switching data mapper to new adapter

lib/cancan/model_adapters/data_mapper_adapter.rb

@@ -1,32 +1,26 @@
 module CanCan
-  module Ability
-    # could use alias_method_chain, but it's not worth adding activesupport as a gem dependency
-    alias_method :query_without_data_mapper_support, :query
-    def query(action, subject)
-      if Object.const_defined?('DataMapper') && subject <= DataMapper::Resource
-        query_with_data_mapper_support(action, subject)
-      else
-        query_without_data_mapper_support(action, subject)
-      end
+  module ModelAdapters
+    class DataMapperAdapter < AbstractAdapter
+      def self.for_class?(model_class)
+        model_class <= DataMapper::Resource
       end
 
-    def query_with_data_mapper_support(action, subject)
-      DataMapperQuery.new(subject, relevant_rules_for_query(action, subject))
+      def database_records
+        scope = @model_class.all(:conditions => ['true=false'])
+        conditions.each do |condition|
+          scope += @model_class.all(:conditions => condition)
         end
-  end
-
-  class DataMapperQuery
-    def initialize(sanitizer, rules)
-      @sanitizer = sanitizer
-      @rules = rules
+        scope
       end
 
       def conditions
-      @rules.map {|r| r.instance_variable_get(:@conditions) }
+        @rules.map(&:conditions)
       end
     end
+  end
+end
 
-  # This module is automatically included into all Active Record models.
+module CanCan
   module DataMapperAdditions
     module ClassMethods
       # Returns a scope which fetches only the records that the passed ability
@@ -47,14 +41,7 @@ module CanCan
       # 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)
-
-        scope = all(:conditions => ['true=false'])
-        query.conditions.each do |condition|
-          scope += all(:conditions => condition)
-        end
-
-        return scope
+        ability.model_adapter(self, action).database_records
       end
     end
   end

spec/cancan/model_adapters/data_mapper_adapter_spec.rb

@@ -1,7 +1,7 @@
 if ENV["MODEL_ADAPTER"] == "data_mapper"
   require "spec_helper"
 
-  describe CanCan::DataMapperAdditions do
+  describe CanCan::ModelAdapters::DataMapperAdapter do
     before(:each) do
       @model_class = Class.new
       @model_class.class_eval do
@@ -13,6 +13,12 @@ if ENV["MODEL_ADAPTER"] == "data_mapper"
       @ability.extend(CanCan::Ability)
     end
 
+    it "should be for only data mapper classes" do
+      CanCan::ModelAdapters::DataMapperAdapter.should_not be_for_class(Object)
+      CanCan::ModelAdapters::DataMapperAdapter.should be_for_class(@model_class)
+      CanCan::ModelAdapters::AbstractAdapter.adapter_class(@model_class).should == CanCan::ModelAdapters::DataMapperAdapter
+    end
+
     it "should return no records when no ability is defined so no records are found" do
       @model_class.accessible_by(@ability, :read).should == 'no-match:'
     end