Consider the following example:
class Foo(models.Model):
_name = 'foo'
_columns = {
'state': fields.selection([('a', 'A')]),
}
class Bar(models.Model):
_inherit = 'foo'
state = fields.Selection(selection_add=[('b', 'B')])
The attribute 'column' of the field does not have the full selection list,
therefore the column object cannot not be reused, even a copy of it. The
solution is to systematically recreate the column from the field's final
specification, except for function fields that have no sensible way for being
recreated.
Raphael Collet