Load locales from I18n.available_locales

Also uses a Railtie to load i18n files instead of the engine (I was
having some trouble with the Engine loading the files at all with Rails
4.2.x).

Pulls code from [devise-i18n](https://github.com/tigrish/devise-i18n).

[closes #8]

Gemfile.lock

@@ -6,12 +6,56 @@ PATH
 GEM
   remote: http://rubygems.org/
   specs:
+    actionpack (4.2.5)
+      actionview (= 4.2.5)
+      activesupport (= 4.2.5)
+      rack (~> 1.6)
+      rack-test (~> 0.6.2)
+      rails-dom-testing (~> 1.0, >= 1.0.5)
+      rails-html-sanitizer (~> 1.0, >= 1.0.2)
+    actionview (4.2.5)
+      activesupport (= 4.2.5)
+      builder (~> 3.1)
+      erubis (~> 2.7.0)
+      rails-dom-testing (~> 1.0, >= 1.0.5)
+      rails-html-sanitizer (~> 1.0, >= 1.0.2)
+    activesupport (4.2.5)
+      i18n (~> 0.7)
+      json (~> 1.7, >= 1.7.7)
+      minitest (~> 5.1)
+      thread_safe (~> 0.3, >= 0.3.4)
+      tzinfo (~> 1.1)
+    builder (3.2.2)
     diff-lcs (1.2.5)
+    erubis (2.7.0)
     i18n (0.7.0)
     i18n-spec (0.6.0)
       iso
     iso (0.2.1)
       i18n
+    json (1.8.3)
+    loofah (2.0.3)
+      nokogiri (>= 1.5.9)
+    mini_portile (0.6.2)
+    minitest (5.8.3)
+    nokogiri (1.6.6.4)
+      mini_portile (~> 0.6.0)
+    rack (1.6.4)
+    rack-test (0.6.3)
+      rack (>= 1.0)
+    rails-deprecated_sanitizer (1.0.3)
+      activesupport (>= 4.2.0.alpha)
+    rails-dom-testing (1.0.7)
+      activesupport (>= 4.2.0.beta, < 5.0)
+      nokogiri (~> 1.6.0)
+      rails-deprecated_sanitizer (>= 1.0.1)
+    rails-html-sanitizer (1.0.2)
+      loofah (~> 2.0)
+    railties (4.2.5)
+      actionpack (= 4.2.5)
+      activesupport (= 4.2.5)
+      rake (>= 0.8.7)
+      thor (>= 0.18.1, < 2.0)
     rake (10.4.2)
     rspec (3.2.0)
       rspec-core (~> 3.2.0)
@@ -26,12 +70,20 @@ GEM
       diff-lcs (>= 1.2.0, < 2.0)
       rspec-support (~> 3.2.0)
     rspec-support (3.2.2)
+    thor (0.19.1)
+    thread_safe (0.3.5)
+    tzinfo (1.2.2)
+      thread_safe (~> 0.1)
 
 PLATFORMS
   ruby
 
 DEPENDENCIES
   doorkeeper-i18n!
   i18n-spec (~> 0.6.0)
+  railties
   rake
   rspec
+
+BUNDLED WITH
+   1.10.6

doorkeeper-i18n.gemspec

@@ -17,4 +17,5 @@ Gem::Specification.new do |s|
   s.add_development_dependency "rake"
   s.add_development_dependency "rspec"
   s.add_development_dependency "i18n-spec", "~> 0.6.0"
+  s.add_development_dependency "railties", ">= 0"
 end

lib/doorkeeper-i18n.rb

@@ -1,4 +1 @@
-module DoorkeeperI18n
-  class Engine < ::Rails::Engine
-  end
-end
+require 'doorkeeper-i18n/railtie' if defined?(Rails)

lib/doorkeeper-i18n/railtie.rb

@@ -0,0 +1,26 @@
+require 'rails'
+
+module DoorkeeperI18n
+  class Railtie < ::Rails::Railtie #:nodoc:
+    initializer 'doorkeeper-i18n' do |app|
+      DoorkeeperI18n::Railtie.instance_eval do
+        pattern = pattern_from app.config.i18n.available_locales
+
+        add("rails/locales/#{pattern}.yml")
+      end
+    end
+
+    protected
+
+    def self.add(pattern)
+      files = Dir[File.join(File.dirname(__FILE__), '../..', pattern)]
+
+      I18n.load_path.concat(files)
+    end
+
+    def self.pattern_from(args)
+      array = Array(args || [])
+      array.blank? ? '*' : "{#{array.join ','}}"
+    end
+  end
+end

spec/doorkeeper-i18n_spec.rb

@@ -1,8 +1,8 @@
 require File.expand_path(File.dirname(__FILE__) + '/spec_helper')
 
-Dir.glob('config/locales/*.yml').each do |locale_file|
+Dir.glob('rails/locales/*.yml').each do |locale_file|
   describe "a doorkeeper-i18n #{locale_file} locale file" do
     it_behaves_like 'a valid locale file', locale_file
-    it { expect(locale_file).to be_a_subset_of 'config/locales/en.yml' }
+    it { expect(locale_file).to be_a_subset_of 'rails/locales/en.yml' }
   end
 end

spec/locale_loading_spec.rb

@@ -0,0 +1,68 @@
+# encoding: utf-8
+require File.expand_path(File.dirname(__FILE__) + '/spec_helper')
+
+describe 'Locale loading' do
+  let(:app) do
+    DoorkeeperI18n::Spec::FakeApp
+  end
+
+  let(:translate_stuff) do
+    lambda do
+      <<-EOS.gsub(/^  */, '')
+        In French: #{I18n.t('doorkeeper.layouts.admin.nav.oauth2_provider', locale: :fr)}
+        In Italian: #{I18n.t('doorkeeper.layouts.admin.nav.oauth2_provider', locale: :it)}
+        In Japanese: #{I18n.t('doorkeeper.layouts.admin.nav.oauth2_provider', locale: :ja)}
+      EOS
+    end
+  end
+
+  context 'when i18n.available_locales are specified in config' do
+    let(:translations) do
+      app.run(translate_stuff) do |config|
+        config.i18n.available_locales = [:fr, :it]
+      end
+    end
+
+    it 'loads only specified locales' do
+      expected_translations = <<-EOS.gsub(/^  */, '')
+        In French: Fournisseur OAuth2
+        In Italian: OAuth2 Provider
+        In Japanese: translation missing: ja.doorkeeper.layouts.admin.nav.oauth2_provider
+      EOS
+
+      expect(translations).to eq(expected_translations)
+    end
+  end
+
+  context 'when single locale is assigned to i18n.available_locales' do
+    let(:translations) do
+      app.run(translate_stuff) do |config|
+        config.i18n.available_locales = 'fr'
+      end
+    end
+
+    it 'loads only this locale' do
+      expected_translations = <<-EOS.gsub(/^  */, '')
+        In French: Fournisseur OAuth2
+        In Italian: translation missing: it.doorkeeper.layouts.admin.nav.oauth2_provider
+        In Japanese: translation missing: ja.doorkeeper.layouts.admin.nav.oauth2_provider
+      EOS
+
+      expect(translations).to eq(expected_translations)
+    end
+  end
+
+  context 'when i18n.available_locales is not set' do
+    let(:translations) { app.run(translate_stuff) }
+
+    it 'loads all locales' do
+      expected_translations = <<-EOS.gsub(/^  */, '')
+        In French: Fournisseur OAuth2
+        In Italian: OAuth2 Provider
+        In Japanese: OAuth2 プロバイダー
+      EOS
+
+      expect(translations).to eq(expected_translations)
+    end
+  end
+end

spec/spec_helper.rb

@@ -3,3 +3,5 @@
 
 require "rspec"
 require "i18n-spec"
+
+Dir["#{File.dirname(__FILE__)}/support/**/*.rb"].each {|f| require f}

spec/support/fake_app.rb

@@ -0,0 +1,45 @@
+module DoorkeeperI18n
+  module Spec
+    module FakeApp
+      #
+      # Starts a new Rails app and runs the given config block before
+      # initializing it
+      #
+      def self.start
+        require 'action_controller/railtie'
+        require 'doorkeeper-i18n'
+
+        app = Class.new(Rails::Application)
+        app.config.eager_load = false
+        app.config.i18n.enforce_available_locales = false
+
+        yield(app.config) if block_given?
+
+        app.initialize!
+      end
+
+      #
+      # Initialize Rails app in a clean environment.
+      #
+      # @param test [Proc] which have to be run after app is initialized
+      # @return [String] Result of calling +test+ after app was initialized
+      #
+      def self.run(test, &block)
+        r, w = IO.pipe
+
+        pid = fork do
+          r.close
+
+          start(&block)
+
+          w.write(test.call)
+        end
+
+        w.close
+        result = r.read
+        Process.wait(pid)
+        result
+      end
+    end
+  end
+end