Merge pull request #29294 from gsamokovarov/attributes-default

Introduce mattr_accessor default option

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

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)

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

actionmailer/lib/action_mailer/delivery_methods.rb

@@ -8,14 +8,9 @@ module ActionMailer
 
     included do
       # Do not make this inheritable, because we always want it to propagate
-      cattr_accessor :raise_delivery_errors
-      self.raise_delivery_errors = true
-
-      cattr_accessor :perform_deliveries
-      self.perform_deliveries = true
-
-      cattr_accessor :deliver_later_queue_name
-      self.deliver_later_queue_name = :mailers
+      cattr_accessor :raise_delivery_errors, default: true
+      cattr_accessor :perform_deliveries, default: true
+      cattr_accessor :deliver_later_queue_name, default: :mailers
 
       class_attribute :delivery_methods, default: {}.freeze
       class_attribute :delivery_method, default: :smtp

actionmailer/lib/action_mailer/preview.rb

@@ -20,8 +20,7 @@ module ActionMailer
       mattr_accessor :show_previews, instance_writer: false
 
       # :nodoc:
-      mattr_accessor :preview_interceptors, instance_writer: false
-      self.preview_interceptors = [ActionMailer::InlinePreviewInterceptor]
+      mattr_accessor :preview_interceptors, instance_writer: false, default: [ActionMailer::InlinePreviewInterceptor]
     end
 
     module ClassMethods

actionpack/lib/action_controller/metal/strong_parameters.rb

@@ -119,8 +119,7 @@ module ActionController
   #   params[:key]  # => "value"
   #   params["key"] # => "value"
   class Parameters
-    cattr_accessor :permit_all_parameters, instance_accessor: false
-    self.permit_all_parameters = false
+    cattr_accessor :permit_all_parameters, instance_accessor: false, default: false
 
     cattr_accessor :action_on_unpermitted_parameters, instance_accessor: false
 
@@ -205,8 +204,7 @@ module ActionController
     # config. For instance:
     #
     #    config.always_permitted_parameters = %w( controller action format )
-    cattr_accessor :always_permitted_parameters
-    self.always_permitted_parameters = %w( controller action )
+    cattr_accessor :always_permitted_parameters, default: %w( controller action )
 
     # Returns a new instance of <tt>ActionController::Parameters</tt>.
     # Also, sets the +permitted+ attribute to the default value of

actionpack/lib/action_dispatch/http/mime_negotiation.rb

@@ -6,8 +6,7 @@ module ActionDispatch
       extend ActiveSupport::Concern
 
       included do
-        mattr_accessor :ignore_accept_header
-        self.ignore_accept_header = false
+        mattr_accessor :ignore_accept_header, default: false
       end
 
       # The MIME type of the HTTP request, such as Mime[:xml].

actionpack/lib/action_dispatch/http/response.rb

@@ -81,8 +81,8 @@ module ActionDispatch # :nodoc:
     LOCATION     = "Location".freeze
     NO_CONTENT_CODES = [100, 101, 102, 204, 205, 304]
 
-    cattr_accessor(:default_charset) { "utf-8" }
-    cattr_accessor(:default_headers)
+    cattr_accessor :default_charset, default: "utf-8"
+    cattr_accessor :default_headers
 
     include Rack::Response::Helpers
     # Aliasing these off because AD::Http::Cache::Response defines them.

actionpack/lib/action_dispatch/http/url.rb

@@ -7,8 +7,7 @@ module ActionDispatch
       HOST_REGEXP     = /(^[^:]+:\/\/)?(\[[^\]]+\]|[^:]+)(?::(\d+$))?/
       PROTOCOL_REGEXP = /^([^:]+)(:)?(\/\/)?$/
 
-      mattr_accessor :tld_length
-      self.tld_length = 1
+      mattr_accessor :tld_length, default: 1
 
       class << self
         # Returns the domain part of a host given the domain level.

actionpack/lib/action_dispatch/middleware/cookies.rb

@@ -432,8 +432,7 @@ module ActionDispatch
         end
       end
 
-      mattr_accessor :always_write_cookie
-      self.always_write_cookie = false
+      mattr_accessor :always_write_cookie, default: false
 
       private
 

actionpack/lib/action_dispatch/middleware/exception_wrapper.rb

@@ -3,9 +3,7 @@ require "rack/utils"
 
 module ActionDispatch
   class ExceptionWrapper
-    cattr_accessor :rescue_responses
-    @@rescue_responses = Hash.new(:internal_server_error)
-    @@rescue_responses.merge!(
+    cattr_accessor :rescue_responses, default: Hash.new(:internal_server_error).merge!(
       "ActionController::RoutingError"               => :not_found,
       "AbstractController::ActionNotFound"           => :not_found,
       "ActionController::MethodNotAllowed"           => :method_not_allowed,
@@ -21,9 +19,7 @@ module ActionDispatch
       "Rack::QueryParser::InvalidParameterError"     => :bad_request
     )
 
-    cattr_accessor :rescue_templates
-    @@rescue_templates = Hash.new("diagnostics")
-    @@rescue_templates.merge!(
+    cattr_accessor :rescue_templates, default: Hash.new("diagnostics").merge!(
       "ActionView::MissingTemplate"         => "missing_template",
       "ActionController::RoutingError"      => "routing_error",
       "AbstractController::ActionNotFound"  => "unknown_action",

actionpack/lib/action_dispatch/request/utils.rb

@@ -1,8 +1,7 @@
 module ActionDispatch
   class Request
     class Utils # :nodoc:
-      mattr_accessor :perform_deep_munge
-      self.perform_deep_munge = true
+      mattr_accessor :perform_deep_munge, default: true
 
       def self.each_param_value(params, &block)
         case params

actionview/lib/action_view/base.rb

@@ -140,30 +140,25 @@ module ActionView #:nodoc:
     include Helpers, ::ERB::Util, Context
 
     # Specify the proc used to decorate input tags that refer to attributes with errors.
-    cattr_accessor :field_error_proc
-    @@field_error_proc = Proc.new { |html_tag, instance| "<div class=\"field_with_errors\">#{html_tag}</div>".html_safe }
+    cattr_accessor :field_error_proc, default: Proc.new { |html_tag, instance| "<div class=\"field_with_errors\">#{html_tag}</div>".html_safe }
 
     # How to complete the streaming when an exception occurs.
     # This is our best guess: first try to close the attribute, then the tag.
-    cattr_accessor :streaming_completion_on_exception
-    @@streaming_completion_on_exception = %("><script>window.location = "/500.html"</script></html>)
+    cattr_accessor :streaming_completion_on_exception, default: %("><script>window.location = "/500.html"</script></html>)
 
     # Specify whether rendering within namespaced controllers should prefix
     # the partial paths for ActiveModel objects with the namespace.
     # (e.g., an Admin::PostsController would render @post using /admin/posts/_post.erb)
-    cattr_accessor :prefix_partial_path_with_controller_namespace
-    @@prefix_partial_path_with_controller_namespace = true
+    cattr_accessor :prefix_partial_path_with_controller_namespace, default: true
 
     # Specify default_formats that can be rendered.
     cattr_accessor :default_formats
 
     # Specify whether an error should be raised for missing translations
-    cattr_accessor :raise_on_missing_translations
-    @@raise_on_missing_translations = false
+    cattr_accessor :raise_on_missing_translations, default: false
 
     # Specify whether submit_tag should automatically disable on click
-    cattr_accessor :automatically_disable_submit_tag
-    @@automatically_disable_submit_tag = true
+    cattr_accessor :automatically_disable_submit_tag, default: true
 
     class_attribute :_routes
     class_attribute :logger

actionview/lib/action_view/helpers/form_helper.rb

@@ -474,7 +474,7 @@ module ActionView
       end
       private :apply_form_for_options!
 
-      mattr_accessor(:form_with_generates_remote_forms) { true }
+      mattr_accessor :form_with_generates_remote_forms, default: true
 
       # Creates a form tag based on mixing URLs, scopes, or models.
       #
@@ -2318,8 +2318,6 @@ module ActionView
   end
 
   ActiveSupport.on_load(:action_view) do
-    cattr_accessor(:default_form_builder, instance_writer: false, instance_reader: false) do
-      ::ActionView::Helpers::FormBuilder
-    end
+    cattr_accessor :default_form_builder, instance_writer: false, instance_reader: false, default: ::ActionView::Helpers::FormBuilder
   end
 end

actionview/lib/action_view/helpers/translation_helper.rb

@@ -11,8 +11,7 @@ module ActionView
       include TagHelper
 
       included do
-        mattr_accessor :debug_missing_translation
-        self.debug_missing_translation = true
+        mattr_accessor :debug_missing_translation, default: true
       end
 
       # Delegates to <tt>I18n#translate</tt> but also performs three additional

actionview/lib/action_view/lookup_context.rb

@@ -14,11 +14,9 @@ module ActionView
   class LookupContext #:nodoc:
     attr_accessor :prefixes, :rendered_format
 
-    mattr_accessor :fallbacks
-    @@fallbacks = FallbackFileSystemResolver.instances
+    mattr_accessor :fallbacks, default: FallbackFileSystemResolver.instances
 
-    mattr_accessor :registered_details
-    self.registered_details = []
+    mattr_accessor :registered_details, default: []
 
     def self.register_detail(name, &block)
       registered_details << name

actionview/lib/action_view/renderer/partial_renderer/collection_caching.rb

@@ -5,7 +5,7 @@ module ActionView
     included do
       # Fallback cache store if Action View is used without Rails.
       # Otherwise overridden in Railtie to use Rails.cache.
-      mattr_accessor(:collection_cache) { ActiveSupport::Cache::MemoryStore.new }
+      mattr_accessor :collection_cache, default: ActiveSupport::Cache::MemoryStore.new
     end
 
     private

actionview/lib/action_view/template/resolver.rb

@@ -125,8 +125,7 @@ module ActionView
         end
     end
 
-    cattr_accessor :caching
-    self.caching = true
+    cattr_accessor :caching, default: true
 
     class << self
       alias :caching? :caching

actionview/test/template/url_helper_test.rb

@@ -7,8 +7,7 @@ class UrlHelperTest < ActiveSupport::TestCase
   # In those cases, we'll set up a simple mock
   attr_accessor :controller, :request
 
-  cattr_accessor :request_forgery
-  self.request_forgery = false
+  cattr_accessor :request_forgery, default: false
 
   routes = ActionDispatch::Routing::RouteSet.new
   routes.draw do

activejob/lib/active_job/logging.rb

@@ -8,7 +8,7 @@ module ActiveJob
     extend ActiveSupport::Concern
 
     included do
-      cattr_accessor(:logger) { ActiveSupport::TaggedLogging.new(ActiveSupport::Logger.new(STDOUT)) }
+      cattr_accessor :logger, default: ActiveSupport::TaggedLogging.new(ActiveSupport::Logger.new(STDOUT))
 
       around_enqueue do |_, block, _|
         tag_logger do

activejob/lib/active_job/queue_name.rb

@@ -4,8 +4,8 @@ module ActiveJob
 
     # Includes the ability to override the default queue name and prefix.
     module ClassMethods
-      mattr_accessor(:queue_name_prefix)
-      mattr_accessor(:default_queue_name) { "default" }
+      mattr_accessor :queue_name_prefix
+      mattr_accessor :default_queue_name, default: "default"
 
       # Specifies the name of the queue to process the job on.
       #

activejob/lib/active_job/queue_priority.rb

@@ -4,7 +4,7 @@ module ActiveJob
 
     # Includes the ability to override the default queue priority.
     module ClassMethods
-      mattr_accessor(:default_priority)
+      mattr_accessor :default_priority
 
       # Specifies the priority of the queue to create the job with.
       #

activejob/test/support/delayed_job/delayed/backend/test.rb

@@ -19,8 +19,7 @@ module Delayed
 
         include Delayed::Backend::Base
 
-        cattr_accessor :id
-        self.id = 0
+        cattr_accessor :id, default: 0
 
         def initialize(hash = {})
           self.attempts = 0

activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb

@@ -54,8 +54,7 @@ module ActiveRecord
       extend ActiveSupport::Concern
 
       included do
-        mattr_accessor :time_zone_aware_attributes, instance_writer: false
-        self.time_zone_aware_attributes = false
+        mattr_accessor :time_zone_aware_attributes, instance_writer: false, default: false
 
         class_attribute :skip_time_zone_conversion_for_attributes, instance_writer: false, default: []
         class_attribute :time_zone_aware_types, instance_writer: false, default: [ :datetime, :time ]

activerecord/lib/active_record/autosave_association.rb

@@ -140,8 +140,7 @@ module ActiveRecord
 
     included do
       Associations::Builder::Association.extensions << AssociationBuilderExtension
-      mattr_accessor :index_nested_attribute_errors, instance_writer: false
-      self.index_nested_attribute_errors = false
+      mattr_accessor :index_nested_attribute_errors, instance_writer: false, default: false
     end
 
     module ClassMethods # :nodoc:

activerecord/lib/active_record/core.rb

@@ -56,8 +56,7 @@ module ActiveRecord
       # :singleton-method:
       # Determines whether to use Time.utc (using :utc) or Time.local (using :local) when pulling
       # dates and times from the database. This is set to :utc by default.
-      mattr_accessor :default_timezone, instance_writer: false
-      self.default_timezone = :utc
+      mattr_accessor :default_timezone, instance_writer: false, default: :utc
 
       ##
       # :singleton-method:
@@ -67,16 +66,14 @@ module ActiveRecord
       # ActiveRecord::Schema file which can be loaded into any database that
       # supports migrations. Use :ruby if you want to have different database
       # adapters for, e.g., your development and test environments.
-      mattr_accessor :schema_format, instance_writer: false
-      self.schema_format = :ruby
+      mattr_accessor :schema_format, instance_writer: false, default: :ruby
 
       ##
       # :singleton-method:
       # Specifies if an error should be raised if the query has an order being
       # ignored when doing batch queries. Useful in applications where the
       # scope being ignored is error-worthy, rather than a warning.
-      mattr_accessor :error_on_ignored_order, instance_writer: false
-      self.error_on_ignored_order = false
+      mattr_accessor :error_on_ignored_order, instance_writer: false, default: false
 
       def self.error_on_ignored_order_or_limit
         ActiveSupport::Deprecation.warn(<<-MSG.squish)
@@ -101,8 +98,7 @@ module ActiveRecord
       ##
       # :singleton-method:
       # Specify whether or not to use timestamps for migration versions
-      mattr_accessor :timestamped_migrations, instance_writer: false
-      self.timestamped_migrations = true
+      mattr_accessor :timestamped_migrations, instance_writer: false, default: true
 
       ##
       # :singleton-method:
@@ -110,8 +106,7 @@ module ActiveRecord
       # db:migrate rake task. This is true by default, which is useful for the
       # development environment. This should ideally be false in the production
       # environment where dumping schema is rarely needed.
-      mattr_accessor :dump_schema_after_migration, instance_writer: false
-      self.dump_schema_after_migration = true
+      mattr_accessor :dump_schema_after_migration, instance_writer: false, default: true
 
       ##
       # :singleton-method:
@@ -120,8 +115,7 @@ module ActiveRecord
       # schema_search_path are dumped. Use :all to dump all schemas regardless
       # of schema_search_path, or a string of comma separated schemas for a
       # custom list.
-      mattr_accessor :dump_schemas, instance_writer: false
-      self.dump_schemas = :schema_search_path
+      mattr_accessor :dump_schemas, instance_writer: false, default: :schema_search_path
 
       ##
       # :singleton-method:
@@ -130,7 +124,6 @@ module ActiveRecord
       # be used to identify queries which load thousands of records and
       # potentially cause memory bloat.
       mattr_accessor :warn_on_records_fetched_greater_than, instance_writer: false
-      self.warn_on_records_fetched_greater_than = nil
 
       mattr_accessor :maintain_test_schema, instance_accessor: false
 

activerecord/lib/active_record/fixtures.rb

@@ -492,8 +492,7 @@ module ActiveRecord
       end
     end
 
-    cattr_accessor :all_loaded_fixtures
-    self.all_loaded_fixtures = {}
+    cattr_accessor :all_loaded_fixtures, default: {}
 
     class ClassCache
       def initialize(class_names, config)

activerecord/lib/active_record/schema_dumper.rb

@@ -13,8 +13,7 @@ module ActiveRecord
     # A list of tables which should not be dumped to the schema.
     # Acceptable values are strings as well as regexp if ActiveRecord::Base.schema_format == :ruby.
     # Only strings are accepted if ActiveRecord::Base.schema_format == :sql.
-    cattr_accessor :ignore_tables
-    @@ignore_tables = []
+    cattr_accessor :ignore_tables, default: []
 
     class << self
       def dump(connection = ActiveRecord::Base.connection, stream = STDOUT, config = ActiveRecord::Base)

activesupport/CHANGELOG.md

@@ -1,3 +1,12 @@
+*   Add default option to module and class attribute accessors.
+
+       mattr_accessor :settings, default: {}
+
+    Works for `mattr_reader`, `mattr_writer`, `cattr_accessor`, `cattr_reader`,
+    and `cattr_writer` as well.
+
+    *Genadi Samokovarov*
+
 *   Add `Date#prev_occurring` and `Date#next_occurring` to return specified next/previous occurring day of week.
 
     *Shota Iguchi*

activesupport/lib/active_support/core_ext/date_and_time/compatibility.rb

@@ -9,6 +9,6 @@ module DateAndTime
     # of the receiver. For backwards compatibility we're overriding
     # this behavior, but new apps will have an initializer that sets
     # this to true, because the new behavior is preferred.
-    mattr_accessor(:preserve_timezone, instance_writer: false) { false }
+    mattr_accessor :preserve_timezone, instance_writer: false, default: false
   end
 end

activesupport/lib/active_support/core_ext/module/attribute_accessors.rb

@@ -38,13 +38,10 @@ class Module
   #
   #   Person.new.hair_colors # => NoMethodError
   #
-  #
-  # Also, you can pass a block to set up the attribute with a default value.
+  # You can set a default value for the attribute.
   #
   #   module HairColors
-  #     mattr_reader :hair_colors do
-  #       [:brown, :black, :blonde, :red]
-  #     end
+  #     mattr_reader :hair_colors, default: [:brown, :black, :blonde, :red]
   #   end
   #
   #   class Person
@@ -52,8 +49,7 @@ class Module
   #   end
   #
   #   Person.new.hair_colors # => [:brown, :black, :blonde, :red]
-  def mattr_reader(*syms)
-    options = syms.extract_options!
+  def mattr_reader(*syms, instance_reader: true, instance_accessor: true, default: nil)
     syms.each do |sym|
       raise NameError.new("invalid attribute name: #{sym}") unless /\A[_A-Za-z]\w*\z/.match?(sym)
       class_eval(<<-EOS, __FILE__, __LINE__ + 1)
@@ -64,14 +60,16 @@ class Module
         end
       EOS
 
-      unless options[:instance_reader] == false || options[:instance_accessor] == false
+      if instance_reader && instance_accessor
         class_eval(<<-EOS, __FILE__, __LINE__ + 1)
           def #{sym}
             @@#{sym}
           end
         EOS
       end
-      class_variable_set("@@#{sym}", yield) if block_given?
+
+      sym_default_value = (block_given? && default.nil?) ? yield : default
+      class_variable_set("@@#{sym}", sym_default_value) unless sym_default_value.nil?
     end
   end
   alias :cattr_reader :mattr_reader
@@ -107,12 +105,10 @@ class Module
   #
   #   Person.new.hair_colors = [:blonde, :red] # => NoMethodError
   #
-  # Also, you can pass a block to set up the attribute with a default value.
+  # You can set a default value for the attribute.
   #
   #   module HairColors
-  #     mattr_writer :hair_colors do
-  #       [:brown, :black, :blonde, :red]
-  #     end
+  #     mattr_writer :hair_colors, default: [:brown, :black, :blonde, :red]
   #   end
   #
   #   class Person
@@ -120,8 +116,7 @@ class Module
   #   end
   #
   #   Person.class_variable_get("@@hair_colors") # => [:brown, :black, :blonde, :red]
-  def mattr_writer(*syms)
-    options = syms.extract_options!
+  def mattr_writer(*syms, instance_writer: true, instance_accessor: true, default: nil)
     syms.each do |sym|
       raise NameError.new("invalid attribute name: #{sym}") unless /\A[_A-Za-z]\w*\z/.match?(sym)
       class_eval(<<-EOS, __FILE__, __LINE__ + 1)
@@ -132,14 +127,16 @@ class Module
         end
       EOS
 
-      unless options[:instance_writer] == false || options[:instance_accessor] == false
+      if instance_writer && instance_accessor
         class_eval(<<-EOS, __FILE__, __LINE__ + 1)
           def #{sym}=(obj)
             @@#{sym} = obj
           end
         EOS
       end
-      send("#{sym}=", yield) if block_given?
+
+      sym_default_value = (block_given? && default.nil?) ? yield : default
+      send("#{sym}=", sym_default_value) unless sym_default_value.nil?
     end
   end
   alias :cattr_writer :mattr_writer
@@ -197,12 +194,10 @@ class Module
   #   Person.new.hair_colors = [:brown]  # => NoMethodError
   #   Person.new.hair_colors             # => NoMethodError
   #
-  # Also you can pass a block to set up the attribute with a default value.
+  # You can set a default value for the attribute.
   #
   #   module HairColors
-  #     mattr_accessor :hair_colors do
-  #       [:brown, :black, :blonde, :red]
-  #     end
+  #     mattr_accessor :hair_colors, default: [:brown, :black, :blonde, :red]
   #   end
   #
   #   class Person
@@ -210,9 +205,9 @@ class Module
   #   end
   #
   #   Person.class_variable_get("@@hair_colors") # => [:brown, :black, :blonde, :red]
-  def mattr_accessor(*syms, &blk)
-    mattr_reader(*syms, &blk)
-    mattr_writer(*syms)
+  def mattr_accessor(*syms, instance_reader: true, instance_writer: true, instance_accessor: true, default: nil, &blk)
+    mattr_reader(*syms, instance_reader: instance_reader, instance_accessor: instance_accessor, default: default, &blk)
+    mattr_writer(*syms, instance_writer: instance_writer, instance_accessor: instance_accessor, default: default)
   end
   alias :cattr_accessor :mattr_accessor
 end

activesupport/lib/active_support/dependencies.rb

@@ -18,8 +18,7 @@ module ActiveSupport #:nodoc:
   module Dependencies #:nodoc:
     extend self
 
-    mattr_accessor :interlock
-    self.interlock = Interlock.new
+    mattr_accessor :interlock, default: Interlock.new
 
     # :doc:
 
@@ -46,46 +45,37 @@ module ActiveSupport #:nodoc:
     # :nodoc:
 
     # Should we turn on Ruby warnings on the first load of dependent files?
-    mattr_accessor :warnings_on_first_load
-    self.warnings_on_first_load = false
+    mattr_accessor :warnings_on_first_load, default: false
 
     # All files ever loaded.
-    mattr_accessor :history
-    self.history = Set.new
+    mattr_accessor :history, default: Set.new
 
     # All files currently loaded.
-    mattr_accessor :loaded
-    self.loaded = Set.new
+    mattr_accessor :loaded, default: Set.new
 
     # Stack of files being loaded.
-    mattr_accessor :loading
-    self.loading = []
+    mattr_accessor :loading, default: []
 
     # Should we load files or require them?
-    mattr_accessor :mechanism
-    self.mechanism = ENV["NO_RELOAD"] ? :require : :load
+    mattr_accessor :mechanism, default: ENV["NO_RELOAD"] ? :require : :load
 
     # The set of directories from which we may automatically load files. Files
     # under these directories will be reloaded on each request in development mode,
     # unless the directory also appears in autoload_once_paths.
-    mattr_accessor :autoload_paths
-    self.autoload_paths = []
+    mattr_accessor :autoload_paths, default: []
 
     # The set of directories from which automatically loaded constants are loaded
     # only once. All directories in this set must also be present in +autoload_paths+.
-    mattr_accessor :autoload_once_paths
-    self.autoload_once_paths = []
+    mattr_accessor :autoload_once_paths, default: []
 
     # An array of qualified constant names that have been loaded. Adding a name
     # to this array will cause it to be unloaded the next time Dependencies are
     # cleared.
-    mattr_accessor :autoloaded_constants
-    self.autoloaded_constants = []
+    mattr_accessor :autoloaded_constants, default: []
 
     # An array of constant names that need to be unloaded on every request. Used
     # to allow arbitrary constants to be marked for unloading.
-    mattr_accessor :explicitly_unloadable_constants
-    self.explicitly_unloadable_constants = []
+    mattr_accessor :explicitly_unloadable_constants, default: []
 
     # The WatchStack keeps a stack of the modules being watched as files are
     # loaded. If a file in the process of being loaded (parent.rb) triggers the
@@ -175,8 +165,7 @@ module ActiveSupport #:nodoc:
     end
 
     # An internal stack used to record which constants are loaded by any block.
-    mattr_accessor :constant_watch_stack
-    self.constant_watch_stack = WatchStack.new
+    mattr_accessor :constant_watch_stack, default: WatchStack.new
 
     # Module includes this module.
     module ModuleConstMissing #:nodoc:

activesupport/lib/active_support/log_subscriber.rb

@@ -49,8 +49,7 @@ module ActiveSupport
     CYAN    = "\e[36m"
     WHITE   = "\e[37m"
 
-    mattr_accessor :colorize_logging
-    self.colorize_logging = true
+    mattr_accessor :colorize_logging, default: true
 
     class << self
       def logger

activesupport/lib/active_support/logger_silence.rb

@@ -6,8 +6,7 @@ module LoggerSilence
   extend ActiveSupport::Concern
 
   included do
-    cattr_accessor :silencer
-    self.silencer = true
+    cattr_accessor :silencer, default: true
   end
 
   # Silences the logger for the duration of the block.

activesupport/test/core_ext/module/attribute_accessor_test.rb

@@ -12,7 +12,14 @@ class ModuleAttributeAccessorTest < ActiveSupport::TestCase
       cattr_accessor(:defa) { "default_accessor_value" }
       cattr_reader(:defr) { "default_reader_value" }
       cattr_writer(:defw) { "default_writer_value" }
+      cattr_accessor(:deff) { false }
       cattr_accessor(:quux) { :quux }
+
+      cattr_accessor :def_accessor, default: "default_accessor_value"
+      cattr_reader :def_reader, default: "default_reader_value"
+      cattr_writer :def_writer, default: "default_writer_value"
+      cattr_accessor :def_false, default: false
+      cattr_accessor(:def_priority, default: false) { :no_priority }
     end
     @class = Class.new
     @class.instance_eval { include m }
@@ -24,6 +31,21 @@ class ModuleAttributeAccessorTest < ActiveSupport::TestCase
     assert_nil @object.foo
   end
 
+  def test_mattr_default_keyword_arguments
+    assert_equal "default_accessor_value", @module.def_accessor
+    assert_equal "default_reader_value", @module.def_reader
+    assert_equal "default_writer_value", @module.class_variable_get(:@@def_writer)
+  end
+
+  def test_mattr_can_default_to_false
+    assert_equal false, @module.def_false
+    assert_equal false, @module.deff
+  end
+
+  def test_mattr_default_priority
+    assert_equal false, @module.def_priority
+  end
+
   def test_should_set_mattr_value
     @module.foo = :test
     assert_equal :test, @object.foo
@@ -91,9 +113,23 @@ class ModuleAttributeAccessorTest < ActiveSupport::TestCase
     assert_equal "default_writer_value", @module.class_variable_get("@@defw")
   end
 
-  def test_should_not_invoke_default_value_block_multiple_times
+  def test_method_invocation_should_not_invoke_the_default_block
     count = 0
+
     @module.cattr_accessor(:defcount) { count += 1 }
+
     assert_equal 1, count
+    assert_no_difference "count" do
+      @module.defcount
+    end
+  end
+
+  def test_declaring_multiple_attributes_at_once_invokes_the_block_multiple_times
+    count = 0
+
+    @module.cattr_accessor(:defn1, :defn2) { count += 1 }
+
+    assert_equal 1, @module.defn1
+    assert_equal 2, @module.defn2
   end
 end

guides/source/active_support_core_extensions.md

@@ -940,8 +940,7 @@ The macros `cattr_reader`, `cattr_writer`, and `cattr_accessor` are analogous to
 ```ruby
 class MysqlAdapter < AbstractAdapter
   # Generates class methods to access @@emulate_booleans.
-  cattr_accessor :emulate_booleans
-  self.emulate_booleans = true
+  cattr_accessor :emulate_booleans, default: true
 end
 ```
 
@@ -950,8 +949,7 @@ Instance methods are created as well for convenience, they are just proxies to t
 ```ruby
 module ActionView
   class Base
-    cattr_accessor :field_error_proc
-    @@field_error_proc = Proc.new{ ... }
+    cattr_accessor :field_error_proc, default: Proc.new { ... }
   end
 end
 ```
@@ -963,7 +961,7 @@ Also, you can pass a block to `cattr_*` to set up the attribute with a default v
 ```ruby
 class MysqlAdapter < AbstractAdapter
   # Generates class methods to access @@emulate_booleans with default value of true.
-  cattr_accessor(:emulate_booleans) { true }
+  cattr_accessor :emulate_booleans, default: true
 end
 ```
 

guides/source/plugins.md

@@ -340,8 +340,7 @@ module Yaffle
 
     module ClassMethods
       def acts_as_yaffle(options = {})
-        cattr_accessor :yaffle_text_field
-        self.yaffle_text_field = (options[:yaffle_text_field] || :last_squawk).to_s
+        cattr_accessor :yaffle_text_field, default: (options[:yaffle_text_field] || :last_squawk).to_s
       end
     end
   end
@@ -411,8 +410,7 @@ module Yaffle
 
     module ClassMethods
       def acts_as_yaffle(options = {})
-        cattr_accessor :yaffle_text_field
-        self.yaffle_text_field = (options[:yaffle_text_field] || :last_squawk).to_s
+        cattr_accessor :yaffle_text_field, default: (options[:yaffle_text_field] || :last_squawk).to_s
 
         include Yaffle::ActsAsYaffle::LocalInstanceMethods
       end

railties/lib/rails/info.rb

@@ -5,8 +5,9 @@ module Rails
   # Rails::InfoController responses. These include the active Rails version,
   # Ruby version, Rack version, and so on.
   module Info
-    mattr_accessor :properties
-    class << (@@properties = [])
+    mattr_accessor :properties, default: []
+
+    class << @@properties
       def names
         map(&:first)
       end

railties/lib/rails/test_unit/minitest_plugin.rb

@@ -134,7 +134,7 @@ module Minitest
     end
   end
 
-  mattr_reader(:run_via) { RunVia.new }
+  mattr_reader :run_via, default: RunVia.new
 end
 
 # Put Rails as the first plugin minitest initializes so other plugins