Error string from leafref assignment can be unhelpful

[tarkatronic]

This was discovered while converting xpath tests to use unittest. Specifically in tests.xpath.01-list_leaflist.XPathListLeaflistTests.test_standalone_ref.

Given this section of the YANG model:

    container standalone {
        list l {
            key x;
            leaf x {
                type int8;
            }
        }

        leaf ref {
            type leafref {
                path "../l/x";
            }
        }
    }

This test would fail:

  def test_standalone_ref(self):
    self.instance.standalone.ref = 1
    self.assertEqual(self.instance.standalone.ref._referenced_object, 1)

With this error message:

ValueError: {'error-string': 'ref must be of a type compatible with leafref', 'generated-type': 'YANGDynClass(base=ReferenceType(referenced_path=\'../l/x\', caller=self._path() + [\'ref\'], path_helper=self._path_helper, require_instance=True), is_leaf=True, yang_name="ref", parent=self, path_helper=self._path_helper, extmethods=self._extmethods, register_paths=True, namespace=\'http://rob.sh/yang/xpathelper/tc01\', defining_module=\'list-tc01\', yang_type=\'leafref\', is_config=True)', 'defined-type': 'leafref'}

This is due to the absence of a line calling self.instance.standalone.l.add(1).

While this is a valid error, the message could be a little more helpful. I don't have a solid suggestion on how to change it, but mentioning that the value assigned must be in the list of values added to the referred leaf would be much more helpful.

[qiaoboyqb]

The same error occurs when i serialise data into obj like bellow:
KeyError: u'key value must be valid, {'error-string': 'vlan_name must be of a type compatible with leafref', 'generated-type': 'YANGDynClass(base=ReferenceType(referenced_path=\'/VLAN/name__\', caller=self._path() + [\'vlan_name\'], path_helper=self._path_helper, require_instance=True), is_leaf=True, yang_name="vlan_name", parent=self, path_helper=self._path_helper, extmethods=self._extmethods, register_paths=True, is_keyval=True, namespace=\'http://north-api.aliababa.com/schema/vlan\\\', defining_module=\'vlan_schema\', yang_type=\'leafref\', is_config=True)', 'defined-type': 'leafref'}'
do you have any suggestion about this ? here is my yang model and json data, thank you:

import ietf-inet-types {
    prefix "inet";
}
import common-types {
    prefix "common";
}

typedef mtu {
    type uint16 {
        range "64 .. 9216";
    }
}
grouping vlan-config {
    list VLAN {
        key name__;
        leaf name__ {
            type string;
            description
              "VLAN name";
        }

        container ipAddress {
            leaf-list ipv4Address {
                type inet:ipv4-prefix;
            }

            leaf-list ipv6Address {
                type inet:ipv6-prefix;
            }

            leaf ipv6Auto {
                type common:enable-status;
            }
        }

        leaf vrf {
            type string;
        }

        leaf adminStatus {
            type common:status;
        }
        leaf aclIn {
            type string;
        }
        leaf aclOut {
            type string;
        }
        leaf mtu {
            type mtu;
        }
        leaf arpProxy {
            type common:status;
        }
        leaf description {
            type string;
        }
        leaf dhcpRelaySrcIP {
            type inet:ip-address;
        }
        leaf-list dhcpSever {
            type inet:ip-address;
        }
        leaf ndpProxy {
            type common:enable-status;
        }
    }
}

grouping vlan_ip {
    list VLAN_IP {
        key vlan_name;

        leaf vlan_name {
            type leafref{
                path "/VLAN/name__";
            }
        }

        container ipAddress {
            leaf-list ipv4Address {
                type inet:ipv4-prefix;
            }

            leaf-list ipv6Address {
                type inet:ipv6-prefix;
            }
        }
    }
}

uses vlan_ip;

uses vlan-config;

}`

{ "VLAN_IP":{ "VLAN10":{ "ipAddress":{ "ipv6Address":[ "fe00::1/64", "fe00::2/64" ] }, "vlan_name":"VLAN10" } }, "VLAN":{ "VLAN10":{ "adminStatus":"down", "description":"default gateway", "ndpProxy":"enable", "aclIn":"AL01", "name__":"VLAN10", "aclOut":"AL02", "mtu":9100, "vrf":"golbal", "arpProxy":"up", "ipAddress":{ "ipv4Address":[ "11.210.88.1/30", "192.168.0.1/30" ], "ipv6Auto":"enable", "ipv6Address":[ "fe00::1/64", "fe00::2/64" ] }, "dhcpSever":[ "100.0.0.2" ], "dhcpRelaySrcIP":"12.162.231.2" } } }