Support configuration on ActiveRecord::Model.

The problem: We need to be able to specify configuration in a way that
can be inherited to models that include ActiveRecord::Model. So it is
no longer sufficient to put 'top level' config on ActiveRecord::Base,
but we do want configuration specified on ActiveRecord::Base and
descendants to continue to work.

So we need something like class_attribute that can be defined on a
module but that is inherited when ActiveRecord::Model is included.

The solution: added ActiveModel::Configuration module which provides a
config_attribute macro. It's a bit specific hence I am not putting this
in Active Support or making it a 'public API' at present.

28 files changed, 498 insertions, 222 deletions

diff --git a/activemodel/lib/active_model.rb b/activemodel/lib/active_model.rb
index d0e2a6f39c..9fc308375f 100644
--- a/activemodel/lib/active_model.rb
+++ b/activemodel/lib/active_model.rb
@@ -32,6 +32,7 @@ module ActiveModel
   autoload :AttributeMethods
   autoload :BlockValidator, 'active_model/validator'
   autoload :Callbacks
+  autoload :Configuration
   autoload :Conversion
   autoload :Dirty
   autoload :EachValidator, 'active_model/validator'
diff --git a/activemodel/lib/active_model/attribute_methods.rb b/activemodel/lib/active_model/attribute_methods.rb
index d7ec7e6ca5..71ab1501c8 100644
--- a/activemodel/lib/active_model/attribute_methods.rb
+++ b/activemodel/lib/active_model/attribute_methods.rb
@@ -61,7 +61,8 @@ module ActiveModel
     CALL_COMPILABLE_REGEXP = /\A[a-zA-Z_]\w*[!?]?\z/
 
     included do
-      class_attribute :attribute_method_matchers, :instance_writer => false
+      extend ActiveModel::Configuration
+      config_attribute :attribute_method_matchers
       self.attribute_method_matchers = [ClassMethods::AttributeMethodMatcher.new]
     end
 
diff --git a/activemodel/lib/active_model/configuration.rb b/activemodel/lib/active_model/configuration.rb
new file mode 100644
index 0000000000..1757c12ebf
--- /dev/null
+++ b/activemodel/lib/active_model/configuration.rb
@@ -0,0 +1,134 @@
+require 'active_support/concern'
+require 'active_support/core_ext/class/attribute'
+require 'active_support/core_ext/class/attribute_accessors'
+
+module ActiveModel
+  # This API is for Rails' internal use and is not currently considered 'public', so
+  # it may change in the future without warning.
+  #
+  # It creates configuration attributes that can be inherited from a module down
+  # to a class that includes the module. E.g.
+  #
+  #   module MyModel
+  #     extend ActiveModel::Configuration
+  #     config_attribute :awesome
+  #     self.awesome = true
+  #   end
+  #
+  #   class Post
+  #     include MyModel
+  #   end
+  #
+  #   Post.awesome # => true
+  #
+  #   Post.awesome = false
+  #   Post.awesome    # => false
+  #   MyModel.awesome # => true
+  #
+  # We assume that the module will have a ClassMethods submodule containing methods
+  # to be transferred to the including class' singleton class.
+  #
+  # Config options can also be defined directly on a class:
+  #
+  #   class Post
+  #     extend ActiveModel::Configuration
+  #     config_attribute :awesome
+  #   end
+  #
+  # So this allows us to define a module that doesn't care about whether it is being
+  # included in a class or a module:
+  #
+  #   module Awesomeness
+  #     extend ActiveSupport::Concern
+  #
+  #     included do
+  #       extend ActiveModel::Configuration
+  #       config_attribute :awesome
+  #       self.awesome = true
+  #     end
+  #   end
+  #
+  #   class Post
+  #     include Awesomeness
+  #   end
+  #
+  #   module AwesomeModel
+  #     include Awesomeness
+  #   end
+  module Configuration #:nodoc:
+    def config_attribute(name, options = {})
+      klass = self.is_a?(Class) ? ClassAttribute : ModuleAttribute
+      klass.new(self, name, options).define
+    end
+
+    class Attribute
+      attr_reader :host, :name, :options
+
+      def initialize(host, name, options)
+        @host, @name, @options = host, name, options
+      end
+
+      def instance_writer?
+        options.fetch(:instance_writer, false)
+      end
+    end
+
+    class ClassAttribute < Attribute
+      def define
+        if options[:global]
+          host.cattr_accessor name, :instance_writer => instance_writer?
+        else
+          host.class_attribute name, :instance_writer => instance_writer?
+        end
+      end
+    end
+
+    class ModuleAttribute < Attribute
+      def class_methods
+        @class_methods ||= begin
+          if host.const_defined?(:ClassMethods, false)
+            host.const_get(:ClassMethods)
+          else
+            host.const_set(:ClassMethods, Module.new)
+          end
+        end
+      end
+
+      def define
+        host.singleton_class.class_eval <<-CODE, __FILE__, __LINE__
+          attr_accessor :#{name}
+          def #{name}?; !!#{name}; end
+        CODE
+
+        name, host = self.name, self.host
+
+        class_methods.class_eval do
+          define_method(name) { host.send(name) }
+          define_method("#{name}?") { !!send(name) }
+        end
+
+        host.class_eval <<-CODE
+          def #{name};  defined?(@#{name}) ? @#{name} : self.class.#{name}; end
+          def #{name}?; !!#{name}; end
+        CODE
+
+        if options[:global]
+          class_methods.class_eval do
+            define_method("#{name}=") { |val| host.send("#{name}=", val) }
+          end
+        else
+          class_methods.class_eval <<-CODE, __FILE__, __LINE__
+            def #{name}=(val)
+              singleton_class.class_eval do
+                remove_possible_method(:#{name})
+                define_method(:#{name}) { val }
+              end
+            end
+          CODE
+        end
+
+        host.send(:attr_writer, name) if instance_writer?
+      end
+    end
+  end
+end
diff --git a/activemodel/lib/active_model/mass_assignment_security.rb b/activemodel/lib/active_model/mass_assignment_security.rb
index c895968f77..9b12d9d281 100644
--- a/activemodel/lib/active_model/mass_assignment_security.rb
+++ b/activemodel/lib/active_model/mass_assignment_security.rb
@@ -10,11 +10,13 @@ module ActiveModel
     extend ActiveSupport::Concern
 
     included do
-      class_attribute :_accessible_attributes
-      class_attribute :_protected_attributes
-      class_attribute :_active_authorizer
+      extend ActiveModel::Configuration
 
-      class_attribute :_mass_assignment_sanitizer
+      config_attribute :_accessible_attributes
+      config_attribute :_protected_attributes
+      config_attribute :_active_authorizer
+
+      config_attribute :_mass_assignment_sanitizer
       self.mass_assignment_sanitizer = :logger
     end
 
@@ -56,7 +58,7 @@ module ActiveModel
     # You can specify your own sanitizer object eg. MySanitizer.new.
     # See <tt>ActiveModel::MassAssignmentSecurity::LoggerSanitizer</tt> for example implementation.
     #
-    # 
+    #
     module ClassMethods
       # Attributes named in this macro are protected from mass-assignment
       # whenever attributes are sanitized before assignment. A role for the
@@ -70,13 +72,13 @@ module ActiveModel
       #
       #   class Customer
       #     include ActiveModel::MassAssignmentSecurity
-      #   
+      #
       #     attr_accessor :name, :email, :logins_count
-      #   
+      #
       #     attr_protected :logins_count
       #     # Suppose that admin can not change email for customer
-      #     attr_protected :logins_count, :email, :as => :admin 
-      #   
+      #     attr_protected :logins_count, :email, :as => :admin
+      #
       #     def assign_attributes(values, options = {})
       #       sanitize_for_mass_assignment(values, options[:as]).each do |k, v|
       #         send("#{k}=", v)
@@ -99,7 +101,7 @@ module ActiveModel
       #   customer.name          # => "David"
       #   customer.email # => nil
       #   customer.logins_count    # => nil
-      #   
+      #
       #   customer.email = "c@d.com"
       #   customer.email # => "c@d.com"
       #
diff --git a/activemodel/lib/active_model/serializers/json.rb b/activemodel/lib/active_model/serializers/json.rb
index c845440120..63ab8e7edc 100644
--- a/activemodel/lib/active_model/serializers/json.rb
+++ b/activemodel/lib/active_model/serializers/json.rb
@@ -10,8 +10,9 @@ module ActiveModel
 
       included do
         extend ActiveModel::Naming
+        extend ActiveModel::Configuration
 
-        class_attribute :include_root_in_json
+        config_attribute :include_root_in_json
         self.include_root_in_json = true
       end
 
diff --git a/activemodel/lib/active_model/validations.rb b/activemodel/lib/active_model/validations.rb
index 8ed392abca..1779efd526 100644
--- a/activemodel/lib/active_model/validations.rb
+++ b/activemodel/lib/active_model/validations.rb
@@ -42,9 +42,9 @@ module ActiveModel
   #
   module Validations
     extend ActiveSupport::Concern
-    include ActiveSupport::Callbacks
 
     included do
+      extend ActiveModel::Callbacks
       extend ActiveModel::Translation
 
       extend  HelperMethods
@@ -53,7 +53,8 @@ module ActiveModel
       attr_accessor :validation_context
       define_callbacks :validate, :scope => :name
 
-      class_attribute :_validators
+      extend ActiveModel::Configuration
+      config_attribute :_validators
       self._validators = Hash.new { |h,k| h[k] = [] }
     end
 
diff --git a/activemodel/test/cases/configuration_test.rb b/activemodel/test/cases/configuration_test.rb
new file mode 100644
index 0000000000..a172fa26a3
--- /dev/null
+++ b/activemodel/test/cases/configuration_test.rb
@@ -0,0 +1,154 @@
+require 'cases/helper'
+
+class ConfigurationOnModuleTest < ActiveModel::TestCase
+  def setup
+    @mod = mod = Module.new do
+      extend ActiveSupport::Concern
+      extend ActiveModel::Configuration
+
+      config_attribute :omg
+      self.omg = "default"
+
+      config_attribute :wtf, global: true
+      self.wtf = "default"
+
+      config_attribute :boolean
+
+      config_attribute :lol, instance_writer: true
+    end
+
+    @klass = Class.new do
+      include mod
+    end
+
+    @subklass = Class.new(@klass)
+  end
+
+  test "default" do
+    assert_equal "default", @mod.omg
+    assert_equal "default", @klass.omg
+    assert_equal "default", @klass.new.omg
+  end
+
+  test "setting" do
+    @mod.omg = "lol"
+    assert_equal "lol", @mod.omg
+  end
+
+  test "setting on class including the module" do
+    @klass.omg = "lol"
+    assert_equal "lol", @klass.omg
+    assert_equal "lol", @klass.new.omg
+    assert_equal "default", @mod.omg
+  end
+
+  test "setting on subclass of class including the module" do
+    @subklass.omg = "lol"
+    assert_equal "lol", @subklass.omg
+    assert_equal "default", @klass.omg
+    assert_equal "default", @mod.omg
+  end
+
+  test "setting on instance" do
+    assert !@klass.new.respond_to?(:omg=)
+
+    @klass.lol = "lol"
+    obj = @klass.new
+    assert_equal "lol", obj.lol
+    obj.lol = "omg"
+    assert_equal "omg", obj.lol
+    assert_equal "lol", @klass.lol
+    assert_equal "lol", @klass.new.lol
+    obj.lol = false
+    assert !obj.lol?
+  end
+
+  test "global attribute" do
+    assert_equal "default", @mod.wtf
+    assert_equal "default", @klass.wtf
+
+    @mod.wtf = "wtf"
+
+    assert_equal "wtf", @mod.wtf
+    assert_equal "wtf", @klass.wtf
+
+    @klass.wtf = "lol"
+
+    assert_equal "lol", @mod.wtf
+    assert_equal "lol", @klass.wtf
+  end
+
+  test "boolean" do
+    assert_equal false, @mod.boolean?
+    assert_equal false, @klass.new.boolean?
+    @mod.boolean = true
+    assert_equal true, @mod.boolean?
+    assert_equal true, @klass.new.boolean?
+  end
+end
+
+class ConfigurationOnClassTest < ActiveModel::TestCase
+  def setup
+    @klass = Class.new do
+      extend ActiveModel::Configuration
+
+      config_attribute :omg
+      self.omg = "default"
+
+      config_attribute :wtf, global: true
+      self.wtf = "default"
+
+      config_attribute :omg2, instance_writer: true
+      config_attribute :wtf2, instance_writer: true, global: true
+    end
+
+    @subklass = Class.new(@klass)
+  end
+
+  test "defaults" do
+    assert_equal "default", @klass.omg
+    assert_equal "default", @klass.wtf
+    assert_equal "default", @subklass.omg
+    assert_equal "default", @subklass.wtf
+  end
+
+  test "changing" do
+    @klass.omg = "lol"
+    assert_equal "lol", @klass.omg
+    assert_equal "lol", @subklass.omg
+  end
+
+  test "changing in subclass" do
+    @subklass.omg = "lol"
+    assert_equal "lol", @subklass.omg
+    assert_equal "default", @klass.omg
+  end
+
+  test "changing global" do
+    @klass.wtf = "wtf"
+    assert_equal "wtf", @klass.wtf
+    assert_equal "wtf", @subklass.wtf
+
+    @subklass.wtf = "lol"
+    assert_equal "lol", @klass.wtf
+    assert_equal "lol", @subklass.wtf
+  end
+
+  test "instance_writer" do
+    obj = @klass.new
+
+    @klass.omg2 = "omg"
+    @klass.wtf2 = "wtf"
+
+    assert_equal "omg", obj.omg2
+    assert_equal "wtf", obj.wtf2
+
+    obj.omg2 = "lol"
+    obj.wtf2 = "lol"
+
+    assert_equal "lol", obj.omg2
+    assert_equal "lol", obj.wtf2
+    assert_equal "omg", @klass.omg2
+    assert_equal "lol", @klass.wtf2
+  end
+end
diff --git a/activerecord/lib/active_record.rb b/activerecord/lib/active_record.rb
index 4d143146d5..360b1218e6 100644
--- a/activerecord/lib/active_record.rb
+++ b/activerecord/lib/active_record.rb
@@ -57,7 +57,6 @@ module ActiveRecord
 
     autoload :Base
     autoload :Callbacks
-    autoload :Configuration
     autoload :Core
     autoload :CounterCache
     autoload :DynamicMatchers
diff --git a/activerecord/lib/active_record/attribute_methods/dirty.rb b/activerecord/lib/active_record/attribute_methods/dirty.rb
index f61e016f46..40e4a97e73 100644
--- a/activerecord/lib/active_record/attribute_methods/dirty.rb
+++ b/activerecord/lib/active_record/attribute_methods/dirty.rb
@@ -13,7 +13,7 @@ module ActiveRecord
           raise "You cannot include Dirty after Timestamp"
         end
 
-        class_attribute :partial_updates
+        config_attribute :partial_updates
         self.partial_updates = true
       end
 
diff --git a/activerecord/lib/active_record/attribute_methods/read.rb b/activerecord/lib/active_record/attribute_methods/read.rb
index 7d2d1db4b5..964c4123ef 100644
--- a/activerecord/lib/active_record/attribute_methods/read.rb
+++ b/activerecord/lib/active_record/attribute_methods/read.rb
@@ -5,7 +5,10 @@ module ActiveRecord
 
       ATTRIBUTE_TYPES_CACHED_BY_DEFAULT = [:datetime, :timestamp, :time, :date]
 
-      Configuration.define :attribute_types_cached_by_default, ATTRIBUTE_TYPES_CACHED_BY_DEFAULT
+      included do
+        config_attribute :attribute_types_cached_by_default, :global => true
+        self.attribute_types_cached_by_default = ATTRIBUTE_TYPES_CACHED_BY_DEFAULT
+      end
 
       module ClassMethods
         # +cache_attributes+ allows you to declare which converted attribute values should
diff --git a/activerecord/lib/active_record/attribute_methods/serialization.rb b/activerecord/lib/active_record/attribute_methods/serialization.rb
index 2ffd91f796..0c8e4e4b9a 100644
--- a/activerecord/lib/active_record/attribute_methods/serialization.rb
+++ b/activerecord/lib/active_record/attribute_methods/serialization.rb
@@ -6,7 +6,7 @@ module ActiveRecord
       included do
         # Returns a hash of all the attributes that have been specified for serialization as
         # keys and their class restriction as values.
-        class_attribute :serialized_attributes
+        config_attribute :serialized_attributes
         self.serialized_attributes = {}
       end
 
diff --git a/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb b/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb
index 5e5392441b..2f86e32f41 100644
--- a/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb
+++ b/activerecord/lib/active_record/attribute_methods/time_zone_conversion.rb
@@ -6,10 +6,11 @@ module ActiveRecord
     module TimeZoneConversion
       extend ActiveSupport::Concern
 
-      Configuration.define :time_zone_aware_attributes, false
-
       included do
-        class_attribute :skip_time_zone_conversion_for_attributes, :instance_writer => false
+        config_attribute :time_zone_aware_attributes, :global => true
+        self.time_zone_aware_attributes = false
+
+        config_attribute :skip_time_zone_conversion_for_attributes
         self.skip_time_zone_conversion_for_attributes = []
       end
 
diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index 6085df7d9f..fbdb50f6b3 100644
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -328,7 +328,6 @@ module ActiveRecord #:nodoc:
   # instances in the current object space.
   class Base
     include ActiveRecord::Model
-    self.connection_handler = ConnectionAdapters::ConnectionHandler.new
   end
 end
 
diff --git a/activerecord/lib/active_record/callbacks.rb b/activerecord/lib/active_record/callbacks.rb
index a175bf003c..8b2fc69b00 100644
--- a/activerecord/lib/active_record/callbacks.rb
+++ b/activerecord/lib/active_record/callbacks.rb
@@ -25,7 +25,7 @@ module ActiveRecord
   # Check out <tt>ActiveRecord::Transactions</tt> for more details about <tt>after_commit</tt> and
   # <tt>after_rollback</tt>.
   #
-  # Lastly an <tt>after_find</tt> and <tt>after_initialize</tt> callback is triggered for each object that 
+  # Lastly an <tt>after_find</tt> and <tt>after_initialize</tt> callback is triggered for each object that
   # is found and instantiated by a finder, with <tt>after_initialize</tt> being triggered after new objects
   # are instantiated as well.
   #
@@ -215,24 +215,48 @@ module ActiveRecord
   # instead of quietly returning +false+.
   #
   # == Debugging callbacks
-  # 
-  # The callback chain is accessible via the <tt>_*_callbacks</tt> method on an object. ActiveModel Callbacks support 
+  #
+  # The callback chain is accessible via the <tt>_*_callbacks</tt> method on an object. ActiveModel Callbacks support
   # <tt>:before</tt>, <tt>:after</tt> and <tt>:around</tt> as values for the <tt>kind</tt> property. The <tt>kind</tt> property
   # defines what part of the chain the callback runs in.
-  # 
-  # To find all callbacks in the before_save callback chain: 
-  # 
+  #
+  # To find all callbacks in the before_save callback chain:
+  #
   #   Topic._save_callbacks.select { |cb| cb.kind.eql?(:before) }
-  # 
+  #
   # Returns an array of callback objects that form the before_save chain.
-  # 
+  #
   # To further check if the before_save chain contains a proc defined as <tt>rest_when_dead</tt> use the <tt>filter</tt> property of the callback object:
-  # 
+  #
   #   Topic._save_callbacks.select { |cb| cb.kind.eql?(:before) }.collect(&:filter).include?(:rest_when_dead)
-  # 
+  #
   # Returns true or false depending on whether the proc is contained in the before_save callback chain on a Topic model.
-  # 
+  #
   module Callbacks
+    # We can't define callbacks directly on ActiveRecord::Model because
+    # it is a module. So we queue up the definitions and execute them
+    # when ActiveRecord::Model is included.
+    module Register #:nodoc:
+      def self.extended(base)
+        base.config_attribute :_callbacks_register
+        base._callbacks_register = []
+      end
+
+      def self.setup(base)
+        base._callbacks_register.each do |item|
+          base.send(*item)
+        end
+      end
+
+      def define_callbacks(*args)
+        self._callbacks_register << [:define_callbacks, *args]
+      end
+
+      def define_model_callbacks(*args)
+        self._callbacks_register << [:define_model_callbacks, *args]
+      end
+    end
+
     extend ActiveSupport::Concern
 
     CALLBACKS = [
@@ -242,8 +266,11 @@ module ActiveRecord
       :before_destroy, :around_destroy, :after_destroy, :after_commit, :after_rollback
     ]
 
+    module ClassMethods
+      include ActiveModel::Callbacks
+    end
+
     included do
-      extend ActiveModel::Callbacks
       include ActiveModel::Validations::Callbacks
 
       define_model_callbacks :initialize, :find, :touch, :only => :after
diff --git a/activerecord/lib/active_record/configuration.rb b/activerecord/lib/active_record/configuration.rb
deleted file mode 100644
index d58ed82258..0000000000
--- a/activerecord/lib/active_record/configuration.rb
+++ /dev/null
@@ -1,36 +0,0 @@
-require 'active_support/concern'
-
-module ActiveRecord
-  # This module allows configuration options to be specified in a way such that
-  # ActiveRecord::Base and ActiveRecord::Model will have access to the same value,
-  # and will automatically get the appropriate readers and writers defined.
-  #
-  # In the future, we should probably move away from defining global config
-  # directly on ActiveRecord::Base / ActiveRecord::Model.
-  module Configuration #:nodoc:
-    extend ActiveSupport::Concern
-
-    module ClassMethods
-    end
-
-    def self.define(name, default = nil)
-      singleton_class.send(:attr_accessor, name)
-
-      [self, ClassMethods].each do |klass|
-        klass.class_eval <<-CODE, __FILE__, __LINE__
-          def #{name}
-            ActiveRecord::Configuration.#{name}
-          end
-        CODE
-      end
-
-      ClassMethods.class_eval <<-CODE, __FILE__, __LINE__
-        def #{name}=(val)
-          ActiveRecord::Configuration.#{name} = val
-        end
-      CODE
-
-      send("#{name}=", default) unless default.nil?
-    end
-  end
-end
diff --git a/activerecord/lib/active_record/core.rb b/activerecord/lib/active_record/core.rb
index 4f118e46a9..c29a0032bc 100644
--- a/activerecord/lib/active_record/core.rb
+++ b/activerecord/lib/active_record/core.rb
@@ -4,70 +4,75 @@ module ActiveRecord
   module Core
     extend ActiveSupport::Concern
 
-    ##
-    # :singleton-method:
-    # Accepts a logger conforming to the interface of Log4r or the default Ruby 1.8+ Logger class,
-    # which is then passed on to any new database connections made and which can be retrieved on both
-    # a class and instance level by calling +logger+.
-    Configuration.define :logger
-
-    ##
-    # :singleton-method:
-    # Contains the database configuration - as is typically stored in config/database.yml -
-    # as a Hash.
-    #
-    # For example, the following database.yml...
-    #
-    #   development:
-    #     adapter: sqlite3
-    #     database: db/development.sqlite3
-    #
-    #   production:
-    #     adapter: sqlite3
-    #     database: db/production.sqlite3
-    #
-    # ...would result in ActiveRecord::Base.configurations to look like this:
-    #
-    #   {
-    #      'development' => {
-    #         'adapter'  => 'sqlite3',
-    #         'database' => 'db/development.sqlite3'
-    #      },
-    #      'production' => {
-    #         'adapter'  => 'sqlite3',
-    #         'database' => 'db/production.sqlite3'
-    #      }
-    #   }
-    Configuration.define :configurations, {}
-
-    ##
-    # :singleton-method:
-    # Determines whether to use Time.local (using :local) or Time.utc (using :utc) when pulling
-    # dates and times from the database. This is set to :local by default.
-    Configuration.define :default_timezone, :local
-
-    ##
-    # :singleton-method:
-    # Specifies the format to use when dumping the database schema with Rails'
-    # Rakefile. If :sql, the schema is dumped as (potentially database-
-    # specific) SQL statements. If :ruby, the schema is dumped as an
-    # 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.
-    Configuration.define :schema_format, :ruby
-
-    ##
-    # :singleton-method:
-    # Specify whether or not to use timestamps for migration versions
-    Configuration.define :timestamped_migrations, true
-
     included do
       ##
       # :singleton-method:
+      # Accepts a logger conforming to the interface of Log4r or the default Ruby 1.8+ Logger class,
+      # which is then passed on to any new database connections made and which can be retrieved on both
+      # a class and instance level by calling +logger+.
+      config_attribute :logger, :global => true
+
+      ##
+      # :singleton-method:
+      # Contains the database configuration - as is typically stored in config/database.yml -
+      # as a Hash.
+      #
+      # For example, the following database.yml...
+      #
+      #   development:
+      #     adapter: sqlite3
+      #     database: db/development.sqlite3
+      #
+      #   production:
+      #     adapter: sqlite3
+      #     database: db/production.sqlite3
+      #
+      # ...would result in ActiveRecord::Base.configurations to look like this:
+      #
+      #   {
+      #      'development' => {
+      #         'adapter'  => 'sqlite3',
+      #         'database' => 'db/development.sqlite3'
+      #      },
+      #      'production' => {
+      #         'adapter'  => 'sqlite3',
+      #         'database' => 'db/production.sqlite3'
+      #      }
+      #   }
+      config_attribute :configurations, :global => true
+      self.configurations = {}
+
+      ##
+      # :singleton-method:
+      # Determines whether to use Time.local (using :local) or Time.utc (using :utc) when pulling
+      # dates and times from the database. This is set to :local by default.
+      config_attribute :default_timezone, :global => true
+      self.default_timezone = :local
+
+      ##
+      # :singleton-method:
+      # Specifies the format to use when dumping the database schema with Rails'
+      # Rakefile. If :sql, the schema is dumped as (potentially database-
+      # specific) SQL statements. If :ruby, the schema is dumped as an
+      # 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.
+      config_attribute :schema_format, :global => true
+      self.schema_format = :ruby
+
+      ##
+      # :singleton-method:
+      # Specify whether or not to use timestamps for migration versions
+      config_attribute :timestamped_migrations, :global => true
+      self.timestamped_migrations = true
+
+      ##
+      # :singleton-method:
       # The connection handler
-      class_attribute :connection_handler, :instance_writer => false
+      config_attribute :connection_handler
+      self.connection_handler = ConnectionAdapters::ConnectionHandler.new
 
-      initialize_generated_modules unless self == Base
+      #
     end
 
     module ClassMethods
diff --git a/activerecord/lib/active_record/explain.rb b/activerecord/lib/active_record/explain.rb
index b5a67afd88..e502d7e52b 100644
--- a/activerecord/lib/active_record/explain.rb
+++ b/activerecord/lib/active_record/explain.rb
@@ -2,9 +2,11 @@ require 'active_support/core_ext/class/attribute'
 
 module ActiveRecord
   module Explain
-    # If a query takes longer than these many seconds we log its query plan
-    # automatically. nil disables this feature.
-    Configuration.define :auto_explain_threshold_in_seconds
+    def self.extended(base)
+      # If a query takes longer than these many seconds we log its query plan
+      # automatically. nil disables this feature.
+      base.config_attribute :auto_explain_threshold_in_seconds, :global => true
+    end
 
     # If auto explain is enabled, this method triggers EXPLAIN logging for the
     # queries triggered by the block if it takes more than the threshold as a
diff --git a/activerecord/lib/active_record/inheritance.rb b/activerecord/lib/active_record/inheritance.rb
index ec57151d40..0e92b7cf41 100644
--- a/activerecord/lib/active_record/inheritance.rb
+++ b/activerecord/lib/active_record/inheritance.rb
@@ -6,7 +6,7 @@ module ActiveRecord
 
     included do
       # Determine whether to store the full constant name including namespace when using STI
-      class_attribute :store_full_sti_class
+      config_attribute :store_full_sti_class
       self.store_full_sti_class = true
     end
 
@@ -88,7 +88,7 @@ module ActiveRecord
       #
       # Mainly for internal use.
       def active_record_super #:nodoc:
-        if self == Base || superclass && superclass < Model::Tag
+        if self == Base || superclass && superclass < Model
           superclass
         else
           Base
@@ -100,7 +100,7 @@ module ActiveRecord
       # Returns the class descending directly from ActiveRecord::Base or an
       # abstract class, if any, in the inheritance hierarchy.
       def class_of_active_record_descendant(klass)
-        unless klass < Model::Tag
+        unless klass < Model
           raise ActiveRecordError, "#{name} doesn't belong in a hierarchy descending from ActiveRecord"
         end
 
diff --git a/activerecord/lib/active_record/locking/optimistic.rb b/activerecord/lib/active_record/locking/optimistic.rb
index b80d01db81..e643c0d437 100644
--- a/activerecord/lib/active_record/locking/optimistic.rb
+++ b/activerecord/lib/active_record/locking/optimistic.rb
@@ -48,7 +48,10 @@ module ActiveRecord
     module Optimistic
       extend ActiveSupport::Concern
 
-      Configuration.define :lock_optimistically, true
+      included do
+        config_attribute :lock_optimistically, :global => true
+        self.lock_optimistically = true
+      end
 
       def locking_enabled? #:nodoc:
         self.class.locking_enabled?
diff --git a/activerecord/lib/active_record/model.rb b/activerecord/lib/active_record/model.rb
index f87be257db..86c4d18534 100644
--- a/activerecord/lib/active_record/model.rb
+++ b/activerecord/lib/active_record/model.rb
@@ -1,4 +1,5 @@
 require 'active_support/deprecation'
+require 'active_support/concern'
 
 module ActiveRecord
   # <tt>ActiveRecord::Model</tt> can be included into a class to add Active Record persistence.
@@ -9,57 +10,61 @@ module ActiveRecord
   #     end
   #
   module Model
-    # So we can recognise an AR class even while self.included is being
-    # executed. (At that time, klass < Model == false.)
-    module Tag #:nodoc:
+    module ClassMethods #:nodoc:
+      include ActiveSupport::Callbacks::ClassMethods
+      include ActiveModel::Naming
+      include QueryCache::ClassMethods
+      include ActiveSupport::Benchmarkable
+      include ActiveSupport::DescendantsTracker
+
+      include Querying
+      include Translation
+      include DynamicMatchers
+      include CounterCache
+      include Explain
     end
 
     def self.included(base)
-      return if base < Tag
+      return if base.singleton_class < ClassMethods
 
       base.class_eval do
-        include Tag
-
-        include Configuration
-
-        include ActiveRecord::Persistence
-        extend ActiveModel::Naming
-        extend QueryCache::ClassMethods
-        extend ActiveSupport::Benchmarkable
-        extend ActiveSupport::DescendantsTracker
-
-        extend Querying
-        include ReadonlyAttributes
-        include ModelSchema
-        extend Translation
-        include Inheritance
-        include Scoping
-        extend DynamicMatchers
-        include Sanitization
-        include Integration
-        include AttributeAssignment
-        include ActiveModel::Conversion
-        include Validations
-        extend CounterCache
-        include Locking::Optimistic, Locking::Pessimistic
-        include AttributeMethods
-        include Callbacks, ActiveModel::Observing, Timestamp
-        include Associations
-        include IdentityMap
-        include ActiveModel::SecurePassword
-        extend Explain
-
-        # AutosaveAssociation needs to be included before Transactions, because we want
-        # #save_with_autosave_associations to be wrapped inside a transaction.
-        include AutosaveAssociation, NestedAttributes
-        include Aggregations, Transactions, Reflection, Serialization, Store
+        extend ClassMethods
+        Callbacks::Register.setup(self)
+        initialize_generated_modules unless self == Base
+      end
+    end
 
-        include Core
+    extend ActiveModel::Configuration
+    extend ActiveModel::Callbacks
+    extend ActiveModel::MassAssignmentSecurity::ClassMethods
+    extend ActiveModel::AttributeMethods::ClassMethods
+    extend Callbacks::Register
+    extend Explain
 
-        self.connection_handler = Base.connection_handler
-      end
+    def self.extend(*modules)
+      ClassMethods.send(:include, *modules)
     end
 
+    include Persistence
+    include ReadonlyAttributes
+    include ModelSchema
+    include Inheritance
+    include Scoping
+    include Sanitization
+    include Integration
+    include AttributeAssignment
+    include ActiveModel::Conversion
+    include Validations
+    include Locking::Optimistic, Locking::Pessimistic
+    include AttributeMethods
+    include Callbacks, ActiveModel::Observing, Timestamp
+    include Associations
+    include IdentityMap
+    include ActiveModel::SecurePassword
+    include AutosaveAssociation, NestedAttributes
+    include Aggregations, Transactions, Reflection, Serialization, Store
+    include Core
+
     module DeprecationProxy #:nodoc:
       class << self
         instance_methods.each { |m| undef_method m unless m =~ /^__|^object_id$|^instance_eval$/ }
diff --git a/activerecord/lib/active_record/model_schema.rb b/activerecord/lib/active_record/model_schema.rb
index adf85c6436..d9d18a9752 100644
--- a/activerecord/lib/active_record/model_schema.rb
+++ b/activerecord/lib/active_record/model_schema.rb
@@ -5,18 +5,18 @@ module ActiveRecord
   module ModelSchema
     extend ActiveSupport::Concern
 
-    ##
-    # :singleton-method:
-    # Accessor for the prefix type that will be prepended to every primary key column name.
-    # The options are :table_name and :table_name_with_underscore. If the first is specified,
-    # the Product class will look for "productid" instead of "id" as the primary column. If the
-    # latter is specified, the Product class will look for "product_id" instead of "id". Remember
-    # that this is a global setting for all Active Records.
-    Configuration.define :primary_key_prefix_type
-
     included do
       ##
       # :singleton-method:
+      # Accessor for the prefix type that will be prepended to every primary key column name.
+      # The options are :table_name and :table_name_with_underscore. If the first is specified,
+      # the Product class will look for "productid" instead of "id" as the primary column. If the
+      # latter is specified, the Product class will look for "product_id" instead of "id". Remember
+      # that this is a global setting for all Active Records.
+      config_attribute :primary_key_prefix_type, :global => true
+
+      ##
+      # :singleton-method:
       # Accessor for the name of the prefix string to prepend to every table name. So if set
       # to "basecamp_", all table names will be named like "basecamp_projects", "basecamp_people",
       # etc. This is a convenient way of creating a namespace for tables in a shared database.
@@ -25,14 +25,14 @@ module ActiveRecord
       # If you are organising your models within modules you can add a prefix to the models within
       # a namespace by defining a singleton method in the parent module called table_name_prefix which
       # returns your chosen prefix.
-      class_attribute :table_name_prefix, :instance_writer => false
+      config_attribute :table_name_prefix
       self.table_name_prefix = ""
 
       ##
       # :singleton-method:
       # Works like +table_name_prefix+, but appends instead of prepends (set to "_basecamp" gives "projects_basecamp",
       # "people_basecamp"). By default, the suffix is the empty string.
-      class_attribute :table_name_suffix, :instance_writer => false
+      config_attribute :table_name_suffix
       self.table_name_suffix = ""
 
       ##
@@ -40,7 +40,7 @@ module ActiveRecord
       # Indicates whether table names should be the pluralized versions of the corresponding class names.
       # If true, the default table name for a Product class will be +products+. If false, it would just be +product+.
       # See table_name for the full rules on table/class naming. This is true, by default.
-      class_attribute :pluralize_table_names, :instance_writer => false
+      config_attribute :pluralize_table_names
       self.pluralize_table_names = true
     end
 
diff --git a/activerecord/lib/active_record/nested_attributes.rb b/activerecord/lib/active_record/nested_attributes.rb
index d2065d701f..a8ee43b598 100644
--- a/activerecord/lib/active_record/nested_attributes.rb
+++ b/activerecord/lib/active_record/nested_attributes.rb
@@ -12,7 +12,7 @@ module ActiveRecord
     extend ActiveSupport::Concern
 
     included do
-      class_attribute :nested_attributes_options, :instance_writer => false
+      config_attribute :nested_attributes_options
       self.nested_attributes_options = {}
     end
 
diff --git a/activerecord/lib/active_record/readonly_attributes.rb b/activerecord/lib/active_record/readonly_attributes.rb
index bf37ab5f14..836b15e2ce 100644
--- a/activerecord/lib/active_record/readonly_attributes.rb
+++ b/activerecord/lib/active_record/readonly_attributes.rb
@@ -6,7 +6,7 @@ module ActiveRecord
     extend ActiveSupport::Concern
 
     included do
-      class_attribute :_attr_readonly, :instance_writer => false
+      config_attribute :_attr_readonly
       self._attr_readonly = []
     end
 
diff --git a/activerecord/lib/active_record/reflection.rb b/activerecord/lib/active_record/reflection.rb
index 794a0526fb..60b73e9fe5 100644
--- a/activerecord/lib/active_record/reflection.rb
+++ b/activerecord/lib/active_record/reflection.rb
@@ -7,7 +7,8 @@ module ActiveRecord
     extend ActiveSupport::Concern
 
     included do
-      class_attribute :reflections
+      extend ActiveModel::Configuration
+      config_attribute :reflections
       self.reflections = {}
     end
 
diff --git a/activerecord/lib/active_record/scoping/default.rb b/activerecord/lib/active_record/scoping/default.rb
index 6b5070808a..5f05d146f2 100644
--- a/activerecord/lib/active_record/scoping/default.rb
+++ b/activerecord/lib/active_record/scoping/default.rb
@@ -7,7 +7,7 @@ module ActiveRecord
 
       included do
         # Stores the default scope for the class
-        class_attribute :default_scopes, :instance_writer => false
+        config_attribute :default_scopes
         self.default_scopes = []
       end
 
diff --git a/activerecord/lib/active_record/timestamp.rb b/activerecord/lib/active_record/timestamp.rb
index 0c760e9850..c717fdea47 100644
--- a/activerecord/lib/active_record/timestamp.rb
+++ b/activerecord/lib/active_record/timestamp.rb
@@ -33,7 +33,7 @@ module ActiveRecord
     extend ActiveSupport::Concern
 
     included do
-      class_attribute :record_timestamps
+      config_attribute :record_timestamps, :instance_writer => true
       self.record_timestamps = true
     end
 
diff --git a/activerecord/test/cases/attribute_methods/read_test.rb b/activerecord/test/cases/attribute_methods/read_test.rb
index 375c207d20..0df9ffc0c5 100644
--- a/activerecord/test/cases/attribute_methods/read_test.rb
+++ b/activerecord/test/cases/attribute_methods/read_test.rb
@@ -18,7 +18,6 @@ module ActiveRecord
           def self.active_record_super; Base; end
           def self.base_class; self; end
 
-          include ActiveRecord::Configuration
           include ActiveRecord::AttributeMethods
 
           def self.column_names
diff --git a/activerecord/test/cases/configuration_test.rb b/activerecord/test/cases/configuration_test.rb
deleted file mode 100644
index 872f1fc33b..0000000000
--- a/activerecord/test/cases/configuration_test.rb
+++ /dev/null
@@ -1,26 +0,0 @@
-require 'cases/helper'
-
-class ConfigurationTest < ActiveRecord::TestCase
-  def test_configuration
-    @klass = Class.new do
-      include ActiveRecord::Configuration
-    end
-
-    ActiveRecord::Configuration.define :omg
-
-    ActiveRecord::Configuration.omg = "omg"
-
-    assert_equal "omg", @klass.new.omg
-    assert !@klass.new.respond_to?(:omg=)
-    assert_equal "omg", @klass.omg
-
-    @klass.omg = "wtf"
-
-    assert_equal "wtf", @klass.omg
-    assert_equal "wtf", @klass.new.omg
-  ensure
-    ActiveRecord::Configuration.send(:undef_method, :omg)
-    ActiveRecord::Configuration::ClassMethods.send(:undef_method, :omg)
-    ActiveRecord::Configuration::ClassMethods.send(:undef_method, :omg=)
-  end
-end