That's funny, I was trying to do exactly the same thing.
First I tried is_cart()
But that only makes the cart and checkout menus visible if you are on the cart page.
Otherwise they go away again . . . that's not the desired functionality i'm looking for.
Since the plugin says it's like Widget Logic only for menus, I asked the Widget Logic author to confirm my logic is correct.
If I echo
global $woocommerce; var_dump($woocommerce->cart->cart_contents_count); it returns int(0) if the cart is empty and an integer greater than 0 if it has contents.
So my "widget logic" is
global $woocommerce; return ( $woocommerce->cart->cart_contents_count > 0);
Logically this should show the Cart and Checkout menu items only if the cart has contents, however the menus display whether the cart has contents or not. Also tried !==0 with the same results.