adding initial MetaWhere support

lib/cancan/model_adapters/abstract_adapter.rb

@@ -26,6 +26,17 @@ module CanCan
         raise NotImplemented, "This model adapter does not support matching on a conditions hash."
       end
 
+      # Used to determine if this model adapter will override the matching behavior for a specific condition.
+      # If this returns true then matches_condition? will be called. See Rule#matches_conditions_hash
+      def self.override_condition_matching?(subject, name, value)
+        false
+      end
+
+      # Override if override_condition_matching? returns true
+      def self.matches_condition?(subject, name, value)
+        raise NotImplemented, "This model adapter does not support matching on a specific condition."
+      end
+
       def initialize(model_class, rules)
         @model_class = model_class
         @rules = rules

lib/cancan/model_adapters/active_record_adapter.rb

@@ -5,6 +5,16 @@ module CanCan
         model_class <= ActiveRecord::Base
       end
 
+      def self.override_condition_matching?(subject, name, value)
+        name.kind_of?(MetaWhere::Column) if defined? MetaWhere
+      end
+
+      def self.matches_condition?(subject, name, value)
+        case name.method
+        when "lt" then subject.send(name.column) < value
+        end
+      end
+
       # Returns conditions intended to be used inside a database query. Normally you will not call this
       # method directly, but instead go through ModelAdditions#accessible_by.
       #

lib/cancan/rule.rb

@@ -100,6 +100,9 @@ module CanCan
           model_adapter(subject).matches_conditions_hash? subject, conditions
         else
           conditions.all? do |name, value|
+            if model_adapter(subject).override_condition_matching? subject, name, value
+              model_adapter(subject).matches_condition? subject, name, value
+            else
               attribute = subject.send(name)
               if value.kind_of?(Hash)
                 if attribute.kind_of? Array
@@ -116,6 +119,7 @@ module CanCan
           end
         end
       end
+    end
 
     def nested_subject_matches_conditions?(subject_hash)
       parent, child = subject_hash.shift

spec/cancan/model_adapters/active_record_adapter_spec.rb

@@ -21,6 +21,7 @@ if ENV["MODEL_ADAPTER"].nil? || ENV["MODEL_ADAPTER"] == "active_record"
       table do |t|
         t.boolean "published"
         t.boolean "secret"
+        t.integer "priority"
         t.integer "category_id"
       end
       model do
@@ -199,5 +200,16 @@ if ENV["MODEL_ADAPTER"].nil? || ENV["MODEL_ADAPTER"] == "active_record"
       @ability.can :read, Article, :project => { :admin => true }
       @ability.model_adapter(Article, :read).joins.should == [:project]
     end
+
+    describe "with MetaWhere" do
+      it "should read articles where priority is less than 2" do
+        @ability.can :read, Article, :priority.lt => 2
+        article1 = Article.create!(:priority => 1)
+        article2 = Article.create!(:priority => 3)
+        Article.accessible_by(@ability).should == [article1]
+        @ability.should be_able_to(:read, article1)
+        @ability.should_not be_able_to(:read, article2)
+      end
+    end
   end
 end