Not getting any error output in Flutter web - flutter

Question

I'm unable to get any error output from my Flutter web app. Printing to the console using
print('some text');
works fine, but no errors get printed. For example, throwing an exception
throw new Exception('testexception');
doesn't result in any output, neither in the browser console nor in IntelliJ. The log level settings in Chrome are set to [Info, Warnings, Errors].
I even tried implementing a custom error handler
void main(){
FlutterError.onError = (FlutterErrorDetails details) {
print('main.onError: details: ${details.toString()}');
};
runApp(new MyApp());
}
but no luck. Do I have to enable error outputs somewhere? I can't find any info about this in the documentation.
I tried running the app both using the Dart Dev Server (which is started when using Run from IntelliJ), as well as calling webdev serve and webdev serve --auto restart from the Terminal.

Answer 1

Flutter Web currently doesn't have a way to be debugged. Will generate a main.dart.js and you can debug it with Chrome console.
One cool trick to "debug" your Web App, is by showing a popup to your browser:
import 'dart:js' as js;
#override
void initState() {
super.initState();
js.context.callMethod("alert", <String>["Your debug message"]);
}

Answer 2

Did you look to see if it was a known issue? Flutter-web is only at developer preview level. If there's not a current issue, create one, and provide a minimal "how to reproduce". I'm sure the Flutter-web team would appreciate it.

Answer 3

I tried in both IDE and its correctly working in Intellij but not in VSCode. Its showing white blank screen give it try to run again flutter run -d chrome and wait in blank screen for 2minutes.
And check the SDK path of flutter in visual code is correct or not.

Answer 4

In JavaScript, the console.log method is used to output to the Web browser's JavaScript console.
So you can do it from Dart by getting the JavaScript console object and invoking that method on it.
import 'dart:js' as javascript; // ignore: avoid_web_libraries_in_flutter
/// Invoke the the JavaScript `console.log` method.
void logToBrowser(String message) {
final console = javascript.context['console'] as javascript.JsObject;
console.callMethod('log', [message]);
}
Since dart:js is only supported for Dart compiled to JavaScript, this means the Flutter app using it will only work as a Flutter Web app. Importing it will mean the code won't work for an app targeting iOS, Android, etc.
Tip: the JavaScript console object has other methods that can be invoked. Instead of log, use info, warn and error. Those last two highlight the entry when they appear in the console.