refs #108: support tuples

Author: huandu

args.go

@@ -222,6 +222,10 @@ func (args *Args) compileArg(buf *strings.Builder, flavor Flavor, values []inter
 	case rawArgs:
 		buf.WriteString(a.expr)
 	case listArgs:
+		if a.isTuple {
+			buf.WriteRune('(')
+		}
+
 		if len(a.args) > 0 {
 			values = args.compileArg(buf, flavor, values, a.args[0])
 		}
@@ -230,6 +234,11 @@ func (args *Args) compileArg(buf *strings.Builder, flavor Flavor, values []inter
 			buf.WriteString(", ")
 			values = args.compileArg(buf, flavor, values, a.args[i])
 		}
+
+		if a.isTuple {
+			buf.WriteRune(')')
+		}
+
 	default:
 		switch flavor {
 		case MySQL, SQLite, CQL, ClickHouse, Presto:

modifiers.go

@@ -47,7 +47,12 @@ func flatten(v reflect.Value) (elem interface{}, flattened []interface{}) {
 	}
 
 	if k != reflect.Slice && k != reflect.Array {
-		return v.Interface(), nil
+		if !v.IsValid() || !v.CanInterface() {
+			return
+		}
+
+		elem = v.Interface()
+		return elem, nil
 	}
 
 	for i, l := 0, v.Len(); i < l; i++ {
@@ -73,13 +78,35 @@ func Raw(expr string) interface{} {
 }
 
 type listArgs struct {
-	args []interface{}
+	args    []interface{}
+	isTuple bool
 }
 
 // List marks arg as a list of data.
 // If arg is `[]int{1, 2, 3}`, it will be compiled to `?, ?, ?` with args `[1 2 3]`.
 func List(arg interface{}) interface{} {
-	return listArgs{Flatten(arg)}
+	return listArgs{
+		args: Flatten(arg),
+	}
+}
+
+// Tuple wraps values into a tuple and can be used as a single value.
+func Tuple(values ...interface{}) interface{} {
+	return listArgs{
+		args:    values,
+		isTuple: true,
+	}
+}
+
+// TupleNames joins names with tuple format.
+// The names is not escaped. Use `EscapeAll` to escape them if necessary.
+func TupleNames(names ...string) string {
+	buf := &strings.Builder{}
+	buf.WriteRune('(')
+	buf.WriteString(strings.Join(names, ", "))
+	buf.WriteRune(')')
+
+	return buf.String()
 }
 
 type namedArgs struct {

modifiers_test.go

@@ -4,6 +4,7 @@
 package sqlbuilder
 
 import (
+	"fmt"
 	"testing"
 
 	"github.com/huandu/go-assert"
@@ -54,3 +55,47 @@ func TestFlatten(t *testing.T) {
 		a.Equal(actual, expected)
 	}
 }
+
+func TestTuple(t *testing.T) {
+	a := assert.New(t)
+	cases := []struct {
+		values   []interface{}
+		expected string
+	}{
+		{
+			nil,
+			"()",
+		},
+		{
+			[]interface{}{1, "bar", nil, Tuple("foo", Tuple(2, "baz"))},
+			"(1, 'bar', NULL, ('foo', (2, 'baz')))",
+		},
+	}
+
+	for _, c := range cases {
+		sql, args := Build("$?", Tuple(c.values...)).Build()
+		actual, err := DefaultFlavor.Interpolate(sql, args)
+		a.NilError(err)
+		a.Equal(actual, c.expected)
+	}
+}
+
+func ExampleTuple() {
+	sb := Select("id", "name").From("user")
+	sb.Where(
+		sb.In(
+			TupleNames("type", "status"),
+			Tuple("web", 1),
+			Tuple("app", 1),
+			Tuple("app", 2),
+		),
+	)
+	sql, args := sb.Build()
+
+	fmt.Println(sql)
+	fmt.Println(args)
+
+	// Output:
+	// SELECT id, name FROM user WHERE (type, status) IN ((?, ?), (?, ?), (?, ?))
+	// [web 1 app 1 app 2]
+}