App designer - custom global error handling

I am trying to add general custom error handling to App Designer application. One of the use cases is e.g. when an unhandled error would trigger a pop-up window with that error. I see this useful to me for a compiled application without command line.

If there is an error in any callback, AppManagementService instance will catch it in the tryCallback method. This method will also notify listeners using fireCallbackErroredEvent.

I naive way to try to listen that callback could be AppManagementService.instance() since it is referencing to a unique singleton.

function startupFcn(app)
    service = appdesigner.internal.service.AppManagementService.instance();
    addlistener(service, 'CallbackErrored',  @app.displayErrorDialog);
end

However, it is not possible to connect to the notifier since access is restricted only to following to classes:

events (ListenAccess = {?appdesigner.internal.appalert.AppAlertController; ...
            ?appdesigner.internal.service.WebAppRunner})
        % This event is fired when there's an exception or error happening
        % in the app's callback or startup function
        CallbackErrored  

I am maybe overengineering the general custom error handling and I am not aware of some functionality in App Designer.

Do you have any suggestions how to approach this problem? Any advice is appreciated.

Edit:

I have created following class inherited from AppAlertController and this class is able to listen CallbackErrored from AppManagementService. It is working in classic Matlab IDE, but not after compilation to standalone app. It seems that supercalss is not being is imported to Matlab runtime.

classdef AppAllertErrorHandler < appdesigner.internal.appalert.AppAlertController
    
    methods
        function obj = AppAllertErrorHandler()
            service = appdesigner.internal.service.AppManagementService.instance();
            obj.CallbackErroredListener = addlistener(service, 'CallbackErrored',  @obj.displayErrorDialog);
        end
    end
    
    methods(Access = protected)
        function doSendErrorAlertToClient(obj, appException)
            % Empty implementation of superclass abstract method
        end
    end
    
    methods(Access = private)
        function displayErrorDialog(obj, event, source)
            % display dialog
            Error = source.Exception;
            msg = sprintf('Unhandled exception \nIdentifier: %s\nMessage: %s in file %s at line %d ',  ...
                Error.identifier, Error.message, Error.stack(1).name, Error.stack(1).line);
            msgbox(msg, 'Unhandled exception');
        end
    end
end

Following error is obtained after compilation

testApp.exe
Error using AppAllertErrorHandler
The specified superclass 'appdesigner.internal.appalert.AppAlertController' contains a parse error, cannot be found on MATLAB's search path, or is shadowed by another file with the same name.

Error in testApp/startupFcn (line 18)

Error in appdesigner.internal.service.AppManagementService/tryCallback (line 371)

Error in appdesigner.internal.service.AppManagementService/runStartupFcn (line 153)

Error in matlab.apps.AppBase/runStartupFcn (line 43)

Error in testApp (line 61)

MATLAB:class:InvalidSuperClass

Answer 1

[Jakub Devera]

I have found a workaround for following error:

The specified superclass 'appdesigner.internal.appalert.AppAlertController' contains a parse error, cannot be found on MATLAB's search path, or is shadowed by another file with the same name.

I have just coppied AppAlertController.m to +appdesigner/+internal/+appalert in my application folder (the file cannot be linked directly since it is in a root folder) and added it as a dependency. I don't particularly like this workaround to shadow Matlab root files, but at least the functionality is working. If error occurs, user is notified by msgbox. If you will have any other tip for similar functionality, please contribute.

[dpb]

This functionality should be automagically available in compiled apps -- as is, one either has to wrap every non-trivial code line in a try...catch block or there's absolutely no way to have a klew if an error does crop up.

At least this way the end user can report the bug and you've got at least a shot of trying to find/fix it...

[R Hermans]

Update (using Matlab 2023a).

I tried to use the code from Jakub (1-apr-2022), with the Accepted answer but this failed for me.

Unfortunately i got an error (maybe something has changed in the matlab internals) between versions?

The problem is that the CallbackErrored event, is not a known event for the class AppManagementService.

I changed the code to use the CallbackErrorHandler instance (instead of AppManagement).

The code works from the matlab IDE, but not when deployed.

Unfortunately then i got the error

'Warning: In "C:\MY_PROJECT\600-PC-Software\644-AA-(sources)\Code\+appdesigner\+internal\+service\AppManagementService.m", "mlapp.internal.MLAPPMetadataReader" are excluded from packaging for the MATLAB Runtime environment according to the MATLAB Compiler license.'

The problem is in the usage of mlapp.internal.MLAPMetadataReader

Does anyone has a clue to solve this?

Regards René

classdef AppAlertErrorHandler < appdesigner.internal.appalert.AppAlertController

% AppAlertErrorHandler is a class which subscribes to event CallBackErrored so that an exception during

% callback can be logged.

%TODO1: this module doesnot work when deployed!! (it works perfect from matlab IDE).

% when creating the deployable below warning is generated:

% Warning: In "C:\MY_PROJECT\600-PC-Software\644-AA-(sources)\Code\+appdesigner\+internal\+service\AppManagementService.m", "mlapp.internal.MLAPPMetadataReader" are excluded from packaging for the MATLAB Runtime environment according to the MATLAB Compiler license.

%

properties (Access = public)

previousExceptionClass;

ExceptionCount int32 = 0;

logger; % reference to logger instance.

end

methods

function obj = AppAlertErrorHandler(logger)

%CONSTRUCTOR

obj.logger = logger;

obj.logger.info('AppAlertErrorHandler enter constructor');

callbackErrorHandler = appdesigner.internal.apprun.CallbackErrorHandler.instance();

if isempty(obj.CallbackErroredListener)

obj.CallbackErroredListener = addlistener(callbackErrorHandler, 'CallbackErrored', @obj.logUnhandledException);

end

obj.logger.info('AppAlertErrorHandler exit constructor');

end

end

methods(Access = protected)

function doSendErrorAlertToClient(obj, appException) %#ok<INUSD>

% Empty implementation of superclass abstract method

end

end

methods(Access = private)

function logUnhandledException(obj, event, source) %#ok<INUSD>

%logUnhandledException logs the exception to the logger.

obj.ExceptionCount = obj.ExceptionCount + 1;

currentException = source.Exception;

stackString = getReport(currentException, 'extended', 'hyperlinks', 'off');

fprintf('Unhandled exception;;Message: %s', stackString);

%Note: when invoking a msgbox at this place, strange things happen: then this handler is more times invoked for

% unknown reason.

end

end

end

[Jakub Devera]

My provided solution sadly stopped working in Matlab2022b. I had the same problem as you, it worked in AppDesigner IDE but not when compiled. The functionality was depending on a callback that reported the error to the IDE and Mathworks is removing this callback for compiled environment. I guess there is no general solution now.