5 files changed, 51 insertions, 1 deletions
diff --git a/railties/CHANGELOG.md b/railties/CHANGELOG.md
index 58470e2f10..f4d3529a37 100644
--- a/railties/CHANGELOG.md
+++ b/railties/CHANGELOG.md
@@ -1,3 +1,7 @@
+*   Add `app:update` task to engines.
+
+    *Yuji Yaginuma*
+
 *   Avoid running system tests by default with the `bin/rails test`
     and `bin/rake test` commands since they may be expensive.
 
diff --git a/railties/lib/rails/engine/updater.rb b/railties/lib/rails/engine/updater.rb
new file mode 100644
index 0000000000..2ecf994a5c
--- /dev/null
+++ b/railties/lib/rails/engine/updater.rb
@@ -0,0 +1,19 @@
+require "rails/generators"
+require "rails/generators/rails/plugin/plugin_generator"
+
+module Rails
+  class Engine
+    class Updater
+      class << self
+        def generator
+          @generator ||= Rails::Generators::PluginGenerator.new ["plugin"],
+            { engine: true }, destination_root: ENGINE_ROOT
+        end
+
+        def run(action)
+          generator.send(action)
+        end
+      end
+    end
+  end
+end
diff --git a/railties/lib/rails/generators/rails/plugin/plugin_generator.rb b/railties/lib/rails/generators/rails/plugin/plugin_generator.rb
index ca48919f9a..118e44d9d0 100644
--- a/railties/lib/rails/generators/rails/plugin/plugin_generator.rb
+++ b/railties/lib/rails/generators/rails/plugin/plugin_generator.rb
@@ -301,7 +301,7 @@ task default: :test
       end
 
       def engine?
-        full? || mountable?
+        full? || mountable? || options[:engine]
       end
 
       def full?
diff --git a/railties/lib/rails/tasks/engine.rake b/railties/lib/rails/tasks/engine.rake
index c92b42f6c1..177b138090 100644
--- a/railties/lib/rails/tasks/engine.rake
+++ b/railties/lib/rails/tasks/engine.rake
@@ -1,6 +1,17 @@
 task "load_app" do
   namespace :app do
     load APP_RAKEFILE
+
+    desc "Update some initially generated files"
+    task update: [ "update:bin" ]
+
+    namespace :update do
+      require "rails/engine/updater"
+      # desc "Adds new executables to the engine bin/ directory"
+      task :bin do
+        Rails::Engine::Updater.run(:create_bin_files)
+      end
+    end
   end
   task environment: "app:environment"
 
diff --git a/railties/test/generators/plugin_generator_test.rb b/railties/test/generators/plugin_generator_test.rb
index 8ec096e5c6..afb37b6a99 100644
--- a/railties/test/generators/plugin_generator_test.rb
+++ b/railties/test/generators/plugin_generator_test.rb
@@ -1,6 +1,7 @@
 require "generators/generators_test_helper"
 require "rails/generators/rails/plugin/plugin_generator"
 require "generators/shared_generator_tests"
+require "rails/engine/updater"
 
 DEFAULT_PLUGIN_FILES = %w(
   .gitignore
@@ -731,6 +732,21 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     end
   end
 
+  def test_app_update_generates_bin_file
+    run_generator [destination_root, "--mountable"]
+
+    Object.const_set("ENGINE_ROOT", destination_root)
+    FileUtils.rm("#{destination_root}/bin/rails")
+
+    quietly { Rails::Engine::Updater.run(:create_bin_files) }
+
+    assert_file "#{destination_root}/bin/rails" do |content|
+      assert_match(%r|APP_PATH = File\.expand_path\('\.\./\.\./test/dummy/config/application', __FILE__\)|, content)
+    end
+  ensure
+    Object.send(:remove_const, "ENGINE_ROOT")
+  end
+
   private
 
     def action(*args, &block)