Support json marshall

Author: leavez

optional.go

@@ -1,5 +1,10 @@
 package optional
 
+import (
+	"encoding/json"
+	"errors"
+)
+
 type Type[T any] struct {
 	wrapped interface{}
 }
@@ -77,3 +82,26 @@ func FromPtr[T any](wrapped *T) Type[T] {
 		return New[T](*wrapped)
 	}
 }
+
+// -- Marshaler and Unmarshaler ---
+
+func (s Type[T]) MarshalJSON() ([]byte, error) {
+	if w, ok := s.Value(); ok {
+		return json.Marshal(w)
+	} else {
+		return json.Marshal(nil)
+	}
+}
+
+func (s *Type[T]) UnmarshalJSON(data []byte) error {
+	if s == nil {
+		return errors.New("optional.Type: UnmarshalJSON on nil pointer")
+	}
+	var w *T
+	err := json.Unmarshal(data, &w)
+	if err != nil {
+		return err
+	}
+	*s = FromPtr(w)
+	return nil
+}

optional_test.go

@@ -1,6 +1,7 @@
 package optional
 
 import (
+	"encoding/json"
 	"log"
 	"testing"
 )
@@ -145,3 +146,28 @@ func TestValueOrDefault(t *testing.T) {
 	assert(t, v2.ValueOrDefault(10) == 10, "ValueOrDefault failed")
 	assert(t, v2.ValueOrLazyDefault(func() int { return 100 }) == 100, "ValueOrLazyDefault failed")
 }
+
+func TestEncodeAndDecode(t *testing.T) {
+	var v = New(New(123))
+	data, err := json.Marshal(v)
+	assert(t, err == nil, "")
+	assert(t, string(data) == "123", "")
+
+	var v2 Type[Type[int]]
+	err = json.Unmarshal(data, &v2)
+	assert(t, err == nil, "")
+	assert(t, !v2.IsNil(), "")
+	if w, ok := Compact(v2).Value(); ok {
+		assert(t, w == 123, "")
+	}
+
+	// empty
+	v3 := Nil[int]()
+	data, err = json.Marshal(v3)
+	assert(t, err == nil, "")
+	assert(t, string(data) == "null", "")
+	var v4 Type[int]
+	err = json.Unmarshal(data, &v4)
+	assert(t, err == nil, "")
+	assert(t, v4.IsNil(), "")
+}