For a certain product, I'd like to be able to limit the shopping cart to one item only. If a second item is added, the first item in the cart is removed.
I have a single product with a custom variable. I'd like to make it so only one of these products is allowed in the cart at any one time. As it stands now, the user can get to the cart with the first product added, go back to the beginning of the checkout process and add the product again with different custom variable.