let config.file_watcher be the way to enable the evented file watcher

Before this commit, the sole presence of the Listen constant
enabled the evented file watcher (unless listen resorted to
the polling backend).

This way, applications may depend on listen for other stuff
independently of this feature. Also, allows teams with mixed
setups to decide at boot time whether the evented watcher
should be enabled for each particular instance.

3 files changed, 16 insertions, 21 deletions

diff --git a/railties/lib/rails/application/configuration.rb b/railties/lib/rails/application/configuration.rb
index a5550df0de..65cff1561a 100644
--- a/railties/lib/rails/application/configuration.rb
+++ b/railties/lib/rails/application/configuration.rb
@@ -44,7 +44,7 @@ module Rails
         @railties_order                  = [:all]
         @relative_url_root               = ENV["RAILS_RELATIVE_URL_ROOT"]
         @reload_classes_only_on_change   = true
-        @file_watcher                    = file_update_checker
+        @file_watcher                    = ActiveSupport::FileUpdateChecker
         @exceptions_app                  = nil
         @autoflush_log                   = true
         @log_formatter                   = ActiveSupport::Logger::SimpleFormatter.new
@@ -191,26 +191,21 @@ module Rails
         SourceAnnotationExtractor::Annotation
       end
 
-      private
-        def file_update_checker
-          ActiveSupport::FileUpdateChecker
+      class Custom #:nodoc:
+        def initialize
+          @configurations = Hash.new
         end
 
-        class Custom #:nodoc:
-          def initialize
-            @configurations = Hash.new
-          end
-
-          def method_missing(method, *args)
-            if method =~ /=$/
-              @configurations[$`.to_sym] = args.first
-            else
-              @configurations.fetch(method) {
-                @configurations[method] = ActiveSupport::OrderedOptions.new
-              }
-            end
+        def method_missing(method, *args)
+          if method =~ /=$/
+            @configurations[$`.to_sym] = args.first
+          else
+            @configurations.fetch(method) {
+              @configurations[method] = ActiveSupport::OrderedOptions.new
+            }
           end
         end
+      end
     end
   end
 end
diff --git a/railties/lib/rails/generators/rails/app/templates/Gemfile b/railties/lib/rails/generators/rails/app/templates/Gemfile
index a0880d5166..975be07622 100644
--- a/railties/lib/rails/generators/rails/app/templates/Gemfile
+++ b/railties/lib/rails/generators/rails/app/templates/Gemfile
@@ -48,10 +48,6 @@ group :development do
   # Spring speeds up development by keeping your application running in the background. Read more: https://github.com/rails/spring
   gem 'spring'
 <% end -%>
-
-  # Loading the listen gem enables an evented file system monitor. Check
-  # https://github.com/guard/listen#listen-adapters if on Windows or *BSD.
-  # gem 'listen', '~> 3.0.5'
 end
 <% end -%>
 
diff --git a/railties/lib/rails/generators/rails/app/templates/config/environments/development.rb.tt b/railties/lib/rails/generators/rails/app/templates/config/environments/development.rb.tt
index 2778dd8247..65c6aeb694 100644
--- a/railties/lib/rails/generators/rails/app/templates/config/environments/development.rb.tt
+++ b/railties/lib/rails/generators/rails/app/templates/config/environments/development.rb.tt
@@ -55,4 +55,8 @@ Rails.application.configure do
 
   # Raises error for missing translations
   # config.action_view.raise_on_missing_translations = true
+
+  # Use an evented file watcher to asynchronously detect changes in source code,
+  # routes, locales, etc. This feature depends on the listen gem.
+  # config.file_watcher = ActiveSupport::EventedFileUpdateChecker
 end