[netmod] Query about invalid XPATH paths in YANG

[William Ivory <[e-mail]>]

Hi,

I'd appreciate clarification on whether a YANG path in an XPATH statement in a must or when statement must point to a valid YANG path or not.  You might wonder why we'd have an invalid path (as opposed to one that's simply not configured right now) but it is occasionally helpful when sharing groupings.  (Possibly we should remodel the YANG but that's another matter!).

As a simple example, is the following allowed?

Container foo {
        Leaf bar {
                Type string;
                Must "not(../nonExistentSiblingNode)";
        }
}

I don't see that this should be any different to a must statement path pointing to an unconfigured node, returning an empty nodeset in both cases.

The reason I ask is that we are seeing a NETCONF client differentiating between unconfigured (ok) and non-existent (error) cases.  It would be useful to know one way or the other, ideally with a pointer to the relevant part of the spec that makes this clear.

Thanks,

William