NSO XPATH : Difference using xpath on Leaf and on WHEN statement

[Maurizio Bau]

Hi Guys

I noticed different behavior of xpath on leaf and on when statement. In particular, i've created a yang file with one leaf that identify a switch model trough xpath and one choice statement with "when condition" about model

When I using xpath on when condition statement, it's possibile to use xpath reference about 

"show devices device <<NAME DEVICE>> platform model;

When i using xpath on leaf with learef, it's must use

"show runnning devices device <<NAME device>> config ios.."

If I using a show device device xpath on leafref, when i lanch a make command i've a following error

yang/GigaBiz.yang:80: error: the node is config, but refers to a non-config leaf 'model' defined at /home/nso/NSO-4.3.6/src/ncs/yang/tailf-ncs-devices.yang:2865

My code is showing in following tab

leaf device_type {
      tailf:info "leaf per identificare la tipologia di NT ";
      type leafref {
        /* path "/ncs:devices/ncs:device[ncs:name=current()/../NT]/ncs:config/ios:hostname";*/
         path "/ncs:devices/ncs:device[ncs:name=current()/../NT]/ncs:platform/ncs:model";
      }
    }
    
... cut ...

      choice interface_nt_tir {
		case gig {
          when "/ncs:devices/ncs:device[ncs:name=current()/NT]/ncs:platform/ncs:model = 'ME-3400G-12CS-A'";
			leaf if_gig_nt_tir {
				mandatory true;
				type leafref {
					path "/ncs:devices/ncs:device[ncs:name=current()/../NT]/ncs:config/ios:interface/ios:GigabitEthernet/ios:name";
						}
					}
				}

I searched a different show to associate a value on leaf, but show running devices device NAME config ios:cached-show is deprecated and it's not function.

Did anyone have the same problem?

thanks a lot

Maurizio

[Michael Maddern]

The device platform model leaf is operational data so you can't use it in a leafref config node. This is a YANG limitation. From section 9.9 of the RFC:

 If the leaf with the leafref type represents configuration data, the
   leaf it refers to MUST also represent configuration.

You could use an enumation instead.