Add bootstrapper.js and requirejs_run_config_json helper

This allows us to cache the runtime configuration instead of duplicating it on every page.
You can also override bootstrapper.js to add other essential resources to be downloaded with require.js
and the configuration.

Bandwidth during the early stages of page loading can be better optimized by loading some scripts synchronously
because the browser can start loading these resources earlier before all images and other scripts start loading.
Because bandwidth isn't saturated early on, stuff like an image lazyloader would be good to load in bootstrapper.js.

app/helpers/requirejs_helper.rb

@@ -23,6 +23,38 @@ def _requirejs_data(name, &block)
     end.join(" ")
   end
 
+  def requirejs_run_config_json(name=nil)
+    requirejs = Rails.application.config.requirejs
+    run_config = requirejs.run_config.dup
+    unless _priority.empty?
+      run_config = run_config.dup
+      run_config[:priority] ||= []
+      run_config[:priority].concat _priority
+    end
+    if Rails.application.config.assets.digest
+      modules = requirejs.build_config['modules'].map { |m| requirejs.module_name_for m }
+
+      # Generate digestified paths from the modules spec
+      paths = {}
+      modules.each { |m| paths[m] = _javascript_path(m).sub /\.js$/,'' }
+
+      if run_config.has_key? 'paths'
+        # Add paths for assets specified by full URL (on a CDN)
+        run_config['paths'].each { |k,v| paths[k] = v if v =~ /^https?:/ }
+      end
+
+      # Override user paths, whose mappings are only relevant in dev mode
+      # and in the build_config.
+      run_config['paths'] = paths
+    end
+
+    run_config['baseUrl'] = base_url(name)
+    # Detect functions in JSON and unescape them so they can be evaluated by RequireJS
+    run_config_json = run_config.to_json.gsub(/"(function\(.*?\)\s*?{.*?}[\s\\n]*)"/) do |f|
+      eval(f).strip.delete("\n")
+    end
+  end
+
   def requirejs_include_tag(name=nil, &block)
     requirejs = Rails.application.config.requirejs
 
@@ -34,42 +66,8 @@ def requirejs_include_tag(name=nil, &block)
     html = ""
 
     _once_guard do
-      unless requirejs.run_config.empty?
-        run_config = requirejs.run_config.dup
-        unless _priority.empty?
-          run_config = run_config.dup
-          run_config[:priority] ||= []
-          run_config[:priority].concat _priority
-        end
-        if Rails.application.config.assets.digest
-          modules = requirejs.build_config['modules'].map { |m| requirejs.module_name_for m }
-
-          # Generate digestified paths from the modules spec
-          paths = {}
-          modules.each { |m| paths[m] = _javascript_path(m).sub /\.js$/,'' }
-
-          if run_config.has_key? 'paths'
-            # Add paths for assets specified by full URL (on a CDN)
-            run_config['paths'].each { |k,v| paths[k] = v if v =~ /^https?:/ }
-          end
-
-          # Override user paths, whose mappings are only relevant in dev mode
-          # and in the build_config.
-          run_config['paths'] = paths
-        end
-
-        run_config['baseUrl'] = base_url(name)
-        # Detect functions in JSON and unescape them so they can be evaluated by RequireJS
-        run_config_json = run_config.to_json.gsub(/"(function\(.*?\)\s*?{.*?}[\s\\n]*)"/) do |f|
-          eval(f).strip.delete("\n")
-        end
-        html.concat <<-HTML
-        <script>var require = #{run_config_json};</script>
-        HTML
-      end
-
       html.concat <<-HTML
-      <script #{_requirejs_data(name, &block)} src="#{_javascript_path 'require.js'}"></script>
+      <script #{_requirejs_data(name, &block)} src="#{_javascript_path 'bootstrapper.js'}"></script>
       HTML
 
       html.html_safe

lib/requirejs/rails/engine.rb

@@ -8,7 +8,7 @@ class Engine < ::Rails::Engine
       ### Configuration setup
       config.before_configuration do |app|
         config.requirejs = Requirejs::Rails::Config.new(app)
-        config.requirejs.precompile = [/require\.js$/]
+        config.requirejs.precompile = [/bootstrapper\.js$/]
         config.requirejs.sprokets_js_compression = false
       end
 

vendor/assets/javascripts/bootstrapper.js.erb

@@ -0,0 +1,4 @@
+/* Copy and override this file to include other essential depenencies with require.js so they get cached
+ *= require requirejs-config
+ *= require require
+ */

vendor/assets/javascripts/requirejs-config.js.erb

@@ -0,0 +1,3 @@
+<%# Allows us to use a helper method from the requirejs-rails gem from within the asset pipeline %>
+<% environment.context_class.instance_eval { include RequirejsHelper } %>
+var require = <%= requirejs_run_config_json %>;