StrictNSQuery should fail on invalid qname input

goresolver.go

@@ -31,6 +31,7 @@ var (
 	ErrRrsigValidityPeriod  = errors.New("invalid RRSIG validity period")
 	ErrUnknownDsDigestType  = errors.New("unknown DS digest type")
 	ErrDsInvalid            = errors.New("DS RR does not match DNSKEY")
+	ErrInvalidQuery         = errors.New("invalid query input")
 )
 
 var resolver *Resolver

lookup.go

@@ -111,7 +111,7 @@ func (resolver *Resolver) LookupIPType(qname string, qtype uint16) (ips []net.IP
 func (resolver *Resolver) StrictNSQuery(qname string, qtype uint16) (rrSet []dns.RR, err error) {
 
 	if len(qname) < 1 {
-		return nil, nil
+		return nil, ErrInvalidQuery
 	}
 
 	answer, err := queryRRset(qname, qtype)

lookup_test.go

@@ -295,3 +295,14 @@ func TestMissingDsRR(t *testing.T) {
 		t.Error("should return no results")
 	}
 }
+
+func TestStrictNSQueryEmptyInput(t *testing.T) {
+	resolver := newResolver(t)
+	rrs, err := resolver.StrictNSQuery("", dns.TypeMX)
+	if err == nil {
+		t.Error("should return err")
+	}
+	if len(rrs) > 0 {
+		t.Error("shouldn't return results")
+	}
+}