Writing a validator to look for cookie data

I store fields from form submissions into a cookie, and then when a
user hits a form, I prepopulate the form with that data.

I want to write a validator that first tries to get values from the
query string, and if that is None, then the validator should check the
cookie.

Here is what I have:

class LookInCookie(FancyValidator):
    """
    Retrieves something from the cookie.  Depends on a state with an
    attribute named 'simple_cookie'.
    """

    def __init__(self, k, d=None):
        """
        Return k from the cookie, or d if it isn't there.
        """
        self.k, self.d = k, d

    def to_python(self, value, state=None):

        log.debug("Inside LookInCookie.to_python with locals: %s"
            % locals())

        if hasattr(state, 'simple_cookie') \
        and state.simple_cookie.has_key(self.k):

            return state.simple_cookie[self.k]

        else:
            return self.d

Then I tried to combine this validator with Any() like this:

>>> from turbogears.util import Bunch
>>> s = Bunch(simple_cookie={'city':1})
>>> v = Any(LookInCookie('city'), validators.Int())
>>> v.to_python('99', s)
99
>>> v.to_python('abc', s)
1

So far, so good!  First, the Int validator runs, then when Int fails,
I get the value from the cookie s.

However, here's where things fall apart.  When there is no value
passed in, nothing comes back out!

>>> v.to_python('', s)
>>> v.to_python(None, s)


How do I force validators to run even when the value is missing?

More generally, is there a better solution to what I'm trying to do?

-- 
Matthew Wilson
[email protected]
http://tplus1.com

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