ytypes.UnmarshalSetRequest does not panic at nil input. (#737)

* [fix] ygot.UnmarshalSetRequest panic at nil request.

This function accesses the fields of req (req.Prefix, req.Delete etc). A input check is added to prevent nil pointer panic.

* [test] Add a nil test case for UnmarshalSetRequest

Add unit test to verify the function works when input request is nil.

Co-authored-by: Wen Bo Li <50884368+wenovus@users.noreply.github.com>

ytypes/gnmi.go

@@ -46,7 +46,9 @@ func UnmarshalNotifications(schema *Schema, ns []*gpb.Notification, opts ...Unma
 func UnmarshalSetRequest(schema *Schema, req *gpb.SetRequest, opts ...UnmarshalOpt) error {
 	preferShadowPath := hasPreferShadowPath(opts)
 	ignoreExtraFields := hasIgnoreExtraFields(opts)
-
+	if req == nil {
+		return nil
+	}
 	root := schema.Root
 	node, nodeName, err := getOrCreateNode(schema.RootSchema(), root, req.Prefix, preferShadowPath)
 	if err != nil {

ytypes/gnmi_test.go

@@ -19,6 +19,15 @@ func TestUnmarshalSetRequest(t *testing.T) {
 		want            ygot.GoStruct
 		wantErr         bool
 	}{{
+		desc: "nil input",
+		inSchema: &Schema{
+			Root: &ListElemStruct1{},
+			SchemaTree: map[string]*yang.Entry{
+				"ListElemStruct1": simpleSchema(),
+			},
+		},
+		want: &ListElemStruct1{},
+	}, {
 		desc: "updates to an empty struct",
 		inSchema: &Schema{
 			Root: &ListElemStruct1{},