Provide a constraint on the Coupons field to verify referenced coupons are available

This adds a constraint to the coupon field which validates if the coupon and promotion apply. If it does not, then a constraint is returned.

This allows validating an order to see if coupons apply or not without blindly applying them and hope they persist, and trying to catch if they'll be removed on the next order refresh.

I think it's just a check I added in case someone attached it on an incorrect base field. I shouldn't do that, just add an assert

Removed that for an assert

Whoops, sorry. Too much multitasking.

Here is a proper patch and it covers placed orders.

I don't know how to upload patches.

The next step here is to 👍 the approach and replace the two areas highlighted in the issue summary to run validation against the field and set the error versus running the logic separately.

Sounds good, and makes sense - why add it to the order to run validation in the inline form when it's available right there. I'll update PromotionOrderProcessor. This made me realize we have no context as to what code.

In the entity reference constraint code I saw we can specify the field item delta using this snippet:

          $this->context->buildViolation($constraint->nullMessage)
            ->atPath((string) $delta)
            ->addViolation();

Here is an updated patch. Turns out PromotionOrderProcessorTest never tested the removal of coupons. I added that to test the changes worked as expected.

Oh, interesting! That was not considered. Thanks.

Coming back around to this.

The error was due to constraints existing from ValidReference

          $this->context->buildViolation($message)
            ->setParameter('%type', $target_type_id)
            ->setParameter('%id', $target_id)
            ->atPath((string) $delta . '.target_id')
            ->setInvalidValue($target_id)
            ->addViolation();

It sets the property path to the field properties of target_id or entity

This addresses #13. The coupon constraint now has the same path setup as invalid reference constraints. As a bonus, this order processor now ensures deleted coupons are removed from the order.

Fix the property path in the assertion.

Tests are no longer passing.

Switched the kernel test to OrderKernelTestBase for schema fix.

Fix setUp against new base test class.

+++ b/modules/promotion/src/Plugin/Validation/Constraint/CouponAvailableConstraint.php
@@ -0,0 +1,26 @@
+  public $message = 'The coupon %code is not available for this order.';

As bojanz pointed out, currently the redemption form uses this wording

The provided coupon code is invalid.

Lets use that.

Adjusted the wording.

+++ b/modules/promotion/src/Plugin/Validation/Constraint/CouponAvailableConstraintValidator.php
@@ -0,0 +1,39 @@
+          ->atPath((string) $delta . '.target_id')

The one thing I wanted to double check was this line. Core uses this as well in ValidReferenceConstraintValidator.

// for entity property / new entities
          ->atPath((string) $delta . '.entity')
          ->setInvalidValue($entity)
// for target_id property
            ->atPath((string) $delta . '.target_id')
            ->setInvalidValue($target_id)

+++ b/modules/promotion/commerce_promotion.module
@@ -140,6 +140,7 @@ function commerce_promotion_entity_base_field_info(EntityTypeInterface $entity_t
+      ->addConstraint('CouponAvailable')

+++ b/modules/promotion/src/Plugin/Validation/Constraint/CouponAvailableConstraint.php
@@ -0,0 +1,26 @@
+ * Coupon valid reference constraint.
...
+ *   id = "CouponAvailable",
+ *   label = @Translation("Coupon available reference", context = "Validation")
...
+class CouponAvailableConstraint extends Constraint {
...
+  public $message = 'The provided coupon code is invalid.';

bojanz pointed out the verbs are all over the place.

This checks available & applies on coupons. So it should be called CouponValid.

s/CouponAvailable/CouponValid

🥳 merged.

I would expect a test for CouponValidConstraintValidator to have a @coversDefaultClass pointing to it, and the test not to need the full order refresh.

I can add the covers annotations. With testCouponRemoval moved to PromotionOrderProcessorTest there's no refresh needed.

    $order->setRefreshState(Order::REFRESH_SKIP);
    $order->save();

That exists so that the store_id constraint doesn't fire, because of entity access checks. And also for recording promotion usage.

Follow up. Should be OK but want DrupalCI to verify.

+++ b/modules/promotion/tests/src/Kernel/CouponValidConstraintValidatorTest.php
@@ -13,6 +13,7 @@ use Drupal\Tests\commerce_order\Kernel\OrderKernelTestBase;
+ * @coversDefaultClass \Drupal\commerce_cart_api\Plugin\Validation\Constraint\CouponValidConstraintValidator

🤦‍♂️

Committed the follow up