(PR created) Allow attachments to be bound to exception more easily

[fzyzcjy]

Why I need this (very much!)

My code is like:

void main_function() {
  try {
    inner_function(); // indeed, functions calling functions calling functions... so the calling stack is deep
  } catch (e,s) {
    Sentry.captureException(e, s);
  }
}

void inner_function() {
  var my_data = ...;
  try {
    do_some_work_that_can_throw_exception(my_data);
  } catch (e,s) {
     Sentry.pleaseBindAttachmentToException(e, my_data); // <-- !!
     rethrow;
  }
}

Notice the Sentry.pleaseBindAttachmentToException, where I want to bind attachment to exception.

However, as we know, we cannot do it. I can create some code to bind extra to exception, because extra can be modified in EventProcessors (so I can manually create a static map holding some extras and bind to exception in my own EventProcessor). However, EventProcessors cannot modify or add attachments. So I have no way to do it :(

Proposed solution

Say, add a field to SentryOptions, e.g. void Function(Scope)? withScopeWhenCapture. Then, in Hub.captureException and similar places, call that callback. This is very simple and I will implement it if you like.

related: #646

Hi @marandaneto could you please have a look (since this thread is strongly related to #646)? Thanks! And @ueman could you please also have a look? Thanks!

[fzyzcjy]

Hi @marandaneto @ueman could you please suggest whether this is acceptable? If so I will make a PR. This is a blocking issue on our app...

[ueman]

If I'm not mistaken you can already do something like this:

Sentry.captureException(exception: ex, withScope:(scope) {
    scope.addAttachment(attachment);
});

I'm not sure if that already works, but you might try that. If not @marandaneto probably appreciates a PR which enable scoped attachments. I'm not a maintainer of this SDK anymore.

Currently is also Christmas season, so most people are probably out of office.

[fzyzcjy]

@ueman No I cannot do that...Notice that I captureException in a outer function, while I addAttachment in a inner function. For example, outer_function() calls func1() which calls func2() which calls func3(), ..., which calls func100() which calls inner_function().

Currently is also Christmas season, so most people are probably out of office.

Ah I did not realized that (I have been doing my project for 2 years without using holidays ;) ). Sorry for disturbing.

[ueman]

Oh I see. In that case the solution would probably be similar to .NETs local scopes. Dart hasn't gotten support for that yet but that would probably the solution for your problem.

[fzyzcjy]

@ueman Well that is a bit the inverse. In my case I want to bind attachment in inner function and capture exception in outer. With the proposed modification, that can be implemented trivially.

[ueman]

Yeah, with mine, too. The code would be something like this:

void main_function() {
Sentry.withScope((scope) {
// within this scope, the attachment is added to the capture exception
  try {
    inner_function(); // indeed, functions calling functions calling functions... so the calling stack is deep
  } catch (e,s) {
    Sentry.captureException(e, s);
  }
}
// here the attachment isn't added to the exception anymore
Sentry.captureException(ex); // this exception has no attachment
}

void inner_function() {
  var my_data = ...;
  try {
    do_some_work_that_can_throw_exception(my_data);
  } catch (e,s) {
     Sentry.addAttachment(my_data);
     rethrow;
  }
}

[fzyzcjy]

Agree. Since that is a bit complex (read: can introduce bugs), I will firstly implement a simpler solution

[fzyzcjy]

PR made: #683

[marandaneto]

I'm on vacay, maybe @bruno-garcia can help

[fzyzcjy]

@marandaneto No problem, I can wait for it