[Dbix-class] Serialize::Storable and dclone

[stephen joseph butler]

THE PROBLEM:

I've been using Storable::dclone to make a clone of a Row before
updating it so that I can later find the differences (I'm using
DBIx::Class::HTMLWidget, so get_dirty_columns isn't available to me).
Here's what my code looks like (using Catalyst):

sub save {
  my ( $self, $c, $id, $widget_result ) = @_;

  my $new_obj = $c->model( 'DB::Object' )->find( $id );
  my $old_obj = dclone( $new_obj );

  $new_obj->populate_from_widget( $widget_result );

  my %diff;
  foreach ($old_obj->result_source->columns) {
    next if $old_obj->get_column( $_ ) eq $new_obj->get_column( $_ );

    $diff{ $_ } = {
      old => $old_obj->$_,
      new => $new_obj->$_
    };
  }

  # render %diff with TT
}

But I keep getting this error whenever I change a column with a
foreign key relationship:

[error] Caught exception in DB::Controller::Object->save "Can't call
method "select_single" on an undefined value at
/usr/lib/perl5/site_perl/5.8.8/DBIx/Class/ResultSet.pm line 537."

Yes, my schema for DB::Object has this at the top:

__PACKAGE__->load_components("HTMLWidget", "Serialize::Storable", "Core");

Still, suspecting that result_source isn't getting set properly on a
thaw, I changed my code to:

sub save {
  my ( $self, $c, $id, $widget_result ) = @_;

  my $new_obj = $c->model( 'DB::Object' )->find( $id );
  my $old_obj = dclone( $new_obj );
  $old_obj->result_source( $new_obj->result_source );

  # rest...
}

Am I doing something wrong? Is this work-around going to bite me in
the ass later?

WHAT I'M TRYING TO DO:

Each DB::Object has a DB::ObjectComment with it. Each time the user
submits edits I want to automatically generate a comment with what's
changed. Before, I was using get_columns before and after the
populate_from_widget() and this worked. But all my foreign keys showed
up as the actual value instead of the fetched row. I'd rather have the
row since I took the time to write pretty overloaded stringification
operators.