Re: [gentoo-dev] New Eclasses: postgres and postgres-multi

[Aaron W. Swenson]

On 2016-01-13 11:11, Ian Stakenvicius wrote:
> The work looks really good, but I noticed that postgres-multi
> determins the variants to build against based on what's installed on
> disk via checking eselect..  I think it'd likely be better to
> instead have proper dependencies based on USE, much like how the
> python and ABI_* multibuilds work.  That would make the
> installations as well as the dependencies be determinstic rather
> than dynamic, which should support binpkgs -much- better (among
> other things).
>
> The "|| ( postgresql:${SLOT1}= postgresql:${SLOT2}= ...)" RDEPEND
> that postgres.eclass works out is a little sketchy IMO,
> unfortunately, as the behaviour that occurs when more than one of
> those slots are installed is afaik a little unstable -- in theory,
> changes (including removal) of any of the options should trigger a
> rebuild but I don't know if it does, and I'm fairly certain that a
> simple --unmerge doesn't trigger a rebuild.  All of that goes away
> if you perform non-OR dependency via use flags.
>
> The drawback of course is yet another USE_EXPAND, or at least a
> bunch of rather long use flags, that will need setting by the user.

What if I made a small adjustment to the DEPEND building like so:

-	POSTGRES_DEP="|| ("
+	POSTGRES_REQ_USE=" || ("
 	for slot in "${POSTGRES_COMPAT[@]}" ; do
+		IUSE+=" postgres_${slot}"
+		POSTGRES_REQ_USE+=" postgres_${slot}"
+
+		! use "postgres_${slot/_/.}" && continue
 		POSTGRES_DEP+=" dev-db/postgresql:${slot}="
 		declare -p POSTGRES_USEDEP &>/dev/null && \
 			POSTGRES_DEP+="[${POSTGRES_USEDEP}]"
 	done
-	POSTGRES_DEP+=" )"
+	POSTGRES_REQ_USE=" )"

I'll have to change from listing the slots in POSTGRES_COMPAT from N.N
to N_N, but that's not terribly difficult given the one ebuild I have it
in.

Is this a change that would require a USE_EXPAND? I know I'll have to
document the USE flags globally.