Add new generator for generating an application.rb from your existing environment.rb code

lib/new_configuration_generator.rb

@@ -0,0 +1,51 @@
+module Rails
+  module Upgrading
+    class NewConfigurationGenerator
+      def generate_new_configurations
+        if has_environment?
+          generate_new_application_rb
+        else
+          raise FileNotFoundError, "Can't find environment.rb [config/environment.rb]!"
+        end
+      end
+      
+      def has_environment?
+        File.exists?("config/environment.rb")
+      end
+      
+      def environment_code
+        File.open("config/environment.rb").read
+      end
+      
+      def generate_new_application_rb
+        environment_file = environment_code
+        
+        initializer_code = ""
+        if matches = environment_file.match(/Rails\:\:Initializer\.run do \|config\|\n(.*)\nend/m)
+          initializer_code = matches[1]
+        else
+          raise "There doesn't seem to be a real environment.rb in your app.  Are you sure config/environment.rb has the right contents?"
+        end
+        
+        frame = "# Put this in config/application.rb
+require File.expand_path('../boot', __FILE__)
+
+module #{app_name.classify}
+  class Application < Rails::Application
+%s
+  end
+end"
+        
+        frame % [indent(initializer_code)]        
+      end
+      
+      def indent(text)
+        text.split("\n").map {|l| "  #{l}"}.join("\n")
+      end
+      
+      def app_name
+        File.basename(Dir.pwd)
+      end
+    end
+  end
+end

tasks/rails_upgrade_tasks.rake

@@ -2,6 +2,7 @@ $:.unshift(File.dirname(__FILE__) + "/../lib")
 require 'routes_upgrader'
 require 'gemfile_generator'
 require 'application_checker'
+require 'new_configuration_generator'
 
 namespace :rails do
   namespace :upgrade do
@@ -26,5 +27,13 @@ namespace :rails do
     
       puts new_routes
     end
+    
+    desc "Extracts your configuration code so you can create a new config/application.rb"
+    task :configuration do
+      upgrader = Rails::Upgrading::NewConfigurationGenerator.new
+      new_config = upgrader.generate_new_application_rb
+      
+      puts new_config
+    end
   end
 end

test/new_configuration_generator_test.rb

@@ -0,0 +1,63 @@
+require 'test_helper'
+require 'new_configuration_generator'
+
+# Stub out methods on upgrader class
+module Rails
+  module Upgrading
+    class NewConfigurationGenerator
+      attr_writer :environment_code
+      
+      def has_environment?
+        true
+      end
+      
+      def environment_code
+        @environment_code
+      end
+      
+      def app_name
+        "my_application"
+      end
+    end
+  end
+end
+
+class NewConfigurationGeneratorTest < ActiveSupport::TestCase
+  FRAME = "# Put this in config/application.rb
+require File.expand_path('../boot', __FILE__)
+
+module MyApplication
+  class Application < Rails::Application
+%s
+  end
+end"
+
+  CONFIG = "  config.what_have_you = 'thing'
+  config.action_controller = 'what'"
+
+  CODE = "require 'w/e'
+
+this_happens_before_the(code)
+more_before_the_code!
+
+Rails::Initializer.run do |config|
+%s
+end
+
+this_is_after_the_code
+"
+
+  def test_raises_error_with_no_code
+    generator = Rails::Upgrading::NewConfigurationGenerator.new
+    generator.environment_code = ""
+    
+    assert_raises(RuntimeError) { generator.generate_new_application_rb }
+  end
+  
+  def test_generates_with_code
+    generator = Rails::Upgrading::NewConfigurationGenerator.new
+    generator.environment_code = CODE % [CONFIG]
+    
+    assert_equal FRAME % [generator.indent(CONFIG)], generator.generate_new_application_rb
+  end
+end