1 files changed, 169 insertions, 0 deletions
diff --git a/railties/lib/rails/commands/commands_tasks.rb b/railties/lib/rails/commands/commands_tasks.rb
new file mode 100644
index 0000000000..6cfbc70c51
--- /dev/null
+++ b/railties/lib/rails/commands/commands_tasks.rb
@@ -0,0 +1,169 @@
+module Rails
+  # This is a class which takes in a rails command and initiates the appropriate
+  # initiation sequence.
+  #
+  # Warning: This class mutates ARGV because some commands require manipulating
+  # it before they are run.
+  class CommandsTasks # :nodoc:
+    attr_reader :argv
+
+    HELP_MESSAGE = <<-EOT
+Usage: rails COMMAND [ARGS]
+
+The most common rails commands are:
+ generate    Generate new code (short-cut alias: "g")
+ console     Start the Rails console (short-cut alias: "c")
+ server      Start the Rails server (short-cut alias: "s")
+ dbconsole   Start a console for the database specified in config/database.yml
+             (short-cut alias: "db")
+ new         Create a new Rails application. "rails new my_app" creates a
+             new application called MyApp in "./my_app"
+
+In addition to those, there are:
+ destroy      Undo code generated with "generate" (short-cut alias: "d")
+ plugin new   Generates skeleton for developing a Rails plugin
+ runner       Run a piece of code in the application environment (short-cut alias: "r")
+
+All commands can be run with -h (or --help) for more information.
+EOT
+
+    COMMAND_WHITELIST = %w(plugin generate destroy console server dbconsole runner new version help)
+
+    def initialize(argv)
+      @argv = argv
+    end
+
+    def run_command!(command)
+      command = parse_command(command)
+      if COMMAND_WHITELIST.include?(command)
+        send(command)
+      else
+        write_error_message(command)
+      end
+    end
+
+    def plugin
+      require_command!("plugin")
+    end
+
+    def generate
+      generate_or_destroy(:generate)
+    end
+
+    def destroy
+      generate_or_destroy(:destroy)
+    end
+
+    def console
+      require_command!("console")
+      options = Rails::Console.parse_arguments(argv)
+
+      # RAILS_ENV needs to be set before config/application is required
+      ENV['RAILS_ENV'] = options[:environment] if options[:environment]
+
+      # shift ARGV so IRB doesn't freak
+      shift_argv!
+
+      require_application_and_environment!
+      Rails::Console.start(Rails.application, options)
+    end
+
+    def server
+      set_application_directory!
+      require_command!("server")
+
+      Rails::Server.new.tap do |server|
+        # We need to require application after the server sets environment,
+        # otherwise the --environment option given to the server won't propagate.
+        require APP_PATH
+        Dir.chdir(Rails.application.root)
+        server.start
+      end
+    end
+
+    def dbconsole
+      require_command!("dbconsole")
+      Rails::DBConsole.start
+    end
+
+    def runner
+      require_command!("runner")
+    end
+
+    def new
+      if %w(-h --help).include?(argv.first)
+        require_command!("application")
+      else
+        exit_with_initialization_warning!
+      end
+    end
+
+    def version
+      argv.unshift '--version'
+      require_command!("application")
+    end
+
+    def help
+      write_help_message
+    end
+
+    private
+
+      def exit_with_initialization_warning!
+        puts "Can't initialize a new Rails application within the directory of another, please change to a non-Rails directory first.\n"
+        puts "Type 'rails' for help."
+        exit(1)
+      end
+
+      def shift_argv!
+        argv.shift if argv.first && argv.first[0] != '-'
+      end
+
+      def require_command!(command)
+        require "rails/commands/#{command}"
+      end
+
+      def generate_or_destroy(command)
+        require 'rails/generators'
+        require_application_and_environment!
+        Rails.application.load_generators
+        require "rails/commands/#{command}"
+      end
+
+      # Change to the application's path if there is no config.ru file in current directory.
+      # This allows us to run `rails server` from other directories, but still get
+      # the main config.ru and properly set the tmp directory.
+      def set_application_directory!
+        Dir.chdir(File.expand_path('../../', APP_PATH)) unless File.exist?(File.expand_path("config.ru"))
+      end
+
+      def require_application_and_environment!
+        require APP_PATH
+        Rails.application.require_environment!
+      end
+
+      def write_help_message
+        puts HELP_MESSAGE
+      end
+
+      def write_error_message(command)
+        puts "Error: Command '#{command}' not recognized"
+        if %x{rake #{command} --dry-run 2>&1 } && $?.success?
+          puts "Did you mean: `$ rake #{command}` ?\n\n"
+        end
+        write_help_message
+        exit(1)
+      end
+
+      def parse_command(command)
+        case command
+        when '--version', '-v'
+          'version'
+        when '--help', '-h'
+          'help'
+        else
+          command
+        end
+      end
+  end
+end