fix #202: NotIn with empty values builds "0 = 0"

cond.go

@@ -207,10 +207,15 @@ func (c *Cond) In(field string, values ...interface{}) string {
 
 // NotIn is used to construct the expression "field NOT IN (value...)".
 func (c *Cond) NotIn(field string, values ...interface{}) string {
-	if len(field) == 0 || len(values) == 0 {
+	if len(field) == 0 {
 		return ""
 	}
 
+	// Empty values means "true".
+	if len(values) == 0 {
+		return "0 = 0"
+	}
+
 	return c.Var(condBuilder{
 		Builder: func(ctx *argsCompileContext) {
 			ctx.WriteString(field)
@@ -427,6 +432,7 @@ func (c *Cond) Not(notExpr string) string {
 	if len(notExpr) == 0 {
 		return ""
 	}
+
 	buf := newStringBuilder()
 
 	// Ensure that there is only 1 memory allocation.

cond_test.go

@@ -49,6 +49,7 @@ func TestCond(t *testing.T) {
 		newTestPair("$a IN ($1, $2, $3)", func(c *Cond) string { return c.In("$a", 1, 2, 3) }),
 		newTestPair("0 = 1", func(c *Cond) string { return c.In("$a") }),
 		newTestPair("$a NOT IN ($1, $2, $3)", func(c *Cond) string { return c.NotIn("$a", 1, 2, 3) }),
+		newTestPair("0 = 0", func(c *Cond) string { return c.NotIn("$a") }),
 		newTestPair("$a LIKE $1", func(c *Cond) string { return c.Like("$a", "%Huan%") }),
 		newTestPair("$a ILIKE $1", func(c *Cond) string { return c.ILike("$a", "%Huan%") }),
 		newTestPair("$a NOT LIKE $1", func(c *Cond) string { return c.NotLike("$a", "%Huan%") }),
@@ -135,7 +136,6 @@ func TestEmptyCond(t *testing.T) {
 		newCond().LessEqualThan("", 123),
 		newCond().In("", 1, 2, 3),
 		newCond().NotIn("", 1, 2, 3),
-		newCond().NotIn("a"),
 		newCond().Like("", "%Huan%"),
 		newCond().ILike("", "%Huan%"),
 		newCond().NotLike("", "%Huan%"),