infer references from Relation#order

2 files changed, 28 insertions, 2 deletions

diff --git a/activerecord/lib/active_record/relation/query_methods.rb b/activerecord/lib/active_record/relation/query_methods.rb
index 75369513e3..b5f202ef6a 100644
--- a/activerecord/lib/active_record/relation/query_methods.rb
+++ b/activerecord/lib/active_record/relation/query_methods.rb
@@ -106,8 +106,14 @@ module ActiveRecord
     def order(*args)
       return self if args.blank?
 
+      args       = args.flatten
+      references = args.reject { |arg| Arel::Node === arg }
+                       .map { |arg| arg =~ /^([a-zA-Z]\w*)\.(\w+)/ && $1 }
+                       .compact
+
       relation = clone
-      relation.order_values += args.flatten
+      relation = relation.references(references) if references.any?
+      relation.order_values += args
       relation
     end
 
diff --git a/activerecord/test/cases/relations_test.rb b/activerecord/test/cases/relations_test.rb
index d8599b1e6d..6d75f31f35 100644
--- a/activerecord/test/cases/relations_test.rb
+++ b/activerecord/test/cases/relations_test.rb
@@ -1176,17 +1176,37 @@ class RelationTest < ActiveRecord::TestCase
     assert !scope.eager_loading?
   end
 
-  def test_automatically_added_references
+  def test_automatically_added_where_references
     scope = Post.where(:comments => { :body => "Bla" })
     assert_equal ['comments'], scope.references_values
 
     scope = Post.where('comments.body' => 'Bla')
     assert_equal ['comments'], scope.references_values
+  end
 
+  def test_automatically_added_having_references
     scope = Post.having(:comments => { :body => "Bla" })
     assert_equal ['comments'], scope.references_values
 
     scope = Post.having('comments.body' => 'Bla')
     assert_equal ['comments'], scope.references_values
   end
+
+  def test_automatically_added_order_references
+    scope = Post.order('comments.body')
+    assert_equal ['comments'], scope.references_values
+
+    scope = Post.order('comments.body', 'yaks.body')
+    assert_equal ['comments', 'yaks'], scope.references_values
+
+    # Don't infer yaks, let's not go down that road again...
+    scope = Post.order('comments.body, yaks.body')
+    assert_equal ['comments'], scope.references_values
+
+    scope = Post.order('comments.body asc')
+    assert_equal ['comments'], scope.references_values
+
+    scope = Post.order('foo(comments.body)')
+    assert_equal [], scope.references_values
+  end
 end