rails--rails/actionpack/lib/action_view/helpers/translation_helper.rb

require 'action_view/helpers/tag_helper'

module ActionView
  # = Action View Translation Helpers
  module Helpers
    module TranslationHelper
      # Delegates to I18n#translate but also performs three additional functions.
      # First, it'll catch MissingTranslationData exceptions and turn them into
      # inline spans that contains the missing key, such that you can see in a
      # view what is missing where.
      #
      # Second, it'll scope the key by the current partial if the key starts
      # with a period. So if you call <tt>translate(".foo")</tt> from the
      # <tt>people/index.html.erb</tt> template, you'll actually be calling
      # <tt>I18n.translate("people.index.foo")</tt>. This makes it less repetitive
      # to translate many keys within the same partials and gives you a simple framework
      # for scoping them consistently. If you don't prepend the key with a period,
      # nothing is converted.
      #
      # Third, it'll mark the translation as safe HTML if the key has the suffix
      # "_html" or the last element of the key is the word "html". For example,
      # calling translate("footer_html") or translate("footer.html") will return
      # a safe HTML string that won't be escaped by other HTML helper methods. This
      # naming convention helps to identify translations that include HTML tags so that
      # you know what kind of output to expect when you call translate in a template.
      def translate(key, options = {})
        translation = I18n.translate(scope_key_by_partial(key), options.merge!(:raise => true))
        if html_safe_translation_key?(key) && translation.respond_to?(:html_safe)
          translation.html_safe
        else
          translation
        end
      rescue I18n::MissingTranslationData => e
        keys = I18n.normalize_keys(e.locale, e.key, e.options[:scope])
        content_tag('span', keys.join(', '), :class => 'translation_missing')
      end
      alias :t :translate

      # Delegates to I18n.localize with no additional functionality.
      def localize(*args)
        I18n.localize(*args)
      end
      alias :l :localize

      private
        def scope_key_by_partial(key)
          if key.to_s.first == "."
            if (path = @_template && @_template.virtual_path)
              path.gsub(%r{/_?}, ".") + key.to_s
            else
              raise "Cannot use t(#{key.inspect}) shortcut because path is not available"
            end
          else
            key
          end
        end

        def html_safe_translation_key?(key)
          key.to_s =~ /(\b|_|\.)html$/
        end
    end
  end
end