Ticket #21592: quick fix for #21592.txt

    @property
    def ordered_forms(self):
        '''
            see https://code.djangoproject.com/ticket/21592
            
            This overrides default behavior and makes this property
            available when is_valid() is False.
            
            Adjusted the property to fall back to form.data if
            form.cleaned_data isn't available
        '''
        """
        Returns a list of form in the order specified by the incoming data.
        Raises an AttributeError if ordering is not allowed.
        """
        if not self.can_order:
            raise AttributeError("'%s' object has no attribute 'ordered_forms'" % self.__class__.__name__)
        # Construct _ordering, which is a list of (form_index, order_field_value)
        # tuples. After constructing this list, we'll sort it by order_field_value
        # so we have a way to get to the form indexes in the order specified
        # by the form data.
        if not hasattr(self, '_ordering'):
            self._ordering = []
            for i in range(0, self.total_form_count()):
                form = self.forms[i]
                # if this is an extra form and hasn't changed, don't consider it
                if i >= self.initial_form_count() and not form.has_changed():
                    continue
                # don't add data marked for deletion to self.ordered_data
                if self.can_delete and self._should_delete_form(form):
                    continue
                
                key = ORDERING_FIELD_NAME
                try:
                    data = form.cleaned_data
                except AttributeError:
                    data = form.data
                    key = "%s-%s" % (form.prefix, key)
                
                self._ordering.append((i, data[key]))
            # After we're done populating self._ordering, sort it.
            # A sort function to order things numerically ascending, but
            # None should be sorted below anything else. Allowing None as
            # a comparison value makes it so we can leave ordering fields
            # blank.
            def compare_ordering_key(k):
                if k[1] is None:
                    return (1, 0) # +infinity, larger than any number
                return (0, k[1])
            self._ordering.sort(key=compare_ordering_key)
        # Return a list of form.cleaned_data dicts in the order specified by
        # the form data.
        return [self.forms[i[0]] for i in self._ordering]