Allows you to enforce Product SKUs to be unique either among the current product type/class or among all products. Returns a form validation error in case of a duplicate SKU.
Simply go to the Content type or Product class settings form for each type you want to activate this for.
I took a lot of inspiration from webmasterkai's Automatic SKU module, but i'm not sure if the two will work together or not as it depends which fires first.
This is the first attempt at this and works well for me with light testing.
Comments and suggestions welcome!