Added eql? and hash on Document to support [].uniq in an expected man…

…ner.

lib/mongoid/document.rb

@@ -118,6 +118,17 @@ def ==(other)
           other.attributes.except(:modified_at).except(:created_at)
       end
 
+      # Delegates to ==
+      def eql?(comparison_object)
+        self == (comparison_object)
+      end
+
+      # Delegates to id in order to allow two records of the same type and id to work with something like:
+      #   [ Person.find(1), Person.find(2), Person.find(3) ] & [ Person.find(1), Person.find(4) ] # => [ Person.find(1) ]
+      def hash
+        id.hash
+      end
+
       # Introduces a child object into the +Document+ object graph. This will
       # set up the relationships between the parent and child and update the
       # attributes of the parent +Document+.

spec/unit/mongoid/document_spec.rb

@@ -67,6 +67,73 @@
 
   end
 
+  describe "#eql?" do
+
+    context "when other object is a Document" do
+
+      context "when attributes are equal" do
+
+        before do
+          @document = Person.new(:_id => 1, :title => "Sir")
+          @other = Person.new(:_id => 1, :title => "Sir")
+        end
+
+        it "returns true" do
+          @document.eql?(@other).should be_true
+        end
+
+      end
+
+      context "when attributes are not equal" do
+
+        before do
+          @document = Person.new(:title => "Sir")
+          @other = Person.new(:title => "Madam")
+        end
+
+        it "returns false" do
+          @document.eql?(@other).should_not be_true
+        end
+
+      end
+
+    end
+
+    context "when other object is not a Document" do
+
+      it "returns false" do
+        Person.new.eql?("Test").should be_false
+      end
+
+    end
+
+    context "when comapring parent to its subclass" do
+
+      it "returns false" do
+        Canvas.new.eql?(Firefox.new).should_not be_true
+      end
+
+    end
+
+  end
+
+  describe "#hash" do
+
+    before do
+      @document = Person.new(:_id => 1, :title => "Sir")
+      @other = Person.new(:_id => 2, :title => "Sir")
+    end
+
+    it "deligates to id" do
+      @document.hash.should == @document.id.hash
+    end
+
+    it "has unique hash per id" do
+      @document.hash.should_not == @other.hash
+    end
+
+  end
+
   describe "#alias_method_chain" do
 
     context "on a field setter" do