Add support for Mongoid documents along with basic specs.

lib/cancan.rb

@@ -3,6 +3,7 @@ require 'cancan/can_definition'
 require 'cancan/controller_resource'
 require 'cancan/controller_additions'
 require 'cancan/active_record_additions'
+require 'cancan/mongoid_additions'
 require 'cancan/exceptions'
 require 'cancan/query'
 require 'cancan/inherited_resource'

lib/cancan/mongoid_additions.rb

@@ -0,0 +1,78 @@
+module CanCan
+
+  module Ability
+    alias_method :query_without_mongoid_support, :query
+    def query(action, subject)
+      if Object.const_defined?(:Mongoid) && subject <= CanCan::MongoidAdditions
+        query_with_mongoid_support(action, subject)
+      else
+        query_without_mongoid_support(action, subject)
+      end
+    end
+    
+    def query_with_mongoid_support(action, subject)
+      MongoidQuery.new(subject, relevant_can_definitions_for_query(action, subject))
+    end
+  end
+  
+  class MongoidQuery
+    def initialize(sanitizer, can_definitions)
+      @sanitizer = sanitizer
+      @can_definitions = can_definitions
+    end    
+    
+    def conditions
+      @can_definitions.first.try(:tableized_conditions)
+    end
+  end
+
+  module MongoidAdditions
+    module ClassMethods
+      # Returns a scope which fetches only the records that the passed ability
+      # can perform a given action on. The action defaults to :read. This
+      # is usually called from a controller and passed the +current_ability+.
+      #
+      #   @articles = Article.accessible_by(current_ability)
+      # 
+      # Here only the articles which the user is able to read will be returned.
+      # If the user does not have permission to read any articles then an empty
+      # result is returned. Since this is a scope it can be combined with any
+      # other scopes or pagination.
+      # 
+      # An alternative action can optionally be passed as a second argument.
+      # 
+      #   @articles = Article.accessible_by(current_ability, :update)
+      # 
+      # Here only the articles which the user can update are returned. This
+      # internally uses Ability#conditions method, see that for more information.
+      def accessible_by(ability, action = :read)
+        query = ability.query(action, self)        
+        if query.conditions.blank?
+          # this query is sure to return no results
+          # we need this so there is a Mongoid::Criteria object to return, since an empty array would cause problems
+          where({:_id => {'$exists' => true, '$type' => 2}})  
+        else   
+          where(query.conditions)
+        end
+      end
+    end
+    
+    def self.included(base)
+      base.extend ClassMethods
+    end
+  end
+end
+
+# Info on monkeypatching Mongoid : 
+# http://log.mazniak.org/post/719062325/monkey-patching-activesupport-concern-and-you#footer
+if defined? Mongoid
+  module Mongoid
+    module Components
+      old_block = @_included_block
+      @_included_block = Proc.new do 
+        class_eval(&old_block) if old_block
+        include CanCan::MongoidAdditions
+      end
+    end
+  end  
+end