Restore eager condition interpolation, document it's differences [Rick]

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@5284 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activerecord/CHANGELOG

@@ -1,5 +1,7 @@
 *SVN*
 
+* Restore eager condition interpolation, document it's differences [Rick]
+
 * Don't rollback in teardown unless a transaction was started. Don't start a transaction in create_fixtures if a transaction is started.  #6282 [Jacob Fugal, Jeremy Kemper]
 
 * Add #delete support to has_many :through associations.  Closes #6049 [Martin Landers]

activerecord/lib/active_record/associations.rb

@@ -358,8 +358,8 @@ module ActiveRecord
     # as there is currently not any way to disambiguate them. Eager loading will not pull additional attributes on join tables, so "rich
     # associations" with has_and_belongs_to_many are not a good fit for eager loading.
     # 
-    # When eager loaded, conditions are not interpolated. This is because the interpolation of lazy loaded conditions happens within the context
-    # of the object; when eager loading the object does not exist yet.
+    # When eager loaded, conditions are interpolated in the context of the model class, not the model instance.  Conditions are lazily interpolated
+    # before the actual model exists.
     # 
     # == Table Aliasing
     #
@@ -1560,7 +1560,7 @@ module ActiveRecord
                 aliased_table_name, 
                 reflection.active_record.connection.quote_column_name(reflection.active_record.inheritance_column), 
                 klass.quote_value(klass.name.demodulize)] unless klass.descends_from_active_record?
-              join << "AND #{sanitize_sql(reflection.options[:conditions])} " if reflection.options[:conditions]
+              join << "AND #{interpolate_sql(sanitize_sql(reflection.options[:conditions]))} " if reflection.options[:conditions]
               join
             end
             
@@ -1576,6 +1576,10 @@ module ActiveRecord
               def table_name_and_alias
                 table_alias_for table_name, @aliased_table_name
               end
+
+              def interpolate_sql(sql)
+                instance_eval("%@#{sql.gsub('@', '\@')}@") 
+              end 
           end
         end
     end

activerecord/test/associations/join_model_test.rb

@@ -351,6 +351,13 @@ class AssociationsJoinModelTest < Test::Unit::TestCase
       assert_equal [1,2,3,5,6,7,8,9,10], author.comments.collect(&:id)
     end
   end
+  
+  def test_eager_load_has_many_through_has_many_with_conditions
+    post = Post.find(:first, :include => :invalid_tags)
+    assert_no_queries do
+      post.invalid_tags
+    end
+  end
 
   def test_eager_belongs_to_and_has_one_not_singularized
     assert_nothing_raised do

activerecord/test/associations_test.rb

@@ -315,7 +315,7 @@ class HasOneAssociationsTest < Test::Unit::TestCase
     assert_equal a, firm.account
     assert_equal a, firm.account(true)
   end
-  
+
   def test_finding_with_interpolated_condition
     firm = Firm.find(:first)
     superior = firm.clients.create(:name => 'SuperiorCo')