MacCatalyst currently doesn't surface unhandled exceptions in user code so we should help MAUI users out

[PureWeen]

Currently AppKit will handle any exception thrown from user code and won't surface it to the user.

The following code

object test = null;
test.GetHashCode();

Will just throw an NRE with no indication to the user that an NRE has occurred

We should wire into the following method

Runtime.MarshalManagedException += Runtime_MarshalManagedException;

And break when a debugger is attached to help the user (and us) be more successful.

We should also wire up our UI Tests so that any exceptions that make it here are surfaced.

Depends on

• Marshalled managed exceptions should be considered unhandled exceptions by the debugger xamarin/xamarin-macios#15037

[mattleibow]

We can add a bit of logic in the platform folder to wire up the event:

class Program
{
    static void Main()
    {
#if DEBUG
        Runtime.MarshalManagedException += (sender, e) => {
            Debugger.Break();
        };
#endif
   }
}

Not sure if it is best in Program.cs or the app delegate... @rolfbjarne where is the best place for an event like this?

[rolfbjarne]

IMHO the sooner the better, so first thing in Main

[mattleibow]

Related to xamarin/xamarin-macios#15037

[ghost]

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[samdoshi]

If anyone else is trying to work around this issue with uncaught exceptions in MacCatalyst code, I've got the following added to my MacCatalyst / Program.cs main function:

        #if DEBUG
        // https://github.com/dotnet/maui/issues/7176
        Runtime.MarshalManagedException += (_, a) => {
            Console.WriteLine("Uncaught MacCatalyst Exception");
            Console.WriteLine(a.Exception.ToString());
            Debugger.Break();
            Environment.Exit(-1);
        };
        #endif

It will fire the debugger but it isn't much use, the printed stack trace is however. Hopefully this is helpful to someone else.

[rolfbjarne]

It might work to set the NSApplicationCrashOnExceptions flag by doing something like this:

var defs = new NSDictionary ((NSString) "NSApplicationCrashOnExceptions", NSValue.FromBoolean (true));
NSUserDefaults.StandardUserDefaults.RegisterDefaults (defs);

Ref: https://learn.microsoft.com/en-us/appcenter/sdk/crashes/macos#enable-catching-uncaught-exceptions-thrown-on-the-main-thread

[Zhanglirong-Winnie]

Verified this issue with VSM 17.6.7 (build 417). Can repro this issue.