book: neues Feld 'description', sperrt btype-->None mit Zeilen + Test

line: verwendet nur kassenbücher mit typ

book.py

@@ -45,6 +45,8 @@ class Book(tree(separator='/'), Workflow, ModelSQL, ModelView):
         required=True, ondelete="RESTRICT")
     name = fields.Char(string='Name', required=True,
         states=STATES, depends=DEPENDS)
+    description = fields.Text(string='Description',
+        states=STATES, depends=DEPENDS)
     btype = fields.Many2One(string='Type',
         help='A cash book with type can contain postings. Without type is a view.',
         model_name='cashbook.type', ondelete='RESTRICT',
@@ -307,6 +309,15 @@ class Book(tree(separator='/'), Workflow, ModelSQL, ModelView):
         actions = iter(args)
         for books, values in zip(actions, actions):
             for book in books:
+                # deny btype-->None if lines not empty
+                if 'btype' in values.keys():
+                    if (values['btype'] is None) and (len(book.lines) > 0):
+                        raise UserError(gettext(
+                            'cashbook.msg_book_btype_with_lines',
+                            cbname = book.rec_name,
+                            numlines = len(book.lines),
+                            ))
+
                 if book.state != 'open':
                     # allow state-update, if its the only action
                     if not (('state' in values.keys()) and (len(values.keys()) == 1)):