As the other constants, RAILS_DEFAULT_LOGGER no more.

railties/lib/rails.rb

@@ -32,11 +32,6 @@
 module Rails
   autoload :Bootstrap, 'rails/bootstrap'
 
-  # Needs to be duplicated from Active Support since its needed before Active
-  # Support is available. Here both Options and Hash are namespaced to prevent
-  # conflicts with other implementations AND with the classes residing in Active Support.
-  # ---
-  # TODO: w0t?
   class << self
     def application
       @@application ||= nil
@@ -48,7 +43,7 @@ def application=(application)
 
     # The Configuration instance used to configure the Rails environment
     def configuration
-      application.configuration
+      application.config
     end
 
     def initialize!
@@ -56,19 +51,19 @@ def initialize!
     end
 
     def initialized?
-      @initialized || false
+      @@initialized || false
     end
 
     def initialized=(initialized)
-      @initialized ||= initialized
+      @@initialized ||= initialized
     end
 
     def logger
-      if defined?(RAILS_DEFAULT_LOGGER)
-        RAILS_DEFAULT_LOGGER
-      else
-        nil
-      end
+      @@logger ||= nil
+    end
+
+    def logger=(logger)
+      @@logger = logger
     end
 
     def backtrace_cleaner

railties/lib/rails/bootstrap.rb

@@ -69,28 +69,23 @@ def initialize(application)
     end
 
     initializer :initialize_logger do
-      # if the environment has explicitly defined a logger, use it
-      next if Rails.logger
-
-      unless logger = config.logger
-        begin
-          logger = ActiveSupport::BufferedLogger.new(config.log_path)
-          logger.level = ActiveSupport::BufferedLogger.const_get(config.log_level.to_s.upcase)
-          if Rails.env.production?
-            logger.auto_flushing = false
-          end
-        rescue StandardError => e
-          logger = ActiveSupport::BufferedLogger.new(STDERR)
-          logger.level = ActiveSupport::BufferedLogger::WARN
-          logger.warn(
-            "Rails Error: Unable to access log file. Please ensure that #{config.log_path} exists and is chmod 0666. " +
-            "The log level has been raised to WARN and the output directed to STDERR until the problem is fixed."
-          )
-        end
+      Rails.logger ||= config.logger || begin
+        logger = ActiveSupport::BufferedLogger.new(config.log_path)
+        logger.level = ActiveSupport::BufferedLogger.const_get(config.log_level.to_s.upcase)
+        logger.auto_flushing = false if Rails.env.production?
+        logger
+      rescue StandardError => e
+        logger = ActiveSupport::BufferedLogger.new(STDERR)
+        logger.level = ActiveSupport::BufferedLogger::WARN
+        logger.warn(
+          "Rails Error: Unable to access log file. Please ensure that #{config.log_path} exists and is chmod 0666. " +
+          "The log level has been raised to WARN and the output directed to STDERR until the problem is fixed."
+        )
+        logger
       end
 
-      # TODO: Why are we silencing warning here?
-      silence_warnings { Object.const_set "RAILS_DEFAULT_LOGGER", logger }
+      # TODO: Wrap it in a deprecation proxy
+      silence_warnings { Object.const_set "RAILS_DEFAULT_LOGGER", Rails.logger }
     end
 
     # Sets the logger for Active Record, Action Controller, and Action Mailer