ygot Validate error, when yang leaf type is union

[songlinglingpml]

Hi, @faraazbrcm

I am using version 202012
When I use restful to send delete messages, sometimes the following error occurs

URL:
restconf/data/openconfig-network-instance:network-instances/network-instance=DEFAULT/protocols/protocol=oc-pol-types:ISIS,DEFAULT/isis/interfaces/interface=Ethernet8/levels/level=2/afi-safi/af=oc-isis-types:IPV4,oc-isis-types:UNICAST/segment-routing/adjacency-sids/adjacency-sid=172.60.61.1,321536

Code1:

baseTreeNode, err := ytypes.GetNode(ygSchema.RootSchema(), deviceObj, path)
basePathObj, ok := (baseTreeNode[0].Data).(ygot.ValidatedGoStruct)
if ok {
err := basePathObj.Validate(&ytypes.LeafrefOptions{IgnoreMissingData: true})
......

Code2:
In the following code, 'fieldVal(321536)' can be converted to both int32 and string, which was committed in ygot patch (
49e5a22)

in sonic-mgmt-common/vendor/github.com/openconfig/ygot/ytypes/list.go
if keyLeafKind == yang.Yunion && strings.HasSuffix(ft.Name(), "_Union") {
	sks, err := getUnionKindsNotEnums(cschema)
	if err != nil {
		return err
	}
	for _, sk := range sks {
		gv, err := StringToType(reflect.TypeOf(yangBuiltinTypeToGoType(sk)), fieldVal)
		if err == nil {
			mn := "To_" + ft.Name()
			mapMethod := val.MethodByName(mn)
			if !mapMethod.IsValid() {
				return fmt.Errorf("%s does not have a %s function", val, mn)
			}
			ec := mapMethod.Call([]reflect.Value{gv})
			if len(ec) != 2 {
				return fmt.Errorf("%s %s function returns %d params", ft.Name(), mn, len(ec))
			}
			ei := ec[0].Interface()
			ee := ec[1].Interface()
			if ee != nil {
				return fmt.Errorf("unmarshaled %v type %T does not have a union type: %v", fieldVal, fieldVal, ee)
			}
			nv = reflect.ValueOf(ei)
			break
		}
	}
	...
}

error-message
"/device/network-instances/network-instance: /device/network-instances/network-instance/protocols/protocol: /device/network-instances/network-instance/protocols/protocol/isis/interfaces: /device/network-instances/network-instance/protocols/protocol/isis/interfaces/interface: /device/network-instances/network-instance/protocols/protocol/isis/interfaces/interface/levels/level: /device/network-instances/network-instance/protocols/protocol/isis/interfaces/interface/levels/level/afi-safi/af: /device/network-instances/network-instance/protocols/protocol/isis/interfaces/interface/levels/level/afi-safi/af/segment-routing/adjacency-sids: /device/network-instances/network-instance/protocols/protocol/isis/interfaces/interface/levels/level/afi-safi/af/segment-routing/adjacency-sids/adjacency-sid: "321536" does not match regular expression pattern "^(([0-9a-fA-F]{1,4}:){7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,5}(:[0-9a-fA-F]{1,4}){1,2}|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,4}:){1,3}(:[0-9a-fA-F]{1,4}){1,4}|([0-9a-fA-F]{1,4}:){1,2}(:[0-9a-fA-F]{1,4}){1,5}|[0-9a-fA-F]{1,4}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:))$" for schema "

yang info:

sid-id is in openconfig-segment-routing.yang，and it's type union

leaf sid-id {
  type oc-srt:sr-sid-type;
  description
    "The Segment Identifier to be used when advertising the IGP Prefix SID.";
}
typedef sr-sid-type {
type union {
type oc-mplst:mpls-label; ===》openconfig-mpls-types.yang
type oc-inet:ipv6-address; ===》openconfig-inet-types.yang
}
description
"The defined value of a segment identifier.";
}