Warning "Use 'const' for final variables initialized to a constant value" in Generated Code

[ahmadjz]

Describe the Bug

In the generated code by Retrofit.dart, there is a warning regarding a final variable that could be const. Specifically, the warning is "Use 'const' for final variables initialized to a constant value". The line of code generating this warning is: final Map<String, dynamic>? _data = null;

To Reproduce

Steps to reproduce the behavior:

1. Create an abstract class for your API calls with Retrofit annotations.
2. Create methods without providing Fields params
3. Run the code generation command for Retrofit (pub run build_runner build or pub run build_runner watch).
4. Check the generated code.
5. See the warning in your console or code editor.

Expected behavior

Generated code should be free of warnings to follow Dart's best practices. if we have no data/fields provided then _data variable should be const not final

Full Code

part 'categories_api_client.g.dart';

@RestApi()
abstract class CategoriesApiClient {
  factory CategoriesApiClient(Dio dio, {String baseUrl}) = _CategoriesApiClient;

  @GET("category")
  Future<List<CategoryResponse>> getCategories();
}

generated code:

// GENERATED CODE - DO NOT MODIFY BY HAND

part of 'categories_api_client.dart';

// **************************************************************************
// RetrofitGenerator
// **************************************************************************

// ignore_for_file: unnecessary_brace_in_string_interps,no_leading_underscores_for_local_identifiers

class _CategoriesApiClient implements CategoriesApiClient {
  _CategoriesApiClient(
    this._dio, {
    this.baseUrl,
  });

  final Dio _dio;

  String? baseUrl;

  @override
  Future<List<CategoryResponse>> getCategories() async {
    const _extra = <String, dynamic>{};
    final queryParameters = <String, dynamic>{};
    final _headers = <String, dynamic>{};
    final Map<String, dynamic>? _data = null;
    final _result = await _dio
        .fetch<List<dynamic>>(_setStreamType<List<CategoryResponse>>(Options(
      method: 'GET',
      headers: _headers,
      extra: _extra,
    )
            .compose(
              _dio.options,
              'category',
              queryParameters: queryParameters,
              data: _data,
            )
            .copyWith(
                baseUrl: _combineBaseUrls(
              _dio.options.baseUrl,
              baseUrl,
            ))));
    var value = _result.data!
        .map(
            (dynamic i) => CategoryResponse.fromJson(i as Map<String, dynamic>))
        .toList();
    return value;
  }

  RequestOptions _setStreamType<T>(RequestOptions requestOptions) {
    if (T != dynamic &&
        !(requestOptions.responseType == ResponseType.bytes ||
            requestOptions.responseType == ResponseType.stream)) {
      if (T == String) {
        requestOptions.responseType = ResponseType.plain;
      } else {
        requestOptions.responseType = ResponseType.json;
      }
    }
    return requestOptions;
  }

  String _combineBaseUrls(
    String dioBaseUrl,
    String? baseUrl,
  ) {
    if (baseUrl == null || baseUrl.trim().isEmpty) {
      return dioBaseUrl;
    }

    final url = Uri.parse(baseUrl);

    if (url.isAbsolute) {
      return url.toString();
    }

    return Uri.parse(dioBaseUrl).resolveUri(url).toString();
  }
}

[RabbitProgram]

@ahmadjz The same phenomenon occurred to me as well. Although it is not a fundamental solution, you can exclude it from the flutter analyze inspection by adding the following to analysis_options.yaml. How about this?

analyzer:
  exclude:
    - "**/*.g.dart"
    - "**/*.freezed.dart"
  errors:
    invalid_annotation_target: ignore

Reference: https://zenn.dev/purigen/articles/23045ba53384f6

[mmotkim]

I know it's been a while but had this been fixed in later versions?