Thank you for your work on SC 3.90 to let us track quantity on hand for size and color simultaneously (see smith_productvariantinventory, smith_productvariantinvlinker tables).

We will be testing it more tonight to see how it works. I assume when a sale is made the quantity is reduced to reflect this. (Since that's the basis for all functionality of this feature.)

What is the behavior when the visitor places an order for an item that has <= 0 quantity on hand. Is there an event we can use as a hook to display a message? We notice on competitor's sites that a message is displayed when an ordered item is out of stock.

Out of stock items do still appear on the pull downs for colors and sizes, which after more consultation with the client, is good.

But an out of stock item may be permanently sold out from the supplier or simply needs a reorder from our client to their supplier. We would like to have different behavior for the shopper ready to go.

I created a test product with cost $1 on our site with size and color variants, big, small and black. I set quantity on hand for black, small and black, big to 1 each. I placed an order for 3 black, bigs. The cart allowed me to place this order passing me off to PayPal Standard where the order summary at login showed an order for $3, quantity 1. After paying $3 and returning to the cart confirm status page, the quantity was back to 3.

This didn't say anything about being out of stock.