onError is not returning any error

[AnkitKh095]

Package

dio

Version

^5.4.3+1

Operating-System

Android, iOS

Adapter

Default Dio

Output of flutter doctor -v

flutter doctor -v 
[✓] Flutter (Channel stable, 3.22.2, on macOS 14.4.1 23E224 darwin-arm64, locale en-IN)
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    • Dart version 3.4.3
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    • ANDROID_SDK_ROOT = /Users/ankitkhaire/Library/Android/sdk
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    ✗ Android license status unknown.
      Run `flutter doctor --android-licenses` to accept the SDK licenses.
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    • Build 15F31d
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[✓] Android Studio (version 2023.3)
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    • Java version OpenJDK Runtime Environment (build 17.0.10+0-17.0.10b1087.21-11572160)

[✓] VS Code (version 1.90.2)
    • VS Code at /Applications/Visual Studio Code.app/Contents
    • Flutter extension version 3.90.0

Dart Version

3.4.3

Steps to Reproduce

• package version:-- ^5.4.3+1.

 onError: (DioException e, handler) async {
         print("e---${e.response?.statusCode}");

         if (e.response?.statusCode == 401 &&
             e.requestOptions.extra['refreshed'] != true) {
           try {
             String? newToken = await refreshTokenAPI();
             if (newToken != null) {
               e.requestOptions.headers['Authorization'] =
                   newToken; // Correctly set the new Bearer token
               e.requestOptions.extra['refreshed'] = true;
               return handler.resolve(await _dio.fetch(e.requestOptions));
             }
           } catch (e) {
             print("Error while refreshing token: $e");
             throw e;
           }
         } else if (e.response?.statusCode == 404) {
           print("404 error: ${e.response?.data}");
         } else {
           print("Non-401 error occurred: ${e.response?.statusCode}");
           print("Non-401 error occurred: ${e.response?.data}");
         }
         return handler.next(e);
       },

Expected Result

• the onError should return the entire error response.

Actual Result

if there is any Error from the api request on Error method from the interceptor not giving any logs for the same.

[AlexV525]

1. Do not return handler.resolve.
2. Use handler.reject rather than throw e.

[AnkitKh095]

hello,
Thank you for the prompt response.
here if I make any api call using same instance and if there is any error like 401 or 422,404 i am not getting any logs in inteceptor's onError.

[AlexV525]

You'll fall into an infinite loop using the same instance. Check the example about how to refresh tokens properly at https://github.com/cfug/dio/blob/main/example_dart/lib/queued_interceptor_crsftoken.dart.