Serialization discrepency between slice vs array of slice with custom MarshalJSON

[skhattane]

Hi,
I have a TestModel with a Users field ([]UserTestModel). I have a MarshalJSON method that overrides this Users field with different values. If I serialize a slice of TestModel, the Users field is overridden correctly. However, if I serialize just one TestModel, the Users field is not serialized at all, regardless of the JSON tag I use.

package controller

import (
	"encoding/json"
	"github.com/liip/sheriff/v2"
	"log"
	"net/http"
)

type TestController struct{}

type UserTestModel struct {
	Id        int    `json:"id" groups:"test"`
	Firstname string `json:"firstname" groups:"test"`
	Lastname  string `json:"lastname" groups:"test"`
}

type TestModel struct {
	Name        string          `json:"name" groups:"test"`
	Description string          `json:"description" groups:"test"`
	Users       []UserTestModel `json:"-" groups:"test"`
}

func (testModel TestModel) MarshalJSON() ([]byte, error) {
	type TestModelAlias TestModel

	return json.Marshal(&struct {
		TestModelAlias
		Users []UserTestModel `json:"users" groups:"test"`
	}{
		TestModelAlias: TestModelAlias(testModel),
		Users: []UserTestModel{
			{
				Id:        999,
				Firstname: "superman",
				Lastname:  "superman",
			},
		},
	})
}

func (testController *TestController) TestHandler(w http.ResponseWriter, r *http.Request) {
	//testModel := TestModel{
	//	Name:        "test",
	//	Description: "this is a test",
	//	Users: []UserTestModel{
	//		{
	//			Id:        1,
	//			Firstname: "steve",
	//			Lastname:  "jobs",
	//		},
	//		{
	//			Id:        2,
	//			Firstname: "anthony",
	//			Lastname:  "hopkins",
	//		},
	//		{
	//			Id:        3,
	//			Firstname: "tom",
	//			Lastname:  "cruise",
	//		},
	//	},
	//}

	testModels := []TestModel{
		{
			Name:        "test",
			Description: "this is a test",
			Users: []UserTestModel{
				{
					Id:        1,
					Firstname: "steve",
					Lastname:  "jobs",
				},
				{
					Id:        2,
					Firstname: "anthony",
					Lastname:  "hopkins",
				},
				{
					Id:        3,
					Firstname: "tom",
					Lastname:  "cruise",
				},
			},
		},
		{
			Name:        "test",
			Description: "this is a test",
			Users: []UserTestModel{
				{
					Id:        1,
					Firstname: "steve",
					Lastname:  "jobs",
				},
				{
					Id:        2,
					Firstname: "anthony",
					Lastname:  "hopkins",
				},
				{
					Id:        3,
					Firstname: "tom",
					Lastname:  "cruise",
				},
			},
		},
	}

	options := &sheriff.Options{
		Groups: []string{
			"test",
		},
	}
	testModelSerialized, _ := sheriff.Marshal(options, testModels)

	if err := Encode(w, http.StatusOK, testModelSerialized); err != nil {
		log.Println(err)
		w.WriteHeader(http.StatusInternalServerError)
		return
	}
}

Result for a slice of TestModel

[
    {
        "name": "test",
        "description": "this is a test",
        "users": [
            {
                "id": 999,
                "firstname": "superman",
                "lastname": "superman"
            }
        ]
    },
    {
        "name": "test",
        "description": "this is a test",
        "users": [
            {
                "id": 999,
                "firstname": "superman",
                "lastname": "superman"
            }
        ]
    }
]

Result for one TestModel

{
    "description": "this is a test",
    "name": "test"
}

[skhattane]

After further investigation, I realized the issue is not related to this library.