Automatic Immutability in Dart using noSuchMethod() with no build_runner

auto_immutability.dart

main() {
  setupImmutable(() => User());

  final user1 = create(User()
  ..name = "uwu"
  ..age = 100);

  final user2 = copy(user1..name = "owo"..child = User());

  final user3 = copy(user2..name = "eheh");

}


abstract class _User {
  String name;
  int age;
  User child;
}

class User extends Immutable<User> implements _User {}

class Change {
  final dynamic key;
  final dynamic value;

  const Change(this.key, this.value);
}

final instanciations = <Type, dynamic Function()>{};
void setupImmutable<T>(T Function() setup) {
  instanciations[T] = setup;
}

T instanciate<T>(Type type) {
  return instanciations[type]();
}

class Immutable<T extends Immutable<dynamic>> {
  Map<String, dynamic> _values = {};
  List<Change> _changes = [];

  @override
  noSuchMethod(Invocation invocation) {
    print(invocation.runtimeType);
    print(invocation.memberName);
    final name = getName(invocation.memberName);
    if (invocation.isGetter) {
      return _values[name];
    }
    if (invocation.isSetter) {
      _changes.add(Change(name, invocation.positionalArguments.first));
      return;
    }
    if (invocation.isMethod) {
      return Function.apply(
        _values[name],
        invocation.positionalArguments,
        invocation.namedArguments,
      );
    }
  }

  //  T merge(T other) {}

  T copyChangesTo(T instance) {
    instance._values = {..._values};
    _changes.forEach((change) {
      instance._values[change.key] = change.value;
    });
    return instance;
  }

  T copy<T extends Immutable>(T changed) {
    return copyChangesTo(changed as dynamic) as dynamic;
  }

  T copyFrom<T extends Immutable>(T changed) {
    return changed.copy(this) as dynamic;
  }

  //   @override
  //   bool operator ==(Object other) {
  //     if (other is Immutable<T>) {
  //       return DeepCollectionEquality().equals(_values, other._values);
  //     }
  //     return false;
  //   }

  //   @override
  //   int get hashCode => DeepCollectionEquality().hash(_values);
   
}

T create<T extends Immutable>(T value) {
  return value.copyChangesTo(value);
}

T copy<T extends Immutable>(T from) {
  final newInstance = instanciate(T);
  return newInstance.copyFrom(from);
}

final _create = create;

String getName(Symbol s) {
  String text = s.toString().replaceFirst("Symbol", "");
  text = text.replaceAll("(", "");
  text = text.replaceAll(")", "");
  text = text.replaceAll("=", "");
  text = text.replaceAll('"', "");
  text = text.replaceAll('"', "");
  return text;
}