Yang conditional type

[franjorge]

Hello,

I have the following yang file, where I am trying to model the connection between a device and its neighbors:

module cr-art {
  list cr-art {
    key DEVICE;
    leaf DEVICE {
      type leafref {
        path "/ncs:devices/ncs:device/ncs:name";
      }
    }
    list NEIGHBOR_ROUTER {
      key NAME;
      leaf NAME {
        type leafref {
            must "current() != ../../DEVICE"{}
            path "/ncs:devices/ncs:device/ncs:name";
        }
      }
      list AGGR_INT {
        key NAME_AGGR_INT;
        leaf NAME_AGGR_INT {
          type leafref {
            path "/cr-art:cr-art[DEVICE=current()/../../NAME]/cr-art:NEIGHBOR_ROUTER[NAME=current()/../../../DEVICE]/cr-art:AGGR_INT/cr-art:REMOTE_AGGR_INT";
          }
        }
        leaf REMOTE_AGGR_INT {
          type string;
        }
      }
    }
  }
}

The leafref in "NAME_AGGR_INT" is working as expected, ie, if I am configuring a device, for "NAME_AGGR_INT" I get the list of ""REMOTE_AGGR_INT" previously defined in the neighbor device.

However, that becomes a problem when configuring the 'original' device, since no other router has it configured as a neighbor, so the leafref is empty.

Is there a way to choose "NAME_AGGR_INT" among the "REMOTE_AGGR_INT" configured in the neighbors if there is any, and just type a string if the leafref is empty?

Thanks.

[vleijon]

The easiest way might be to use the annotation tailf:no-leafref-check or possibly tailf:non-strict-leafref, see the man page tailf_yang_extensions for details.

An alternative, stricter, interpretation might be that this reference integrity is crucial, that pointing to a non-existing neighbor is senseless: Then you’d force the user to enter at least two devices initially rather than doing them one by one.

[franjorge]

Hi,

Thanks four your answer.

I will try your suggestion regarding tailf:no-leafref-check / tailf:non-strict-leafref.

I do not think the second approach will work, since I am not able to even configure the first device without having configured its neighbor first.

Best regards.