Only load generators when needed

- use hook_for to hook in the serializer and remove load_generators
- move generators so they can be found by rails
- move to_prepare block to railtie config

This commit improves the way the generators are loaded and how
they extend the resource generator.

* The initializer block has been changed to a `generator` block which is only executed when generators are needed.
* The call to `app.load_generators` has been removed. There is no need to load *all* generators.
* The `resource_override.rb` has been changed to use `hook_for` to extend the resource generator.
* The directory for the generators has been moved to match the way Rails looks to load generators.

With `hook_for` it would now be possible for a user to pass `--no-serializer` to skip that option.
The `--serialize` option also now shows up in the generator help with `rails g resource --help`.

These changes follow the way the Draper gem extends the `controller` generator.

lib/active_model_serializers/railtie.rb

@@ -2,13 +2,14 @@ require 'rails/railtie'
 
 module ActiveModelSerializers
   class Railtie < Rails::Railtie
+    config.to_prepare do
+      ActiveModel::Serializer.serializers_cache.clear
+    end
+
     initializer 'active_model_serializers.action_controller' do
       ActiveSupport.on_load(:action_controller) do
         ActiveSupport.run_load_hooks(:active_model_serializers, ActiveModelSerializers)
         include ::ActionController::Serialization
-        ActionDispatch::Reloader.to_prepare do
-          ActiveModel::Serializer.serializers_cache.clear
-        end
       end
     end
 
@@ -25,9 +26,8 @@ module ActiveModelSerializers
       end
     end
 
-    initializer 'active_model_serializers.generators' do |app|
-      app.load_generators
-      require 'generators/serializer/resource_override'
+    generators do
+      require 'generators/rails/resource_override'
     end
 
     if Rails.env.test?

lib/generators/rails/resource_override.rb

@@ -4,9 +4,7 @@ require 'rails/generators/rails/resource/resource_generator'
 module Rails
   module Generators
     class ResourceGenerator
-      def add_serializer
-        invoke 'serializer'
-      end
+      hook_for :serializer, default: true, boolean: true
     end
   end
 end

lib/generators/rails/serializer_generator.rb

@@ -15,11 +15,11 @@ module Rails
       private
 
       def attributes_names
-        [:id] + attributes.select { |attr| !attr.reference? }.map { |a| a.name.to_sym }
+        [:id] + attributes.reject(&:reference?).map! { |a| a.name.to_sym }
       end
 
       def association_names
-        attributes.select { |attr| attr.reference? }.map { |a| a.name.to_sym }
+        attributes.select(&:reference?).map! { |a| a.name.to_sym }
       end
 
       def parent_class_name
@@ -34,4 +34,3 @@ module Rails
     end
   end
 end
-

test/generators/scaffold_controller_generator_test.rb

@@ -1,4 +1,5 @@
 require 'test_helper'
+require 'generators/rails/resource_override'
 
 class ResourceGeneratorTest < Rails::Generators::TestCase
   destination File.expand_path('../../../tmp/generators', __FILE__)

test/generators/serializer_generator_test.rb

@@ -1,5 +1,6 @@
 require 'test_helper'
-require 'generators/serializer/serializer_generator'
+require 'generators/rails/resource_override'
+require 'generators/rails/serializer_generator'
 
 class SerializerGeneratorTest < Rails::Generators::TestCase
   destination File.expand_path('../../../tmp/generators', __FILE__)