Address code review comments

list.go

@@ -53,25 +53,25 @@ func (list *List) UnmarshalJSON(rawData []byte) error {
 
 /*
 MarshalJSON returns a top level object for the "data" attribute if a single object. In
-all other cases returns a JSON encoded list for "data".
+all other cases returns a JSON encoded list for "data". We use a pointer receiver here
+so we are able to distinguish between nil (don't serialize) and empty (serialize as []).
 */
 func (list *List) MarshalJSON() ([]byte, error) {
 	// avoid stack overflow by using this subtype for marshaling
 	type MarshalList List
-	marshalList := (*MarshalList)(list)
-	isnil := marshalList == nil
-	count := 0
-	if !isnil {
-		count = len(*marshalList)
+
+	if list == nil {
+		return nil, nil
 	}
 
+	marshalList := MarshalList(*list)
+	count := len(marshalList)
+
 	switch {
-	case isnil:
-		return nil, nil
 	case count == 0:
 		return []byte("[]"), nil
 	case count == 1:
-		return json.Marshal((*marshalList)[0])
+		return json.Marshal(marshalList[0])
 	default:
 		return json.Marshal(marshalList)
 	}