Implement old-skool eagerloading for has_one :through

Signed-off-by: Jeremy Kemper <jeremy@bitsweat.net>

activerecord/lib/active_record/associations.rb

@@ -1815,7 +1815,7 @@ def initialize(reflection, join_dependency, parent = nil)
                 @aliased_join_table_name = aliased_table_name_for(reflection.options[:join_table], "_join")
               end
 
-              if reflection.macro == :has_many && reflection.options[:through]
+              if [:has_many, :has_one].include?(reflection.macro) && reflection.options[:through]
                 @aliased_join_table_name = aliased_table_name_for(reflection.through_reflection.klass.table_name, "_join")
               end
             end
@@ -1839,7 +1839,7 @@ def association_join
                      ]
                 when :has_many, :has_one
                   case
-                    when reflection.macro == :has_many && reflection.options[:through]
+                    when reflection.options[:through]
                       through_conditions = through_reflection.options[:conditions] ? "AND #{interpolate_sql(sanitize_sql(through_reflection.options[:conditions]))}" : ''
 
                       jt_foreign_key = jt_as_extra = jt_source_extra = jt_sti_extra = nil

activerecord/test/cases/associations/has_one_through_associations_test.rb

@@ -75,4 +75,20 @@ def test_eager_has_one_through_polymorphic_with_source_type
     assert_not_nil assert_no_queries {clubs[0].sponsored_member}
   end
 
+  def test_has_one_through_nonpreload_eagerloading
+    members = assert_queries(1) do
+      Member.find(:all, :include => :club, :conditions => ["members.name = ?", "Groucho Marx"], :order => 'clubs.name') #force fallback
+    end
+    assert_equal 1, members.size
+    assert_not_nil assert_no_queries {members[0].club}
+  end
+
+  def test_has_one_through_nonpreload_eager_loading_through_polymorphic
+    members = assert_queries(1) do
+      Member.find(:all, :include => :sponsor_club, :conditions => ["members.name = ?", "Groucho Marx"], :order => 'clubs.name') #force fallback
+    end
+    assert_equal 1, members.size
+    assert_not_nil assert_no_queries {members[0].sponsor_club}
+  end
+
 end