ACP2E-3498: Incorrect discount value when multiple cart price rules are applied simultaneously with discounted/special priced products

Author: aplapana

app/code/Magento/SalesRule/Model/Rule/Action/Discount/ExistingDiscountRuleCollector.php

@@ -7,14 +7,18 @@
 
 namespace Magento\SalesRule\Model\Rule\Action\Discount;
 
-class ExistingDiscountRuleCollector
+use Magento\Framework\ObjectManager\ResetAfterRequestInterface;
+
+class ExistingDiscountRuleCollector implements ResetAfterRequestInterface
 {
     /**
      * @var array
      */
     private array $ruleDiscounts = [];
 
     /**
+     * Store discounts that are applied to affected items by previous rules
+     *
      * @param int $ruleId
      * @param float $discountAmount
      * @return void
@@ -25,11 +29,21 @@ public function setExistingRuleDiscount(int $ruleId, float $discountAmount): voi
     }
 
     /**
+     * Retrieve discount that was applied to affected items by previous rule
+     *
      * @param int $ruleId
      * @return float|null
      */
     public function getExistingRuleDiscount(int $ruleId): ?float
     {
         return $this->ruleDiscounts[$ruleId] ?? null;
     }
+
+    /**
+     * @inheritDoc
+     */
+    public function _resetState(): void
+    {
+        $this->ruleDiscounts = [];
+    }
 }

app/code/Magento/SalesRule/Test/Unit/Model/Rule/Action/Discount/CartFixedTest.php

@@ -19,6 +19,7 @@
 use Magento\SalesRule\Model\Rule\Action\Discount\CartFixed;
 use Magento\SalesRule\Model\Rule\Action\Discount\Data;
 use Magento\SalesRule\Model\Rule\Action\Discount\DataFactory;
+use Magento\SalesRule\Model\Rule\Action\Discount\ExistingDiscountRuleCollector;
 use Magento\SalesRule\Model\Validator;
 use Magento\Store\Model\Store;
 use PHPUnit\Framework\MockObject\MockObject;
@@ -81,6 +82,11 @@ class CartFixedTest extends TestCase
      */
     protected $cartFixedDiscountHelper;
 
+    /**
+     * @var ExistingDiscountRuleCollector|MockObject
+     */
+    private ExistingDiscountRuleCollector $existingDiscountRuleCollector;
+
     /**
      * @inheritdoc
      */
@@ -136,11 +142,16 @@ protected function setUp(): void
             ->disableOriginalConstructor()
             ->getMock();
 
+        $this->existingDiscountRuleCollector = $this->createMock(ExistingDiscountRuleCollector::class);
+        $this->existingDiscountRuleCollector->expects($this->any())
+            ->method('getExistingRuleDiscount')
+            ->willReturn(0.00);
         $this->model = new CartFixed(
             $this->validator,
             $dataFactory,
             $this->priceCurrency,
             $this->deltaPriceRound,
+            $this->existingDiscountRuleCollector,
             $this->cartFixedDiscountHelper
         );
     }
@@ -150,7 +161,7 @@ protected function setUp(): void
      * @dataProvider dataProviderActions
      * @param array $shipping
      * @param array $ruleDetails
-     * @throws LocalizedException
+     * @throws LocalizedException|\PHPUnit\Framework\MockObject\Exception
      * @SuppressWarnings(PHPMD.ExcessiveMethodLength)
      */
     public function testCalculate(array $shipping, array $ruleDetails): void