Add ActionCable.deprecator

This commit adds `ActionCable.deprecator`, and adds it to
`Rails.application.deprecators` so that it can be configured via
settings such as `config.active_support.report_deprecations`.

actioncable/lib/action_cable.rb

@@ -30,7 +30,8 @@ require "zeitwerk"
 Zeitwerk::Loader.for_gem.tap do |loader|
   loader.ignore(
     "#{__dir__}/rails", # Contains generators, templates, docs, etc.
-    "#{__dir__}/action_cable/gem_version.rb"
+    "#{__dir__}/action_cable/gem_version.rb",
+    "#{__dir__}/action_cable/deprecator.rb",
   )
 
   loader.do_not_eager_load(
@@ -44,6 +45,7 @@ end.setup
 
 module ActionCable
   require_relative "action_cable/version"
+  require_relative "action_cable/deprecator"
 
   INTERNAL = {
     message_types: {

actioncable/lib/action_cable/deprecator.rb

@@ -0,0 +1,7 @@
+# frozen_string_literal: true
+
+module ActionCable
+  def self.deprecator # :nodoc:
+    @deprecator ||= ActiveSupport::Deprecation.new
+  end
+end

actioncable/lib/action_cable/engine.rb

@@ -10,6 +10,10 @@ module ActionCable
     config.action_cable.mount_path = ActionCable::INTERNAL[:default_mount_path]
     config.action_cable.precompile_assets = true
 
+    initializer "action_cable.deprecator" do |app|
+      app.deprecators[:action_cable] = ActionCable.deprecator
+    end
+
     initializer "action_cable.helpers" do
       ActiveSupport.on_load(:action_view) do
         include ActionCable::Helpers::ActionCableHelper

railties/test/application/configuration_test.rb

@@ -3889,6 +3889,7 @@ module ApplicationTests
       app "production"
 
       assert_includes Rails.application.deprecators.each, ActiveSupport::Deprecation.instance
+      assert_equal ActionCable.deprecator, Rails.application.deprecators[:action_cable]
       assert_equal AbstractController.deprecator, Rails.application.deprecators[:action_controller]
       assert_equal ActionController.deprecator, Rails.application.deprecators[:action_controller]
       assert_equal ActionDispatch.deprecator, Rails.application.deprecators[:action_dispatch]