add is_valid fake method to enable beanstream credit cards

[Chris7]

The credit card beanstream uses does not have an is_valid method so the validation method fails. This puts in a fake is_valid method if one doesn't exist (so if they ever do add a method it will work seamlessly).

[tuxcanfly]

Might be better to limit this to if validate, otherwise looks correct.

[Chris7]

Do you mean in the validate_card method?

[tuxcanfly]

Well, something like:

     if validate:
        if not hasattr(card, 'is_valid'):
            # there is no is_valid on the beanstream credit card object
            def is_valid():
                return True
            card.is_valid = is_valid
         self.validate_card(card)

This way if someone passes validate=False, we can avoid the monkey patch.

[Chris7]

Here's a different approach I like better since it extends to all cards and avoids monkey patches as well as an extra lookup of is_valid.

[tuxcanfly]

I think it's far better to just get rid of validation in convert_cc. validate_card expects a merchant.billing.utils.CreditCard, but we're passing it a beanstream.billing.CreditCard, which happens to have some attrs in common, which is asking for trouble. Ideally convert_cc should have been private but it's not a part of the Gateway interface so I think there's no harm in modifying it.

[Chris7]

You would know better. I agree that combining libraries with the same method signatures is dangerous as well, but is probably just one of those unfortunate choices that are outside of our control and we just have to deal with. However, because I'm unaware if other cards may have the same issue, I opted to add this logic here. It's a hard choice, for instance you can convert everything to a merchant CC and reject anything that isn't a subclass of it to avoid complications arising from common attributes, but then you'd have to keep up with god knows how many APIs that using their own CC instance handles.