async_emails_i18n.rb

require 'resque_mailer'
require 'devise/async'

# pop and set locale from the args before running
module PerformWithLocale
  def perform(*args)
    I18n.with_locale(args.pop) do
      super(*args)
    end
  end
end

module DeliverWithLocale
  def deliver
    # @args are not used when rendered inline, only when enqueueing
    @args << I18n.locale.to_s
    super
  end
end

#= resque_mailer locale support
if defined?(Resque::Mailer)
  module Resque::Mailer
    # push locale onto the args when queueing
    MessageDecoy.send :prepend, DeliverWithLocale
    # pop when dequeueing
    ClassMethods.send :prepend, PerformWithLocale
  end
end

#= devise/async locale support
if defined?(Devise::Async)
  module Devise::Async
    module EnqueueWithLocale
      def enqueue(*args)
        super *(args + [I18n.locale])
      end
    end
    class Worker
      class << self
        prepend Devise::Async::EnqueueWithLocale
      end
    end
    class Backend::Resque
      class << self
        prepend PerformWithLocale
      end
    end
  end
end