Mobx.dart: Bad state: Unexpected diagnostics: flutter\bin\cache\dart-sdk\lib\internal\internal.dart:172:16

[omneimneh]

I'm running into this exception after flutter update to 1.17. It basically keeps retrying to generate files forever.

main.dart

import 'package:flutter/material.dart';
import 'package:flutterapp/counter_store.dart';

void main() {
  runApp(MyApp());
}

final CounterStore store = CounterStore();

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Demo',
      theme: ThemeData(
        //

        primarySwatch: Colors.blue,

        visualDensity: VisualDensity.adaptivePlatformDensity,
      ),
      home: MyHomePage(title: 'Flutter Demo Home Page'),
    );
  }
}

class MyHomePage extends StatelessWidget {
  MyHomePage({Key key, this.title}) : super(key: key);
  final String title;

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text(title),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            Text(
              'You have pushed the button this many times:',
            ),
            Text(
              '${store.count}',
              style: Theme.of(context).textTheme.headline4,
            ),
          ],
        ),
      ),
      floatingActionButton: FloatingActionButton(
        onPressed: () => store.count++,
        tooltip: 'Increment',
        child: Icon(Icons.add),
      ),
    );
  }
}

counter_store.dart

import 'package:mobx/mobx.dart';

part 'counter_store.g.dart';

class CounterStore extends _Store with _$Store {}

abstract class _Store with CounterStore {
  @observable
  int count = 0;

  @action
  Future throwException() {
    throw new Exception("Some exception happened");
  }
}

pubspec.yaml

name: flutterapp
description: A new Flutter application.

# The following line prevents the package from being accidentally published to
# pub.dev using `pub publish`. This is preferred for private packages.
publish_to: 'none' # Remove this line if you wish to publish to pub.dev

# The following defines the version and build number for your application.
# A version number is three numbers separated by dots, like 1.2.43
# followed by an optional build number separated by a +.
# Both the version and the builder number may be overridden in flutter
# build by specifying --build-name and --build-number, respectively.
# In Android, build-name is used as versionName while build-number used as versionCode.
# Read more about Android versioning at https://developer.android.com/studio/publish/versioning
# In iOS, build-name is used as CFBundleShortVersionString while build-number used as CFBundleVersion.
# Read more about iOS versioning at
# https://developer.apple.com/library/archive/documentation/General/Reference/InfoPlistKeyReference/Articles/CoreFoundationKeys.html
version: 1.0.0+1

environment:
  sdk: ">=2.8.0 <3.0.0"

dependencies:
  flutter:
    sdk: flutter
  mobx:
  flutter_mobx:

  # The following adds the Cupertino Icons font to your application.
  # Use with the CupertinoIcons class for iOS style icons.
  cupertino_icons: ^0.1.3

dev_dependencies:
  flutter_test:
    sdk: flutter
  mobx_codegen:
  build_runner:

# For information on the generic Dart part of this file, see the
# following page: https://dart.dev/tools/pub/pubspec

# The following section is specific to Flutter.
flutter:

  # The following line ensures that the Material Icons font is
  # included with your application, so that you can use the icons in
  # the material Icons class.
  uses-material-design: true

  # To add assets to your application, add an assets section, like this:
  # assets:
  #   - images/a_dot_burr.jpeg
  #   - images/a_dot_ham.jpeg

  # An image asset can refer to one or more resolution-specific "variants", see
  # https://flutter.dev/assets-and-images/#resolution-aware.

  # For details regarding adding assets from package dependencies, see
  # https://flutter.dev/assets-and-images/#from-packages

  # To add custom fonts to your application, add a fonts section here,
  # in this "flutter" section. Each entry in this list should have a
  # "family" key with the font family name, and a "fonts" key with a
  # list giving the asset and other descriptors for the font. For
  # example:
  # fonts:
  #   - family: Schyler
  #     fonts:
  #       - asset: fonts/Schyler-Regular.ttf
  #       - asset: fonts/Schyler-Italic.ttf
  #         style: italic
  #   - family: Trajan Pro
  #     fonts:
  #       - asset: fonts/TrajanPro.ttf
  #       - asset: fonts/TrajanPro_Bold.ttf
  #         weight: 700
  #
  # For details regarding fonts from package dependencies,
  # see https://flutter.dev/custom-fonts/#from-packages

flutter pub run build_runner watch

Bad state: Unexpected diagnostics:
D:\libs\Android\flutter\bin\cache\dart-sdk\lib\internal\internal.dart:172:16 - This requires the 'non-nullable' language feature to be enabled.
[SEVERE] mobx_codegen:mobx_generator on lib/counter_store.dart:

flutter doctor -v

[√] Flutter (Channel master, 1.19.0-1.0.pre.13, on Microsoft Windows [Version 10.0.18363.778], locale en-US)
    • Flutter version 1.19.0-1.0.pre.13 at D:\libs\Android\flutter
    • Framework revision f865ac7e25 (32 hours ago), 2020-05-08 12:06:15 -0700
    • Engine revision 9b905d3f03
    • Dart version 2.9.0 (build 2.9.0-7.0.dev 617bc54b71)


[√] Android toolchain - develop for Android devices (Android SDK version 29.0.2)
    • Android SDK at D:\libs\Android\android-sdk
    • Platform android-29, build-tools 29.0.2
    • ANDROID_HOME = D:\libs\Android\android-sdk
    • Java binary at: C:\Program Files\Android\Android Studio Preview\jre\bin\java
    • Java version OpenJDK Runtime Environment (build 1.8.0_212-release-1586-b04)
    • All Android licenses accepted.

[√] Chrome - develop for the web
    • Chrome at C:\Program Files (x86)\Google\Chrome\Application\chrome.exe

[√] Visual Studio - develop for Windows (Visual Studio Community 2019 16.5.4)
    • Visual Studio at C:\Program Files (x86)\Microsoft Visual Studio\2019\Community
    • Visual Studio Community 2019 version 16.5.30011.22

[√] Android Studio (version 3.5)
    • Android Studio at C:\Program Files\Android\Android Studio
    • Flutter plugin version 44.0.2
    • Dart plugin version 192.7761
    • Java version OpenJDK Runtime Environment (build 1.8.0_202-release-1483-b03)

[√] Android Studio (version 3.6)
    • Android Studio at C:\Program Files\Android\Android Studio Preview
    • Flutter plugin version 45.1.1
    • Dart plugin version 192.7761
    • Java version OpenJDK Runtime Environment (build 1.8.0_212-release-1586-b04)

[√] IntelliJ IDEA Community Edition (version 2019.3)
    • IntelliJ at C:\Program Files\JetBrains\IntelliJ IDEA Community Edition 2018.2.2
    • Flutter plugin version 43.0.3
    • Dart plugin version 193.6494.35

[√] VS Code, 64-bit edition (version 1.44.2)
    • VS Code at C:\Program Files\Microsoft VS Code
    • Flutter extension version 3.10.1

[√] Connected device (5 available)
    • Mi A3                     • 6b02ac5194ce  • android-arm64  • Android 10 (API 29)
    • Android SDK built for x86 • emulator-5556 • android-x86    • Android 10 (API 29) (emulator)
    • Windows                   • Windows       • windows-x64    • Microsoft Windows [Version 10.0.18363.778]
    • Web Server                • web-server    • web-javascript • Flutter Tools
    • Chrome                    • chrome        • web-javascript • Google Chrome 81.0.4044.138

• No issues found!

[stephane3434]

hello,
i have the same problem on visual code on a mac or a pc
all version is the last version for channel master

[omneimneh]

@stephane3434 It's weird that sometimes this error occurs sometimes not after updating. You could try to switch to stable or dev it worked for me on both.

[stephane3434]

i have found a solution,

i have replace build_runner: 1.9.0 (version Apr 22, 2020)

with the last one 1.10

dev_dependencies:
build_runner: ^1.10.0

and all is ok now

[d-apps]

i have found a solution,

i have replace build_runner: 1.9.0 (version Apr 22, 2020)

with the last one 1.10

dev_dependencies:
build_runner: ^1.10.0

and all is ok now

I had the same problem, this solved :)