made asc sorting optional and added regression tests

filter.go

@@ -115,27 +115,23 @@ func NewQuery(s string) (q *Query, err error) {
 		}
 		if !q.s.enabled {
 			s := strings.SplitN(v, ":", 3)
-			if len(s) == 3 {
-				if s[0] == "sort" {
+			if s[0] == "sort" && len(s) >= 2 {
+				q.s.fields = strings.Split(s[1], ".")
+				if err = checkFields(q.s.fields, v); err != nil {
+					return
+				}
+				if len(s) == 3 {
 					switch s[2] {
-					case asc, desc:
-						q.s.fields = strings.Split(s[1], ".")
-						if err = checkFields(q.s.fields, v); err != nil {
-							return
-						}
-						if len(q.s.fields) > 0 {
-							if s[2] == desc {
-								q.s.desc = true
-							}
-							q.s.enabled = true
-						}
-						continue
+					case desc:
+						q.s.desc = true
+					case asc:
 					default:
 						err = newErr("invalid sort: " + v)
 						return
 					}
-
 				}
+				q.s.enabled = true
+				continue
 			}
 		}
 		m := strings.SplitN(v, ":", 2)