On Tue, Feb 26, 2019 at 03:00:58PM +0100, Andrea Bolognani wrote: > On Tue, 2019-02-26 at 11:00 +0000, Daniel P. Berrangé wrote: > > For example to prevent Xen being installed on any s390x > > > > xen: > > default-s390x: > > deb: libxen-dev > > Fedora: xen-devel > > > > Or the inverse to only install Xen on x86_64 on Debian, but allow > > it on all archs on Fedora > > > > xen: > > deb-x86_64: libxen-dev > > Fedora: xen-devel > > > > Note that the architecture specific matches are considered after > > all the non-architcture matches. > > I feel like the order entries are processed with this implementation > can be quite counter-intuitive. The root problem of course is that up > until this point we have had a single axis to work on, and we're now > introducing a second one which is independent of the existing one but > which we still have to fit along with it into the same flat hierarchy > somehow... > > Consider an example such as > > foo: > Fedora: oldfoo > Fedora-s390x: > FedoraRawhide: foo > > The general intuition up until now has been that appending something > to a label would make it more specific, and only one item on each > level would possibly match, but now both Fedora-s390x and > FedoraRawhide appear to be on the same level and *both* could apply > to an s390x Fedora Rawhide machine, making it less clear which one > would take precedence. Yes, I wasn't entirely happy with that. > I suggest that the example above would be rewritten as > > foo: > Fedora: oldfoo > FedoraRawhide: foo > s390x-Fedora: > > where two changes happened: first of all, the lines have been > shuffled around to match the order they would actually be processed, > which is something that we could have done with the above as well, > but more importantly the architecture name is now *prepended* to the > existing labels to clearly signal that it's part of a completely > separate hierarchy. The ambiguity is now gone entirely, and which > entry has precedence is easier to see at a glance. I wouldn't say its unambigous, but it is less bad than before which is nice :-) Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :| -- libvir-list mailing list libvir-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/libvir-list
