Re: [gentoo-dev] "Lazy" use flags?

[Kent Fredric]

On 11 February 2016 at 15:51, Rich Freeman <rich0@g.o> wrote:
> In this case you just wouldn't enable python 2.7 support, but you
> wouldn't disable it either.  Portage would just pull it in where it is
> needed.


But you still need a mechanism in place if you *dont* want that to happen.

I might choose to forbid python2.7 support, and portage really
shouldn't "auto enable" python 2.7 support if I've explicitly
indicated I don't want python 2.7 support.

Unless of course you're suggesting "USE=-python_targets_python2_7"
would not be "auto-enableable"

But then you're *still* requiring a tri-state USE.

USE="-foo" + IUSE="+foo" => "-foo"  => autouse enables foo if required
USE=""  + IUSE="+foo" => "foo"        => standard EFFECTIVE_USE="foo"
USE="foo" + IUSE = "+foo" => "foo" => standard EFFECTIVE_USE="foo"
USE="-foo" + IUSE="foo" => "-foo"  => autouse enables foo if required
USE="" + IUSE="foo" => "-foo"         => autouse enables foo if required
USE="foo"  + IUSE="foo" => "foo"   => standard EFFECTIVE_USE="foo"


So the logic composing USE + IUSE has to change in generating the
effective USE set so that USE + IUSE can emit a 3rd and 4th state.

USE="-foo" + IUSE="+foo" => "-foo!!"  => autouse fails if foo is required
USE=""  + IUSE="+foo" => "foo"        =>  standard
EFFECTIVE_USE="foo", auto-unuses foo if blocked by a dep
USE="foo" + IUSE = "+foo" => "foo!!" => standard EFFECTIVE_USE="foo",
fails if foo is "blocked" by a dep
USE="-foo" + IUSE="foo" => "-foo!!"  => autouse fails if foo is required
USE="" + IUSE="foo" => "-foo"         => autouse enables foo if required
USE="foo"  + IUSE="foo" => "foo!!"   => standard EFFECTIVE_USE="foo",
fails if "foo" is blocked by a dep.


Mentally keeping track of this accounting magic would be complicating matters.

-- 
Kent

KENTNL - https://metacpan.org/author/KENTNL