Add the ability to use a custom serializer for storing the object in the database

README.md

@@ -727,6 +727,16 @@ Or a block:
 end
 ```
 
+## Using a custom serializer
+
+By default, PaperTrail stores your changes as a YAML dump. You can override this with the serializer config option:
+
+```ruby
+>> PaperTrail.serializer = MyCustomSerializer
+```
+
+The serializer needs to be a class that responds to a `load` and `dump` method.
+
 ## Deleting Old Versions
 
 Over time your `versions` table will grow to an unwieldy size.  Because each version is self-contained (see the Diffing section above for more) you can simply delete any records you don't want any more.  For example:

lib/paper_trail.rb

@@ -5,6 +5,7 @@ require 'paper_trail/config'
 require 'paper_trail/controller'
 require 'paper_trail/has_paper_trail'
 require 'paper_trail/version'
+require 'paper_trail/serializers/yaml'
 
 # PaperTrail's module methods can be called in both models and controllers.
 module PaperTrail
@@ -69,6 +70,9 @@ module PaperTrail
     paper_trail_store[:controller_info] = value
   end
 
+  def self.serializer
+    PaperTrail.config.serializer
+  end
 
   private
 

lib/paper_trail/config.rb

@@ -1,12 +1,13 @@
 module PaperTrail
   class Config
     include Singleton
-    attr_accessor :enabled, :timestamp_field
+    attr_accessor :enabled, :timestamp_field, :serializer
 
     def initialize
       # Indicates whether PaperTrail is on or off.
       @enabled         = true
       @timestamp_field = :created_at
+      @serializer      = PaperTrail::Serializers::Yaml
     end
   end
 end

lib/paper_trail/has_paper_trail.rb

@@ -162,9 +162,10 @@ module PaperTrail
           }
           if version_class.column_names.include? 'object_changes'
             # The double negative (reject, !include?) preserves the hash structure of self.changes.
-            data[:object_changes] = self.changes.reject do |key, value|
+            changes = self.changes.reject do |key, value|
               !notably_changed.include?(key)
-            end.to_yaml
+            end
+            data[:object_changes] = PaperTrail.serializer.dump(changes)
           end
           send(self.class.versions_association_name).build merge_metadata(data)
         end
@@ -215,7 +216,7 @@ module PaperTrail
       end
 
       def object_to_string(object)
-        object.attributes.except(*self.class.skip).to_yaml
+        PaperTrail.serializer.dump object.attributes.except(*self.class.skip)
       end
 
       def changed_notably?

lib/paper_trail/serializers/yaml.rb

@@ -0,0 +1,23 @@
+require 'yaml'
+
+module PaperTrail
+  module Serializers
+    class Yaml
+      def self.load(string)
+        new.load(string)
+      end
+
+      def self.dump(hash)
+        new.dump(hash)
+      end
+
+      def load(string)
+        YAML.load(string)
+      end
+
+      def dump(hash)
+        YAML.dump(hash)
+      end
+    end
+  end
+end

lib/paper_trail/version.rb

@@ -55,7 +55,7 @@ class Version < ActiveRecord::Base
       options.reverse_merge! :has_one => false
 
       unless object.nil?
-        attrs = YAML::load object
+        attrs = PaperTrail.serializer.load object
 
         # Normally a polymorphic belongs_to relationship allows us
         # to get the object we belong to by calling, in this case,
@@ -103,7 +103,7 @@ class Version < ActiveRecord::Base
   def changeset
     if self.class.column_names.include? 'object_changes'
       if changes = object_changes
-        HashWithIndifferentAccess[YAML::load(changes)]
+        HashWithIndifferentAccess[PaperTrail.serializer.load(changes)]
       else
         {}
       end

test/unit/model_test.rb

@@ -49,11 +49,11 @@ class HasPaperTrailModelTest < ActiveSupport::TestCase
         end
 
         should 'have removed the skipped attributes when saving the previous version' do
-          assert_equal nil, YAML::load(@old_article.object)['file_upload']
+          assert_equal nil, PaperTrail.serializer.load(@old_article.object)['file_upload']
         end
 
         should 'have kept the non-skipped attributes in the previous version' do
-          assert_equal 'Some text here.', YAML::load(@old_article.object)['content']
+          assert_equal 'Some text here.', PaperTrail.serializer.load(@old_article.object)['content']
         end
       end
     end
@@ -184,7 +184,7 @@ class HasPaperTrailModelTest < ActiveSupport::TestCase
         end
 
         should 'have stored changes' do
-          assert_equal ({'name' => ['Henry', 'Harry']}), YAML::load(@widget.versions.last.object_changes)
+          assert_equal ({'name' => ['Henry', 'Harry']}), PaperTrail.serializer.load(@widget.versions.last.object_changes)
           assert_equal ({'name' => ['Henry', 'Harry']}), @widget.versions.last.changeset
         end
 

test/unit/serializer_test.rb

@@ -0,0 +1,69 @@
+require 'test_helper'
+
+class CustomSerializer
+  require 'json'
+  def self.dump(object_hash)
+    JSON.dump object_hash
+  end
+
+  def self.load(string)
+    JSON.parse string
+  end
+end
+
+class SerializerTest < ActiveSupport::TestCase
+
+  context 'YAML Serializer' do
+    setup do
+      Fluxor.instance_eval <<-END
+        has_paper_trail
+      END
+
+      @fluxor = Fluxor.create :name => 'Some text.'
+      @fluxor.update_attributes :name => 'Some more text.'
+    end
+
+    should 'work with the default yaml serializer' do
+      # Normal behaviour
+      assert_equal 2, @fluxor.versions.length
+      assert_nil @fluxor.versions[0].reify
+      assert_equal 'Some text.', @fluxor.versions[1].reify.name
+
+
+      # Check values are stored as YAML.
+      assert_equal "---\nwidget_id: \nname: Some text.\nid: 1\n", @fluxor.versions[1].object
+      assert_equal ({"widget_id" => nil,"name" =>"Some text.","id" =>1}), YAML.load(@fluxor.versions[1].object)
+
+    end
+  end
+
+  context 'Custom Serializer' do
+    setup do
+      PaperTrail.config.serializer = CustomSerializer
+
+      Fluxor.instance_eval <<-END
+        has_paper_trail
+      END
+
+      @fluxor = Fluxor.create :name => 'Some text.'
+      @fluxor.update_attributes :name => 'Some more text.'
+    end
+
+    teardown do
+      PaperTrail.config.serializer = PaperTrail::Serializers::Yaml
+    end
+
+    should 'work with custom serializer' do
+      # Normal behaviour
+      assert_equal 2, @fluxor.versions.length
+      assert_nil @fluxor.versions[0].reify
+      assert_equal 'Some text.', @fluxor.versions[1].reify.name
+
+      # Check values are stored as JSON.
+      assert_equal "{\"widget_id\":null,\"name\":\"Some text.\",\"id\":1}", @fluxor.versions[1].object
+      assert_equal ({"widget_id" => nil,"name" =>"Some text.","id" =>1}), JSON.parse(@fluxor.versions[1].object)
+
+    end
+  end
+
+end