Load the first and not the last has_one result when doing join-based …

…eager loading

This matters when the has_one is defined with an order in which case
there is an expectation that the first one will be loaded.

[#904 state:resolved]

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

activerecord/lib/active_record/associations.rb

@@ -1734,6 +1734,7 @@ def construct_association(record, join, row)
                   collection.target.push(association)
                 when :has_one
                   return if record.id.to_s != join.parent.record_id(row).to_s
+                  return if record.instance_variable_defined?("@#{join.reflection.name}")
                   association = join.instantiate(row) unless row[join.aliased_primary_key].nil?
                   record.send("set_#{join.reflection.name}_target", association)
                 when :belongs_to

activerecord/test/cases/associations/eager_test.rb

@@ -38,6 +38,12 @@ def test_loading_with_one_association
     assert_equal Post.find(1).last_comment, post.last_comment
   end
 
+  def test_loading_with_one_association_with_non_preload
+    posts = Post.find(:all, :include => :last_comment, :order => 'comments.id DESC')
+    post = posts.find { |p| p.id == 1 }
+    assert_equal Post.find(1).last_comment, post.last_comment
+  end
+
   def test_loading_conditions_with_or
     posts = authors(:david).posts.find(:all, :include => :comments, :conditions => "comments.body like 'Normal%' OR comments.#{QUOTED_TYPE} = 'SpecialComment'")
     assert_nil posts.detect { |p| p.author_id != authors(:david).id },

activerecord/test/cases/associations/has_one_through_associations_test.rb

@@ -91,4 +91,14 @@ def test_has_one_through_nonpreload_eager_loading_through_polymorphic
     assert_not_nil assert_no_queries {members[0].sponsor_club}
   end
 
+  def test_has_one_through_nonpreload_eager_loading_through_polymorphic_with_more_than_one_through_record
+    Sponsor.new(:sponsor_club => clubs(:crazy_club), :sponsorable => members(:groucho)).save!
+    members = assert_queries(1) do
+      Member.find(:all, :include => :sponsor_club, :conditions => ["members.name = ?", "Groucho Marx"], :order => 'clubs.name DESC') #force fallback
+    end
+    assert_equal 1, members.size
+    assert_not_nil assert_no_queries { members[0].sponsor_club }
+    assert_equal clubs(:crazy_club), members[0].sponsor_club
+  end
+
 end