Add Dumpable plugin for specific control over marshalling. Add specs …

…to cover #330.

lib/mongo_mapper.rb

@@ -36,6 +36,7 @@ module Plugins
     autoload :Dirty,              'mongo_mapper/plugins/dirty'
     autoload :Document,           'mongo_mapper/plugins/document'
     autoload :DynamicQuerying,    'mongo_mapper/plugins/dynamic_querying'
+    autoload :Dumpable,           'mongo_mapper/plugins/dumpable'
     autoload :EmbeddedCallbacks,  'mongo_mapper/plugins/embedded_callbacks'
     autoload :EmbeddedDocument,   'mongo_mapper/plugins/embedded_document'
     autoload :Equality,           'mongo_mapper/plugins/equality'

lib/mongo_mapper/document.rb

@@ -6,6 +6,7 @@ module Document
 
     include Plugins::ActiveModel
     include Plugins::Document
+    include Plugins::Dumpable
     include Plugins::Querying # for now needs to be before associations (save_to_collection)
     include Plugins::Associations
     include Plugins::Caching

lib/mongo_mapper/plugins/dumpable.rb

@@ -0,0 +1,22 @@
+require 'set'
+
+module MongoMapper
+  module Plugins
+    module Dumpable
+      DUMP_BLACKLIST = Set.new([:@_mm_default_keys, :@_mm_keys])
+
+      def marshal_dump
+        instance_variables.inject({}) do |h, var|
+          h[var] = instance_variable_get(var) unless DUMP_BLACKLIST.include?(var)
+          h
+        end
+      end
+
+      def marshal_load(data)
+        data.each do |k, v|
+          instance_variable_set(k, v)
+        end
+      end
+    end
+  end
+end

lib/mongo_mapper/plugins/keys.rb

@@ -297,8 +297,6 @@ def load_from_database(attrs)
               internal_write_key key, value, false
             end
           end
-
-          @_mm_keys = nil  # If we don't nil this, it causes problems for Marshal#dump
         end
 
         def set_parent_document(key, value)
@@ -327,13 +325,12 @@ def internal_write_key(name, value, cast = true)
         end
 
         def initialize_default_values(except = {})
-          @default_keys ||= self.class.keys.values.select(&:default?)
-          @default_keys.each do |key|
+          @_mm_default_keys ||= self.class.keys.values.select(&:default?)
+          @_mm_default_keys.each do |key|
             if !(except && except.key?(key.name))
               internal_write_key key.name, key.default_value, false
             end
           end
-          @_mm_keys = nil  # If we don't nil this, it causes problems for Marshal#dump
         end
       #end private
     end

spec/functional/dumpable_spec.rb

@@ -0,0 +1,24 @@
+require 'spec_helper'
+require 'active_support/cache/memory_store'
+
+describe "Documents with the Dumpable plugin" do
+  let(:doc) { Doc { key :foo, String } }
+  let(:answer) { Answer.create(:body => "answer body") }
+  let(:store)  { ActiveSupport::Cache::MemoryStore.new(:size => 1.megabyte) }
+
+  it "should be able to be marshalled" do
+    expect { Marshal.dump(answer) }.to_not raise_error
+  end
+
+  it "should be able to be unmarshalled" do
+    dumped = Marshal.dump(answer)
+    reconstituted_answer = Marshal.load(dumped)
+    reconstituted_answer.attributes.should == answer.attributes
+  end
+
+  it "should be able to be saved in a Rails cache" do
+    fetched = store.fetch("foo") { Answer.find(answer._id) }
+    fetched.body.should == "answer body"
+    fetched._id.should == answer._id
+  end
+end