Fix Flutter Web crash with ANSI colored logs containing invalid UTF-8

[Copilot]

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Flutter Web crashes with Bad UTF-8 encoding (U+FFFD; REPLACEMENT CHARACTER) when logging HTTP responses containing replacement characters with ANSI color codes enabled. The browser console's UTF-8 decoder chokes on the combination of ANSI escape sequences and special characters.

Fix: Disable ANSI colors by default on Flutter Web in TalkerFlutter.init().

• Added _defaultFlutterLogger() helper that sets enableColors: !kIsWeb
• Users can still pass a custom logger with colors enabled if desired

// Before: Colors always enabled, crashes on web with certain characters
logger: logger ?? TalkerLogger(output: _defaultFlutterOutput)

// After: Colors disabled on web by default
logger: logger ?? _defaultFlutterLogger()

Fixes #289

Original prompt

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This section details on the original issue you should resolve

<issue_title>Flutter Web crash with Talker + Dio logger due to bad UTF-8 / ANSI colored logs</issue_title> <issue_description> Describe the bug When using TalkerFlutter together with TalkerDioLogger in a Flutter Web app, the Flutter Web dev runner sometimes crashes with:

Bad UTF-8 encoding (U+FFFD; REPLACEMENT CHARACTER) found while decoding string

This happens when a logged HTTP response contains a replacement character (�) and is printed with ANSI colors and box-drawing characters (│). Mobile builds with the same configuration work fine; the crash is specific to Web + console logging.

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To Reproduce Steps to reproduce the behavior:

1. Configure TalkerFlutter and TalkerDioLogger like this:

   final Talker appLog = TalkerFlutter.init(
     settings: TalkerSettings(
       useHistory: true,
       maxHistoryItems: 100,
       useConsoleLogs: kDebugMode || !kIsWeb,
     ),
     logger: TalkerLogger(
       settings: TalkerLoggerSettings(
         maxLineWidth: 80,
         enableColors: true,
       ),
     ),
   );
   

   final dio = Dio(
     BaseOptions(
       baseUrl: 'https://example.com/api/',
       contentType: 'application/json',
       connectTimeout: const Duration(seconds: 30),
       receiveTimeout: const Duration(seconds: 30),
     ),
   );
   
   if (kDebugMode) {
     dio.interceptors.add(
       TalkerDioLogger(
         settings: TalkerDioLoggerSettings(
           printRequestData: true,
           printResponseData: true,
         ),
         talker: appLog,
       ),
     );
   }
   

2. Make a request that returns JSON with a field containing a replacement character, for example:

   {
     "name": "JOHN�DOE"
   }
   

3. Run the app on Flutter Web in debug mode, e.g.:

   flutter run -d chrome
   

4. When the response is logged, the Web runner crashes with:

   Finished with error: Bad UTF-8 encoding (U+FFFD; REPLACEMENT CHARACTER) found while decoding string: [38;5;46m│       "name": "JOHN�DOE",[0m
   The source bytes were:
   [27, 91, 51, 56, 59, 53, 59, 52, 54, 109, 226, 148, 130, 32, 32, 32, 32, 32, 32, 32, 34, 110, 97, 109, 101, 34, 58, 32, 34, 74, 79, 72, 78, 239, 191, 189, 68, 79, 69, 34, 44, 27, 91, 48, 109, 10]
   

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Expected behavior Talker / TalkerDioLogger should not cause the Flutter Web dev runner to crash, even if the response body contains invalid/partial UTF-8 or replacement characters. At worst, logs on Web should be safely sanitized (for example, without ANSI color codes or truncated) so that console output doesn’t break UTF-8 decoding.

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Screenshots N/A – this is a console / dev-runner crash, see log output above.

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Desktop (please complete the following information):

• OS: Windows 10 22H2, macOS Sonoma 14.2
• Browser: Chrome (via flutter run -d chrome)
• Version: 143.0.7499.40

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Smartphone (please complete the following information):

N/A – issue is specific to Flutter Web.

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Additional context

• The problem only appears when:

  • useConsoleLogs is enabled on Web
  • enableColors is true
  • TalkerDioLogger prints the response body with problematic characters.

• Workaround I’m currently using:

  final Talker appLog = TalkerFlutter.init(
    settings: TalkerSettings(
      useHistory: true,
      maxHistoryItems: 100,
      useConsoleLogs: kDebugMode && !kIsWeb, // no console logs on Web
    ),
    logger: TalkerLogger(
      settings: TalkerLoggerSettings(
        maxLineWidth: 80,
        enableColors: !kIsWeb, // no ANSI colors on Web
      ),
    ),
  );
  

  if (kDebugMode) {
    dio.interceptors.add(
      TalkerDioLogger(
        settings: TalkerDioLoggerSettings(
          printRequestData: !kIsWeb,
          printResponseData: !kIsWeb, // don’t print body on Web
        ),
        talker: appLog,
      ),
    );
  }
  

• With this configuration the crash no longer happens on Web.

• I’d be happy to open a PR to:

  • adjust defaults for Web (e.g. disable colors / console logs by default on kIsWeb), or
  • add a documented “web-safe” configuration/example in the README.

• Environment:

  • Flutter: 3.38.1
  • Dart: 3.10.0
  • talker: 5.0.2
  • talker_flutter: 5.0.2
  • talker_dio_logger: 5.0.2 </issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Frezyx/talker#448

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