hello all i'am workig on leaves conditions module in version 10 , i added a validation that rais when no joining date asigneed to the employee , it;s working well,

but it's also raise while requesting allocation by employee tag , although i am tried a tag with only one employee in this tag and i am assigned a joining date for him

here is the code 

@api.constrains('state', 'date_from', 'holiday_status_id',)
def _check_hire_date(self):

    if self.employee_id.joining_date:
        jo_dt = fields.Datetime.from_string(self.employee_id.joining_date)
    else:
        raise ValidationError("you must define joining date")

​