gocraft#248 fix Panic on nil pointer to driver.Valuer interface

interpolate.go

@@ -94,6 +94,20 @@ var (
 	typeTime = reflect.TypeOf(time.Time{})
 )
 
+func isInterfaceInvalidOrNil(value interface{}) bool {
+	v := reflect.ValueOf(value)
+	if !v.IsValid() {
+		return true
+	}
+
+	switch v.Kind() {
+	case reflect.Chan, reflect.Func, reflect.Map, reflect.Ptr, reflect.UnsafePointer, reflect.Interface, reflect.Slice:
+		return v.IsNil()
+	default:
+		return false
+	}
+}
+
 func (i *interpolator) encodePlaceholder(value interface{}, topLevel bool) error {
 	if builder, ok := value.(Builder); ok {
 		pbuf := NewBuffer()
@@ -120,9 +134,13 @@ func (i *interpolator) encodePlaceholder(value interface{}, topLevel bool) error
 	}
 
 	if valuer, ok := value.(driver.Valuer); ok {
-		// get driver.Valuer's data
 		var err error
-		value, err = valuer.Value()
+		if isInterfaceInvalidOrNil(valuer) {
+			value = nil
+		} else {
+			// get driver.Valuer's data
+			value, err = valuer.Value()
+		}
 		if err != nil {
 			return err
 		}

interpolate_test.go

@@ -1,6 +1,7 @@
 package dbr
 
 import (
+	"database/sql/driver"
 	"strings"
 	"testing"
 	"time"
@@ -9,6 +10,13 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+type TestValuer struct {
+}
+
+func (m TestValuer) Value() (driver.Value, error) {
+	return nil, nil
+}
+
 func TestInterpolateIgnoreBinary(t *testing.T) {
 	for _, test := range []struct {
 		query     string
@@ -22,6 +30,12 @@ func TestInterpolateIgnoreBinary(t *testing.T) {
 			wantQuery: "1",
 			wantValue: nil,
 		},
+		{
+			query:     "?",
+			value:     []interface{}{(*TestValuer)(nil)},
+			wantQuery: "NULL",
+			wantValue: nil,
+		},
 		{
 			query:     "?",
 			value:     []interface{}{[]byte{1, 2, 3}},