Flutter Dio interceptor: DioError [DioErrorType.DEFAULT]: Bad state: Can‘t finalize a finalized MultipartFile - flutter

Question

Hi i'm trying refreshtoken logic in Dio interceptor. it's working fine for json body params, but its throwing DioError [DioErrorType.DEFAULT]: Bad state: Can‘t finalize a finalized MultipartFile when i tried uploading images.
onError: (DioError error) async {
// Do something with response error
if (error.response?.statusCode == 401) {
// _dio.interceptors.requestLock.lock();
Response response;
RequestOptions options = error.response.request;
response = await _dio
.post('/user/refresh', data: {"refreshToken": _refreshToken});
if (response.statusCode == 200) {
final userData = json.encode(
{
'token': response.data["accessToken"],
'tokenType': _tokenType,
'refreshToken': response.data["refreshToken"]
},
);
prefs.setString('userData', userData);
options.data = formData;
}
options.headers["Authorization"] =
"$_tokenType ${response.data['accessToken']}";
return await _dio.request(options.path, options: options);
} else {
throw error;
}

Answer 1

I put together a workaround for this issue which basically consists of rebuilding the FormData before retrying. It feels a bit hacky but it works. I start by passing any info I need for the reconstruction in via the "extra" map in the request options so the interceptor has access to it. Here is some pseudo code:
//original request
dioResponse = await dio.post(
'http://my/api/endpoint',
data: myOriginalFormData,
options: Options(
headers: myHeaders,
extra: {'pathToMyFile': pathToMyFile},
),
);
//and in my interceptor I use it to construct a fresh FormData that has not been finalized
final FormData newFormData = FormData.fromMap({
'file': await MultipartFile.fromFile(
requestOptions.extra['pathToMyFile'],
contentType: MediaType('application/json', 'json')),
});
//retry with the fresh FormData
return dio.request(
requestOptions.path,
data: newFormData,
options: requestOptions,
cancelToken: requestOptions.cancelToken,
onReceiveProgress: requestOptions.onReceiveProgress,
onSendProgress: requestOptions.onSendProgress,
queryParameters: requestOptions.queryParameters,
);
Anyone have thoughts on this approach? Any major downsides?