[This is one of several posts on upgrading a Ruby on Rails app from Rails 1.x to 2.2.2.]

Rails 2.x added some nice support for internationalization. I’m using this to “Canadianize” the UI of my app by translating a few words from the EN-US locale to EN-CA. “Favorite” becomes “favourite”, “huh?” becomes “eh?”, “Coors Light” becomes “water”, and so on.

One gotcha I ran into is that translation errors don’t manifest themselves as exceptions. The default I18n implementation rescues translation errors and returns the failed translation keys as a string. This behavior is nice in the development environment, because you can see the strings showing up in your application’s UI. On the other hand it makes testing dangerous, because translation errors can easily go unnoticed, especially when running automated tests.

I prefer my tests to fail noisily. (Hmm… perhaps this should be the default behavior?) To that end, here’s a patch, also available on Pastie.

# The code below patches I18n to raise exceptions for all errors, including translation errors.
# The default (unpatched) behavior in Rails 2.2.2 rescues translation errors and returns the failed 
# translation keys as a string. This behavior is undesirable in test, because it makes it too
# easy for translation errors to go unnoticed when running automated tests. Instead, we want to fail noisily.
#
# == Usage
# (within test_helper)
# require File.dirname(__FILE__) + '/i18n_patch'      

# Patch translation within views

module ActionView
  module Helpers
    module TranslationHelper
      def translate(key, options = {})
        options[:raise] = true
        I18n.translate(key, options)
      rescue I18n::MissingTranslationData => e
        raise e if RAILS_ENV == 'test'  # <<< this line is the patch. everything else in this method is original.
        keys = I18n.send(:normalize_translation_keys, e.locale, e.key, e.options[:scope])
        content_tag('span', keys.join(', '), :class => 'translation_missing')
      end
      alias :t :translate

      def localize(*args)
        I18n.localize *args
      end
      alias :l :localize
    end
  end
end

# Patch translation in models and controllers
module I18n
  class << self
    def raise_all_exceptions(*args)
      raise args.first
    end
  end
end

I18n.exception_handler = :raise_all_exceptions