Comment 6 for bug 518467

OK, so there were two different :feature features, none documented, and only one semi-working, the one used by Nikodemus. I just removed it, because it was seriously cheating with the dependency graph and got in the way of a major simplification I did in 2.26.21.

The other one has been present for quite some time, but never working. Indeed, I after fixing a bug in it, I put it behind a cerror telling people to contact me if they saw the message, and no one did. Actually, now that I think of it more, even if I remove the cerror, it doesn't make sense (it allows for conditional dependency, not conditional modules), so I'll delete it.

Closing as WONTFIX.

The real solution is adding an extra slot to components for a feature expression to check before actually including the component in the object graph.

I added just that in 2.26.22.

A component can have an arbitrary :if-feature (:or :some-feature (:not :other-feature)) feature expression among its initargs, and the component will be included in the build graph if and only if the feature expression is true.

Now to document it in asdf.texinfo.