Fix pointer marshal

sheriff.go

@@ -283,10 +283,21 @@ func marshalValue(options *Options, v reflect.Value) (interface{}, error) {
 	// types which are e.g. structs, slices or maps and implement one of the following interfaces should not be
 	// marshalled by sheriff because they'll be correctly marshalled by json.Marshal instead.
 	// Otherwise (e.g. net.IP) a byte slice may be output as a list of uints instead of as an IP string.
+	// This needs to be checked for both value and pointer types.
 	switch val.(type) {
 	case json.Marshaler, encoding.TextMarshaler, fmt.Stringer:
 		return val, nil
 	}
+
+	if v.CanAddr() {
+		addrVal := v.Addr().Interface()
+
+		switch addrVal.(type) {
+		case json.Marshaler, encoding.TextMarshaler, fmt.Stringer:
+			return addrVal, nil
+		}
+	}
+
 	k := v.Kind()
 
 	switch k {

sheriff_test.go

@@ -2,6 +2,7 @@ package sheriff
 
 import (
 	"encoding/json"
+	"fmt"
 	"net"
 	"reflect"
 	"testing"
@@ -583,16 +584,48 @@ type TestMarshal_NamedEmbedded struct {
 	Qux string `json:"qux" groups:"test"`
 }
 
+// TestMarshal_EmbeddedCustom is used to test an embedded struct with a custom marshaler that is not a pointer.
+type TestMarshal_EmbeddedCustom struct {
+	Val int
+	Set bool
+}
+
+func (t TestMarshal_EmbeddedCustom) MarshalJSON() ([]byte, error) {
+	if t.Set {
+		return []byte(fmt.Sprintf("%d", t.Val)), nil
+	}
+
+	return nil, nil
+}
+
+// TestMarshal_EmbeddedCustomPtr is used to test an embedded struct with a custom marshaler that is a pointer.
+type TestMarshal_EmbeddedCustomPtr struct {
+	Val int
+	Set bool
+}
+
+func (t *TestMarshal_EmbeddedCustomPtr) MarshalJSON() ([]byte, error) {
+	if t.Set {
+		return []byte(fmt.Sprintf("%d", t.Val)), nil
+	}
+
+	return nil, nil
+}
+
 type TestMarshal_EmbeddedParent struct {
 	*TestMarshal_Embedded
 	*TestMarshal_NamedEmbedded `json:"embedded"`
+	*TestMarshal_EmbeddedCustom    `json:"value"`
+	*TestMarshal_EmbeddedCustomPtr `json:"value_ptr"`
 	Bar                        string `json:"bar" groups:"test"`
 }
 
 func TestMarshal_EmbeddedField(t *testing.T) {
 	v := TestMarshal_EmbeddedParent{
 		&TestMarshal_Embedded{"Hello"},
 		&TestMarshal_NamedEmbedded{"Big"},
+		&TestMarshal_EmbeddedCustom{10, true},
+		&TestMarshal_EmbeddedCustomPtr{20, true},
 		"World",
 	}
 	o := &Options{Groups: []string{"test"}}
@@ -614,6 +647,8 @@ func TestMarshal_EmbeddedField(t *testing.T) {
 		expectedMap, err := json.Marshal(map[string]interface{}{
 			"bar": "World",
 			"foo": "Hello",
+			"value":     10,
+			"value_ptr": 20,
 			"embedded": map[string]interface{}{
 				"qux": "Big",
 			},