Handle case when config.logger is already a BroadcastLogger:

- This commit avoids having `Rails.logger` be a two level nested
  BroadcastLogger. Side note that Nesting BroadcastLogger works and is
  supported by the implementation but we shouldn't do it in that
  case as it's confusing for the user.

Author: Edouard-chin

railties/lib/rails/application/bootstrap.rb

@@ -56,9 +56,11 @@ module Bootstrap
         end
         Rails.logger.level = ActiveSupport::Logger.const_get(config.log_level.to_s.upcase)
 
-        broadcast_logger = ActiveSupport::BroadcastLogger.new(Rails.logger)
-        broadcast_logger.formatter = Rails.logger.formatter
-        Rails.logger = broadcast_logger
+        unless Rails.logger.is_a?(ActiveSupport::BroadcastLogger)
+          broadcast_logger = ActiveSupport::BroadcastLogger.new(Rails.logger)
+          broadcast_logger.formatter = Rails.logger.formatter
+          Rails.logger = broadcast_logger
+        end
 
         unless config.consider_all_requests_local
           Rails.error.logger = Rails.logger

railties/test/application/configuration_test.rb

@@ -1893,6 +1893,26 @@ def index
       assert_equal Logger::DEBUG, Rails.logger.level
     end
 
+    test "config.logger when logger is already a Broadcast Logger" do
+      logger = ActiveSupport::BroadcastLogger.new
+
+      make_basic_app do |application|
+        application.config.logger = logger
+      end
+      assert_same(logger, Rails.logger)
+    end
+
+    test "config.logger when logger is not a Broadcast Logger" do
+      logger = Logger.new(STDOUT)
+
+      make_basic_app do |application|
+        application.config.logger = logger
+      end
+
+      assert_instance_of(ActiveSupport::BroadcastLogger, Rails.logger)
+      assert_includes(Rails.logger.broadcasts, logger)
+    end
+
     test "respond_to? accepts include_private" do
       make_basic_app