generateForAnnotatedElement method

@override dynamic generateForAnnotatedElement(Element element, ConstantReader annotation, BuildStep buildStep)

Implement to return source code to generate for element.

This method is invoked based on finding elements annotated with an instance of T. The annotation is provided as a ConstantReader.

Supported return values include a single String or multiple String instances within an Iterable or Stream. It is also valid to return a Future of String, Iterable, or Stream.

Implementations should return null when no content is generated. Empty or whitespace-only String instances are also ignored.

Implementation

@override
generateForAnnotatedElement(
  Element element,
  ConstantReader annotation,
  BuildStep buildStep,
) {
  if (element is! ClassElement) {
    throw InvalidGenerationSourceError(
        'Generator cannot target `${element.name}`.',
        todo: 'Remove the EnumGeneration annotation from `${element.name}`.',
        element: element);
  }

  Set<String> fields = {};

  for (var interface in (element).constructors) {
    for (final param in interface.parameters) {
      fields.add(param.name);
    }
  }

  if (fields.isEmpty) {
    throw InvalidGenerationSourceError(
      "There's no field in ${element.name}.",
    );
  }

  final enumName = '${element.name}Field';
  final enumContent = fields.map((name) => '  $name').join(',\n');

  // enum定義を返す
  return 'enum $enumName {\n$enumContent\n}';
}