Synopsis: I've deleted an ancient payment method extension from my magento install, and now orders made using this payment method cannot be viewed and result in an exception.
Specifically, our store has been using an ancient payment method extension which I am now in the process of upgrading to a brand spanking new version, from a different vendor.
The old extension is badly written and a complete mess, so I just wanted to get rid of it. The new extension is for the same payment provider, but uses a different $_code and is incompatible with the old extension.
Trying to view any order where this payment method is used, in either the back end or the customer account page, results in an exception: "The requested Payment Method is not available."
How do I get around this? I don't care about the payment method for these old orders, I just want to be able to view further details about the order without it crashing.
I cannot change the payment method code on the orders themselves to the new payment method code as they are incompatible and generate further errors. Is it possible to create a "skeleton" payment method that uses the $_code from the old payment method for the sole purpose of satisfying magento needs, and how difficult would this be? Or is there another way round this problem which doesn't involve me keeping the old legacy extension kicking around?