Exceptions thrown in the formatter should be catchable by `rescue_from :all`

[lucaspiller]

I added a basic error handler using rescue_from :all that logs exceptions, notifies Airbrake and returns a basic 500 response. Unfortunately this doesn't work as described in the documentation, and this isn't called for all exceptions.

We had an issue with a decorator not being found, and so the formatter (we are using Rabl) was throwing an exception. This was caught here, and thrown again:

lib/grape/middleware/formatter.rb

This was caught in the error middleware and passed directly to error_response with no options for logging or changing it (other than by hacking around with error_formatter):

lib/grape/middleware/error.rb

In the end I changed the error middleware to raise an exception for this exception (...) which isn't great, but it allows me to return consistent errors when something goes wrong. It would be great if rescue_from :all worked as described, and allowed you to rescue from all exceptions 😄

[dblock]

I think it's a real problem. Would be amazing if you could write a test that reproduces this, to start.

[kbarrette]

I've just run afoul of this as well - I have a entity that was exposing a method that raised an exception, and rather than generating a backtrace in the logs, etc, Grape was just swallowing the exception here https://github.com/intridea/grape/blob/master/lib/grape/middleware/formatter.rb#L31 and returning an error response via https://github.com/intridea/grape/blob/master/lib/grape/middleware/error.rb#L25

It seems wrong to have the formatter middleware blindly rescue all exceptions. Looks like this was part of the fix for #309 - how about having the XML formatter raise a more specific error and catching just that?

[dblock]

This was resolved.