Bug 238887 – Extension to IUSE syntax

• Product: Gentoo Hosted Projects
• Status: RESOLVED DUPLICATE

[Description Daniel Pielmeier 2008-09-27 18:29:01 UTC]

I don't want to duplicate everything that has already been discussed on irc, so I just paste the log below. The reason for this question coming up was that with the new use deps built_with_use + die could be avoided. So I thought probably this also possible for the case when at least one/more/all flags from a set of use flags have to be enabled for the package to work properly. With a functionality like this another case of unnecessary abortion of the build process could be removed.

<billie> is it possible to avid the following with the new use deps?
<billie> if ! use flag1 && ! use flag2 ; then eerror "build at least with flag1 or flag2" die "both flags are unset" fi
<Arfrever> billie: No.
<billie> Arfrever: thanks
<Arfrever> billie: Use dependencies check if USE flags are enabled/disabled in other packages, not in package currently being installed.
<Betelgeuse> billie: That would be an extension to IUSE syntax.
<Betelgeuse> billie: IUSE="|| ( flag1 flag2 )"
<Betelgeuse> billie: file a reuest
<Caster> makes no sense
<tanderson> ah...paludis is going to do that with annotations iirc
<Betelgeuse> Caster: Yeah selecting a default and makingthe other a use flag makes moresense
<Betelgeuse> Damn space is getting old.
<Caster> tanderson: annotations sounds like something optional
<billie> but what if you hava a client server app
<billie> one would build the server and one the client
<tanderson> Caster: well, it'd be like this: IUSE=" server [[ require = client ]]"
<billie> so a default also does not make much sense
<Caster> I'm not sure about overloading IUSE
<Caster> that much
<Caster> maybe add something as IUSE_RESTRICT=""
<Caster> could set both stuff like "one of these must be enabled" or "flag1 and flag2 can't be both enabled"
<tanderson> well, you could use pkg_pretend and an eclass to do it
<Caster> except there's no pkg_pretend :)
<solar> :)
<tanderson> I know :(
<tanderson> I'm just saying how it could be solved
<zmedico> syntax would be better though
<zmedico> spawning bash for that is a waste of resources

[Comment 1 Ciaran McCreesh 2008-09-27 19:26:31 UTC]

http://lists.exherbo.org/pipermail/exherbo-dev/2008-August/000241.html
http://lists.exherbo.org/pipermail/exherbo-dev/2008-September/000293.html

These threads may be of use. In particular note the list of use cases, and how they don't map nicely onto || or any existing construct.

[Comment 2 Doug Goldstein (RETIRED) 2008-10-13 19:56:28 UTC]

Could it potentially be expressed in a syntax similar to the USE depends syntax?

IUSE="flag1[flag2]" # if flag1 is set, requires flag2 to be set.
IUSE="flag1[-flag2]" # if flag1 is set, requires flag2 not to be set.
IUSE="flag1[flag2,flag3" # if flag1 is set, requires flag2 and flag3 to be set.
IUSE="flag1[-flag2,flag3]" # if flag1 is set, requires flag2 not to be set and flag3 to be set.

IUSE="-flag1[-flag2]" # if flag1, isn't set, requires flag2 not to be set

[Comment 3 Ciaran McCreesh 2008-10-13 20:00:33 UTC]

How would you express the common use cases discussed in the threads I linked to using those formats?

[Comment 4 Zac Medico 2008-12-15 06:30:06 UTC]

FWIW, with EAPI 2 use deps, it's possible to express at least some cases of what's being requested here. This can be accomplished by making a package have a circular RDEPEND use-dep on itself.

[Comment 5 Nirbheek Chauhan (RETIRED) 2008-12-15 06:37:01 UTC]

(In reply to comment #4)
> FWIW, with EAPI 2 use deps, it's possible to express at least some cases of
> what's being requested here. This can be accomplished by making a package have
> a circular RDEPEND use-dep on itself.
> 

And to prevent two different versions of the same package from being pulled together, one can use 

use1? ( =this-cat/${PF}[use2] )

assuming that =pkg-1.0-r0 will properly match =pkg-1.0 as well

[Comment 6 Nirbheek Chauhan (RETIRED) 2008-12-15 06:47:25 UTC]

(In reply to comment #5)
> And to prevent two different versions of the same package from being pulled
> together, one can use 
> 
> use1? ( =this-cat/${PF}[use2] )
> 
> assuming that =pkg-1.0-r0 will properly match =pkg-1.0 as well

A clarification: one way in which two different versions of the same package can be pulled-in is due to version-specific EAPI=1 +use IUSE enabling. However, this will probably be a non-issue once automatic-use-deps are done.

[Comment 7 Ciaran McCreesh 2008-12-15 14:19:59 UTC]

Uhm. No you can't. This means you need the package already installed with a particular flag in order to install it. It has a whole different meaning, and relying upon bugs in how Portage handles it is a very bad idea.

[Comment 8 Zac Medico 2010-01-07 18:56:51 UTC]

*** Bug 300020 has been marked as a duplicate of this bug. ***

[Comment 9 Ulrich Müller 2011-02-26 06:18:04 UTC]

*** This bug has been marked as a duplicate of bug 347353 ***