[netmod] draft-ietf-netmod-geo-location-01: an optional location info

[Jan Kundrát <[e-mail]>]

Hi,
I'm augmenting the ietf-network and ietf-network-topology from RFC 8345, 
trying to add geolocation information to the network nodes. I found your 
draft (thanks for it!), draft-ietf-netmod-geo-location-01. What I am 
struggling with is adding the geolocation as an *optional* element.

When I try this YANG construct:

  augment "/nw:networks/nw:network/nw:node" {
    when "../nw:network-types/my-topo:topology-type";
    description "Optical elements within a network";

    uses geo:geo-location;
  }

...then my YANG instance data validator, libyang, complains when the 
location is missing:

err : Mandatory choice "location" missing a case branch. 
(/ietf-network:networks/network[network-id='...']/node[node-id='...']/my-topo:location/geo-location)

I can do the augmentation with one more container (a presence one) like 
this:

  augment "/nw:networks/nw:network/nw:node" {
    when "../nw:network-types/my-topo:topology-type";
    description "Optical elements within a network";

    container location {
      presence true;
      uses geo:geo-location;
    }    
  }

The resulting data then contain an extra level of nesting. I think that 
this is suboptimal.

I have two questions:

- Is that perhaps a bug in libyang?
- If libyang is correct, is there a way of making the location info 
optional without that one more level of nesting?

Also, the example does not work as-is because it's importing the module 
using a wrong name. Here's a tiny patch:

index 7bd8622c..088621a1 100644
--- 
a/experimental/ietf-extracted-YANG-modules/[e-mail]
+++ 
b/experimental/ietf-extracted-YANG-modules/[e-mail]
@@ -2,7 +2,7 @@ module ietf-uses-geo-location {
   namespace
     "urn:ietf:params:xml:ns:yang:ietf-uses-geo-location";
   prefix ugeo;
-  import geo-location { prefix geo; }
+  import ietf-geo-location { prefix geo; }
   organization "Empty Org";
   contact "Example Author <[e-mail]>";
   description "Example use of geo-location";

The -00 version was correct in this, BTW.

With kind regards,
Jan