ajson

-- import "."

Package ajson provides a way to marshal and unmarshal JSON with unknown fields.

Installation

go get -u go.devnw.com/ajson

Usage

func Marshal

func Marshal[T comparable](t T, mm map[string]any) ([]byte, error)

MarshalJSON marshals the given struct to json and then merges the unknown fields into the json from the map[string]any object

Example usage:

type Sample struct {
	Name string     `json:"name"`
	Age  int        `json:"age"`
	Sub  *SubSample `json:"sub,omitempty"`
}

type SubSample struct {
	Name string `json:"name"`
}

func main() {
	sample := Sample{
		Name: "John",
		Age:  30,
	}

	unknowns := map[string]any{
		"location": "USA",
	}

	data, err := MarshalJSON(sample, unknowns)
	if err != nil {
		panic(err)
	}

	fmt.Println(string(data))
}

// Output:
// {"name":"John","age":30,"location":"USA"}

Example with embeded unknown and custom marshaler:

type Sample struct {
	Name 		string
	Age  		int
	Unknowns	map[string]any
}

func (s Sample) MarshalJSON() ([]byte, error) {
	return MarshalJSON(struct {
		ID   string `json:"id"`
		Name string `json:"name"`
	}{
		ID:   t.ID,
		Name: t.Name,
	}, t.Unknowns)
}

func Unmarshal

func Unmarshal[T comparable](data []byte) (T, map[string]any, error)

UnmarshalJSON unmarshals the given json into the given struct and then returns the unknown fields as a map[string]any object.

Example usage:

type Sample struct {
	Name string     `json:"name"`
	Age  int        `json:"age"`
	Sub  *SubSample `json:"sub,omitempty"`
}

type SubSample struct {
	Name string `json:"name"`
}

func main() {
	data := []byte(`{"name":"John","age":30,"location":"USA"}`)

	var sample Sample
	unknowns, err := UnmarshalJSON(data, &sample)
	if err != nil {
		panic(err)
	}

	fmt.Println(sample)
	fmt.Println(unknowns)
}

// Output:
// {John 30 &{ }}
// map[location:USA]

Example with embeded unknown and custom unmarshaler:

type Sample struct {
	Name 		string
	Age  		int
	Unknowns	map[string]any
}

func (s *Sample) UnmarshalJSON(data []byte) error {
	var t struct {
		ID   string `json:"id"`
		Name string `json:"name"`
	}

	unknowns, err := UnmarshalJSON(data, &t)
	if err != nil {
		return err
	}

	s.Name = t.Name
	s.Age = t.Age
	s.Unknowns = unknowns

	return nil
}