Manual for new version devise 1.5 and omniauth 1.0.0 facebook with Mongoid
Could not find a valid mapping for #<Mongoid::Criteria
  selector: {:email=>"emailusercomebackfacebook"},
  options:  {},
  class:    User,
  embedded: false>

if user = (User.where(email:(data.email)).map.first)

Mongoid::Errors::Validations in

Users::OmniauthCallbacksController#facebook

Validation failed - Password can't be blank, Name can't be blank.

Rails.root: /home/ubuntu/Desktop/app
Application Trace | Framework Trace | Full Trace
app/models/user.rb:21:in 'find_for_facebook_oauth'
app/controllers/users/omniauth_callbacks_controller.rb:4:in 'facebook'

else # Create a user with a stub password.
    User.create!(:email => data.email, :encrypted_password => Devise.friendly_token[0,20])