jquery_include_tag helper

Implement the jquery_include_tag helper, which is used in several
views but was not implemented in the code. This helper attempts to
load jQuery from the Google CDN (matching the version of the vendored
jquery.js in jquery-rails), falling back to the vendored copy if the
google CDN fails. The helper also loads jquery_ujs.js from jquery-rails.

A jquery_cdn setting is added to application.yml to enable or disable
serving jQuery from the Google CDN (for those podmins who would rather
not use Google's services).

Update app/views/application.html.haml to use the jquery_include_tag
helper since it was the only view that was including the vendored
copy of jquery directly with jquery_include_tag.

app/helpers/application_helper.rb

@@ -35,4 +35,19 @@ module ApplicationHelper
   def diaspora_id_host
     User.diaspora_id_host
   end
+
+  # Require jQuery from CDN if possible, falling back to vendored copy, and require
+  # vendored jquery_ujs
+  def jquery_include_tag
+    buf = []
+    if AppConfig[:jquery_cdn]
+      version = Jquery::Rails::JQUERY_VERSION
+      buf << [ javascript_include_tag("//ajax.googleapis.com/ajax/libs/jquery/#{version}/jquery.min.js") ]
+      buf << [ javascript_tag("!window.jQuery && document.write(unescape('#{j javascript_include_tag("jquery")}'));") ]
+    else
+      buf << [ javascript_include_tag('jquery') ]
+    end
+    buf << [ javascript_include_tag('jquery_ujs') ]
+    buf.join("\n").html_safe
+  end
 end

app/views/layouts/application.html.haml

@@ -29,7 +29,7 @@
     = javascript_include_tag :ie
     <![endif]-->
 
-    = javascript_include_tag 'jquery', 'jquery_ujs'
+    = jquery_include_tag
 
     - unless @landing_page
       = javascript_include_tag :main, :templates

config/application.yml.example

@@ -39,6 +39,9 @@ defaults: &defaults
   # let your reverse proxy/webserver do it.
   serve_static_assets: false
 
+  # Serve jQuery from Google's CDN
+  jquery_cdn: true
+
   #
   # Settings
   #

spec/helpers/application_helper_spec.rb

@@ -48,4 +48,35 @@ describe ApplicationHelper do
       all_services_connected?.should be_false
     end
   end
+
+  describe "#jquery_include_tag" do
+    describe "with google cdn" do
+      before do
+        AppConfig[:jquery_cdn] = true
+      end
+
+      it 'inclues jquery.js from google cdn' do
+        jquery_include_tag.should match(/googleapis\.com/)
+      end
+
+      it 'falls back to asset pipeline on cdn failure' do
+        jquery_include_tag.should match(/document\.write/)
+      end
+    end
+
+    describe "without google cdn" do
+      before do
+        AppConfig[:jquery_cdn] = false
+      end
+
+      it 'includes jquery.js from asset pipeline' do
+        jquery_include_tag.should match(/jquery\.js/)
+        jquery_include_tag.should_not match(/googleapis\.com/)
+      end
+    end
+
+    it 'inclues jquery_ujs.js' do
+      jquery_include_tag.should match(/jquery_ujs\.js/)
+    end
+  end
 end