fix for move_to_child_with_index method

when moving a node downward (but not to the bottom) within its current parent the
`move_to_child_with_index` method would insert the node in the wrong place.

This is because when moving a node downward the positioning needs to take into account the fact
that the moving node is being removed from its current position.

also, add code to handle a no-op call -- moving a node to the position it's already at -- w/o raising an error.

lib/awesome_nested_set/model/movable.rb

@@ -46,7 +46,17 @@ def move_to_child_with_index(node, index)
  elsif node.children.count == index
  move_to_right_of(node.children.last)
  else
- move_to_left_of(node.children[index])
+ my_position = node.children.index(self)
+ if my_position && my_position < index
+ # e.g. if self is at position 0 and we want to move self to position 1 then self
+ # needs to move to the *right* of the node at position 1. That's because the node
+ # that is currently at position 1 will be at position 0 after the move completes.
+ move_to_right_of(node.children[index])
+ elsif my_position && my_position == index
+ # do nothing. already there.
+ else
+ move_to_left_of(node.children[index])
+ end
  end
  end
 

spec/awesome_nested_set_spec.rb

@@ -539,6 +539,23 @@
  categories(:child_2).right.should == 7
  end
 
+ it "move downward within current parent" do
+ categories(:child_1).move_to_child_with_index(categories(:top_level), 1)
+ categories(:child_1).parent_id.should == categories(:top_level).id
+ categories(:child_1).left.should == 6
+ categories(:child_1).right.should == 7
+ categories(:child_2).reload
+ categories(:child_2).parent_id.should == categories(:top_level).id
+ categories(:child_2).left.should == 2
+ categories(:child_2).right.should == 5
+ end
+
+ it "move to the same position within current parent" do
+ categories(:child_1).move_to_child_with_index(categories(:top_level), 0)
+ categories(:child_1).parent_id.should == categories(:top_level).id
+ categories(:child_1).left.should == 2
+ categories(:child_1).right.should == 3
+ end
  end
 
  it "move_to_child_of_appends_to_end" do