[firebase_messaging] configure parameters do not surface Exceptions in flutter console

[mintymac]

Describe the bug
Any runtime exceptions in the .configure named parameters do not show in the console. i.e. onMessage

To Reproduce
Steps to reproduce the behavior:

1. Configure the onMessage parameter on the FirebaseMessaging class and throw any exception

_fcm.configure(
      onMessage: (Map<String, dynamic> pushMessage) async {
        print("onMessage: $pushMessage");
        throw (Exception(["Thrown in configure"]));
        await handleIncomingMessage(pushMessage);
      }

2. Send the device a push message via the fcm token 
3. Notice no Exception

**Expected behavior**
All exceptions not in try-catch constructs should be shown in the flutter console.

**Additional context**
Any code called from within this onMessage parameter will not surface exceptions

**Flutter doctor**

Run `flutter doctor` and paste the output below:
[✓] Flutter (Channel stable, 1.20.2, on Mac OS X 10.15.6 19G2021, locale en-US)
 
[✓] Android toolchain - develop for Android devices (Android SDK version 29.0.3)
[✓] Xcode - develop for iOS and macOS (Xcode 11.6)
[✓] Android Studio (version 4.0)
[✓] VS Code (version 1.47.3)
[✓] Connected device (2 available)

• No issues found!

[TahaTesser]

Hi @mintymac
Can you please provide your pubspec.yaml, and a minimal complete reproducible code sample?
Thank you

[mintymac]

@TahaTesser Sure. I will provide the project example code.

[mintymac]

import 'dart:async';

import 'package:firebase_messaging/firebase_messaging.dart';
import 'package:flutter/material.dart';

final Map<String, Item> _items = <String, Item>{};
Item _itemForMessage(Map<String, dynamic> message) {
  final dynamic data = message['data'] ?? message;
  final String itemId = data['id'];
  final Item item = _items.putIfAbsent(itemId, () => Item(itemId: itemId))
    ..status = data['status'];
  return item;
}

class Item {
  Item({this.itemId});
  final String itemId;

  StreamController<Item> _controller = StreamController<Item>.broadcast();
  Stream<Item> get onChanged => _controller.stream;

  String _status;
  String get status => _status;
  set status(String value) {
    _status = value;
    _controller.add(this);
  }

  static final Map<String, Route<void>> routes = <String, Route<void>>{};
  Route<void> get route {
    final String routeName = '/detail/$itemId';
    return routes.putIfAbsent(
      routeName,
      () => MaterialPageRoute<void>(
        settings: RouteSettings(name: routeName),
        builder: (BuildContext context) => DetailPage(itemId),
      ),
    );
  }
}

class DetailPage extends StatefulWidget {
  DetailPage(this.itemId);
  final String itemId;
  @override
  _DetailPageState createState() => _DetailPageState();
}

class _DetailPageState extends State<DetailPage> {
  Item _item;
  StreamSubscription<Item> _subscription;

  @override
  void initState() {
    super.initState();
    _item = _items[widget.itemId];
    _subscription = _item.onChanged.listen((Item item) {
      if (!mounted) {
        _subscription.cancel();
      } else {
        setState(() {
          _item = item;
        });
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Item ${_item.itemId}"),
      ),
      body: Material(
        child: Center(child: Text("Item status: ${_item.status}")),
      ),
    );
  }
}

class PushMessagingExample extends StatefulWidget {
  @override
  _PushMessagingExampleState createState() => _PushMessagingExampleState();
}

class _PushMessagingExampleState extends State<PushMessagingExample> {
  String _homeScreenText = "Waiting for token...";
  bool _topicButtonsDisabled = false;

  final FirebaseMessaging _firebaseMessaging = FirebaseMessaging();
  final TextEditingController _topicController =
      TextEditingController(text: 'topic');

  Widget _buildDialog(BuildContext context, Item item) {
    return AlertDialog(
      content: Text("Item ${item.itemId} has been updated"),
      actions: <Widget>[
        FlatButton(
          child: const Text('CLOSE'),
          onPressed: () {
            Navigator.pop(context, false);
          },
        ),
        FlatButton(
          child: const Text('SHOW'),
          onPressed: () {
            Navigator.pop(context, true);
          },
        ),
      ],
    );
  }

  void _showItemDialog(Map<String, dynamic> message) {
    showDialog<bool>(
      context: context,
      builder: (_) => _buildDialog(context, _itemForMessage(message)),
    ).then((bool shouldNavigate) {
      if (shouldNavigate == true) {
        _navigateToItemDetail(message);
      }
    });
  }

  void _navigateToItemDetail(Map<String, dynamic> message) {
    final Item item = _itemForMessage(message);
    // Clear away dialogs
    Navigator.popUntil(context, (Route<dynamic> route) => route is PageRoute);
    if (!item.route.isCurrent) {
      Navigator.push(context, item.route);
    }
  }

  @override
  void initState() {
    super.initState();
    _firebaseMessaging.configure(
      onMessage: (Map<String, dynamic> message) async {
        print("onMessage: $message");
        throw(Exception(["onMessageException"]));
        _showItemDialog(message);
      },
      onLaunch: (Map<String, dynamic> message) async {
        print("onLaunch: $message");
        _navigateToItemDetail(message);
      },
      onResume: (Map<String, dynamic> message) async {
        print("onResume: $message");
        _navigateToItemDetail(message);
      },
    );
    _firebaseMessaging.requestNotificationPermissions(
        const IosNotificationSettings(
            sound: true, badge: true, alert: true, provisional: true));
    _firebaseMessaging.onIosSettingsRegistered
        .listen((IosNotificationSettings settings) {
      print("Settings registered: $settings");
    });
    _firebaseMessaging.getToken().then((String token) {
      assert(token != null);
      setState(() {
        _homeScreenText = "Push Messaging token: $token";
      });
      print(_homeScreenText);
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: const Text('Push Messaging Demo'),
        ),
        // For testing -- simulate a message being received
        floatingActionButton: FloatingActionButton(
          onPressed: () => _showItemDialog(<String, dynamic>{
            "data": <String, String>{
              "id": "2",
              "status": "out of stock",
            },
          }),
          tooltip: 'Simulate Message',
          child: const Icon(Icons.message),
        ),
        body: Material(
          child: Column(
            children: <Widget>[
              Center(
                child: Text(_homeScreenText),
              ),
              Row(children: <Widget>[
                Expanded(
                  child: TextField(
                      controller: _topicController,
                      onChanged: (String v) {
                        setState(() {
                          _topicButtonsDisabled = v.isEmpty;
                        });
                      }),
                ),
                FlatButton(
                  child: const Text("subscribe"),
                  onPressed: _topicButtonsDisabled
                      ? null
                      : () {
                          _firebaseMessaging
                              .subscribeToTopic(_topicController.text);
                          _clearTopicText();
                        },
                ),
                FlatButton(
                  child: const Text("unsubscribe"),
                  onPressed: _topicButtonsDisabled
                      ? null
                      : () {
                          _firebaseMessaging
                              .unsubscribeFromTopic(_topicController.text);
                          _clearTopicText();
                        },
                ),
              ])
            ],
          ),
        ));
  }

  void _clearTopicText() {
    setState(() {
      _topicController.text = "";
      _topicButtonsDisabled = true;
    });
  }
}

void main() {
  runApp(
    MaterialApp(
      home: PushMessagingExample(),
    ),
  );
}
```

[mintymac]

pubspec.yaml

dependencies:
  flutter:
    sdk: flutter


  firebase_core: 0.5.0

  firebase_messaging: ^7.0.0

[TahaTesser]

I cannot reproduce any exception on purpose, sending empty data doesn't throw any exception

I/flutter (16697): onMessage: {notification: {title: null, body: null}, data: {}}

code sample

// // Copyright 2019 The Chromium Authors. All rights reserved.
// // Use of this source code is governed by a BSD-style license that can be
// // found in the LICENSE file.

// import 'dart:async';

// import 'package:firebase_messaging/firebase_messaging.dart';
// import 'package:flutter/material.dart';

// Future<dynamic> myBackgroundMessageHandler(Map<String, dynamic> message) {
//   if (message.containsKey('data')) {
//     // Handle data message
//     final dynamic data = message['data'];
//   }

//   if (message.containsKey('notification')) {
//     // Handle notification message
//     final dynamic notification = message['notification'];
//   }

//   // Or do other work.
// }

// final Map<String, Item> _items = <String, Item>{};
// Item _itemForMessage(Map<String, dynamic> message) {
//   final dynamic data = message['data'] ?? message;
//   final String itemId = data['id'];
//   final Item item = _items.putIfAbsent(itemId, () => Item(itemId: itemId))
//     ..status = data['status'];
//   return item;
// }

// class Item {
//   Item({this.itemId});
//   final String itemId;

//   StreamController<Item> _controller = StreamController<Item>.broadcast();
//   Stream<Item> get onChanged => _controller.stream;

//   String _status;
//   String get status => _status;
//   set status(String value) {
//     _status = value;
//     _controller.add(this);
//   }

//   static final Map<String, Route<void>> routes = <String, Route<void>>{};
//   Route<void> get route {
//     final String routeName = '/detail/$itemId';
//     return routes.putIfAbsent(
//       routeName,
//       () => MaterialPageRoute<void>(
//         settings: RouteSettings(name: routeName),
//         builder: (BuildContext context) => DetailPage(itemId),
//       ),
//     );
//   }
// }

// class DetailPage extends StatefulWidget {
//   DetailPage(this.itemId);
//   final String itemId;
//   @override
//   _DetailPageState createState() => _DetailPageState();
// }

// class _DetailPageState extends State<DetailPage> {
//   Item _item;
//   StreamSubscription<Item> _subscription;

//   @override
//   void initState() {
//     super.initState();
//     _item = _items[widget.itemId];
//     _subscription = _item.onChanged.listen((Item item) {
//       if (!mounted) {
//         _subscription.cancel();
//       } else {
//         setState(() {
//           _item = item;
//         });
//       }
//     });
//   }

//   @override
//   Widget build(BuildContext context) {
//     return Scaffold(
//       appBar: AppBar(
//         title: Text("Item ${_item.itemId}"),
//       ),
//       body: Material(
//         child: Center(child: Text("Item status: ${_item.status}")),
//       ),
//     );
//   }
// }

// class PushMessagingExample extends StatefulWidget {
//   @override
//   _PushMessagingExampleState createState() => _PushMessagingExampleState();
// }

// class _PushMessagingExampleState extends State<PushMessagingExample> {
//   String _homeScreenText = "Waiting for token...";
//   bool _topicButtonsDisabled = false;

//   final FirebaseMessaging _firebaseMessaging = FirebaseMessaging();
//   final TextEditingController _topicController =
//       TextEditingController(text: 'topic');

//   Widget _buildDialog(BuildContext context, Item item) {
//     return AlertDialog(
//       content: Text("Item ${item.itemId} has been updated"),
//       actions: <Widget>[
//         FlatButton(
//           child: const Text('CLOSE'),
//           onPressed: () {
//             Navigator.pop(context, false);
//           },
//         ),
//         FlatButton(
//           child: const Text('SHOW'),
//           onPressed: () {
//             Navigator.pop(context, true);
//           },
//         ),
//       ],
//     );
//   }

//   void _showItemDialog(Map<String, dynamic> message) {
//     showDialog<bool>(
//       context: context,
//       builder: (_) => _buildDialog(context, _itemForMessage(message)),
//     ).then((bool shouldNavigate) {
//       if (shouldNavigate == true) {
//         _navigateToItemDetail(message);
//       }
//     });
//   }

//   void _navigateToItemDetail(Map<String, dynamic> message) {
//     final Item item = _itemForMessage(message);
//     // Clear away dialogs
//     Navigator.popUntil(context, (Route<dynamic> route) => route is PageRoute);
//     if (!item.route.isCurrent) {
//       Navigator.push(context, item.route);
//     }
//   }

//   @override
//   void initState() {
//     super.initState();
//     _firebaseMessaging.configure(
//       onMessage: (Map<String, dynamic> message) async {
//         print("onMessage: $message");
//         _showItemDialog(message);
//       },
//       onBackgroundMessage: myBackgroundMessageHandler,
//       onLaunch: (Map<String, dynamic> message) async {
//         print("onLaunch: $message");
//         _navigateToItemDetail(message);
//       },
//       onResume: (Map<String, dynamic> message) async {
//         print("onResume: $message");
//         _navigateToItemDetail(message);
//       },
//     );
//     _firebaseMessaging.requestNotificationPermissions(
//         const IosNotificationSettings(
//             sound: true, badge: true, alert: true, provisional: true));
//     _firebaseMessaging.onIosSettingsRegistered
//         .listen((IosNotificationSettings settings) {
//       print("Settings registered: $settings");
//     });
//     _firebaseMessaging.getToken().then((String token) {
//       assert(token != null);
//       setState(() {
//         _homeScreenText = "Push Messaging token: $token";
//       });
//       print(_homeScreenText);
//     });
//   }

//   @override
//   Widget build(BuildContext context) {
//     return Scaffold(
//         appBar: AppBar(
//           title: const Text('Push Messaging Demo'),
//         ),
//         // For testing -- simulate a message being received
//         floatingActionButton: FloatingActionButton(
//           onPressed: () => _showItemDialog(<String, dynamic>{
//             "data": <String, String>{
//               "id": "2",
//               "status": "out of stock",
//             },
//           }),
//           tooltip: 'Simulate Message',
//           child: const Icon(Icons.message),
//         ),
//         body: Material(
//           child: Column(
//             children: <Widget>[
//               Center(
//                 child: Text(_homeScreenText),
//               ),
//               Row(children: <Widget>[
//                 Expanded(
//                   child: TextField(
//                       controller: _topicController,
//                       onChanged: (String v) {
//                         setState(() {
//                           _topicButtonsDisabled = v.isEmpty;
//                         });
//                       }),
//                 ),
//                 FlatButton(
//                   child: const Text("subscribe"),
//                   onPressed: _topicButtonsDisabled
//                       ? null
//                       : () {
//                           _firebaseMessaging
//                               .subscribeToTopic(_topicController.text);
//                           _clearTopicText();
//                         },
//                 ),
//                 FlatButton(
//                   child: const Text("unsubscribe"),
//                   onPressed: _topicButtonsDisabled
//                       ? null
//                       : () {
//                           _firebaseMessaging
//                               .unsubscribeFromTopic(_topicController.text);
//                           _clearTopicText();
//                         },
//                 ),
//               ])
//             ],
//           ),
//         ));
//   }

//   void _clearTopicText() {
//     setState(() {
//       _topicController.text = "";
//       _topicButtonsDisabled = true;
//     });
//   }
// }

// void main() {
//   runApp(
//     MaterialApp(
//       home: PushMessagingExample(),
//     ),
//   );
// }

import 'dart:async';

import 'package:firebase_messaging/firebase_messaging.dart';
import 'package:flutter/material.dart';

final Map<String, Item> _items = <String, Item>{};
Item _itemForMessage(Map<String, dynamic> message) {
  final dynamic data = message['data'] ?? message;
  final String itemId = data['id'];
  final Item item = _items.putIfAbsent(itemId, () => Item(itemId: itemId))
    ..status = data['status'];
  return item;
}

class Item {
  Item({this.itemId});
  final String itemId;

  StreamController<Item> _controller = StreamController<Item>.broadcast();
  Stream<Item> get onChanged => _controller.stream;

  String _status;
  String get status => _status;
  set status(String value) {
    _status = value;
    _controller.add(this);
  }

  static final Map<String, Route<void>> routes = <String, Route<void>>{};
  Route<void> get route {
    final String routeName = '/detail/$itemId';
    return routes.putIfAbsent(
      routeName,
      () => MaterialPageRoute<void>(
        settings: RouteSettings(name: routeName),
        builder: (BuildContext context) => DetailPage(itemId),
      ),
    );
  }
}

class DetailPage extends StatefulWidget {
  DetailPage(this.itemId);
  final String itemId;
  @override
  _DetailPageState createState() => _DetailPageState();
}

class _DetailPageState extends State<DetailPage> {
  Item _item;
  StreamSubscription<Item> _subscription;

  @override
  void initState() {
    super.initState();
    _item = _items[widget.itemId];
    _subscription = _item.onChanged.listen((Item item) {
      if (!mounted) {
        _subscription.cancel();
      } else {
        setState(() {
          _item = item;
        });
      }
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("Item ${_item.itemId}"),
      ),
      body: Material(
        child: Center(child: Text("Item status: ${_item.status}")),
      ),
    );
  }
}

class PushMessagingExample extends StatefulWidget {
  @override
  _PushMessagingExampleState createState() => _PushMessagingExampleState();
}

class _PushMessagingExampleState extends State<PushMessagingExample> {
  String _homeScreenText = "Waiting for token...";
  bool _topicButtonsDisabled = false;

  final FirebaseMessaging _firebaseMessaging = FirebaseMessaging();
  final TextEditingController _topicController =
      TextEditingController(text: 'topic');

  Widget _buildDialog(BuildContext context, Item item) {
    return AlertDialog(
      content: Text("Item ${item.itemId} has been updated"),
      actions: <Widget>[
        FlatButton(
          child: const Text('CLOSE'),
          onPressed: () {
            Navigator.pop(context, false);
          },
        ),
        FlatButton(
          child: const Text('SHOW'),
          onPressed: () {
            Navigator.pop(context, true);
          },
        ),
      ],
    );
  }

  void _showItemDialog(Map<String, dynamic> message) {
    showDialog<bool>(
      context: context,
      builder: (_) => _buildDialog(context, _itemForMessage(message)),
    ).then((bool shouldNavigate) {
      if (shouldNavigate == true) {
        _navigateToItemDetail(message);
      }
    });
  }

  void _navigateToItemDetail(Map<String, dynamic> message) {
    final Item item = _itemForMessage(message);
    // Clear away dialogs
    Navigator.popUntil(context, (Route<dynamic> route) => route is PageRoute);
    if (!item.route.isCurrent) {
      Navigator.push(context, item.route);
    }
  }

  @override
  void initState() {
    super.initState();
    _firebaseMessaging.configure(
      onMessage: (Map<String, dynamic> message) async {
        print("onMessage: $message");
        _showItemDialog(message);
        throw (Exception(["onMessageException"]));
      },
      onLaunch: (Map<String, dynamic> message) async {
        print("onLaunch: $message");
        _navigateToItemDetail(message);
      },
      onResume: (Map<String, dynamic> message) async {
        print("onResume: $message");
        _navigateToItemDetail(message);
      },
    );
    _firebaseMessaging.requestNotificationPermissions(
        const IosNotificationSettings(
            sound: true, badge: true, alert: true, provisional: true));
    _firebaseMessaging.onIosSettingsRegistered
        .listen((IosNotificationSettings settings) {
      print("Settings registered: $settings");
    });
    _firebaseMessaging.getToken().then((String token) {
      assert(token != null);
      setState(() {
        _homeScreenText = "Push Messaging token: $token";
      });
      print(_homeScreenText);
    });
  }

  @override
  Widget build(BuildContext context) {
    return Scaffold(
        appBar: AppBar(
          title: const Text('Push Messaging Demo'),
        ),
        // For testing -- simulate a message being received
        floatingActionButton: FloatingActionButton(
          onPressed: () => _showItemDialog(<String, dynamic>{
            "data": <String, String>{
              "id": "2",
              "status": "out of stock",
            },
          }),
          tooltip: 'Simulate Message',
          child: const Icon(Icons.message),
        ),
        body: Material(
          child: Column(
            children: <Widget>[
              Center(
                child: Text(_homeScreenText),
              ),
              Row(children: <Widget>[
                Expanded(
                  child: TextField(
                      controller: _topicController,
                      onChanged: (String v) {
                        setState(() {
                          _topicButtonsDisabled = v.isEmpty;
                        });
                      }),
                ),
                FlatButton(
                  child: const Text("subscribe"),
                  onPressed: _topicButtonsDisabled
                      ? null
                      : () {
                          _firebaseMessaging
                              .subscribeToTopic(_topicController.text);
                          _clearTopicText();
                        },
                ),
                FlatButton(
                  child: const Text("unsubscribe"),
                  onPressed: _topicButtonsDisabled
                      ? null
                      : () {
                          _firebaseMessaging
                              .unsubscribeFromTopic(_topicController.text);
                          _clearTopicText();
                        },
                ),
              ])
            ],
          ),
        ));
  }

  void _clearTopicText() {
    setState(() {
      _topicController.text = "";
      _topicButtonsDisabled = true;
    });
  }
}

void main() {
  runApp(
    MaterialApp(
      home: PushMessagingExample(),
    ),
  );
}

DATA='{ "to": "<fcm-token>"}'
curl https://fcm.googleapis.com/fcm/send -H "Content-Type:application/json" -X POST -d "$DATA" -H "Authorization: key=<server-key>"

  firebase_messaging: ^7.0.0
  firebase_core: ^0.5.0

flutter doctor -v

[✓] Flutter (Channel dev, 1.22.0-1.0.pre, on Mac OS X 10.15.6 19G2021, locale en-GB)
• Flutter version 1.22.0-1.0.pre at /Users/tahatesser/Code/flutter_dev
• Framework revision ce40de69b7 (7 days ago), 2020-08-20 07:31:50 -0700
• Engine revision 81027ab0cc
• Dart version 2.10.0 (build 2.10.0-45.0.dev)

[✓] Android toolchain - develop for Android devices (Android SDK version 30.0.1)
• Android SDK at /Users/tahatesser/Code/sdk
• Platform android-30, build-tools 30.0.1
• ANDROID_HOME = /Users/tahatesser/Code/sdk
• Java binary at: /Applications/Android
Studio.app/Contents/jre/jdk/Contents/Home/bin/java
• Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6222593)
• All Android licenses accepted.

[✓] Xcode - develop for iOS and macOS (Xcode 11.6)
• Xcode at /Applications/Xcode.app/Contents/Developer
• Xcode 11.6, Build version 11E708
• CocoaPods version 1.9.3

[✓] Chrome - develop for the web
• Chrome at /Applications/Google Chrome.app/Contents/MacOS/Google Chrome

[✓] Android Studio (version 4.0)
• Android Studio at /Applications/Android Studio.app/Contents
• Flutter plugin version 48.1.2
• Dart plugin version 193.7547
• Java version OpenJDK Runtime Environment (build 1.8.0_242-release-1644-b3-6222593)

[✓] VS Code (version 1.48.2)
• VS Code at /Applications/Visual Studio Code.app/Contents
• Flutter extension version 3.13.2

[✓] Connected device (4 available)
• RMX2001 (mobile) • EUYTFEUSQSRGDA6D • android-arm64 • Android 10 (API 29)
• macOS (desktop) • macos • darwin-x64 • Mac OS X 10.15.6 19G2021
• Web Server (web) • web-server • web-javascript • Flutter Tools
• Chrome (web) • chrome • web-javascript • Google Chrome 84.0.4147.135

• No issues found!

[mintymac]

@TahaTesser Is there anyway we can get this labelled critical and/or do you have an idea of how to patch this to surface exceptions? I'm sure many projects are failing at runtime and not realizing it, severely reducing the usefulness of the library.