Add support for Valuer Interface parsing

goqu.go

@@ -37,6 +37,12 @@ type SQLValuer struct {
 
 // Value converts the given value to the correct drive.Value.
 func (t SQLValuer) Value() (driver.Value, error) {
+	if valuer, ok := t.V.(driver.Valuer); ok {
+		if reflect.TypeOf(t.V).Kind() == reflect.Pointer && reflect.ValueOf(t.V).IsZero() {
+			return nil, nil
+		}
+		return valuer.Value()
+	}
 	switch t.V.(type) {
 	case []string, []bool, []float32, []float64, []int, []int64, []int32:
 		value, err := pq.Array(t.V).Value()

goqu_test.go

@@ -1,11 +1,27 @@
 package goqux
 
 import (
+	"database/sql/driver"
+	"encoding/json"
 	"testing"
 
 	"github.com/stretchr/testify/assert"
 )
 
+type structField struct {
+	V map[string]interface{} `json:"v"`
+}
+
+func (s structField) Value() (driver.Value, error) {
+	return json.Marshal(s)
+}
+
+type structValuerArray []structField
+
+func (s structValuerArray) Value() (driver.Value, error) {
+	return json.Marshal(s)
+}
+
 func TestSQLValuer_Value(t *testing.T) {
 	tableTestValues := []struct {
 		name          string
@@ -65,6 +81,61 @@ func TestSQLValuer_Value(t *testing.T) {
 			},
 			expected: "{\"test\"}",
 		},
+		{
+			name: "struct_implements_valuer",
+			value: structField{
+				V: map[string]interface{}{
+					"test": "test",
+				},
+			},
+			expected: []byte(`{"v":{"test":"test"}}`),
+		},
+		{
+			name: "valuer_pointer",
+			value: &structField{
+				V: map[string]interface{}{
+					"test": "test",
+				},
+			},
+			expected: []byte(`{"v":{"test":"test"}}`),
+		},
+		{
+			name:     "valuer_nil_pointer",
+			value:    (*structField)(nil),
+			expected: nil,
+		},
+		{
+			name:     "empty_struct",
+			value:    structField{},
+			expected: []byte(`{"v":null}`),
+		},
+		{
+			name:     "empty_struct_pointer",
+			value:    &structField{},
+			expected: []byte(`{"v":null}`),
+		},
+		{
+			name: "valuer_array_struct",
+			value: structValuerArray{
+				{
+					V: map[string]interface{}{
+						"test": "test",
+					},
+				},
+			},
+			expected: []byte(`[{"v":{"test":"test"}}]`),
+		},
+		{
+			name: "valuer_array_pointer",
+			value: &structValuerArray{
+				{
+					V: map[string]interface{}{
+						"test": "test",
+					},
+				},
+			},
+			expected: []byte(`[{"v":{"test":"test"}}]`),
+		},
 	}
 	for _, tt := range tableTestValues {
 		t.Run(tt.name, func(t *testing.T) {