Add Relation extensions

7 files changed, 68 insertions, 15 deletions

diff --git a/activerecord/CHANGELOG b/activerecord/CHANGELOG
index e379f4f967..e0625c3dbb 100644
--- a/activerecord/CHANGELOG
+++ b/activerecord/CHANGELOG
@@ -1,5 +1,15 @@
 *Rails 3.0.0 [Beta 2] (pending)*
 
+* Add Relation extensions. [Pratik Naik]
+
+  users = User.where(:admin => true).extending(User::AdminPowers)
+
+  latest_users = User.order('created_at DESC') do
+    def posts_count
+      Post.count(:user_id => to_a.map(&:id))
+    end
+  end
+
 * To prefix the table names of all models in a module, define self.table_name_prefix on the module.  #4032 [Andrew White]
 
 * Silenced "SHOW FIELDS" and "SET SQL_AUTO_IS_NULL=0" statements from the MySQL driver to improve log signal to noise ration in development [DHH]
diff --git a/activerecord/lib/active_record/named_scope.rb b/activerecord/lib/active_record/named_scope.rb
index 9abf979cd0..3456332227 100644
--- a/activerecord/lib/active_record/named_scope.rb
+++ b/activerecord/lib/active_record/named_scope.rb
@@ -133,19 +133,16 @@ module ActiveRecord
       delegate :scopes, :with_scope, :with_exclusive_scope, :scoped_methods, :scoped, :to => :klass
 
       def self.init(klass, options, &block)
-        relation = new(klass, klass.arel_table)
+        relation = new(klass, klass.arel_table, &block)
 
         scope = if options.is_a?(Hash)
-          klass.scoped.apply_finder_options(options.except(:extend))
+          klass.scoped.apply_finder_options(options)
         else
           options ? klass.scoped.merge(options) : klass.scoped
         end
 
         relation = relation.merge(scope)
 
-        Array.wrap(options[:extend]).each {|extension| relation.send(:extend, extension) } if options.is_a?(Hash)
-        relation.send(:extend, Module.new(&block)) if block_given?
-
         relation.current_scoped_methods_when_defined = klass.send(:current_scoped_methods)
         relation
       end
diff --git a/activerecord/lib/active_record/relation.rb b/activerecord/lib/active_record/relation.rb
index 8577ec58f7..dde20532af 100644
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -4,7 +4,7 @@ module ActiveRecord
   class Relation
     JoinOperation = Struct.new(:relation, :join_class, :on)
     ASSOCIATION_METHODS = [:includes, :eager_load, :preload]
-    MULTI_VALUE_METHODS = [:select, :group, :order, :joins, :where, :having]
+    MULTI_VALUE_METHODS = [:select, :group, :order, :joins, :where, :having, :extends]
     SINGLE_VALUE_METHODS = [:limit, :offset, :lock, :readonly, :create_with, :from]
 
     include FinderMethods, Calculations, SpawnMethods, QueryMethods, Batches
@@ -13,8 +13,9 @@ module ActiveRecord
     delegate :insert, :to => :arel
 
     attr_reader :table, :klass
+    attr_accessor :extensions
 
-    def initialize(klass, table)
+    def initialize(klass, table, &block)
       @klass, @table = klass, table
 
       @implicit_readonly = nil
@@ -22,6 +23,9 @@ module ActiveRecord
 
       SINGLE_VALUE_METHODS.each {|v| instance_variable_set(:"@#{v}_value", nil)}
       (ASSOCIATION_METHODS + MULTI_VALUE_METHODS).each {|v| instance_variable_set(:"@#{v}_values", [])}
+      @extensions = []
+
+      apply_modules(Module.new(&block)) if block_given?
     end
 
     def new(*args, &block)
diff --git a/activerecord/lib/active_record/relation/query_methods.rb b/activerecord/lib/active_record/relation/query_methods.rb
index e224781016..b5e8b7570a 100644
--- a/activerecord/lib/active_record/relation/query_methods.rb
+++ b/activerecord/lib/active_record/relation/query_methods.rb
@@ -10,8 +10,9 @@ module ActiveRecord
 
         next if [:where, :having].include?(query_method)
         class_eval <<-CEVAL
-          def #{query_method}(*args)
+          def #{query_method}(*args, &block)
             new_relation = clone
+            new_relation.send(:apply_modules, Module.new(&block)) if block_given?
             value = Array.wrap(args.flatten).reject {|x| x.blank? }
             new_relation.#{query_method}_values += value if value.present?
             new_relation
@@ -21,8 +22,9 @@ module ActiveRecord
 
       [:where, :having].each do |query_method|
         class_eval <<-CEVAL
-          def #{query_method}(*args)
+          def #{query_method}(*args, &block)
             new_relation = clone
+            new_relation.send(:apply_modules, Module.new(&block)) if block_given?
             value = build_where(*args)
             new_relation.#{query_method}_values += [*value] if value.present?
             new_relation
@@ -34,8 +36,9 @@ module ActiveRecord
         attr_accessor :"#{query_method}_value"
 
         class_eval <<-CEVAL
-          def #{query_method}(value = true)
+          def #{query_method}(value = true, &block)
             new_relation = clone
+            new_relation.send(:apply_modules, Module.new(&block)) if block_given?
             new_relation.#{query_method}_value = value
             new_relation
           end
@@ -43,8 +46,16 @@ module ActiveRecord
       end
     end
 
-    def lock(locks = true)
+    def extending(*modules)
+      new_relation = clone
+      new_relation.send :apply_modules, *modules
+      new_relation
+    end
+
+    def lock(locks = true, &block)
       relation = clone
+      relation.send(:apply_modules, Module.new(&block)) if block_given?
+
       case locks
       when String, TrueClass, NilClass
         clone.tap {|new_relation| new_relation.lock_value = locks || true }
@@ -191,6 +202,12 @@ module ActiveRecord
 
     private
 
+    def apply_modules(modules)
+      values = Array.wrap(modules)
+      @extensions += values if values.present?
+      values.each {|extension| extend(extension) }
+    end
+
     def reverse_sql_order(order_query)
       order_query.to_s.split(/,/).each { |s|
         if s.match(/\s(asc|ASC)$/)
diff --git a/activerecord/lib/active_record/relation/spawn_methods.rb b/activerecord/lib/active_record/relation/spawn_methods.rb
index 63246079cb..8fdd64afcc 100644
--- a/activerecord/lib/active_record/relation/spawn_methods.rb
+++ b/activerecord/lib/active_record/relation/spawn_methods.rb
@@ -7,9 +7,8 @@ module ActiveRecord
       return merged_relation unless r
 
       (Relation::ASSOCIATION_METHODS + Relation::MULTI_VALUE_METHODS).reject {|m| [:joins, :where].include?(m)}.each do |method|
-        unless (value = r.send(:"#{method}_values")).blank?
-          merged_relation.send(:"#{method}_values=", value)
-        end
+        value = r.send(:"#{method}_values")
+        merged_relation.send(:"#{method}_values=", value) if value.present?
       end
 
       merged_relation = merged_relation.joins(r.joins_values)
@@ -34,6 +33,9 @@ module ActiveRecord
 
       merged_relation.lock_value = r.lock_value unless merged_relation.lock_value
 
+      # Apply scope extension modules
+      merged_relation.send :apply_modules, r.extensions
+
       merged_relation
     end
 
@@ -69,7 +71,7 @@ module ActiveRecord
       result
     end
 
-    VALID_FIND_OPTIONS = [ :conditions, :include, :joins, :limit, :offset,
+    VALID_FIND_OPTIONS = [ :conditions, :include, :joins, :limit, :offset, :extend,
                            :order, :select, :readonly, :group, :having, :from, :lock ]
 
     def apply_finder_options(options)
@@ -84,6 +86,7 @@ module ActiveRecord
 
       relation = relation.where(options[:conditions]) if options.has_key?(:conditions)
       relation = relation.includes(options[:include]) if options.has_key?(:include)
+      relation = relation.extending(options[:extend]) if options.has_key?(:extend)
 
       relation
     end
diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index 1e345399f5..7b9e680c02 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -572,4 +572,20 @@ class RelationTest < ActiveRecord::TestCase
     assert_equal Post.all, all_posts.all
   end
 
+  def test_anonymous_extension
+    relation = Post.where(:author_id => 1).order('id ASC') do
+      def author
+        'lifo'
+      end
+    end
+
+    assert_equal "lifo", relation.author
+    assert_equal "lifo", relation.limit(1).author
+  end
+
+  def test_named_extension
+    relation = Post.where(:author_id => 1).order('id ASC').extending(Post::NamedExtension)
+    assert_equal "lifo", relation.author
+    assert_equal "lifo", relation.limit(1).author
+  end
 end
diff --git a/activerecord/test/models/post.rb b/activerecord/test/models/post.rb
index 704313649a..d092c4bf09 100644
--- a/activerecord/test/models/post.rb
+++ b/activerecord/test/models/post.rb
@@ -1,4 +1,10 @@
 class Post < ActiveRecord::Base
+  module NamedExtension
+    def author
+      'lifo'
+    end
+  end
+
   scope :containing_the_letter_a, where("body LIKE '%a%'")
   scope :ranked_by_comments, order("comments_count DESC")
   scope :limit_by, lambda {|l| limit(l) }