17 files changed, 23 insertions, 27 deletions
diff --git a/actioncable/README.md b/actioncable/README.md
index e044f54b45..6946dbefb0 100644
--- a/actioncable/README.md
+++ b/actioncable/README.md
@@ -409,7 +409,7 @@ application. The recommended basic setup is as follows:
 
 ```ruby
 # cable/config.ru
-require ::File.expand_path('../../config/environment', __FILE__)
+require_relative '../config/environment'
 Rails.application.eager_load!
 
 run ActionCable.server
diff --git a/actioncable/Rakefile b/actioncable/Rakefile
index bda8c7b6c8..e21843bb44 100644
--- a/actioncable/Rakefile
+++ b/actioncable/Rakefile
@@ -3,15 +3,13 @@ require "pathname"
 require "open3"
 require "action_cable"
 
-dir = File.dirname(__FILE__)
-
 task default: :test
 
 task package: %w( assets:compile assets:verify )
 
 Rake::TestTask.new do |t|
   t.libs << "test"
-  t.test_files = Dir.glob("#{dir}/test/**/*_test.rb")
+  t.test_files = Dir.glob("#{__dir__}/test/**/*_test.rb")
   t.warning = true
   t.verbose = true
   t.ruby_opts = ["--dev"] if defined?(JRUBY_VERSION)
@@ -46,7 +44,7 @@ namespace :assets do
   desc "Verify compiled Action Cable assets"
   task :verify do
     file = "lib/assets/compiled/action_cable.js"
-    pathname = Pathname.new("#{dir}/#{file}")
+    pathname = Pathname.new("#{__dir__}/#{file}")
 
     print "[verify] #{file} exists "
     if pathname.exist?
@@ -64,8 +62,8 @@ namespace :assets do
       fail
     end
 
-    print "[verify] #{dir} can be required as a module "
-    stdout, stderr, status = Open3.capture3("node", "--print", "window = {}; require('#{dir}');")
+    print "[verify] #{__dir__} can be required as a module "
+    _, stderr, status = Open3.capture3("node", "--print", "window = {}; require('#{__dir__}');")
     if status.success?
       puts "[OK]"
     else
diff --git a/actioncable/actioncable.gemspec b/actioncable/actioncable.gemspec
index 6d95f022fa..05ffd655e8 100644
--- a/actioncable/actioncable.gemspec
+++ b/actioncable/actioncable.gemspec
@@ -1,4 +1,4 @@
-version = File.read(File.expand_path("../../RAILS_VERSION", __FILE__)).strip
+version = File.read(File.expand_path("../RAILS_VERSION", __dir__)).strip
 
 Gem::Specification.new do |s|
   s.platform    = Gem::Platform::RUBY
diff --git a/actioncable/bin/test b/actioncable/bin/test
index a7beb14b27..470ce93f10 100755
--- a/actioncable/bin/test
+++ b/actioncable/bin/test
@@ -1,4 +1,4 @@
 #!/usr/bin/env ruby
 
 COMPONENT_ROOT = File.expand_path("..", __dir__)
-require File.expand_path("../tools/test", COMPONENT_ROOT)
+require_relative "../../tools/test"
diff --git a/actioncable/lib/action_cable/channel/periodic_timers.rb b/actioncable/lib/action_cable/channel/periodic_timers.rb
index c9daa0bcd3..90c68cfe84 100644
--- a/actioncable/lib/action_cable/channel/periodic_timers.rb
+++ b/actioncable/lib/action_cable/channel/periodic_timers.rb
@@ -4,8 +4,7 @@ module ActionCable
       extend ActiveSupport::Concern
 
       included do
-        class_attribute :periodic_timers, instance_reader: false
-        self.periodic_timers = []
+        class_attribute :periodic_timers, instance_reader: false, default: []
 
         after_subscribe   :start_periodic_timers
         after_unsubscribe :stop_periodic_timers
diff --git a/actioncable/lib/action_cable/connection/identification.rb b/actioncable/lib/action_cable/connection/identification.rb
index c91a1d1fd7..ffab359429 100644
--- a/actioncable/lib/action_cable/connection/identification.rb
+++ b/actioncable/lib/action_cable/connection/identification.rb
@@ -6,8 +6,7 @@ module ActionCable
       extend ActiveSupport::Concern
 
       included do
-        class_attribute :identifiers
-        self.identifiers = Set.new
+        class_attribute :identifiers, default: Set.new
       end
 
       class_methods do
diff --git a/actioncable/lib/action_cable/remote_connections.rb b/actioncable/lib/action_cable/remote_connections.rb
index d2856bc6ae..e689fbf21b 100644
--- a/actioncable/lib/action_cable/remote_connections.rb
+++ b/actioncable/lib/action_cable/remote_connections.rb
@@ -45,7 +45,7 @@ module ActionCable
         end
 
         # Returns all the identifiers that were applied to this connection.
-        def identifiers
+        redefine_method :identifiers do
           server.connection_identifiers
         end
 
diff --git a/actioncable/lib/action_cable/server/base.rb b/actioncable/lib/action_cable/server/base.rb
index 419eccd73c..3b3a17a532 100644
--- a/actioncable/lib/action_cable/server/base.rb
+++ b/actioncable/lib/action_cable/server/base.rb
@@ -10,7 +10,7 @@ module ActionCable
       include ActionCable::Server::Broadcasting
       include ActionCable::Server::Connections
 
-      cattr_accessor(:config, instance_accessor: true) { ActionCable::Server::Configuration.new }
+      cattr_accessor :config, instance_accessor: true, default: ActionCable::Server::Configuration.new
 
       def self.logger; config.logger; end
       delegate :logger, to: :config
diff --git a/actioncable/lib/action_cable/subscription_adapter/evented_redis.rb b/actioncable/lib/action_cable/subscription_adapter/evented_redis.rb
index ed8f315791..ae71708240 100644
--- a/actioncable/lib/action_cable/subscription_adapter/evented_redis.rb
+++ b/actioncable/lib/action_cable/subscription_adapter/evented_redis.rb
@@ -17,11 +17,11 @@ module ActionCable
 
       # Overwrite this factory method for EventMachine Redis connections if you want to use a different Redis connection library than EM::Hiredis.
       # This is needed, for example, when using Makara proxies for distributed Redis.
-      cattr_accessor(:em_redis_connector) { ->(config) { EM::Hiredis.connect(config[:url]) } }
+      cattr_accessor :em_redis_connector, default: ->(config) { EM::Hiredis.connect(config[:url]) }
 
       # Overwrite this factory method for Redis connections if you want to use a different Redis connection library than Redis.
       # This is needed, for example, when using Makara proxies for distributed Redis.
-      cattr_accessor(:redis_connector) { ->(config) { ::Redis.new(url: config[:url]) } }
+      cattr_accessor :redis_connector, default: ->(config) { ::Redis.new(url: config[:url]) }
 
       def initialize(*)
         ActiveSupport::Deprecation.warn(<<-MSG.squish)
diff --git a/actioncable/lib/action_cable/subscription_adapter/redis.rb b/actioncable/lib/action_cable/subscription_adapter/redis.rb
index 41a6e55822..a31ed33bdb 100644
--- a/actioncable/lib/action_cable/subscription_adapter/redis.rb
+++ b/actioncable/lib/action_cable/subscription_adapter/redis.rb
@@ -10,7 +10,7 @@ module ActionCable
 
       # Overwrite this factory method for redis connections if you want to use a different Redis library than Redis.
       # This is needed, for example, when using Makara proxies for distributed Redis.
-      cattr_accessor(:redis_connector) { ->(config) { ::Redis.new(url: config[:url]) } }
+      cattr_accessor :redis_connector, default: ->(config) { ::Redis.new(url: config[:url]) }
 
       def initialize(*)
         super
diff --git a/actioncable/lib/rails/generators/channel/channel_generator.rb b/actioncable/lib/rails/generators/channel/channel_generator.rb
index 984b78bc9c..80f512c94c 100644
--- a/actioncable/lib/rails/generators/channel/channel_generator.rb
+++ b/actioncable/lib/rails/generators/channel/channel_generator.rb
@@ -1,7 +1,7 @@
 module Rails
   module Generators
     class ChannelGenerator < NamedBase
-      source_root File.expand_path("../templates", __FILE__)
+      source_root File.expand_path("templates", __dir__)
 
       argument :actions, type: :array, default: [], banner: "method method"
 
diff --git a/actioncable/test/subscription_adapter/async_test.rb b/actioncable/test/subscription_adapter/async_test.rb
index 7bc2e55d40..8a447c7a4f 100644
--- a/actioncable/test/subscription_adapter/async_test.rb
+++ b/actioncable/test/subscription_adapter/async_test.rb
@@ -1,5 +1,5 @@
 require "test_helper"
-require_relative "./common"
+require_relative "common"
 
 class AsyncAdapterTest < ActionCable::TestCase
   include CommonSubscriptionAdapterTest
diff --git a/actioncable/test/subscription_adapter/evented_redis_test.rb b/actioncable/test/subscription_adapter/evented_redis_test.rb
index 256458bc24..5453511549 100644
--- a/actioncable/test/subscription_adapter/evented_redis_test.rb
+++ b/actioncable/test/subscription_adapter/evented_redis_test.rb
@@ -1,6 +1,6 @@
 require "test_helper"
-require_relative "./common"
-require_relative "./channel_prefix"
+require_relative "common"
+require_relative "channel_prefix"
 
 class EventedRedisAdapterTest < ActionCable::TestCase
   include CommonSubscriptionAdapterTest
diff --git a/actioncable/test/subscription_adapter/inline_test.rb b/actioncable/test/subscription_adapter/inline_test.rb
index 52bfa00aba..eafa3df2df 100644
--- a/actioncable/test/subscription_adapter/inline_test.rb
+++ b/actioncable/test/subscription_adapter/inline_test.rb
@@ -1,5 +1,5 @@
 require "test_helper"
-require_relative "./common"
+require_relative "common"
 
 class InlineAdapterTest < ActionCable::TestCase
   include CommonSubscriptionAdapterTest
diff --git a/actioncable/test/subscription_adapter/postgresql_test.rb b/actioncable/test/subscription_adapter/postgresql_test.rb
index beb6efab28..ada4c2e2bd 100644
--- a/actioncable/test/subscription_adapter/postgresql_test.rb
+++ b/actioncable/test/subscription_adapter/postgresql_test.rb
@@ -1,5 +1,5 @@
 require "test_helper"
-require_relative "./common"
+require_relative "common"
 
 require "active_record"
 
diff --git a/actioncable/test/subscription_adapter/redis_test.rb b/actioncable/test/subscription_adapter/redis_test.rb
index 4df5e0cbcd..11120b3f85 100644
--- a/actioncable/test/subscription_adapter/redis_test.rb
+++ b/actioncable/test/subscription_adapter/redis_test.rb
@@ -1,6 +1,6 @@
 require "test_helper"
-require_relative "./common"
-require_relative "./channel_prefix"
+require_relative "common"
+require_relative "channel_prefix"
 
 class RedisAdapterTest < ActionCable::TestCase
   include CommonSubscriptionAdapterTest
diff --git a/actioncable/test/test_helper.rb b/actioncable/test/test_helper.rb
index a47032753b..5d246c2b76 100644
--- a/actioncable/test/test_helper.rb
+++ b/actioncable/test/test_helper.rb
@@ -11,7 +11,7 @@ rescue LoadError
 end
 
 # Require all the stubs and models
-Dir[File.dirname(__FILE__) + "/stubs/*.rb"].each { |file| require file }
+Dir[File.expand_path("stubs/*.rb", __dir__)].each { |file| require file }
 
 class ActionCable::TestCase < ActiveSupport::TestCase
   def wait_for_async