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.

1 files changed, 39 insertions, 12 deletions

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