1 files changed, 116 insertions, 0 deletions
diff --git a/railties/lib/rails/engine/commands_tasks.rb b/railties/lib/rails/engine/commands_tasks.rb
new file mode 100644
index 0000000000..fa3ee59b7d
--- /dev/null
+++ b/railties/lib/rails/engine/commands_tasks.rb
@@ -0,0 +1,116 @@
+require 'rails/commands/rake_proxy'
+
+module Rails
+  class Engine
+    class CommandsTasks # :nodoc:
+      include Rails::RakeProxy
+
+      attr_reader :argv
+
+      HELP_MESSAGE = <<-EOT
+Usage: rails COMMAND [ARGS]
+
+The common Rails commands available for engines are:
+ generate    Generate new code (short-cut alias: "g")
+ destroy     Undo code generated with "generate" (short-cut alias: "d")
+ test        Run tests (short-cut alias: "t")
+
+All commands can be run with -h for more information.
+
+If you want to run any commands that need to be run in context
+of the application, like `rails server` or `rails console`,
+you should do it from application's directory (typically test/dummy).
+
+In addition to those commands, there are:
+  EOT
+
+      COMMAND_WHITELIST = %w(generate destroy version help test)
+
+      def initialize(argv)
+        @argv = argv
+      end
+
+      def run_command!(command)
+        command = parse_command(command)
+
+        if COMMAND_WHITELIST.include?(command)
+          send(command)
+        else
+          run_rake_task(command)
+        end
+      end
+
+      def generate
+        generate_or_destroy(:generate)
+      end
+
+      def destroy
+        generate_or_destroy(:destroy)
+      end
+
+      def test
+        require_command!("test")
+      end
+
+      def version
+        argv.unshift '--version'
+        require_command!("application")
+      end
+
+      def help
+        write_help_message
+        write_commands(formatted_rake_tasks)
+      end
+
+      private
+
+        def require_command!(command)
+          require "rails/commands/#{command}"
+        end
+
+        def generate_or_destroy(command)
+          load_generators
+          require_command!(command)
+        end
+
+        def load_generators
+          require 'rails/generators'
+          require ENGINE_PATH
+
+          engine = ::Rails::Engine.find(ENGINE_ROOT)
+          Rails::Generators.namespace = engine.railtie_namespace
+          engine.load_generators
+        end
+
+        def write_help_message
+          puts HELP_MESSAGE
+        end
+
+        def write_commands(commands)
+          width = commands.map { |name, _| name.size }.max || 10
+          commands.each { |command| printf(" %-#{width}s   %s\n", *command) }
+        end
+
+        def parse_command(command)
+          case command
+          when '--version', '-v'
+            'version'
+          when '--help', '-h'
+            'help'
+          else
+            command
+          end
+        end
+
+        def rake_tasks
+          return @rake_tasks if defined?(@rake_tasks)
+
+          load_generators
+          Rake::TaskManager.record_task_metadata = true
+          Rake.application.init('rails')
+          Rake.application.load_rakefile
+          @rake_tasks = Rake.application.tasks.select(&:comment)
+        end
+    end
+  end
+end