opt.Optional[string].MarshalJSON()

optional.go

@@ -2,6 +2,7 @@ package opt
 
 import (
 	"fmt"
+	"encoding/json"
 )
 
 // Optional represents an optional value.
@@ -169,6 +170,15 @@ func (receiver Optional[T]) GoString() string {
 	return fmt.Sprintf("opt.Something[%T](%#v)", receiver.value, receiver.value)
 }
 
+// MarshalJSON makes it so json.Marshaler is implemented.
+func (receiver Optional[string]) MarshalJSON() ([]byte, error) {
+	if !receiver.something {
+		return nil, fmt.Errorf("cannot marshal opt.Nothing[%T]()", receiver.value)
+	}
+
+	return json.Marshal(receiver.value)
+}
+
 // WhenNothing will call ‘fn’ when ‘receiver’ is holding nothing.
 //
 // It will not call ‘fn’ when ‘receier’ is hold something.