use backtrace_cleaners when using Deprecation#warn

I've attached a patch which does this. I didn't include any tests, because I didn't find any good examples of tests verifying the use of Rails.backtrace_cleaner in other parts of the code base.

I was able to verify its use though:

rails 3015-verification
cd 3015-verification
script/generate scaffold beers
# edit app/controller/beers_controller.rb to use redirect to formatted_beers_url in a few places
script/server
# go to http://localhost:3000/beers then click new, and create
# check server log to see the deprecation notice points at the line the deprecated formated_beers_url was used.

This seems like something that'd be useful in 2-3-stable, so attached a patch that applies cleanly there.

I tried to reproduce the problem on frozen rails release=2.3.3, but couldn't. I followed Josh's steps to verify the patch, before applying the patch, and always got a reference to the correct line in my beers controller.

P.S. When I executed script/generate scaffold beers (plural model name) per Josh's steps, the scaffold generator created a broken app! It warned of a plural model/using singularized, and created a Beer model, but the BeersController referenced a Beers model! Is that a known bug?

The scaffold should probably be the singular 'beer', pardon my much anticipation for some plural beers which were to happen later in the eveing. The issue you are running into seem to be more generator oriented. Use script/generate beer instead.

+1 verified 2-3-stable patch applies cleanly and produces a nice deprecation warning with file and line number:

DEPRECATION WARNING: formatted_beers_url() has been deprecated.
Please pass format to the standard beers_url method instead.

(called from create at /Users/dancroak/dev/3015/app/controllers/beers_controller.rb:48)

For anyone else looking to verify, my steps, including generating a Rails app with the applied patch:

downloaded the 3015-stable patch into a bugmash directory
git apply ~/bugmash/3015-stable-clean_deprecation_callstack.patch
ruby ~/dev/rails/railties/bin/rails 3015
cd 3015
script/generate scaffold beer
rake db:migrate
edit line 48 of app/controllers/beers_controller.rb to include redirect_to(formatted_beers_url)
script/server
created a beer, observed the backtrace in the development log

I've attached a patch that is a test to make sure the "called from #{method} at #{file}:#{line_number}" shows in the deprecation warning, but it passes without Josh's patch.

I did some print debugging without Josh's patch and the warnings all had method/file/line_number information in the deprecation.

Screwed around a bit with mocking the Rails.cleaner. Diff:

http://gist.github.com/164808

But getting an error:

test_assert_deprecation_backtrace_is_cleaned(DeprecationTest):
NoMethodError: You have a nil object when you didn't expect it!
You might have expected an instance of Array.
The error occurred while evaluating nil.first

I'm giving up on an "integration" test with Rails.cleaner.

I'd say Josh's patch is commit-able as-is. My unit test may be useful for regressions but not as proof of this particular patch.