This Rails module takes locales into account when rendering a link to the current path. It takes into consideration all parameters. This is useful when you want a user to be able to switch languages and you want the user to stay on the same URL. When passing the default locale, it will be stripped off. For other details, take a look at the spec.

path_helper.rb

module PathHelper

  class LocaleUtil
    def delocalize_url(url)
      result = url.sub(/^\/(?:#{locales_in_correct_order.join('|')})/, '')
      [result, '/'].reject(&:blank?).first
    end

    def locales_in_correct_order
      I18n.available_locales.map(&:to_s).sort_by(&:length).reverse
    end

  end

  def current_path(options={})
    locale = options[:locale]
    r = request.env['ORIGINAL_FULLPATH']
    r = LocaleUtil.new.delocalize_url(r)

    if locale.blank? || locale == I18n.default_locale
      r
    else
      "/#{locale}#{r}"
    end
  end

end

path_helper_spec.rb

require "spec_helper"

describe PathHelper do
  include PathHelper

  it "does not add a locale to the URL when not passing any" do
    @path = "/gigs"

    I18n.available_locales.each do |locale|
      I18n.default_locale = locale
      current_path.should eq @path
    end
  end

  it "returns a URL based on the given locale" do
    @path = "/gigs"

    I18n.available_locales.each do |locale|
      I18n.default_locale = I18n.available_locales.reject{|l| l == locale}.sample
      current_path(locale: locale).should eq "/#{locale}#{@path}"
    end
  end

  it "should blank the locale when passed locale is same as default" do
    @path = "/gigs"

    I18n.default_locale = :nl
    current_path(locale: :nl).should eq @path
  end

  it "returns a localized URL and strip off a previous locale" do
    locales = I18n.available_locales
    locales_without_default = locales.reject{|l| l == I18n.default_locale}

    locales.each do |current_locale|
      locales_without_default.each do |locale|
        @path = "/#{current_locale}/gigs"
        current_path(locale: locale).should eq("/#{locale}/gigs")
      end
    end
  end

  it "delocalizes URLs" do
    locale_util = PathHelper::LocaleUtil.new
    locale_util.delocalize_url("/").should eq "/"
    locale_util.delocalize_url("/gigs").should eq "/gigs"

    I18n.available_locales.each do |locale|
      locale_util.delocalize_url("/#{locale}/gigs").should eq "/gigs"
      locale_util.delocalize_url("/#{locale}/").should eq "/"
      locale_util.delocalize_url("/#{locale}").should eq "/"
    end
  end

  def request
    stub(env: {'ORIGINAL_FULLPATH' => @path})
  end

end