Return nil for key that is not found instead of raising exception. Ex…

…ception is way to harsh. This makes it behave more like a hash.

lib/mongo_mapper.rb

@@ -8,7 +8,6 @@ module MongoMapper
   autoload :Connection,             'mongo_mapper/connection'
 
   autoload :Error,                  'mongo_mapper/exceptions'
-  autoload :KeyNotFound,            'mongo_mapper/exceptions'
   autoload :DocumentNotFound,       'mongo_mapper/exceptions'
   autoload :InvalidScheme,          'mongo_mapper/exceptions'
   autoload :DocumentNotValid,       'mongo_mapper/exceptions'

lib/mongo_mapper/exceptions.rb

@@ -3,9 +3,6 @@ module MongoMapper
   # generic MM error
   class Error < StandardError; end
 
-  # raised when key expected to exist but not found
-  class KeyNotFound < Error; end
-
   # raised when document expected but not found
   class DocumentNotFound < Error; end
 

lib/mongo_mapper/plugins/keys.rb

@@ -290,8 +290,6 @@ def read_key(key_name)
               value = key.get(instance_variable_get(:"@#{key_name}"))
               set_parent_document(key, value)
               instance_variable_set(:"@#{key_name}", value)
-            else
-              raise KeyNotFound, "Could not find key: #{key_name.inspect}"
             end
           end
 

test/unit/test_embedded_document.rb

@@ -387,9 +387,9 @@ def passwd
             doc[:name].should == 'string'
           end
 
-          should "raise exception when key not found" do
+          should "return nil when not found" do
             doc = @document.new(:name => 'string')
-            assert_raises(MongoMapper::KeyNotFound) { doc[:not_here] }
+            doc[:not_here].should be_nil
           end
         end