Fix `BroadcastLogger#dup` so that it duplicates the logger's `broadcasts`.

activesupport/CHANGELOG.md

@@ -1,3 +1,7 @@
+*   Fix `BroadcastLogger#dup` so that it duplicates the logger's `broadcasts`.
+
+    *Andrew Novoselac*
+
 *   Fix issue where `bootstrap.rb` overwrites the `level` of a `BroadcastLogger`'s `broadcasts`.
 
     *Andrew Novoselac*

activesupport/lib/active_support/broadcast_logger.rb

@@ -218,6 +218,14 @@ module ActiveSupport
       dispatch { |logger| logger.fatal! }
     end
 
+    def initialize_copy(other)
+      @broadcasts = []
+      @progname = other.progname.dup
+      @formatter = other.formatter.dup
+
+      broadcast_to(*other.broadcasts.map(&:dup))
+    end
+
     private
       def dispatch(&block)
         @broadcasts.each { |logger| block.call(logger) }

activesupport/test/broadcast_logger_test.rb

@@ -290,6 +290,18 @@ module ActiveSupport
       assert(logger.qux(param: "foo"))
     end
 
+    test "#dup duplicates the broadcasts" do
+      logger = CustomLogger.new
+      logger.level = ::Logger::WARN
+      broadcast_logger = BroadcastLogger.new(logger)
+
+      duplicate = broadcast_logger.dup
+
+      assert_equal ::Logger::WARN, duplicate.broadcasts.sole.level
+      assert_not_same logger, duplicate.broadcasts.sole
+      assert_same logger, broadcast_logger.broadcasts.sole
+    end
+
     class CustomLogger
       attr_reader :adds, :closed, :chevrons
       attr_accessor :level, :progname, :formatter, :local_level