generateForAnnotatedElement method

@override Future<String> generateForAnnotatedElement(Element classElement, 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
Future<String> generateForAnnotatedElement(Element classElement,
    ConstantReader annotation, BuildStep buildStep) async {
  if (classElement is! ClassElement) {
    throw 'This annotation can only be used on classes. Offending Element: $classElement';
  }

  final configList = annotation.read('configFiles').listValue;

  if (configList.isEmpty) {
    throw 'configFiles list cannot be empty!  Offending Element: $classElement';
  }

  final buffer = StringBuffer();

  for (final configFile in configList) {
    final filePath = configFile.getField('path')?.toStringValue();
    if (filePath == null) {
      throw "error: path was null in ${configFile} from at annotation ${annotation}";
    }
    final assets = await buildStep
        .findAssets(Glob(filePath, caseSensitive: true))
        .toList();
    if (assets.isEmpty) {
      throw "no file found for argument $filePath";
    }
    if (assets.length > 1) {
      throw "error: multiple files found that match $filePath!";
    }
    final assetId = assets.first;
    final jsonString = await buildStep.readAsString(assetId);
    final configName = configFile.getField('configName')?.toStringValue();
    final code =
        generateCodeForFile(filePath, classElement, jsonString, configName);
    buffer.write(code);
  }
  return buffer.toString();
}