jsonEncode, extensions gotcha

jsonEncodeGotcha.dart

// See https://stackoverflow.com/questions/70272959/jsonencode-doesnt-work-with-enum-extensions-is-there-a-workaround

import 'dart:convert';

enum Day { monday, tuesday }

extension ParseToJsonString on Day {
  String toJson() {
    return this.toString().split('.').last;
  }
}

class Saturday {
  String toJson() => "WOOHOO Saturday";
}

main() {
  //works!
  Saturday s = Saturday();
  print(s.toJson());
  print(jsonEncode(s));

  Day m = Day.monday;
  print(m.toJson()); //prints 'monday'
  print(m); //prints Day.Monday
  // print(jsonEncode(m)); // Uncaught Error: Converting object to an encodable object failed: Instance of 'Day'
  print('continues');
  print(jsonEncode(
    m,
    toEncodable: (x) {
      Day recastX = x as Day;
      return recastX.toJson();
    },
  ));
}