[API] Prevent from using inexistent shipping method

features/checkout/shipping_order/preventing_not_available_shipping_method_selection.feature

@@ -86,3 +86,13 @@ Feature: Preventing not available shipping method selection
         When I specify the billing address as "Ankh Morpork", "Frost Alley", "90210", "United States" for "Jon Snow"
         And I complete the addressing step
         Then I should not be able to select "Dragon Post" shipping method
+
+    @api
+    Scenario: Not being able to select inexistent shipping method
+        Given the store has "Raven Post" shipping method with "$10.00" fee
+        And I have product "Targaryen T-Shirt" in the cart
+        And I am at the checkout addressing step
+        When I specify the billing address as "Ankh Morpork", "Frost Alley", "90210", "United States" for "Jon Snow"
+        And I complete the addressing step
+        And I try to select "Inexistent" shipping method
+        Then I should be informed that shipping method with code "Inexistent" does not exist

src/Sylius/Behat/Context/Api/Shop/CheckoutContext.php

@@ -28,6 +28,7 @@
 use Sylius\Component\Core\Model\PaymentMethodInterface;
 use Sylius\Component\Core\Model\ProductInterface;
 use Sylius\Component\Core\Model\ProductVariantInterface;
+use Sylius\Component\Core\Model\ShippingMethod;
 use Sylius\Component\Core\Model\ShippingMethodInterface;
 use Sylius\Component\Core\Model\ShopUserInterface;
 use Sylius\Component\Core\OrderCheckoutStates;
@@ -345,6 +346,24 @@ public function iProceededWithShippingMethod(ShippingMethodInterface $shippingMe
         $this->selectShippingMethod($shippingMethod);
     }
 
+    /**
+     * @When I try to select :shippingMethodCode shipping method
+     */
+    public function iTryToSelectShippingMethod(string $shippingMethodCode): void
+    {
+        $request = Request::customItemAction(
+            'shop',
+            'orders',
+            $this->sharedStorage->get('cart_token'),
+            HTTPRequest::METHOD_PATCH,
+            sprintf('shipments/%s', $this->getCart()['shipments'][0]['id'])
+        );
+
+        $request->setContent(['shippingMethod' => $this->iriConverter->getItemIriFromResourceClass(ShippingMethod::class, ['code' => $shippingMethodCode])]);
+
+        $this->ordersClient->executeCustomRequest($request);
+    }
+
     /**
      * @When I try to select :paymentMethodCode payment method
      */
@@ -363,6 +382,17 @@ public function iTryToSelectPaymentMethod(string $paymentMethodCode): void
         $this->ordersClient->executeCustomRequest($request);
     }
 
+    /**
+     * @Then I should be informed that shipping method with code :code does not exist
+     */
+    public function iShouldBeInformedThatShippingMethodWithCodeDoesNotExist(string $code): void
+    {
+        Assert::true($this->isViolationWithMessageInResponse(
+            $this->ordersClient->getLastResponse(),
+            sprintf('The shipping method with %s code does not exist.', $code)
+        ));
+    }
+
     /**
      * @Then the visitor has no access to proceed with :shippingMethod shipping method in the customer cart
      * @Then the visitor has no access to proceed with :paymentMethod payment in the customer cart

src/Sylius/Bundle/ApiBundle/Resources/translations/validators.en.yaml

@@ -17,4 +17,5 @@ sylius:
     shipment:
         shipped: 'You cannot ship a shipment that was shipped before.'
     shipping_method:
+        not_found: 'The shipping method with %code% code does not exist.'
         not_available: 'The shipping method %name% is not available for this order. Please reselect your shipping method.'

src/Sylius/Bundle/ApiBundle/Validator/Constraints/ChosenShippingMethodEligibility.php

@@ -21,6 +21,9 @@ final class ChosenShippingMethodEligibility extends Constraint
     /** @var string */
     public $message = 'sylius.shipping_method.not_available';
 
+    /** @var string */
+    public $notFoundMessage = 'sylius.shipping_method.not_found';
+
     public function validatedBy(): string
     {
         return 'sylius_api_validator_chosen_shipping_method_eligibility';

src/Sylius/Bundle/ApiBundle/Validator/Constraints/ChosenShippingMethodEligibilityValidator.php

@@ -55,7 +55,11 @@ public function validate($value, Constraint $constraint): void
 
         /** @var ShippingMethodInterface|null $shippingMethod */
         $shippingMethod = $this->shippingMethodRepository->findOneBy(['code' => $value->shippingMethodCode]);
-        Assert::notNull($shippingMethod);
+        if (null === $shippingMethod) {
+            $this->context->addViolation($constraint->notFoundMessage, ['%code%' => $value->shippingMethodCode]);
+
+            return;
+        }
 
         /** @var ShipmentInterface|null $shipment */
         $shipment = $this->shipmentRepository->find($value->shipmentId);