On Fri, 2012-03-23 at 12:50 -0400, Mike Gilbert wrote:
> On Fri, Mar 23, 2012 at 12:02 PM, Ciaran McCreesh
> <ciaran.mccreesh@...> wrote:
> > On Fri, 23 Mar 2012 11:58:47 -0400
> > Mike Gilbert <floppym@g.o> wrote:
> >> > oasis_src_compile() {
> >> >     oasis_src_compile_no_doc
> >> >     if has doc ${IUSE} && use doc; then
> >> >             ocaml setup.ml -doc || die
> >> >     fi
> >> > }
> >>
> >> This should probably call use_if_iuse from eutils.eclass, which
> >> handles IUSE="[+-]doc".
> >
> > Actually, neither way works. The spec says:
> >
> >    Global variables must only contain invariant values
> >    (see~\ref{sec:metadata-invariance}). If a global variable's value is
> >    invariant, it may have the value that would be generated at any
> >    given point in the build sequence.
> >
> > So you can't rely upon IUSE having the "merged" value in an eclass.
> >
> 
> use_if_iuse is called from functions in several eclasses already in
> the tree. See chromium, kde4-base, qt4-build, and toolchain.
> 
> Are all of these usages incorrect? Do you have an alternate solution?

By my count, there are already at least 19 eclasses in the tree that
access an ebuild's IUSE from eclass code (autotools-utils, chromium,
clutter, db, enlightenment, eutils, gnome2, gnome-python-common,
java-ant-2, java-pkg-2, java-utils-2, mozconfig-3, pam, qt4-build,
qt4-r2, ruby-ng, xfconf, x-modular, and xorg-2).

-Alexandre Rostovtsev.