Very similar to MONGOID-1154 except it only seems to happen when the embedded document is destroyed via nested attributes.

class Order
  
  include Mongoid::Document
  
  embeds_many :line_items, :cascade_callbacks => true
  
  accepts_nested_attributes_for :line_items, :allow_destroy => true

  def recalculate_discounts!
    # do stuff
  end

end

class LineItem

  include Mongoid::Document

  embedded_in :order

end

class LineItemObserver < Mongoid::Observer
  
  def after_destroy(line_item)
    line_item.order.recalculate_discounts!
  end

end

Everything works as expected when I call destroy directly on the line_item in rails console:

order = Order.last
line_item = order.line_items.first
line_item.destroy

1. => after_destroy is triggered and recalculate_discounts! is successfully called

However when I try to destroy the embedded document via nested attributes (_destroy = "1"), the callback is triggered but the order object is nil:

order = Order.last
order.attributes = {:_id => '4fe257701defe75606000001',:line_items_attributes => [{:_id => '4fe268771defe79807000001',:_destroy => "1"}]}
order.save

1. => undefined method `recalculate_discounts!' for nil:NilClass

Is this intended behaviour or a bug?

I get the same result in Mongoid 2.4.10, 2.4.11 and 3.0.0.rc