From c14b98c28a5962281dd3bc6fb2ca6c6cf79fbc2a Mon Sep 17 00:00:00 2001
From: Andrew Novoselac <andrew.novoselac@shopify.com>
Date: Fri, 20 Oct 2023 10:26:03 -0400
Subject: [PATCH] Fix `BroadcastLogger#dup` so that it duplicates the logger's
 `broadcasts`.

---
 activesupport/CHANGELOG.md                           |  4 ++++
 activesupport/lib/active_support/broadcast_logger.rb |  8 ++++++++
 activesupport/test/broadcast_logger_test.rb          | 12 ++++++++++++
 3 files changed, 24 insertions(+)

diff --git a/activesupport/CHANGELOG.md b/activesupport/CHANGELOG.md
index 38a1c9dd9e2b7..83f00e5d9b769 100644
--- a/activesupport/CHANGELOG.md
+++ b/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*
diff --git a/activesupport/lib/active_support/broadcast_logger.rb b/activesupport/lib/active_support/broadcast_logger.rb
index e5bf7232c115f..4d752faeed172 100644
--- a/activesupport/lib/active_support/broadcast_logger.rb
+++ b/activesupport/lib/active_support/broadcast_logger.rb
@@ -218,6 +218,14 @@ def fatal!
       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) }
diff --git a/activesupport/test/broadcast_logger_test.rb b/activesupport/test/broadcast_logger_test.rb
index 3bff7838e9de1..a5b4f189d4a93 100644
--- a/activesupport/test/broadcast_logger_test.rb
+++ b/activesupport/test/broadcast_logger_test.rb
@@ -290,6 +290,18 @@ def info(msg, &block)
       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