Merge commit 'mainstream/master'

Conflicts:
	actionpack/lib/action_controller.rb
	actionpack/lib/action_controller/base/base.rb
	actionpack/lib/action_view/template/path.rb
	activesupport/lib/active_support/json/encoders/hash.rb

23 files changed, 315 insertions, 352 deletions

diff --git a/activerecord/lib/active_record.rb b/activerecord/lib/active_record.rb
index ee6f99edb5..63eb5c3eeb 100644
--- a/activerecord/lib/active_record.rb
+++ b/activerecord/lib/active_record.rb
@@ -59,7 +59,7 @@ module ActiveRecord
   autoload :Migrator, 'active_record/migration'
   autoload :NamedScope, 'active_record/named_scope'
   autoload :NestedAttributes, 'active_record/nested_attributes'
-  autoload :Observing, 'active_record/observer'
+  autoload :Observer, 'active_record/observer'
   autoload :QueryCache, 'active_record/query_cache'
   autoload :Reflection, 'active_record/reflection'
   autoload :Schema, 'active_record/schema'
diff --git a/activerecord/lib/active_record/associations.rb b/activerecord/lib/active_record/associations.rb
index 2134266f72..d3c859ccf4 100755
--- a/activerecord/lib/active_record/associations.rb
+++ b/activerecord/lib/active_record/associations.rb
@@ -1308,13 +1308,8 @@ module ActiveRecord
               association = association_proxy_class.new(self, reflection)
             end
 
-            if association_proxy_class == HasOneThroughAssociation
-              association.create_through_record(new_value)
-              self.send(reflection.name, new_value)
-            else
-              association.replace(new_value)
-              association_instance_set(reflection.name, new_value.nil? ? nil : association)
-            end
+            association.replace(new_value)
+            association_instance_set(reflection.name, new_value.nil? ? nil : association)
           end
 
           define_method("set_#{reflection.name}_target") do |target|
diff --git a/activerecord/lib/active_record/associations/association_collection.rb b/activerecord/lib/active_record/associations/association_collection.rb
index c3e5bd8575..e67ccfb228 100644
--- a/activerecord/lib/active_record/associations/association_collection.rb
+++ b/activerecord/lib/active_record/associations/association_collection.rb
@@ -351,7 +351,19 @@ module ActiveRecord
       protected
         def construct_find_options!(options)
         end
-        
+
+        def construct_counter_sql
+          if @reflection.options[:counter_sql]
+            @counter_sql = interpolate_sql(@reflection.options[:counter_sql])
+          elsif @reflection.options[:finder_sql]
+            # replace the SELECT clause with COUNT(*), preserving any hints within /* ... */
+            @reflection.options[:counter_sql] = @reflection.options[:finder_sql].sub(/SELECT\b(\/\*.*?\*\/ )?(.*)\bFROM\b/im) { "SELECT #{$1}COUNT(*) FROM" }
+            @counter_sql = interpolate_sql(@reflection.options[:counter_sql])
+          else
+            @counter_sql = @finder_sql
+          end
+        end
+
         def load_target
           if !@owner.new_record? || foreign_key_present
             begin
diff --git a/activerecord/lib/active_record/associations/has_and_belongs_to_many_association.rb b/activerecord/lib/active_record/associations/has_and_belongs_to_many_association.rb
index af9ce3dfb2..fd23e59e82 100644
--- a/activerecord/lib/active_record/associations/has_and_belongs_to_many_association.rb
+++ b/activerecord/lib/active_record/associations/has_and_belongs_to_many_association.rb
@@ -85,15 +85,7 @@ module ActiveRecord
 
           @join_sql = "INNER JOIN #{@owner.connection.quote_table_name @reflection.options[:join_table]} ON #{@reflection.quoted_table_name}.#{@reflection.klass.primary_key} = #{@owner.connection.quote_table_name @reflection.options[:join_table]}.#{@reflection.association_foreign_key}"
 
-          if @reflection.options[:counter_sql]
-            @counter_sql = interpolate_sql(@reflection.options[:counter_sql])
-          elsif @reflection.options[:finder_sql]
-            # replace the SELECT clause with COUNT(*), preserving any hints within /* ... */
-            @reflection.options[:counter_sql] = @reflection.options[:finder_sql].sub(/SELECT (\/\*.*?\*\/ )?(.*)\bFROM\b/im) { "SELECT #{$1}COUNT(*) FROM" }
-            @counter_sql = interpolate_sql(@reflection.options[:counter_sql])
-          else
-            @counter_sql = @finder_sql
-          end
+          construct_counter_sql
         end
 
         def construct_scope
diff --git a/activerecord/lib/active_record/associations/has_many_association.rb b/activerecord/lib/active_record/associations/has_many_association.rb
index 73dd50dd07..e4b631bc54 100644
--- a/activerecord/lib/active_record/associations/has_many_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_association.rb
@@ -97,15 +97,7 @@ module ActiveRecord
               @finder_sql << " AND (#{conditions})" if conditions
           end
 
-          if @reflection.options[:counter_sql]
-            @counter_sql = interpolate_sql(@reflection.options[:counter_sql])
-          elsif @reflection.options[:finder_sql]
-            # replace the SELECT clause with COUNT(*), preserving any hints within /* ... */
-            @reflection.options[:counter_sql] = @reflection.options[:finder_sql].sub(/SELECT (\/\*.*?\*\/ )?(.*)\bFROM\b/im) { "SELECT #{$1}COUNT(*) FROM" }
-            @counter_sql = interpolate_sql(@reflection.options[:counter_sql])
-          else
-            @counter_sql = @finder_sql
-          end
+          construct_counter_sql
         end
 
         def construct_scope
diff --git a/activerecord/lib/active_record/associations/has_many_through_association.rb b/activerecord/lib/active_record/associations/has_many_through_association.rb
index e8dbae9011..e21ef90391 100644
--- a/activerecord/lib/active_record/associations/has_many_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_many_through_association.rb
@@ -1,6 +1,10 @@
+require "active_record/associations/through_association_scope"
+
 module ActiveRecord
   module Associations
     class HasManyThroughAssociation < HasManyAssociation #:nodoc:
+      include ThroughAssociationScope
+
       alias_method :new, :build
 
       def create!(attrs = nil)
@@ -72,114 +76,7 @@ module ActiveRecord
 
         def find_target
           return [] unless target_reflection_has_associated_record?
-          @reflection.klass.find(:all,
-            :select     => construct_select,
-            :conditions => construct_conditions,
-            :from       => construct_from,
-            :joins      => construct_joins,
-            :order      => @reflection.options[:order],
-            :limit      => @reflection.options[:limit],
-            :group      => @reflection.options[:group],
-            :readonly   => @reflection.options[:readonly],
-            :include    => @reflection.options[:include] || @reflection.source_reflection.options[:include]
-          )
-        end
-
-        # Construct attributes for associate pointing to owner.
-        def construct_owner_attributes(reflection)
-          if as = reflection.options[:as]
-            { "#{as}_id" => @owner.id,
-              "#{as}_type" => @owner.class.base_class.name.to_s }
-          else
-            { reflection.primary_key_name => @owner.id }
-          end
-        end
-
-        # Construct attributes for :through pointing to owner and associate.
-        def construct_join_attributes(associate)
-          # TODO: revist this to allow it for deletion, supposing dependent option is supported
-          raise ActiveRecord::HasManyThroughCantAssociateThroughHasManyReflection.new(@owner, @reflection) if @reflection.source_reflection.macro == :has_many
-          join_attributes = construct_owner_attributes(@reflection.through_reflection).merge(@reflection.source_reflection.primary_key_name => associate.id)
-          if @reflection.options[:source_type]
-            join_attributes.merge!(@reflection.source_reflection.options[:foreign_type] => associate.class.base_class.name.to_s)
-          end
-          join_attributes
-        end
-
-        # Associate attributes pointing to owner, quoted.
-        def construct_quoted_owner_attributes(reflection)
-          if as = reflection.options[:as]
-            { "#{as}_id" => owner_quoted_id,
-              "#{as}_type" => reflection.klass.quote_value(
-                @owner.class.base_class.name.to_s,
-                reflection.klass.columns_hash["#{as}_type"]) }
-          elsif reflection.macro == :belongs_to
-            { reflection.klass.primary_key => @owner[reflection.primary_key_name] }
-          else
-            { reflection.primary_key_name => owner_quoted_id }
-          end
-        end
-
-        # Build SQL conditions from attributes, qualified by table name.
-        def construct_conditions
-          table_name = @reflection.through_reflection.quoted_table_name
-          conditions = construct_quoted_owner_attributes(@reflection.through_reflection).map do |attr, value|
-            "#{table_name}.#{attr} = #{value}"
-          end
-          conditions << sql_conditions if sql_conditions
-          "(" + conditions.join(') AND (') + ")"
-        end
-
-        def construct_from
-          @reflection.quoted_table_name
-        end
-
-        def construct_select(custom_select = nil)
-          distinct = "DISTINCT " if @reflection.options[:uniq]
-          selected = custom_select || @reflection.options[:select] || "#{distinct}#{@reflection.quoted_table_name}.*"
-        end
-
-        def construct_joins(custom_joins = nil)
-          polymorphic_join = nil
-          if @reflection.source_reflection.macro == :belongs_to
-            reflection_primary_key = @reflection.klass.primary_key
-            source_primary_key     = @reflection.source_reflection.primary_key_name
-            if @reflection.options[:source_type]
-              polymorphic_join = "AND %s.%s = %s" % [
-                @reflection.through_reflection.quoted_table_name, "#{@reflection.source_reflection.options[:foreign_type]}",
-                @owner.class.quote_value(@reflection.options[:source_type])
-              ]
-            end
-          else
-            reflection_primary_key = @reflection.source_reflection.primary_key_name
-            source_primary_key     = @reflection.through_reflection.klass.primary_key
-            if @reflection.source_reflection.options[:as]
-              polymorphic_join = "AND %s.%s = %s" % [
-                @reflection.quoted_table_name, "#{@reflection.source_reflection.options[:as]}_type",
-                @owner.class.quote_value(@reflection.through_reflection.klass.name)
-              ]
-            end
-          end
-
-          "INNER JOIN %s ON %s.%s = %s.%s %s #{@reflection.options[:joins]} #{custom_joins}" % [
-            @reflection.through_reflection.quoted_table_name,
-            @reflection.quoted_table_name, reflection_primary_key,
-            @reflection.through_reflection.quoted_table_name, source_primary_key,
-            polymorphic_join
-          ]
-        end
-
-        def construct_scope
-          { :create => construct_owner_attributes(@reflection),
-            :find   => { :from        => construct_from,
-                         :conditions  => construct_conditions,
-                         :joins       => construct_joins,
-                         :include     => @reflection.options[:include],
-                         :select      => construct_select,
-                         :order       => @reflection.options[:order],
-                         :limit       => @reflection.options[:limit],
-                         :readonly    => @reflection.options[:readonly],
-             } }
+          with_scope(construct_scope) { @reflection.klass.find(:all) }
         end
 
         def construct_sql
@@ -193,59 +90,9 @@ module ActiveRecord
               @finder_sql = construct_conditions
           end
 
-          if @reflection.options[:counter_sql]
-            @counter_sql = interpolate_sql(@reflection.options[:counter_sql])
-          elsif @reflection.options[:finder_sql]
-            # replace the SELECT clause with COUNT(*), preserving any hints within /* ... */
-            @reflection.options[:counter_sql] = @reflection.options[:finder_sql].sub(/SELECT (\/\*.*?\*\/ )?(.*)\bFROM\b/im) { "SELECT #{$1}COUNT(*) FROM" }
-            @counter_sql = interpolate_sql(@reflection.options[:counter_sql])
-          else
-            @counter_sql = @finder_sql
-          end
-        end
-
-        def conditions
-          @conditions = build_conditions unless defined?(@conditions)
-          @conditions
+          construct_counter_sql
         end
 
-        def build_conditions
-          association_conditions = @reflection.options[:conditions]
-          through_conditions = build_through_conditions
-          source_conditions = @reflection.source_reflection.options[:conditions]
-          uses_sti = !@reflection.through_reflection.klass.descends_from_active_record?
-
-          if association_conditions || through_conditions || source_conditions || uses_sti
-            all = []
-
-            [association_conditions, source_conditions].each do |conditions|
-              all << interpolate_sql(sanitize_sql(conditions)) if conditions
-            end
-
-            all << through_conditions  if through_conditions
-            all << build_sti_condition if uses_sti
-
-            all.map { |sql| "(#{sql})" } * ' AND '
-          end
-        end
-
-        def build_through_conditions
-          conditions = @reflection.through_reflection.options[:conditions]
-          if conditions.is_a?(Hash)
-            interpolate_sql(sanitize_sql(conditions)).gsub(
-              @reflection.quoted_table_name,
-              @reflection.through_reflection.quoted_table_name)
-          elsif conditions
-            interpolate_sql(sanitize_sql(conditions))
-          end
-        end
-        
-        def build_sti_condition
-          @reflection.through_reflection.klass.send(:type_condition)
-        end
-
-        alias_method :sql_conditions, :conditions
-
         def has_cached_counter?
           @owner.attribute_present?(cached_counter_attribute_name)
         end
diff --git a/activerecord/lib/active_record/associations/has_one_association.rb b/activerecord/lib/active_record/associations/has_one_association.rb
index b72b84343b..c2568d0c0c 100644
--- a/activerecord/lib/active_record/associations/has_one_association.rb
+++ b/activerecord/lib/active_record/associations/has_one_association.rb
@@ -1,6 +1,6 @@
 module ActiveRecord
   module Associations
-    class HasOneAssociation < BelongsToAssociation #:nodoc:
+    class HasOneAssociation < AssociationProxy #:nodoc:
       def initialize(owner, reflection)
         super
         construct_sql
@@ -77,7 +77,7 @@ module ActiveRecord
           the_target = @reflection.klass.find(:first,
             :conditions => @finder_sql,
             :select     => @reflection.options[:select],
-            :order      => @reflection.options[:order], 
+            :order      => @reflection.options[:order],
             :include    => @reflection.options[:include],
             :readonly   => @reflection.options[:readonly]
           )
@@ -88,7 +88,7 @@ module ActiveRecord
         def construct_sql
           case
             when @reflection.options[:as]
-              @finder_sql = 
+              @finder_sql =
                 "#{@reflection.quoted_table_name}.#{@reflection.options[:as]}_id = #{owner_quoted_id} AND " +
                 "#{@reflection.quoted_table_name}.#{@reflection.options[:as]}_type = #{@owner.class.quote_value(@owner.class.base_class.name.to_s)}"
             else
@@ -96,7 +96,7 @@ module ActiveRecord
           end
           @finder_sql << " AND (#{conditions})" if conditions
         end
-        
+
         def construct_scope
           create_scoping = {}
           set_belongs_to_association_for(create_scoping)
@@ -113,7 +113,7 @@ module ActiveRecord
           end
 
           if replace_existing
-            replace(record, true) 
+            replace(record, true)
           else
             record[@reflection.primary_key_name] = @owner.id unless @owner.new_record?
             self.target = record
diff --git a/activerecord/lib/active_record/associations/has_one_through_association.rb b/activerecord/lib/active_record/associations/has_one_through_association.rb
index d93c8e7852..830aa1808a 100644
--- a/activerecord/lib/active_record/associations/has_one_through_association.rb
+++ b/activerecord/lib/active_record/associations/has_one_through_association.rb
@@ -1,6 +1,16 @@
+require "active_record/associations/through_association_scope"
+
 module ActiveRecord
   module Associations
-    class HasOneThroughAssociation < HasManyThroughAssociation
+    class HasOneThroughAssociation < HasOneAssociation
+      include ThroughAssociationScope
+
+      def replace(new_value)
+        create_through_record(new_value)
+        @target = new_value
+      end
+
+      private
 
       def create_through_record(new_value) #nodoc:
         klass = @reflection.through_reflection.klass
@@ -15,16 +25,8 @@ module ActiveRecord
       end
 
     private
-      def find(*args)
-        super(args.merge(:limit => 1))
-      end
-
       def find_target
-        super.first
-      end
-
-      def reset_target!
-        @target = nil
+        with_scope(construct_scope) { @reflection.klass.find(:first) }
       end
     end
   end
diff --git a/activerecord/lib/active_record/associations/through_association_scope.rb b/activerecord/lib/active_record/associations/through_association_scope.rb
new file mode 100644
index 0000000000..8e7ce33814
--- /dev/null
+++ b/activerecord/lib/active_record/associations/through_association_scope.rb
@@ -0,0 +1,154 @@
+module ActiveRecord
+  module Associations
+    module ThroughAssociationScope
+
+      protected
+
+      def construct_scope
+        { :create => construct_owner_attributes(@reflection),
+          :find   => { :from        => construct_from,
+                       :conditions  => construct_conditions,
+                       :joins       => construct_joins,
+                       :include     => @reflection.options[:include] || @reflection.source_reflection.options[:include],
+                       :select      => construct_select,
+                       :order       => @reflection.options[:order],
+                       :limit       => @reflection.options[:limit],
+                       :readonly    => @reflection.options[:readonly],
+           } }
+      end
+
+      # Build SQL conditions from attributes, qualified by table name.
+      def construct_conditions
+        table_name = @reflection.through_reflection.quoted_table_name
+        conditions = construct_quoted_owner_attributes(@reflection.through_reflection).map do |attr, value|
+          "#{table_name}.#{attr} = #{value}"
+        end
+        conditions << sql_conditions if sql_conditions
+        "(" + conditions.join(') AND (') + ")"
+      end
+
+      # Associate attributes pointing to owner, quoted.
+      def construct_quoted_owner_attributes(reflection)
+        if as = reflection.options[:as]
+          { "#{as}_id" => owner_quoted_id,
+            "#{as}_type" => reflection.klass.quote_value(
+              @owner.class.base_class.name.to_s,
+              reflection.klass.columns_hash["#{as}_type"]) }
+        elsif reflection.macro == :belongs_to
+          { reflection.klass.primary_key => @owner[reflection.primary_key_name] }
+        else
+          { reflection.primary_key_name => owner_quoted_id }
+        end
+      end
+
+      def construct_from
+        @reflection.quoted_table_name
+      end
+
+      def construct_select(custom_select = nil)
+        distinct = "DISTINCT " if @reflection.options[:uniq]
+        selected = custom_select || @reflection.options[:select] || "#{distinct}#{@reflection.quoted_table_name}.*"
+      end
+
+      def construct_joins(custom_joins = nil)
+        polymorphic_join = nil
+        if @reflection.source_reflection.macro == :belongs_to
+          reflection_primary_key = @reflection.klass.primary_key
+          source_primary_key     = @reflection.source_reflection.primary_key_name
+          if @reflection.options[:source_type]
+            polymorphic_join = "AND %s.%s = %s" % [
+              @reflection.through_reflection.quoted_table_name, "#{@reflection.source_reflection.options[:foreign_type]}",
+              @owner.class.quote_value(@reflection.options[:source_type])
+            ]
+          end
+        else
+          reflection_primary_key = @reflection.source_reflection.primary_key_name
+          source_primary_key     = @reflection.through_reflection.klass.primary_key
+          if @reflection.source_reflection.options[:as]
+            polymorphic_join = "AND %s.%s = %s" % [
+              @reflection.quoted_table_name, "#{@reflection.source_reflection.options[:as]}_type",
+              @owner.class.quote_value(@reflection.through_reflection.klass.name)
+            ]
+          end
+        end
+
+        "INNER JOIN %s ON %s.%s = %s.%s %s #{@reflection.options[:joins]} #{custom_joins}" % [
+          @reflection.through_reflection.quoted_table_name,
+          @reflection.quoted_table_name, reflection_primary_key,
+          @reflection.through_reflection.quoted_table_name, source_primary_key,
+          polymorphic_join
+        ]
+      end
+
+      # Construct attributes for associate pointing to owner.
+      def construct_owner_attributes(reflection)
+        if as = reflection.options[:as]
+          { "#{as}_id" => @owner.id,
+            "#{as}_type" => @owner.class.base_class.name.to_s }
+        else
+          { reflection.primary_key_name => @owner.id }
+        end
+      end
+
+      # Construct attributes for :through pointing to owner and associate.
+      def construct_join_attributes(associate)
+        # TODO: revist this to allow it for deletion, supposing dependent option is supported
+        raise ActiveRecord::HasManyThroughCantAssociateThroughHasManyReflection.new(@owner, @reflection) if @reflection.source_reflection.macro == :has_many
+
+        join_attributes = construct_owner_attributes(@reflection.through_reflection).merge(@reflection.source_reflection.primary_key_name => associate.id)
+
+        if @reflection.options[:source_type]
+          join_attributes.merge!(@reflection.source_reflection.options[:foreign_type] => associate.class.base_class.name.to_s)
+        end
+
+        if @reflection.through_reflection.options[:conditions].is_a?(Hash)
+          join_attributes.merge!(@reflection.through_reflection.options[:conditions])
+        end
+
+        join_attributes
+      end
+
+      def conditions
+        @conditions = build_conditions unless defined?(@conditions)
+        @conditions
+      end
+
+      def build_conditions
+        association_conditions = @reflection.options[:conditions]
+        through_conditions = build_through_conditions
+        source_conditions = @reflection.source_reflection.options[:conditions]
+        uses_sti = !@reflection.through_reflection.klass.descends_from_active_record?
+
+        if association_conditions || through_conditions || source_conditions || uses_sti
+          all = []
+
+          [association_conditions, source_conditions].each do |conditions|
+            all << interpolate_sql(sanitize_sql(conditions)) if conditions
+          end
+
+          all << through_conditions  if through_conditions
+          all << build_sti_condition if uses_sti
+
+          all.map { |sql| "(#{sql})" } * ' AND '
+        end
+      end
+
+      def build_through_conditions
+        conditions = @reflection.through_reflection.options[:conditions]
+        if conditions.is_a?(Hash)
+          interpolate_sql(sanitize_sql(conditions)).gsub(
+            @reflection.quoted_table_name,
+            @reflection.through_reflection.quoted_table_name)
+        elsif conditions
+          interpolate_sql(sanitize_sql(conditions))
+        end
+      end
+
+      def build_sti_condition
+        @reflection.through_reflection.klass.send(:type_condition)
+      end
+
+      alias_method :sql_conditions, :conditions
+    end
+  end
+end
diff --git a/activerecord/lib/active_record/base.rb b/activerecord/lib/active_record/base.rb
index 26ac2e0de4..bb7342ca6e 100755
--- a/activerecord/lib/active_record/base.rb
+++ b/activerecord/lib/active_record/base.rb
@@ -11,6 +11,7 @@ require 'active_support/core_ext/hash/indifferent_access'
 require 'active_support/core_ext/hash/slice'
 require 'active_support/core_ext/string/behavior'
 require 'active_support/core_ext/symbol'
+require 'active_support/core_ext/object/metaclass'
 
 module ActiveRecord #:nodoc:
   # Generic Active Record exception class.
@@ -66,6 +67,25 @@ module ActiveRecord #:nodoc:
   class StatementInvalid < ActiveRecordError
   end
 
+  # Parent class for all specific exceptions which wrap database driver exceptions
+  # provides access to the original exception also.
+  class WrappedDatabaseException < StatementInvalid
+    attr_reader :original_exception
+
+    def initialize(message, original_exception)
+      super(message)
+      @original_exception, = original_exception
+    end
+  end
+
+  # Raised when a record cannot be inserted because it would violate a uniqueness constraint.
+  class RecordNotUnique < WrappedDatabaseException
+  end
+
+  # Raised when a record cannot be inserted or updated because it references a non-existent record.
+  class InvalidForeignKey < WrappedDatabaseException
+  end
+
   # Raised when number of bind variables in statement given to <tt>:condition</tt> key (for example, when using +find+ method)
   # does not match number of expected variables.
   #
@@ -1420,14 +1440,14 @@ module ActiveRecord #:nodoc:
       end
 
       # Transform the modelname into a more humane format, using I18n.
-      # Defaults to the basic humanize method.
+      # By default, it will underscore then humanize the class name (BlogPost.human_name #=> "Blog post").
       # Default scope of the translation is activerecord.models
       # Specify +options+ with additional translating options.
       def human_name(options = {})
         defaults = self_and_descendants_from_active_record.map do |klass|
           :"#{klass.name.underscore}"
-        end 
-        defaults << self.name.humanize
+        end
+        defaults << self.name.underscore.humanize
         I18n.translate(defaults.shift, {:scope => [:activerecord, :models], :count => 1, :default => defaults}.merge(options))
       end
 
@@ -2076,7 +2096,7 @@ module ActiveRecord #:nodoc:
         #     end
         #   end
         def define_attr_method(name, value=nil, &block)
-          sing = class << self; self; end
+          sing = metaclass
           sing.send :alias_method, "original_#{name}", name
           if block_given?
             sing.send :define_method, name, &block
@@ -2886,6 +2906,13 @@ module ActiveRecord #:nodoc:
         @attributes.frozen?
       end
 
+      # Returns duplicated record with unfreezed attributes.
+      def dup
+        obj = super
+        obj.instance_variable_set('@attributes', instance_variable_get('@attributes').dup)
+        obj
+      end
+
       # Returns +true+ if the record is read only. Records loaded through joins with piggy-back
       # attributes will be marked as read only since they cannot be saved.
       def readonly?
@@ -3079,11 +3106,11 @@ module ActiveRecord #:nodoc:
       def execute_callstack_for_multiparameter_attributes(callstack)
         errors = []
         callstack.each do |name, values|
-          klass = (self.class.reflect_on_aggregation(name.to_sym) || column_for_attribute(name)).klass
-          if values.empty?
-            send(name + "=", nil)
-          else
-            begin
+          begin
+            klass = (self.class.reflect_on_aggregation(name.to_sym) || column_for_attribute(name)).klass
+            if values.empty?
+              send(name + "=", nil)
+            else
               value = if Time == klass
                 instantiate_time_object(name, values)
               elsif Date == klass
@@ -3097,9 +3124,9 @@ module ActiveRecord #:nodoc:
               end
 
               send(name + "=", value)
-            rescue => ex
-              errors << AttributeAssignmentError.new("error on assignment #{values.inspect} to #{name}", ex, name)
             end
+          rescue => ex
+            errors << AttributeAssignmentError.new("error on assignment #{values.inspect} to #{name}", ex, name)
           end
         end
         unless errors.empty?
@@ -3125,7 +3152,7 @@ module ActiveRecord #:nodoc:
       end
 
       def type_cast_attribute_value(multiparameter_name, value)
-        multiparameter_name =~ /\([0-9]*([a-z])\)/ ? value.send("to_" + $1) : value
+        multiparameter_name =~ /\([0-9]*([if])\)/ ? value.send("to_" + $1) : value
       end
 
       def find_parameter_position(multiparameter_name)
@@ -3180,12 +3207,13 @@ module ActiveRecord #:nodoc:
   end
 
   Base.class_eval do
+    extend ActiveModel::Naming
     extend QueryCache::ClassMethods
     include Validations
     include Locking::Optimistic, Locking::Pessimistic
     include AttributeMethods
     include Dirty
-    include Callbacks, Observing, Timestamp
+    include Callbacks, ActiveModel::Observing, Timestamp
     include Associations, AssociationPreload, NamedScope
 
     # AutosaveAssociation needs to be included before Transactions, because we want
diff --git a/activerecord/lib/active_record/callbacks.rb b/activerecord/lib/active_record/callbacks.rb
index 36f5f2ce47..01e41c04df 100644
--- a/activerecord/lib/active_record/callbacks.rb
+++ b/activerecord/lib/active_record/callbacks.rb
@@ -353,10 +353,5 @@ module ActiveRecord
 
         return result
       end
-
-      def notify(method) #:nodoc:
-        self.class.changed
-        self.class.notify_observers(method, self)
-      end
   end
 end
diff --git a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
index a41912a703..2473c772e3 100644
--- a/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb
@@ -109,7 +109,7 @@ module ActiveRecord
         table_definition = TableDefinition.new(self)
         table_definition.primary_key(options[:primary_key] || Base.get_primary_key(table_name)) unless options[:id] == false
 
-        yield table_definition
+        yield table_definition if block_given?
 
         if options[:force] && table_exists?(table_name)
           drop_table(table_name, options)
diff --git a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
index 91b111ab55..c533d4cdb6 100755
--- a/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/abstract_adapter.rb
@@ -211,9 +211,14 @@ module ActiveRecord
           @last_verification = 0
           message = "#{e.class.name}: #{e.message}: #{sql}"
           log_info(message, name, 0)
-          raise ActiveRecord::StatementInvalid, message
+          raise translate_exception(e, message)
         end
 
+      def translate_exception(e, message)
+        # override in derived class
+        ActiveRecord::StatementInvalid.new(message)
+      end
+
         def format_log_entry(message, dump = nil)
           if ActiveRecord::Base.colorize_logging
             if @@row_even
diff --git a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
index d5536e4d67..83cb9cff15 100644
--- a/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/mysql_adapter.rb
@@ -563,6 +563,19 @@ module ActiveRecord
         where_sql
       end
 
+      protected
+
+        def translate_exception(exception, message)
+          case exception.errno
+          when 1062
+            RecordNotUnique.new(message, exception)
+          when 1452
+            InvalidForeignKey.new(message, exception)
+          else
+            super
+          end
+        end
+
       private
         def connect
           encoding = @config[:encoding]
diff --git a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
index 002696d2c4..e77ae93c21 100644
--- a/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb
@@ -288,7 +288,13 @@ module ActiveRecord
 
       # Escapes binary strings for bytea input to the database.
       def escape_bytea(value)
-        if PGconn.respond_to?(:escape_bytea)
+        if @connection.respond_to?(:escape_bytea)
+          self.class.instance_eval do
+            define_method(:escape_bytea) do |value|
+              @connection.escape_bytea(value) if value
+            end
+          end
+        elsif PGconn.respond_to?(:escape_bytea)
           self.class.instance_eval do
             define_method(:escape_bytea) do |value|
               PGconn.escape_bytea(value) if value
@@ -377,7 +383,13 @@ module ActiveRecord
 
       # Quotes strings for use in SQL input in the postgres driver for better performance.
       def quote_string(s) #:nodoc:
-        if PGconn.respond_to?(:escape)
+        if @connection.respond_to?(:escape)
+          self.class.instance_eval do
+            define_method(:quote_string) do |s|
+              @connection.escape(s)
+            end
+          end
+        elsif PGconn.respond_to?(:escape)
           self.class.instance_eval do
             define_method(:quote_string) do |s|
               PGconn.escape(s)
@@ -929,6 +941,17 @@ module ActiveRecord
             end
         end
 
+        def translate_exception(exception, message)
+          case exception.message
+          when /duplicate key value violates unique constraint/
+            RecordNotUnique.new(message, exception)
+          when /violates foreign key constraint/
+            InvalidForeignKey.new(message, exception)
+          else
+            super
+          end
+        end
+
       private
         # The internal PostgreSQL identifier of the money data type.
         MONEY_COLUMN_TYPE_OID = 790 #:nodoc:
diff --git a/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb b/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
index c9d0c9574f..5e5e30776a 100644
--- a/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
+++ b/activerecord/lib/active_record/connection_adapters/sqlite_adapter.rb
@@ -245,7 +245,7 @@ module ActiveRecord
       end
 
       def rename_table(name, new_name)
-        execute "ALTER TABLE #{name} RENAME TO #{new_name}"
+        execute "ALTER TABLE #{quote_table_name(name)} RENAME TO #{quote_table_name(new_name)}"
       end
 
       # See: http://www.sqlite.org/lang_altertable.html
@@ -431,6 +431,16 @@ module ActiveRecord
             'INTEGER PRIMARY KEY NOT NULL'.freeze
           end
         end
+
+        def translate_exception(exception, message)
+          case exception.message
+          when /column(s)? .* (is|are) not unique/
+            RecordNotUnique.new(message, exception)
+          else
+            super
+          end
+        end
+
     end
 
     class SQLite2Adapter < SQLiteAdapter # :nodoc:
diff --git a/activerecord/lib/active_record/migration.rb b/activerecord/lib/active_record/migration.rb
index a7be3539d5..467d955a49 100644
--- a/activerecord/lib/active_record/migration.rb
+++ b/activerecord/lib/active_record/migration.rb
@@ -1,3 +1,5 @@
+require 'active_support/core_ext/object/metaclass'
+
 module ActiveRecord
   class IrreversibleMigration < ActiveRecordError#:nodoc:
   end
@@ -300,8 +302,7 @@ module ActiveRecord
 
           case sym
             when :up, :down
-              klass = (class << self; self; end)
-              klass.send(:alias_method_chain, sym, "benchmarks")
+              metaclass.send(:alias_method_chain, sym, "benchmarks")
           end
         ensure
           @ignore_new_methods = false
diff --git a/activerecord/lib/active_record/named_scope.rb b/activerecord/lib/active_record/named_scope.rb
index 1b22fa5e24..dd2a90b8e5 100644
--- a/activerecord/lib/active_record/named_scope.rb
+++ b/activerecord/lib/active_record/named_scope.rb
@@ -1,5 +1,6 @@
 require 'active_support/core_ext/array'
 require 'active_support/core_ext/hash/except'
+require 'active_support/core_ext/object/metaclass'
 
 module ActiveRecord
   module NamedScope
@@ -99,7 +100,7 @@ module ActiveRecord
               end
           end, &block)
         end
-        (class << self; self end).instance_eval do
+        metaclass.instance_eval do
           define_method name do |*args|
             scopes[name].call(self, *args)
           end
diff --git a/activerecord/lib/active_record/observer.rb b/activerecord/lib/active_record/observer.rb
index 89ec0962bf..a34ff4a47a 100644
--- a/activerecord/lib/active_record/observer.rb
+++ b/activerecord/lib/active_record/observer.rb
@@ -2,56 +2,6 @@ require 'singleton'
 require 'set'
 
 module ActiveRecord
-  module Observing # :nodoc:
-    extend ActiveSupport::Concern
-
-    module ClassMethods
-      # Activates the observers assigned. Examples:
-      #
-      #   # Calls PersonObserver.instance
-      #   ActiveRecord::Base.observers = :person_observer
-      #
-      #   # Calls Cacher.instance and GarbageCollector.instance
-      #   ActiveRecord::Base.observers = :cacher, :garbage_collector
-      #
-      #   # Same as above, just using explicit class references
-      #   ActiveRecord::Base.observers = Cacher, GarbageCollector
-      #
-      # Note: Setting this does not instantiate the observers yet. +instantiate_observers+ is
-      # called during startup, and before each development request.
-      def observers=(*observers)
-        @observers = observers.flatten
-      end
-
-      # Gets the current observers.
-      def observers
-        @observers ||= []
-      end
-
-      # Instantiate the global Active Record observers.
-      def instantiate_observers
-        return if @observers.blank?
-        @observers.each do |observer|
-          if observer.respond_to?(:to_sym) # Symbol or String
-            observer.to_s.camelize.constantize.instance
-          elsif observer.respond_to?(:instance)
-            observer.instance
-          else
-            raise ArgumentError, "#{observer} must be a lowercase, underscored class name (or an instance of the class itself) responding to the instance method. Example: Person.observers = :big_brother # calls BigBrother.instance"
-          end
-        end
-      end
-
-      protected
-        # Notify observers when the observed class is subclassed.
-        def inherited(subclass)
-          super
-          changed
-          notify_observers :observed_class_inherited, subclass
-        end
-    end
-  end
-
   # Observer classes respond to lifecycle callbacks to implement trigger-like
   # behavior outside the original class. This is a great way to reduce the
   # clutter that normally comes when the model class is burdened with
@@ -137,56 +87,19 @@ module ActiveRecord
   # load their observers by calling <tt>ModelObserver.instance</tt> before. Observers are
   # singletons and that call instantiates and registers them.
   #
-  class Observer
-    include Singleton
-
-    class << self
-      # Attaches the observer to the supplied model classes.
-      def observe(*models)
-        models.flatten!
-        models.collect! { |model| model.is_a?(Symbol) ? model.to_s.camelize.constantize : model }
-        define_method(:observed_classes) { Set.new(models) }
-      end
-
-      # The class observed by default is inferred from the observer's class name:
-      #   assert_equal Person, PersonObserver.observed_class
-      def observed_class
-        if observed_class_name = name[/(.*)Observer/, 1]
-          observed_class_name.constantize
-        else
-          nil
-        end
-      end
-    end
-
-    # Start observing the declared classes and their subclasses.
+  class Observer < ActiveModel::Observer
     def initialize
-      Set.new(observed_classes + observed_subclasses).each { |klass| add_observer! klass }
-    end
-
-    # Send observed_method(object) if the method exists.
-    def update(observed_method, object) #:nodoc:
-      send(observed_method, object) if respond_to?(observed_method)
-    end
-
-    # Special method sent by the observed class when it is inherited.
-    # Passes the new subclass.
-    def observed_class_inherited(subclass) #:nodoc:
-      self.class.observe(observed_classes + [subclass])
-      add_observer!(subclass)
+      super
+      observed_subclasses.each { |klass| add_observer!(klass) }
     end
 
     protected
-      def observed_classes
-        Set.new([self.class.observed_class].compact.flatten)
-      end
-
       def observed_subclasses
         observed_classes.sum([]) { |klass| klass.send(:subclasses) }
       end
 
       def add_observer!(klass)
-        klass.add_observer(self)
+        super
         if respond_to?(:after_find) && !klass.method_defined?(:after_find)
           klass.class_eval 'def after_find() end'
         end
diff --git a/activerecord/lib/active_record/serialization.rb b/activerecord/lib/active_record/serialization.rb
index 7959f2b510..23d085bea9 100644
--- a/activerecord/lib/active_record/serialization.rb
+++ b/activerecord/lib/active_record/serialization.rb
@@ -3,8 +3,9 @@ module ActiveRecord #:nodoc:
     class Serializer #:nodoc:
       attr_reader :options
 
-      def initialize(record, options = {})
-        @record, @options = record, options.dup
+      def initialize(record, options = nil)
+        @record = record
+        @options = options ? options.dup : {}
       end
 
       # To replicate the behavior in ActiveRecord#attributes,
diff --git a/activerecord/lib/active_record/serializers/json_serializer.rb b/activerecord/lib/active_record/serializers/json_serializer.rb
index 67e2b2abb3..21afcd6e5c 100644
--- a/activerecord/lib/active_record/serializers/json_serializer.rb
+++ b/activerecord/lib/active_record/serializers/json_serializer.rb
@@ -1,4 +1,5 @@
 require 'active_support/json'
+require 'active_model/naming'
 
 module ActiveRecord #:nodoc:
   module Serialization
@@ -74,36 +75,17 @@ module ActiveRecord #:nodoc:
     #                    "title": "Welcome to the weblog"},
     #                   {"comments": [{"body": "Don't think too hard"}],
     #                    "title": "So I was thinking"}]}
-    def to_json(options = {})
-      json = JsonSerializer.new(self, options).to_s
-      if include_root_in_json
-        "{#{self.class.json_class_name}:#{json}}"
-      else
-        json
-      end
+    def encode_json(encoder)
+      hash = Serializer.new(self, encoder.options).serializable_record
+      hash = { self.class.model_name.element => hash } if include_root_in_json
+      ActiveSupport::JSON.encode(hash)
     end
 
+    def as_json(options = nil) self end #:nodoc:
+
     def from_json(json)
       self.attributes = ActiveSupport::JSON.decode(json)
       self
     end
-
-    private
-      # For compatibility with ActiveSupport::JSON.encode
-      def rails_to_json(options, *args)
-        to_json(options)
-      end
-
-    class JsonSerializer < ActiveRecord::Serialization::Serializer #:nodoc:
-      def serialize
-        ActiveSupport::JSON.encode(serializable_record)
-      end
-    end
-
-    module ClassMethods
-      def json_class_name
-        @json_class_name ||= name.demodulize.underscore.inspect
-      end
-    end
   end
 end
diff --git a/activerecord/lib/active_record/validations.rb b/activerecord/lib/active_record/validations.rb
index 14c7699705..a7fa98756e 100644
--- a/activerecord/lib/active_record/validations.rb
+++ b/activerecord/lib/active_record/validations.rb
@@ -40,6 +40,7 @@ module ActiveRecord
       full_messages = []
 
       each do |attribute, messages|
+        messages = Array.wrap(messages)
         next if messages.empty?
 
         if attribute == :base
@@ -193,10 +194,6 @@ module ActiveRecord
       def errors
         @errors ||= Errors.new(self)
       end
-
-      def get_attribute_value(attribute)
-        respond_to?(attribute.to_sym) ? send(attribute.to_sym) : self[attribute.to_sym]
-      end
     end
   end
 end
diff --git a/activerecord/lib/active_record/version.rb b/activerecord/lib/active_record/version.rb
index 852807b4c5..10ef9d7594 100644
--- a/activerecord/lib/active_record/version.rb
+++ b/activerecord/lib/active_record/version.rb
@@ -1,8 +1,8 @@
 module ActiveRecord
   module VERSION #:nodoc:
-    MAJOR = 2
-    MINOR = 3
-    TINY  = 2
+    MAJOR = 3
+    MINOR = 0
+    TINY  = "pre"
 
     STRING = [MAJOR, MINOR, TINY].join('.')
   end