installed any particular translation.
> 
> Uh, the entire point of the (+) is that it's *not* a fatal error if you
> have a default.

That suggests that the EAPI ought to define a second category of
USE_EXPAND flags, one that has a different treatment of (+)/(-).

Something like the following:

A dependency on $foo[linguas_bar(+)] would be considered satisfied by an
ebuild X matching $foo iff:
1. X has linguas_bar in IUSE and enabled; or
2. X does not have linguas_bar in IUSE, but there exists an ebuild Y
(which may or may not equal X) matching $foo such that Y has at least
one linguas_* flag in IUSE.

-Alexandre.