Added save! for rails compatibility.

lib/mongo_mapper.rb

@@ -19,6 +19,12 @@
 
 module MongoMapper
   class DocumentNotFound < StandardError; end
+  class DocumentNotValid < StandardError
+    def initialize(document)
+      @document = document
+      super("Validation failed: #{@document.errors.full_messages.join(", ")}")
+    end
+  end
 
   def self.connection
     @@connection ||= XGen::Mongo::Driver::Mongo.new

lib/mongo_mapper/save_with_validation.rb

@@ -7,7 +7,11 @@ def self.included(base)
       end
     end
 
-    private    
+    def save!
+      save_with_validation || raise(DocumentNotValid.new(self))
+    end
+
+    private
       def save_with_validation
         new? ? run_callbacks(:before_validation_on_create) : 
                run_callbacks(:before_validation_on_update)

test/test_validations.rb

@@ -180,6 +180,22 @@ class ValidationsTest < Test::Unit::TestCase
     end
   end
 
+  context "Saving a document that is invalid (destructive)" do
+    setup do
+      @document = Class.new do
+        include MongoMapper::Document
+        key :name, String, :required => true
+      end
+
+      @document.collection.clear
+    end
+
+    should "raise error" do
+      doc = @document.new
+      lambda { doc.save! }.should raise_error(MongoMapper::DocumentNotValid)
+    end
+  end
+
   context "Saving an existing document that is invalid" do
     setup do
       @document = Class.new do