Fixes issue where ancestors would be returned in natural order instead of their actual order. Fixes benedikt#39

Author: benedikt

lib/mongoid/tree.rb

@@ -103,7 +103,7 @@ module Tree
     end
 
     ##
-    # This module implements class methods that will be available 
+    # This module implements class methods that will be available
     # on the document that includes Mongoid::Tree
     module ClassMethods
 
@@ -213,7 +213,7 @@ def leaves
     #   @note Generated by Mongoid
     #
     #   @param [Mongoid::Tree] document
-    
+
     ##
     # @!method parent_ids
     #   Returns a list of the document's parent_ids, starting with the root node.
@@ -272,7 +272,7 @@ def root
     #
     # @return [Mongoid::Criteria] Mongoid criteria to retrieve the documents ancestors
     def ancestors
-      base_class.where(:_id.in => parent_ids)
+      base_class.or(parent_ids.map { |id| { :_id => id } })
     end
 
     ##

spec/mongoid/tree_spec.rb

@@ -270,8 +270,24 @@
     end
 
     describe 'ancestors' do
-      it "#ancestors should return the documents ancestors" do
-        node(:subchild).ancestors.to_a.should == [node(:root), node(:child)]
+      describe '#ancestors' do
+        it "should return the documents ancestors" do
+          node(:subchild).ancestors.to_a.should == [node(:root), node(:child)]
+        end
+
+        it "should return the ancestors in correct order even after rearranging" do
+          setup_tree <<-ENDTREE
+            - root:
+              - child:
+                - subchild
+          ENDTREE
+
+          child = node(:child); child.parent = nil; child.save!
+          root = node(:root); root.parent = node(:child); root.save!
+          subchild = node(:subchild); subchild.parent = root; subchild.save!
+
+          subchild.ancestors.to_a.should == [child, root]
+        end
       end
 
       it "#ancestors_and_self should return the documents ancestors and itself" do