adding joins clause to accessible_by when conditions are across associations

CHANGELOG.rdoc

+* Adding joins clause to accessible_by when conditions are across associations
+
 1.1.1 (April 17, 2010)
 
 * Fixing behavior in Rails 3 by properly initializing ResourceAuthorization

lib/cancan/ability.rb

@@ -200,6 +200,16 @@ module CanCan
       end
     end
     
+    # Returns the associations used in conditions. This is usually used in the :joins option for a search.
+    # See ActiveRecordAdditions#accessible_by for use in Active Record.
+    def association_joins(action, subject)
+      can_definition = matching_can_definition(action, subject)
+      if can_definition
+        raise Error, "Cannot determine association joins from block for #{action.inspect} #{subject.inspect}" if can_definition.block
+        can_definition.association_joins
+      end
+    end
+
     private
     
     def can_definitions

lib/cancan/active_record_additions.rb

@@ -21,10 +21,11 @@ module CanCan
       # internally uses Ability#conditions method, see that for more information.
       def accessible_by(ability, action = :read)
         conditions = ability.conditions(action, self) || {:id => nil}
+        joins = ability.association_joins(action, self)
         if respond_to? :where
-          where(conditions)
+          where(conditions).joins(joins)
         else
-          scoped(:conditions => conditions)
+          scoped(:conditions => conditions, :joins => joins)
         end
       end
     end

lib/cancan/can_definition.rb

@@ -25,6 +25,21 @@ module CanCan
       result = can_without_base_behavior?(action, subject, extra_args)
       @base_behavior ? result : !result
     end
+
+    def association_joins(conditions = @conditions)
+      joins = []
+      conditions.each do |name, value|
+        if value.kind_of? Hash
+          nested = association_joins(value)
+          if nested
+            joins << {name => nested}
+          else
+            joins << name
+          end
+        end
+      end
+      joins unless joins.empty?
+    end
     
     private
     

spec/cancan/active_record_additions_spec.rb

@@ -10,19 +10,19 @@ describe CanCan::ActiveRecordAdditions do
   end
   
   it "should call where(:id => nil) when no ability is defined so no records are found" do
-    stub(@model_class).where(:id => nil) { :no_where }
+    stub(@model_class).where(:id => nil).stub!.joins(nil) { :no_where }
     @model_class.accessible_by(@ability, :read).should == :no_where
   end
   
   it "should call where with matching ability conditions" do
-    @ability.can :read, @model_class, :foo => 1
-    stub(@model_class).where(:foo => 1) { :found_records }
+    @ability.can :read, @model_class, :foo => {:bar => 1}
+    stub(@model_class).where(:foo => { :bar => 1 }).stub!.joins([:foo]) { :found_records }
     @model_class.accessible_by(@ability, :read).should == :found_records
   end
   
   it "should default to :read ability and use scoped when where isn't available" do
-    @ability.can :read, @model_class, :foo => 1
-    stub(@model_class).scoped(:conditions => {:foo => 1}) { :found_records }
+    @ability.can :read, @model_class, :foo => {:bar => 1}
+    stub(@model_class).scoped(:conditions => {:foo => {:bar => 1}}, :joins => [:foo]) { :found_records }
     @model_class.accessible_by(@ability).should == :found_records
   end
 end

spec/cancan/can_definition_spec.rb

+require "spec_helper"
+
+describe CanCan::CanDefinition do
+  before(:each) do
+    @conditions = {}
+    @can = CanCan::CanDefinition.new(true, :read, Integer, @conditions, nil)
+  end
+  
+  it "should return no association joins if none exist" do
+    @can.association_joins.should be_nil
+  end
+
+  it "should return no association for joins if just attributes" do
+    @conditions[:foo] = :bar
+    @can.association_joins.should be_nil
+  end
+
+  it "should return single association for joins" do
+    @conditions[:foo] = {:bar => 1}
+    @can.association_joins.should == [:foo]
+  end
+
+  it "should return multiple associations for joins" do
+    @conditions[:foo] = {:bar => 1}
+    @conditions[:test] = {1 => 2}
+    @can.association_joins.map(&:to_s).sort.should == [:foo, :test].map(&:to_s).sort
+  end
+
+  it "should return nested associations for joins" do
+    @conditions[:foo] = {:bar => {1 => 2}}
+    @can.association_joins.should == [{:foo => [:bar]}]
+  end
+end