From: Rob Sanheim <rsanheim@...>
Date: 2006-08-05T17:58:04+09:00
Subject: why can't I catch this exception?

(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

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

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
-- 
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