Use standard config/application.rb in plugin dummy

The `config/application.rb` file of a plugin test dummy app should be
the same as in a standard Rails app, with the exception of an additional
`require` statement to load the plugin itself.  However, prior to this
commit, the plugin generator used a specialized template for a portion
of this file, which tended to drift out-of-sync with the standard app
generator's template.  Specifically, this drift could result in missing
`require` statements of newer Rails frameworks when the plugin generator
was run with any `--skip-xxxx` option.

This commit changes the plugin generator to insert its additional
`require` statement into the standard `config/application.rb` file
generated by the app generator.

railties/lib/rails/generators/rails/plugin/plugin_generator.rb

@@ -1,5 +1,6 @@
 # frozen_string_literal: true
 
+require "active_support/core_ext/hash/except"
 require "rails/generators/rails/app/app_generator"
 require "date"
 
@@ -92,13 +93,10 @@ task default: :test
       end
     end
 
-    PASSTHROUGH_OPTIONS = [
-      :skip_active_record, :skip_active_storage, :skip_action_mailer, :skip_javascript, :skip_action_cable, :skip_sprockets, :database,
-      :api, :quiet, :pretend, :skip
-    ]
+    DUMMY_IGNORE_OPTIONS = %i[dev edge master template]
 
     def generate_test_dummy(force = false)
-      opts = (options.dup || {}).keep_if { |k, _| PASSTHROUGH_OPTIONS.map(&:to_s).include?(k) }
+      opts = options.transform_keys(&:to_sym).except(*DUMMY_IGNORE_OPTIONS)
       opts[:force] = force
       opts[:skip_bundle] = true
       opts[:skip_listen] = true
@@ -113,7 +111,11 @@ task default: :test
 
     def test_dummy_config
       template "rails/boot.rb", "#{dummy_path}/config/boot.rb", force: true
-      template "rails/application.rb", "#{dummy_path}/config/application.rb", force: true
+
+      insert_into_file "#{dummy_path}/config/application.rb", <<~RUBY, after: /^Bundler\.require.+\n/
+        require #{namespaced_name.inspect}
+      RUBY
+
       if mountable?
         template "rails/routes.rb", "#{dummy_path}/config/routes.rb", force: true
       end
@@ -283,7 +285,6 @@ task default: :test
         say_status :vendor_app, dummy_path
         mute do
           build(:generate_test_dummy)
-          store_application_definition!
           build(:test_dummy_config)
           build(:test_dummy_assets)
           build(:test_dummy_clean)
@@ -383,18 +384,6 @@ task default: :test
         end
       end
 
-      def application_definition
-        @application_definition ||= begin
-
-          dummy_application_path = File.expand_path("#{dummy_path}/config/application.rb", destination_root)
-          unless options[:pretend] || !File.exist?(dummy_application_path)
-            contents = File.read(dummy_application_path)
-            contents[(contents.index(/module ([\w]+)\n(.*)class Application/m))..-1]
-          end
-        end
-      end
-      alias :store_application_definition! :application_definition
-
       def get_builder_class
         defined?(::PluginBuilder) ? ::PluginBuilder : Rails::PluginBuilder
       end

railties/lib/rails/generators/rails/plugin/templates/rails/application.rb.tt

@@ -1,23 +0,0 @@
-require_relative "boot"
-
-<% if include_all_railties? -%>
-require "rails/all"
-<% else -%>
-require "rails"
-# Pick the frameworks you want:
-require "active_model/railtie"
-require "active_job/railtie"
-<%= comment_if :skip_active_record %>require "active_record/railtie"
-<%= comment_if :skip_active_storage %>require "active_storage/engine"
-require "action_controller/railtie"
-<%= comment_if :skip_action_mailer %>require "action_mailer/railtie"
-require "action_view/railtie"
-<%= comment_if :skip_action_cable %>require "action_cable/engine"
-<%= comment_if :skip_sprockets %>require "sprockets/railtie"
-<%= comment_if :skip_test %>require "rails/test_unit/railtie"
-<% end -%>
-
-Bundler.require(*Rails.groups)
-require "<%= namespaced_name %>"
-
-<%= application_definition %>

railties/test/generators/plugin_generator_test.rb

@@ -455,6 +455,12 @@ class PluginGeneratorTest < Rails::Generators::TestCase
     end
   end
 
+  def test_dummy_application_loads_plugin
+    run_generator
+
+    assert_file "test/dummy/config/application.rb", /^require "bukkits"/
+  end
+
   def test_dummy_application_uses_dynamic_rails_version_number
     run_generator