How can variant B imply variant A?

[Joshua Root]

On 2012-8-22 21:46 , Clemens Lang wrote:
> On Wed, Aug 22, 2012 at 01:32:40PM +0200, Mojca Miklavec wrote:
>> Something just came to my mind. Doesn't the following code do
>> *exactly* that?
>>     depends_lib-append      path:lib/pkgconfig/pango.pc:pango
>>
>> That is: if pango-devel is already installed, it would use
>> pango-devel, else it would use or install pango.
> 
> Yes. You can only use that if pango and pango-devel are binary
> compatible, though (i.e., if a binary built against pango will also work
> when pango-devel is installed).

It would be nice to be able to specify somehow whether the choice of
different ports to fulfil the dependency is valid at runtime or only at
build time. Cf. <https://trac.macports.org/ticket/34833>

This should no doubt all be part of the fabled dependency engine rewrite.

- Josh