Error handling in Application.onException and Application.onError when raising exception

WEB TMS WEB Core
1

Hi

I atached simple program to show the problem.
raiseerror.zip (2.2 MB)

  1. I set my own procedures for Application.OnError and Application.OnException like below:
procedure TForm1.WebFormCreate(Sender: TObject);
begin
  Application.OnError := AppError;
  Application.OnException := AppException;
end;
  1. The procedures are simple:
procedure TForm1.AppException(Sender: TObject; Error: Exception);
begin
  console.log('From Application.OnException: '+Error.Message);
  console.log('Object from Application.OnException');
  console.log(Error);
end;

procedure TForm1.AppError(Sender: TObject; AError: TApplicationError; var Handled:Boolean);
begin
  Handled:=True;
  console.log('From Application.OnError: '+AError.AMessage);
  console.log('Object from Application.OnError');
  console.log(AError);
end;
  1. On button click I raise an exception.
procedure TForm1.wbtn1Click(Sender: TObject);
begin
  raise Exception.Create('Error from raise');
end;

I don't unerstand how it works or should be.

case1:
When I raised exception I see in console:

image
image1507×387 66 KB

Why message from Application.OnError is Uncaught [object Object]?
Message from Application.OnException is OK.

case2:
I commented Application.OnException:

procedure TForm1.WebFormCreate(Sender: TObject);
begin
  Application.OnError := AppError;
  //Application.OnException := AppException;
end;

When I raised exception I see in console:

image
image1474×229 40.2 KB

Why did i get it again Uncaught [object Object]?
Is it bug or feature?

2

OnException is specific to Object Pascal code exceptions.
OnError catches everything, also underlying JavaScript related error. It doesn't do deeper checks on the error type.

3

then ... if OnError catches everything (Pascal and JS exceptions) why when I raise Exception.Create('Error from raise') I get an exception object with AMessage Uncaught [object Object] but not Error from raise ?

The console.log(AError.AMessage) in procedure AppError is Uncaught [object Object] not Error from raise

procedure source below:

procedure TForm1.AppError(Sender: TObject; AError: TApplicationError; var Handled:Boolean);
begin
  Handled:=True;
  console.log(AError.AMessage);
end;
4

We'll check this with the pas2js team as this is really transpiler related.

5

Ok ... thank you ... I think that this is transpiler releated too, but maybe good idea will be ask pas2js team by the way additionally about await version.

For example:

procedure TForm1.wbtn3Click(Sender: TObject);
begin
  await(aaa);
end;

procedure TForm1.aaa;
begin
  //JS Exception
  console.log(document.getElementById('aaa').id);
  //Pascal raise Exception
  raise Exception.Create('Error Message from await');
end;

Never mind if inside async procedure I raise error via

raise Exception.Create('Error Message from await');

or js error

console.log(document.getElementById('aaa').id);

The Application.OnError procedure and console.log(AError.AMessage) return Undefined Javascript Exception which is wrong too.

Should be for JS Exception "Cannot read properties of null (reading 'id')" and for Pascal Exception "Error Message from await"

Thank you for wanting to address this as the use Application.OnError (single point for app error handling) doesn't make sense at the moment.

6

Hi @brunofierens , any news from pas2js Team concerning this issue?

7

No conclusion/result yet.

8

Hi,

I see some new info in release 2.6.1.1.

image

It means that the problem was solved? Can you add here some detailed information?

9

The event object for an error raised from a promise was not properly parsed and this was fixed in v2.6.1.1

1 Like
10

I am getting the same issue in the current version.

I am using Application.OnException

If I bracket the code with try except, I catch the exception.

If I remove the try except, it doesn't go to the Handler.

11

I retested with:

procedure TForm1.aaa;
begin
  //JS Exception
  console.log(document.getElementById('aaa').id);
  //Pascal raise Exception
  raise Exception.Create('Error Message from await');
end;

procedure TForm1.ExceptionHandler(Sender: TObject; E: Exception);
begin
  console.log('exception handler');
end;

procedure TForm1.WebButton1Click(Sender: TObject);
begin
  await(aaa);
end;

procedure TForm1.WebFormCreate(Sender: TObject);
begin
  application.OnException := ExceptionHandler;
end;

and Application.OnException is triggered