Empty response body is read as null

[jeiea]

Package

dio

Version

5.1.2

Output of flutter doctor -v

[✓] Flutter (Channel stable, 3.10.2, on macOS 13.3.1 22E772610a darwin-arm64, locale en-KR)
    • Flutter version 3.10.2 on channel stable at /Users/jeiea/.asdf/installs/flutter/2.10.3-stable
    • Upstream repository https://github.com/flutter/flutter.git
    • Framework revision 9cd3d0d9ff (28 hours ago), 2023-05-23 20:57:28 -0700
    • Engine revision 90fa3ae28f
    • Dart version 3.0.2
    • DevTools version 2.23.1

[✓] Android toolchain - develop for Android devices (Android SDK version 33.0.2)
    • Android SDK at /Users/jeiea/Library/Android/sdk
    • Platform android-33, build-tools 33.0.2
    • Java binary at: /Users/jeiea/.asdf/shims/java
    • Java version OpenJDK Runtime Environment Temurin-11.0.15+10 (build 11.0.15+10)
    • All Android licenses accepted.

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    • Chrome (web)       • chrome                    • web-javascript • Google Chrome 113.0.5672.126

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! Doctor found issues in 1 category.

Dart Version

No response

Steps to Reproduce

Run the following dart source.

import 'package:dio/dio.dart';

Future<void> main() async {
  final dio = Dio();
  final response = await dio.get('https://jeiea.free.beeceptor.com/empty');
  final data = response.data;
  print(data);
}

Expected Result

Print empty string.

I found this from my app's breaking behavior so think v4 would return empty string in this situation.

Also I think regarding as empty string is correct because the response has text/html content type and 200 OK, not no content.

Actual Result

> dart run src/main.dart
null

[kuhnroyal]

@AlexV525 This was changed in cce167e - what do you think?

[AlexV525]

@AlexV525 This was changed in cce167e - what do you think?

Yeah I saw this one. I was thinking to make it only modify the result to null only when the request and the response type is JSON.

[AlexV525]

@jeiea If the response type is defined as JSON (by default), in order to return a valid JSON response, the response body must be null, otherwise an empty string is an expected result for parsing a JSON. Setting the response type to others will keep the original result after #1874.

[jeiea]

@AlexV525 I'm still receiving null with this pubspec and the original code snippet. I may have missed something, but could you double check?

dependencies:
  dio:
    git:
      url: https://github.com/cfug/dio.git
      path: dio
      ref: fix/null-response-body-only-when-response-type-json

[AlexV525]

PR updated.

[bgenidy]

made a comment on it, I think enabling users to easily keep back compatibility with Dio v4 decoding would significantly help reduce chances for apis to break post upgrade. Also this wasn't explicitly called out in the change logs for Dio v5, if possible it would be great to update documentation to include it as part of the breaking changes post v4 upgrade.