[close #22917] Don't output to `STDOUT` twice

When `rails console` or `rails server` are used along with a logger set to output to `STDOUT` then the contents will show up twice. This happens because the logger is extended with `ActiveSupportLogger.broadcast` with a destination of STDOUT even if it is already outputting to `STDOUT`.

Previously PR #22592 attempted to fix this issue, but it ended up causing NoMethodErrors. A better approach than relying on adding a method and flow control is to inspect the log destination directly. For this `ActiveSupport::Logger.logger_outputs_to?` was introduced

```ruby
logger = Logger.new(STDOUT)
ActiveSupport::Logger.logger_outputs_to?(logger, STDOUT)
# => true
```

To accomplish this we must look inside of an instance variable of standard lib's Logger `@logdev`. There is a related Ruby proposal to expose this method in a standard way: https://bugs.ruby-lang.org/issues/11955

1 files changed, 4 insertions, 2 deletions

diff --git a/railties/lib/rails/commands/server.rb b/railties/lib/rails/commands/server.rb
index d3ea441f8e..45d649ec31 100644
--- a/railties/lib/rails/commands/server.rb
+++ b/railties/lib/rails/commands/server.rb
@@ -133,11 +133,13 @@ module Rails
       def log_to_stdout
         wrapped_app # touch the app so the logger is set up
 
-        console = ActiveSupport::Logger.new($stdout)
+        console = ActiveSupport::Logger.new(STDOUT)
         console.formatter = Rails.logger.formatter
         console.level = Rails.logger.level
 
-        Rails.logger.extend(ActiveSupport::Logger.broadcast(console))
+        unless ActiveSupport::Logger.logger_outputs_to?(Rails.logger, STDOUT)
+          Rails.logger.extend(ActiveSupport::Logger.broadcast(console))
+        end
       end
   end
 end