clear cookie if failing

cmd/checkout/pool-server.go

@@ -210,7 +210,14 @@ func (s *CheckoutPoolServer) StartCheckoutHandler(w http.ResponseWriter, r *http
 	}
 
 	// Create checkout with same ID as cart
-	checkoutId := checkout.CheckoutId(cartId)
+	var checkoutId checkout.CheckoutId = cart.MustNewCartId()
+	cookie, err := r.Cookie(checkoutCookieName)
+	if err == nil {
+		parsed, ok := cart.ParseCartId(cookie.Value)
+		if ok {
+			checkoutId = parsed
+		}
+	}
 
 	// Initialize checkout with cart state wrapped in Any
 	cartStateAny := &messages.InitializeCheckout{
@@ -225,13 +232,14 @@ func (s *CheckoutPoolServer) StartCheckoutHandler(w http.ResponseWriter, r *http
 
 	result, err := s.ApplyLocal(r.Context(), checkoutId, cartStateAny)
 	if err != nil {
+		setCheckoutCookie(w, 0, r.TLS != nil)
 		logger.Error("failed to initialize checkout", "error", err)
 		http.Error(w, "failed to initialize checkout", http.StatusInternalServerError)
 		return
 	}
 
 	// Set checkout cookie
-	setCheckoutCookie(w, result.Result.Id, r.TLS != nil)
+	setCheckoutCookie(w, checkoutId, r.TLS != nil)
 
 	if err := s.WriteResult(w, result.Result); err != nil {
 		logger.Error("failed to write result", "error", err)

cmd/checkout/utils.go

@@ -68,6 +68,17 @@ func (a *CheckoutPoolServer) reserveInventory(ctx context.Context, grain *checko
 const checkoutCookieName = "checkoutid"
 
 func setCheckoutCookie(w http.ResponseWriter, checkoutId checkout.CheckoutId, tls bool) {
+	if checkoutId == 0 {
+		http.SetCookie(w, &http.Cookie{
+			Name:     checkoutCookieName,
+			Value:    checkoutId.String(),
+			Secure:   tls,
+			HttpOnly: true,
+			Path:     "/",
+			Expires:  time.Unix(0, 0),
+			SameSite: http.SameSiteLaxMode,
+		})
+	} else {
 		http.SetCookie(w, &http.Cookie{
 			Name:     checkoutCookieName,
 			Value:    checkoutId.String(),
@@ -78,6 +89,7 @@ func setCheckoutCookie(w http.ResponseWriter, checkoutId checkout.CheckoutId, tl
 			SameSite: http.SameSiteLaxMode,
 		})
 	}
+}
 
 func CookieCheckoutIdHandler(fn func(w http.ResponseWriter, r *http.Request, checkoutId checkout.CheckoutId) error) func(w http.ResponseWriter, r *http.Request) {
 	return func(w http.ResponseWriter, r *http.Request) {