Add locking feature to prevent stale code

README.md

@@ -58,18 +58,13 @@ EmberCLI.configure do |c|
 end
 ```
 
-Once you've updated your initializer to taste, you need to tell EmberCLI that
-you want the meta tag to be served in your javascript. Open up your
-`Brocfile.js` inside your EmberCLI app and add `{storeConfigInMeta: false}`.
+Once you've updated your initializer to taste, you need to install the
+[ember-cli-rails-addon](https://github.com/rondale-sc/ember-cli-rails-addon).
 
-It should look something like this (if you've left it unchanged):
+For each of your EmberCLI applications install the addon with:
 
-```javascript
-var EmberApp = require('ember-cli/lib/broccoli/ember-app');
-
-var app = new EmberApp({storeConfigInMeta: false});
-
-// etc...
+```sh
+npm install --save-dev ember-cli-rails-addon@0.0.3
 ```
 
 And that's it!

lib/ember-cli-rails.rb

@@ -7,6 +7,7 @@ module EmberCLI
   autoload :Configuration, "ember-cli/configuration"
   autoload :ViewHelpers,   "ember-cli/view_helpers"
   autoload :Helpers,       "ember-cli/helpers"
+  autoload :Middleware,    "ember-cli/middleware"
 
   def configure
     yield configuration
@@ -26,20 +27,7 @@ def prepare!
 
   def enable!
     prepare!
-
-    Rails.application.singleton_class.class_eval do
-      alias_method :call_without_ember_cli, :call
-
-      def call(env)
-        @_ember_cli_enabled ||= begin
-          EmberCLI.compile!
-          EmberCLI.run! if Rails.env.development?
-          true
-        end
-
-        call_without_ember_cli(env)
-      end
-    end
+    Rails.configuration.middleware.use Middleware
   end
 
   def run!
@@ -56,6 +44,10 @@ def stop!
     each_app &:stop
   end
 
+  def wait!
+    each_app &:wait
+  end
+
   def root
     @root ||= Rails.root.join("tmp", "ember-cli-#{uid}")
   end

lib/ember-cli/app.rb

@@ -1,5 +1,9 @@
+require "timeout"
+
 module EmberCLI
   class App
+    ADDON_VERSION = "0.0.3"
+
     attr_reader :name, :options, :pid
 
     def initialize(name, options={})
@@ -32,20 +36,76 @@ def exposed_css_assets
       %W[#{name}/vendor #{name}/#{ember_app_name}]
     end
 
+    def wait
+      Timeout.timeout(build_timeout) do
+        sleep 0.1 while lockfile.exist?
+      end
+    rescue Timeout::Error
+      suggested_timeout = build_timeout + 5
+
+      warn <<-MSG.strip_heredoc
+        ============================= WARNING! =============================
+
+          Seems like Ember #{name} application takes more than #{build_timeout}
+          seconds to compile.
+
+          To prevent race conditions consider adjusting build timeout
+          configuration in your ember initializer:
+
+            EmberCLI.configure do |config|
+              config.build_timeout = #{suggested_timeout} # in seconds
+            end
+
+          Alternatively, you can set build timeout per application like this:
+
+            EmberCLI.configure do |config|
+              config.app :#{name}, build_timeout: #{suggested_timeout}
+            end
+
+        ============================= WARNING! =============================
+      MSG
+    end
+
     private
 
     delegate :ember_path, to: :configuration
     delegate :tee_path, to: :configuration
     delegate :configuration, to: :EmberCLI
 
+    def build_timeout
+      options.fetch(:build_timeout){ configuration.build_timeout }
+    end
+
+    def lockfile
+      app_path.join("tmp", "build.lock")
+    end
+
     def prepare
       @prepared ||= begin
+        check_addon!
+        FileUtils.touch lockfile
         symlink_to_assets_root
         add_assets_to_precompile_list
         true
       end
     end
 
+    def check_addon!
+      dependencies = package_json.fetch("devDependencies", {})
+
+      unless dependencies["ember-cli-rails-addon"] == ADDON_VERSION
+        fail <<-MSG.strip_heredoc
+          EmberCLI Rails requires your Ember app to have an addon.
+
+          Please run:
+
+            $ npm install --save-dev ember-cli-rails-addon@#{ADDON_VERSION}`
+
+          in you Ember application root: #{app_path}
+        MSG
+      end
+    end
+
     def symlink_to_assets_root
       symlink_path = dist_path.join("assets")
       assets_path.join(name).make_symlink symlink_path unless symlink_path.exist?
@@ -65,9 +125,7 @@ def log_pipe
     end
 
     def ember_app_name
-      @ember_app_name ||= options.fetch(:name) do
-        JSON.parse(app_path.join("package.json").read).fetch("name")
-      end
+      @ember_app_name ||= options.fetch(:name){ package_json.fetch(:name) }
     end
 
     def app_path
@@ -92,5 +150,9 @@ def assets_path
     def environment
       Helpers.non_production?? "development" : "production"
     end
+
+    def package_json
+      @package_json ||= JSON.parse(app_path.join("package.json").read).with_indifferent_access
+    end
   end
 end

lib/ember-cli/configuration.rb

@@ -23,6 +23,10 @@ def ember_path
       end
     end
 
-    attr_writer :ember_path
+    def build_timeout
+      @build_timeout ||= 5
+    end
+
+    attr_writer :ember_path, :build_timeout
   end
 end

lib/ember-cli/middleware.rb

@@ -0,0 +1,28 @@
+module EmberCLI
+  class Middleware
+    def initialize(app)
+      @app = app
+    end
+
+    def call(env)
+      enable_ember_cli
+      EmberCLI.wait!
+
+      @app.call(env)
+    end
+
+    private
+
+    def enable_ember_cli
+      @enabled ||= begin
+        if Rails.env.development?
+          EmberCLI.run!
+        else
+          EmberCLI.compile!
+        end
+
+        true
+      end
+    end
+  end
+end