Add class to woocommerce_before_shop_loop_item

Currently my render code is…

li class=product type-product post-387 status-publish instock product_cat-uncategorized has-post-thumbnail shipping-taxable purchasable product-type-simple
    a href=https://#/product/#/ class=woocommerce-LoopProduct-link woocommerce-loop-product__link
etc…

Which appears to be generated from the woocommerce_before_shop_loop_item function.

I'd like to add an if condition within the anchor class to check if something exists. I've looked for this function within woocommerce but it doesn't appear to offer a way of editing the anchor classes?