Datamapper DataMapper

Hi. The bug I am reporting is entitled clear enough, but here is a report:

irb(main):011:0> Tag.all
=> []
irb(main):012:0> pr = Post.new
=> #<Post id=nil slug=nil name=nil content=nil frozen_tag_list=nil frozen_category_list=nil>
irb(main):013:0> pr.tag_list = "abc, def, ghi"
=> "abc, def, ghi"
irb(main):014:0> pr.tags
=> []
irb(main):015:0> pr.tag_list
=> ["abc", "def", "ghi"]
irb(main):016:0> pr.name = "Test on tags"
=> "Test on tags"
irb(main):017:0> pr.content = "abcdef"
=> "abcdef"
irb(main):018:0> pr.category_list = "Morocco"
=> "Morocco"
irb(main):019:0> pr.save
=> true
irb(main):020:0> Post.all
=> [#<Post id=74 slug="chaft" name="Chaft" content=<not loaded> frozen_tag_list="boun,dakh" frozen_category_list="niahaha">, #<Post id=75 slug="test-floun" name="Test floun" content=<not loaded> frozen_tag_list="how,moroccan,western sahara" frozen_category_list="Morocco,Sahara">, #<Post id=76 slug="chaft-boun-dakh" name="Chaft Boun Dakh" content=<not loaded> frozen_tag_list="benomar,hadak eddebarh" frozen_category_list="cole">, #<Post id=77 slug="thing" name="Thing" content=<not loaded> frozen_tag_list="ac,def,mn,op" frozen_category_list="Casablanca,Maroc">, #<Post id=78 slug="test-on-tags" name="Test on tags" content=<not loaded> frozen_tag_list="abc,def,ghi" frozen_category_list="Morocco">]
irb(main):021:0> Tag.all
=> [#<Tag id=1 name="abc">, #<Tag id=2 name="def">, #<Tag id=3 name="ghi">, #<Tag id=4 name="Morocco">]
irb(main):022:0> Post.tagged_with('abc')
=> [#<Post id=78 slug="test-on-tags" name="Test on tags" content=<not loaded> frozen_tag_list="abc,def,ghi" frozen_category_list="Morocco">]