BroadcastLogger#tagged without a block returns an array instead of a logger

[mroach]

Steps to reproduce

1. Use BroadcastLogger#broadcast_to(logger) to add a new logger
2. Use BroadcastLogger#tagged("MyTag") without a block to return a new tagged logger
3. Try to use that new tagged logger

# frozen_string_literal: true

require "bundler/inline"

gemfile(true) do
  source "https://rubygems.org"

  git_source(:github) { |repo| "https://github.com/#{repo}.git" }

  gem "rails", github: "rails/rails", branch: "main"
  gem "pry"
end

require "active_support"
require "active_support/core_ext/object/blank"
require "minitest/autorun"

class BugTest < Minitest::Test
  def test_broadcast_to_multiple_tagged_loggers
    iologger1 = Logger.new($stdout)
    iologger1 = ActiveSupport::TaggedLogging.new(iologger1)

    logger = ActiveSupport::BroadcastLogger.new(iologger1)

    # This works fine
    logger.tagged("Test1").info("OK")

    iologger2 = Logger.new($stderr)
    iologger2 = ActiveSupport::TaggedLogging.new(iologger2)

    logger.broadcast_to(iologger2)

    # This works fine
    logger.tagged("Test1") { _1.info "OK" }

    # Now we have a problem. `logger.tagged` returns an Array
    # NoMethodError: undefined method `info' for [#<Logger
    #
    # https://github.com/rails/rails/blob/ca5132b78a44677f708045905dc1b092a02f6b30/activesupport/lib/active_support/broadcast_logger.rb#L242
    logger.tagged("Test2").info("OK")

    # We'll never get here, but this fails
    assert logger.is_a?(ActiveSupport::BroadcastLogger)
  end
end

Expected behavior

Using ActiveSupport::BroadcastLogger#tagged without a block returns a tagged logger that can be used for logging as normal.

Actual behavior

When broadcasting to more than one logger that supports tagging, an Array is returned rather than an object that you can log to directly.

The specific use case where this came up: in some tests, I want to capture logs so I can test them. Previously I was replacing Rails.logger entirely, but now I tried adding and removing a broadcast target and I noticed this didn't work.

This appears to be caused by the method_missing implementation:

rails/activesupport/lib/active_support/broadcast_logger.rb

Line 242 in ca5132b

loggers.map { |logger| logger.send(name, *args, **kwargs, &block) }

System configuration

Rails version: 7.1.1

Ruby version: 3.2.2

[akhilgkrishnan]

looks like a similar issue of #49745. Need to investigate further more.

[davidstosik]

Similar yes. Basically #tagged is broken, with and without a block.
I suggested a work-around in my issue, but honestly, I am not confident with it yet as I haven't been able to run our application with more than one broadcasted logger...

[akhilgkrishnan]

@Edouard-chin Do you have any thoughts on this issue?

[Edouard-chin]

Thanks for the ping, I didn't see this issue and David's one. I have a few changes stashed that I originally wrote it to fix an unrelated issue with Broadcasting + Tagged logging, and this should also fix those two issues.

Will open a PR !