added empty query checks

filter.go

@@ -101,11 +101,12 @@ func NewQuery(s string) (q *Query, err error) {
 		return
 	}
 	qm := make(map[string]struct{})
-	fields := strings.Split(s, " ")
+	fields := clearFields(s)
+	if len(fields) == 0 {
+		err = errors.New("query is empty")
+		return
+	}
 	for _, v := range fields {
-		if v == "" {
-			continue
-		}
 		if q.l == undefined {
 			l, ok := parseLogic(v)
 			q.l = l
@@ -160,8 +161,10 @@ func NewQuery(s string) (q *Query, err error) {
 			boolFunc(m[1]),
 		})
 	}
-	if len(q.m) == 0 {
+	if len(q.m) == 0 && q.s.enabled {
 		q.s.only = true
+	} else if len(q.m) == 0 {
+		err = errors.New("query is empty")
 	}
 	if len(q.m) == 1 && q.l != not {
 		q.l = or

filter_test.go

@@ -69,6 +69,16 @@ func TestNewQuery(t *testing.T) {
 	if err == nil {
 		t.Error("invalid sort")
 	}
+
+	_, err = NewQuery("   ")
+	if err == nil {
+		t.Error("empty query")
+	}
+
+	_, err = NewQuery("OR")
+	if err == nil {
+		t.Error("empty query")
+	}
 }
 
 const (

helper.go

@@ -21,6 +21,19 @@ func checkFields(s []string, val string) error {
 	return nil
 }
 
+func clearFields(s string) []string {
+	a := strings.Split(s, " ")
+	b := make([]string, len(a))
+	c := 0
+	for _, v := range a {
+		if v != "" {
+			b[c] = v
+			c++
+		}
+	}
+	return b[:c]
+}
+
 type less func(i, j int) bool
 
 func reverse(f less) less {