serialize method

@override Object? serialize(DartType targetType, String expression, TypeHelperContext context)

Returns Dart code that serializes an expression representing a Dart object of type targetType.

If targetType is not supported, returns null.

Let's say you want to serialize a class Foo as just its id property of type int.

Treating expression as a opaque Dart expression, the serialize implementation could be a simple as:

String serialize(DartType targetType, String expression) =>
  "$expression.id";
```.

Implementation

@override
Object? serialize(
    DartType targetType, String expression, TypeHelperContext context) {
  if (!typeChecker.isAssignableFromType(targetType)) {
    return null;
  }
  final args = targetType.typeArgumentsOf(typeChecker)!;
  assert(args.length == 2);

  final keyType = args[0];
  final valueType = args[1];

  checkSafeKeyType(expression, keyType);

  final subFieldValue = context.serialize(valueType, closureArg);
  final subKeyValue = forType(keyType)?.serialize(keyType, keyParam, false) ??
      context.serialize(keyType, keyParam);

  final targetTypeIsNullable = targetType.isNullableType;

  final optionalQuestion = targetTypeIsNullable ? '?' : '';

  if (closureArg == subFieldValue && keyParam == subKeyValue) {
    return serializeToMapExpression(
        expression, keyType, valueType, targetTypeIsNullable);
  }

  return serializeToMapExpression(
          expression, keyType, valueType, targetTypeIsNullable) +
      '$optionalQuestion.map(($keyParam, $closureArg) => MapEntry($subKeyValue, $subFieldValue))';
}