Re: [netmod] Deviating away /interfaces-state

On Mon, 2018-09-10 at 11:48 +0200, Balazs Lengyel wrote:
> Hello,
> We would like to remove the if:interfaces-state with a deviation as it will
> never contain any information. So we wanted to use 
> deviation /if:interfaces-state {
>   deviate not-supported;
> }
> 
> However after this we get an error as ietf-interfaces has a definition:

I think this check really goes overboard. Sec. 9.9.2 in RFC 7950 says:

   The "path" expression evaluates to a node set consisting of zero,
   one, or more nodes.  If the "require-instance" property is "true",
   this node set MUST be non-empty.

However, evaluating an XPath expression make sense only in the context of a
concrete instance data tree. Therefore, no error should be reported unless an
instance of a leaf with the "instance-state-ref" type exists. With the typedef
below, we are two steps away from that.

Lada  

>      /*
>       * Legacy typedefs
>       */
> 
>      typedef interface-state-ref {
>        type leafref {
>          path "/if:interfaces-state/if:interface/if:name";
>        }
>        status deprecated;
>        description
>          "This type is used by data models that need to reference
>           the operationally present interfaces.";
>      }
> 
> Here the path statement will point at a non-existent branch.
> 
> So is there a correct way to indicate we do not support /interface-state ?
> regards Balazs 
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Ladislav Lhotka
Head, CZ.NIC Labs
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