ACP2E-2005: applied_rule_ids in the quote_item table does not list all applied rule IDs

Author: bubasuma

app/code/Magento/SalesRule/Model/Quote/Discount.php

@@ -158,7 +158,7 @@ public function collect(
         $address->setCartFixedRules([]);
         $quote->setCartFixedRules([]);
         foreach ($items as $item) {
-            $this->rulesApplier->setAppliedRuleIds($item, []);
+            $item->setAppliedRuleIds(null);
             if ($item->getExtensionAttributes()) {
                 $item->getExtensionAttributes()->setDiscounts(null);
             }

app/code/Magento/SalesRule/Model/RulesApplier.php

@@ -413,7 +413,7 @@ public function setAppliedRuleIds(AbstractItem $item, array $appliedRuleIds)
         $address = $item->getAddress();
         $quote = $item->getQuote();
 
-        $item->setAppliedRuleIds(join(',', $appliedRuleIds));
+        $item->setAppliedRuleIds($this->validatorUtility->mergeIds($item->getAppliedRuleIds(), $appliedRuleIds));
         $address->setAppliedRuleIds($this->validatorUtility->mergeIds($address->getAppliedRuleIds(), $appliedRuleIds));
         $quote->setAppliedRuleIds($this->validatorUtility->mergeIds($quote->getAppliedRuleIds(), $appliedRuleIds));
 

app/code/Magento/SalesRule/Test/Unit/Model/RulesApplierTest.php

@@ -306,12 +306,15 @@ public function testSetAppliedRuleIds()
         $item = $this->getPreparedItem();
         $ruleId = 1;
         $appliedRuleIds = [$ruleId => $ruleId];
+        $previouslyAppliedRuleIds = '3';
+        $expectedAppliedRuleIds = '3,1';
 
         $item->expects($this->once())
             ->method('setAppliedRuleIds')
-            ->with($ruleId);
-        $item->expects($this->never())
-            ->method('getAppliedRuleIds');
+            ->with($expectedAppliedRuleIds);
+        $item->expects($this->once())
+            ->method('getAppliedRuleIds')
+            ->willReturn($previouslyAppliedRuleIds);
 
         $this->rulesApplier->setAppliedRuleIds($item, $appliedRuleIds);
     }

dev/tests/integration/testsuite/Magento/SalesRule/Model/Quote/DiscountTest.php

@@ -363,6 +363,13 @@ private function getQuote(string $reservedOrderId): Quote
     public function testDiscountOnSimpleProductWithDiscardSubsequentRule(): void
     {
         $cartId = (int)$this->fixtures->get('cart')->getId();
+        $rule1Id = (int)$this->fixtures->get('rule1')->getId();
+        $rule2Id = (int)$this->fixtures->get('rule2')->getId();
+        $rule3Id = (int)$this->fixtures->get('rule3')->getId();
+        $product1Id = (int) $this->fixtures->get('p1')->getId();
+        $product2Id = (int) $this->fixtures->get('p2')->getId();
+        $product3Id = (int) $this->fixtures->get('p3')->getId();
+        $product4Id = (int) $this->fixtures->get('p4')->getId();
         $quote = $this->quote->get($cartId);
         $quote->setStoreId(1)->setIsActive(true)->setIsMultiShipping(0)->setCouponCode('test');
         $address = $quote->getShippingAddress();
@@ -372,5 +379,15 @@ public function testDiscountOnSimpleProductWithDiscardSubsequentRule(): void
         $this->subtotalCollector->collect($quote, $this->shippingAssignment, $this->total);
         $this->discountCollector->collect($quote, $this->shippingAssignment, $this->total);
         $this->assertEquals(-32, $this->total->getDiscountAmount());
+        $items = [];
+        foreach ($quote->getAllItems() as $item) {
+            $items[$item->getProductId()] = $item;
+        }
+        $this->assertEqualsCanonicalizing([$rule1Id,$rule2Id,$rule3Id], explode(',', $quote->getAppliedRuleIds()));
+        $this->assertEqualsCanonicalizing([$rule1Id,$rule2Id,$rule3Id], explode(',', $address->getAppliedRuleIds()));
+        $this->assertEqualsCanonicalizing([$rule1Id], explode(',', $items[$product1Id]->getAppliedRuleIds()));
+        $this->assertEqualsCanonicalizing([$rule1Id,$rule2Id], explode(',', $items[$product2Id]->getAppliedRuleIds()));
+        $this->assertEqualsCanonicalizing([$rule2Id], explode(',', $items[$product3Id]->getAppliedRuleIds()));
+        $this->assertEqualsCanonicalizing([$rule3Id], explode(',', $items[$product4Id]->getAppliedRuleIds()));
     }
 }