Empty value on optional DateInputField causes error

[Shohan]

Description

A form that has an optional DateInputField raises a ValueError if user submits the form leaving the date field blank.

Cause

This is caused by

tbxforms/tbxforms/fields.py

Line 123 in f1f5c26

 return self.compress([]) 

which fails at

tbxforms/tbxforms/fields.py

Lines 170 to 182 in f1f5c26

     def compress(self, data_list): 
         """ 
         Convert the values entered into the fields as a ``date``. 
  
         Args: 
             data_list (tuple): a 3-tuple the of values entered into the fields. 
  
         Returns: 
             the ``date`` for the values entered in the day, month and year 
                 fields. If any of the field are blank then None is returned. 
  
         """ 
         day, month, year = data_list 

because it expects data_list to be a 3-tuple and instead receives an empty list

Solution

The solution, unless I am missing something, is to simply check if data_list indeed contains 3 values, before unpacking them

if len(data_list) != 3:
    return None