dialect/sql: make sql.In() with empty args fallback to False() (#2735)

* dialect/sql/builder: make sql.In() with empty args fallback to False()

* fix indent

* added comment

* remove the equilvalent logic in the codegen side

* comment fix, run go generate

dialect/sql/builder.go

@@ -1535,8 +1535,10 @@ func In(col string, args ...interface{}) *Predicate {
 
 // In appends the `IN` predicate.
 func (p *Predicate) In(col string, args ...interface{}) *Predicate {
+	// if no arguments were provided, append the FALSE constants,
+	// since we can't apply "IN ()". This will make this predicate falsy.
 	if len(args) == 0 {
-		return p
+		return p.False()
 	}
 	return p.Append(func(b *Builder) {
 		b.Ident(col).WriteOp(OpIn)

dialect/sql/builder_test.go

@@ -2004,6 +2004,14 @@ func TestReusePredicates(t *testing.T) {
 			wantQuery: `SELECT * FROM "users" WHERE "a" = $1 OR "b" = $2`,
 			wantArgs:  []interface{}{"a", "b"},
 		},
+		{
+			p: Or(
+				EQ("a", "a"),
+				In("b"),
+			),
+			wantQuery: `SELECT * FROM "users" WHERE "a" = $1 OR FALSE`,
+			wantArgs:  []interface{}{"a"},
+		},
 		{
 			p: And(
 				EQ("active", true),