# Why can't I catch this exception? **URL:** \ **Category:** Ruby\ **Created:** [August 5, 2006, 10:59am UTC](https://www.ruby-forum.com/t/why-cant-i-catch-this-exception/101496 "2006-08-05T10:59:55Z")\ **Posts on this page:** 5\ **Page:** 1
**Author:** ![rsanheim](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/47e85d/32.png) [@rsanheim](https://www.ruby-forum.com/u/rsanheim)\ **Post date:** [August 5, 2006, 10:59am UTC](https://www.ruby-forum.com/t/why-cant-i-catch-this-exception/101496/1 "2006-08-05T10:59:55Z")
(this is in the context of Rails, buts its primarily a Ruby question dealing with exception handling) This is driving me nuts - I’m tracking down a bug in ActionPack that causes rails to do a 500 error with no info, or when testing causes an immediate exit with no information or stack trace. I’ve tracked it down to ActionView::TemplateError, where numerous things can happen that cause an exception to be thrown from w/o the TemplateError. For instance, the following controller will cause the error to happen: class FooController \< ApplicationController def bad\_file\_with\_full\_path\_false render :file =\> “unknown”, :use\_full\_path =\> false end end And I cannot get the exception to be caught in a test case, no matter what I do. For example, w/i a standard FooControllerTest: def test\_bad\_file\_render\_with\_full\_path\_false assert\_raises ActionController::MissingTemplate do get :bad\_file\_with\_full\_path\_false end rescue Exception =\> e flunk(“failed”) end This just exits - no flunk msg, assert\_raise doesn’t catch, nothing. I also commented out an “ensure” in ActionController::Base#process, to make sure that wouldn’t halt the exception. It still exits. I tracked it down into TemplateError via a lot of tedious logging, and it seems the line here throws an error (though I cant figure out why, it works in irb): [http://dev.rubyonrails.org/browser/trunk/actionpack/lib/action\_view/template\_error.rb#L79](http://dev.rubyonrails.org/browser/trunk/actionpack/lib/action_view/template_error.rb#L79) and this line can also throw an exception, which makes sense because @file\_name refers to a non-existent file: [http://dev.rubyonrails.org/browser/trunk/actionpack/lib/action\_view/template\_error.rb#L29](http://dev.rubyonrails.org/browser/trunk/actionpack/lib/action_view/template_error.rb#L29) And of course none of that answers why I can’t rescue the exception back in my calling code, no matter what I do. Any ideas? - thanks, - Rob ---
**Author:** ![rsanheim](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/47e85d/32.png) [@rsanheim](https://www.ruby-forum.com/u/rsanheim)\ **Post date:** [August 5, 2006, 6:06pm UTC](https://www.ruby-forum.com/t/why-cant-i-catch-this-exception/101496/2 "2006-08-05T18:06:18Z")
On 8/5/06, Rob S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > This just exits - no flunk msg, assert\_raise doesn’t catch, nothing. If it _is_ raising the exception, you won’t reach that rescue – #assert\_raises rescues the exception internally. Perhaps you meant to use #assert\_nothing\_raised ? – Regards, John W. > **[John Wilger](http://johnwilger.com)** > > The personal website of John Wilger; Dad, Cyclist, Software Developer ---
**Author:** ![rsanheim](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/47e85d/32.png) [@rsanheim](https://www.ruby-forum.com/u/rsanheim)\ **Post date:** [August 5, 2006, 9:30pm UTC](https://www.ruby-forum.com/t/why-cant-i-catch-this-exception/101496/3 "2006-08-05T21:30:31Z")
On 8/5/06, John W. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > > end > > > > This just exits - no flunk msg, assert\_raise doesn’t catch, nothing. > > If it _is_ raising the exception, you won’t reach that rescue – > #assert\_raises rescues the exception internally. Perhaps you meant to > use #assert\_nothing\_raised ? > > – > Regards, > John W. John, I realize assert\_raises _should_ rescue it, but then it should either pass or fail based on the class of the exception. My main issue is that the program just exits, with out success or failure for that test class. So its basically as if it was calling exit (which its not). Doing this will also show the same behavior: def test\_bad\_file\_render\_with\_full\_path\_false get :bad\_file\_with\_full\_path\_false end So my question is, what is happening inside TemplateError that it causes the whole process to do a hard exit? - Rob ---
**Author:** ![rsanheim](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/47e85d/32.png) [@rsanheim](https://www.ruby-forum.com/u/rsanheim)\ **Post date:** [August 5, 2006, 10:12pm UTC](https://www.ruby-forum.com/t/why-cant-i-catch-this-exception/101496/4 "2006-08-05T22:12:34Z")
On 8/5/06, Rob S. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > I realize assert\_raises _should_ rescue it, but then it should either > pass or fail based on the class of the exception. My main issue is > that the program just exits, with out success or failure for that test > class. So its basically as if it was calling exit (which its not). Ah, OK. I misunderstood and simply thought that you had a test that was passing when you expected it to fail. I tried out your example on my OSX system (ruby 1.8.4, compiled form src). I had the same result both with the latest release of Rails and after freezing to edge Rails. Not much help, I know – but it’s not just you, FWIW. – Regards, John W. > **[John Wilger](http://johnwilger.com)** > > The personal website of John Wilger; Dad, Cyclist, Software Developer ---
**Author:** ![rsanheim](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/47e85d/32.png) [@rsanheim](https://www.ruby-forum.com/u/rsanheim)\ **Post date:** [August 5, 2006, 10:18pm UTC](https://www.ruby-forum.com/t/why-cant-i-catch-this-exception/101496/5 "2006-08-05T22:18:35Z")
On 8/5/06, John W. [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) wrote: > src). I had the same result both with the latest release of Rails and > after freezing to edge Rails. Not much help, I know – but it’s not > just you, FWIW. Thanks for confirming that I’m not going crazy =). I understand that it should error out for a bad file (which I’m going to submit a patch for), but I don’t understand what kind of error would cause it to just crash like that w/o a “rescuable” exception. - rob