Use namespace if it's a mountable engine

railties/lib/rails/engine/commands.rb

@@ -15,6 +15,7 @@
 case command
 when 'generate', 'destroy'
   require 'rails/generators'
+  Rails::Generators.namespace = engine.railtie_namespace
   engine.load_generators
   require "rails/commands/#{command}"
 

railties/lib/rails/generators.rb

@@ -90,6 +90,16 @@ def self.options #:nodoc:
       @options ||= DEFAULT_OPTIONS.dup
     end
 
+    def self.namespace
+      @namespace ||= if defined?(Rails) && Rails.application
+         Rails.application.class.parents.detect { |n| n.respond_to?(:_railtie) }
+      end
+    end
+
+    def self.namespace=(namespace)
+      @namespace ||= namespace
+    end
+
     # Hold configured generators fallbacks. If a plugin developer wants a
     # generator group to fallback to another group in case of missing generators,
     # they can add a fallback.

railties/lib/rails/generators/named_base.rb

@@ -63,9 +63,7 @@ def inside_template?
         end
 
         def namespace
-          @namespace ||= if defined?(Rails) && Rails.application
-            Rails.application.class.parents.detect { |n| n.respond_to?(:_railtie) }
-          end
+          Rails::Generators.namespace
         end
 
         def namespaced?

railties/lib/rails/railtie.rb

 require 'rails/initializable'
 require 'rails/configuration'
 require 'active_support/inflector'
+require 'active_support/core_ext/module/introspection'
 
 module Rails
   # Railtie is the core of the Rails framework and provides several hooks to extend
@@ -192,5 +193,9 @@ def load_tasks(app)
     def load_generators(app)
       self.class.generators.each { |block| block.call(app) }
     end
+
+    def railtie_namespace
+      @railtie_namespace ||= self.class.parents.detect { |n| n.respond_to?(:_railtie) }
+    end
   end
 end

railties/test/railties/generators_test.rb

@@ -30,11 +30,13 @@ def rails(cmd)
       `#{Gem.ruby} #{require_environment} #{RAILS_FRAMEWORK_ROOT}/bin/rails #{cmd}`
     end
 
-    def build_engine
+    def build_engine(is_mountable=false)
       FileUtils.mkdir_p(engine_path)
       FileUtils.rm_r(engine_path)
 
-      rails("plugin new #{engine_path} --full --mountable")
+      mountable = is_mountable ? "--mountable" : ""
+
+      rails("plugin new #{engine_path} --full #{mountable}")
 
       Dir.chdir(engine_path) do
         File.open("Gemfile", "w") do |f|
@@ -52,32 +54,65 @@ def build_engine
       end
     end
 
+    def build_mountable_engine
+      build_engine(true)
+    end
+
     def setup
-      build_engine
     end
 
-    def test_controllers_are_correctly_namespaced
+    def test_controllers_are_correctly_namespaced_when_engine_is_mountable
+      build_mountable_engine
       Dir.chdir(engine_path) do
         bundled_rails("g controller topics")
-        assert_file "app/controllers/foo_bar/topics_controller.rb", /FooBar::TopicsController/
+        assert_file "app/controllers/foo_bar/topics_controller.rb", /module FooBar\n  class TopicsController/
         assert_no_file "app/controllers/topics_controller.rb"
       end
     end
 
-    def test_models_are_correctly_namespaced
+    def test_models_are_correctly_namespaced_when_engine_is_mountable
+      build_mountable_engine
       Dir.chdir(engine_path) do
         bundled_rails("g model topic")
-        assert_file "app/models/foo_bar/topic.rb", /FooBar::Topic/
+        assert_file "app/models/foo_bar/topic.rb", /module FooBar\n  class Topic/
         assert_no_file "app/models/topic.rb"
       end
     end
 
-    def test_helpers_are_correctly_namespaced
+    def test_helpers_are_correctly_namespaced_when_engine_is_mountable
+      build_mountable_engine
       Dir.chdir(engine_path) do
         bundled_rails("g helper topics")
-        assert_file "app/helpers/foo_bar/topics_helper.rb", /FooBar::TopicsHelper/
+        assert_file "app/helpers/foo_bar/topics_helper.rb", /module FooBar\n  module TopicsHelper/
         assert_no_file "app/helpers/topics_helper.rb"
       end
     end
+
+    def test_controllers_are_not_namespaced_when_engine_is_not_mountable
+      build_engine
+      Dir.chdir(engine_path) do
+        bundled_rails("g controller topics")
+        assert_file "app/controllers/topics_controller.rb", /class TopicsController/
+        assert_no_file "app/controllers/foo_bar/topics_controller.rb"
+      end
+    end
+
+    def test_models_are_not_namespaced_when_engine_is_not_mountable
+      build_engine
+      Dir.chdir(engine_path) do
+        bundled_rails("g model topic")
+        assert_file "app/models/topic.rb", /class Topic/
+        assert_no_file "app/models/foo_bar/topic.rb"
+      end
+    end
+
+    def test_helpers_are_not_namespaced_when_engine_is_not_mountable
+      build_engine
+      Dir.chdir(engine_path) do
+        bundled_rails("g helper topics")
+        assert_file "app/helpers/topics_helper.rb", /module TopicsHelper/
+        assert_no_file "app/helpers/foo_bar/topics_helper.rb"
+      end
+    end
   end
 end