generateForAnnotatedElement method

@override Stream<String> 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
Stream<String> generateForAnnotatedElement(
  Element element,
  ConstantReader annotation,
  BuildStep buildStep,
) async* {
  await validateSdkConstraint(buildStep);

  if (element is! ClassElement) {
    final friendlyName = element.displayName;
    throw InvalidGenerationSourceError(
      'Generator cannot target `$friendlyName`. '
      '`@CliOptions` can only be applied to a class.',
      todo: 'Remove the `@CliOptions` annotation from `$friendlyName`.',
      element: element,
    );
  }

  // Get all of the fields that need to be assigned
  // TODO: We only care about constructor things + writable fields, right?
  final fieldsList = createSortedFieldSet(element);

  // Explicitly using `LinkedHashMap` – we want these ordered.
  final fields = LinkedHashMap<String, FieldElement>.fromIterable(
    fieldsList,
    key: (f) => (f as FieldElement).name,
  );

  // Get the constructor to use for the factory

  final populateParserName = '_\$populate${element.name}Parser';
  final parserFieldName = '_\$parserFor${element.name}';
  final resultParserName = '_\$parse${element.name}Result';

  if (fieldsList.any((fe) => fe.type.isEnum)) {
    yield enumValueHelper;

    if (fieldsList.any(
      (fe) =>
          fe.type.isEnum &&
          fe.type.nullabilitySuffix != NullabilitySuffix.none,
    )) {
      yield nullableEnumValueHelper;
    }
  }

  if (fieldsList.any((fe) => numChecker.isAssignableFromType(fe.type))) {
    yield r'''
T _$badNumberFormat<T extends num>(
String source,
String type,
String argName,
) =>
throw FormatException(
  'Cannot parse "$source" into `$type` for option "$argName".',
);
''';
  }

  var buffer = StringBuffer()
    ..write(
      '''
${element.name} $resultParserName(ArgResults result) =>''',
    );

  String deserializeForField(
    String fieldName, {
    ParameterElement? ctorParam,
  }) =>
      _deserializeForField(fields[fieldName]!, ctorParam, fields);

  final usedFields = writeConstructorInvocation(
    buffer,
    element,
    fields.keys,
    fields.values.where((fe) => !fe.isFinal).map((fe) => fe.name),
    {},
    deserializeForField,
  );

  final unusedFields = fields.keys.toSet()..removeAll(usedFields);

  if (unusedFields.isNotEmpty) {
    final fieldsString = unusedFields.map((f) => '`$f`').join(', ');
    log.warning('Skipping unassignable fields on `$element`: $fieldsString');

    unusedFields.forEach(fields.remove);
  }
  yield buffer.toString();

  final provideOverrides =
      fields.map((k, v) => MapEntry(k, ArgInfo.fromField(v)))
        ..removeWhere(
          (k, v) => !(v.optionData?.provideDefaultToOverride ?? false),
        );

  final fyis = <String>[];

  /// If an override has a converter, then we don't support passing the
  /// override in via the source type. You have to pass it in as a [String].
  String typeForOverride(String fieldName, ArgInfo info) {
    assert(info.optionData!.provideDefaultToOverride);
    String typeInfo;
    if (converterDataFromOptions(info.optionData!) == null) {
      typeInfo = info.dartType.getDisplayString(withNullability: false);
    } else {
      fyis.add(
        'The value for [${_overrideParamName(fieldName)}] must be a '
        '[String] that is convertible to '
        '[${info.dartType.getDisplayString(withNullability: false)}].',
      );
      typeInfo = 'String';
    }

    typeInfo = '$typeInfo?';

    return '$typeInfo ${_overrideParamName(fieldName)},';
  }

  var overrideArgs = '';
  if (provideOverrides.isNotEmpty) {
    overrideArgs = provideOverrides.entries
        .map((e) => typeForOverride(e.key, e.value))
        .join('\n');
    overrideArgs = ',{$overrideArgs}';
  }

  buffer = StringBuffer()
    ..writeAll(fyis.map((e) => '/// $e\n'))
    ..write(
      'ArgParser $populateParserName(ArgParser parser$overrideArgs) => '
      'parser',
    );
  for (var f in fields.values) {
    if (f.type.isEnum) {
      yield enumValueMapFromType(f.type)!;
    }

    _parserOptionFor(buffer, f);
  }
  buffer.write(';');
  yield buffer.toString();

  yield 'final $parserFieldName = $populateParserName(ArgParser());';

  yield '''
${element.name} parse${element.name}(List<String> args) {
final result = $parserFieldName.parse(args);
return $resultParserName(result);
}
''';

  final createCommand = annotation.read('createCommand').boolValue;
  if (createCommand) {
    yield '''
abstract class _\$${element.name}Command<T> extends Command<T> {
_\$${element.name}Command() {
  $populateParserName(argParser);
}

late final _options = $resultParserName(argResults!);
}
    ''';
  }
}