ENGCOM-3035: [Forwardport] Make sure all linked products (related, upsells, crosss… #18207

 - Merge Pull Request #18207 from hostep/magento2:fix-for-issue-13720-for-magento-2.3
 - Merged commits:
   1. 74e1ea9
   2. d5b6231

Author: magento-engcom-team

app/code/Magento/Catalog/Model/ProductLink/CollectionProvider.php

@@ -9,6 +9,9 @@
 use Magento\Catalog\Model\ProductLink\Converter\ConverterPool;
 use Magento\Framework\Exception\NoSuchEntityException;
 
+/**
+ * Provides a collection of linked product items (crosssells, related, upsells, ...)
+ */
 class CollectionProvider
 {
     /**
@@ -47,22 +50,20 @@ public function getCollection(\Magento\Catalog\Model\Product $product, $type)
 
         $products = $this->providers[$type]->getLinkedProducts($product);
         $converter = $this->converterPool->getConverter($type);
-        $output = [];
         $sorterItems = [];
         foreach ($products as $item) {
-            $output[$item->getId()] = $converter->convert($item);
+            $itemId = $item->getId();
+            $sorterItems[$itemId] = $converter->convert($item);
+            $sorterItems[$itemId]['position'] = $sorterItems[$itemId]['position'] ?? 0;
         }
 
-        foreach ($output as $item) {
-            $itemPosition = $item['position'];
-            if (!isset($sorterItems[$itemPosition])) {
-                $sorterItems[$itemPosition] = $item;
-            } else {
-                $newPosition = $itemPosition + 1;
-                $sorterItems[$newPosition] = $item;
-            }
-        }
-        ksort($sorterItems);
+        usort($sorterItems, function ($itemA, $itemB) {
+            $posA = intval($itemA['position']);
+            $posB = intval($itemB['position']);
+
+            return $posA <=> $posB;
+        });
+
         return $sorterItems;
     }
 }

app/code/Magento/Catalog/Test/Unit/Model/CollectionProviderTest.php

@@ -57,10 +57,14 @@ public function testGetCollection()
         $linkedProductOneMock = $this->createMock(Product::class);
         $linkedProductTwoMock = $this->createMock(Product::class);
         $linkedProductThreeMock = $this->createMock(Product::class);
+        $linkedProductFourMock = $this->createMock(Product::class);
+        $linkedProductFiveMock = $this->createMock(Product::class);
 
         $linkedProductOneMock->expects($this->once())->method('getId')->willReturn(1);
         $linkedProductTwoMock->expects($this->once())->method('getId')->willReturn(2);
         $linkedProductThreeMock->expects($this->once())->method('getId')->willReturn(3);
+        $linkedProductFourMock->expects($this->once())->method('getId')->willReturn(4);
+        $linkedProductFiveMock->expects($this->once())->method('getId')->willReturn(5);
 
         $this->converterPoolMock->expects($this->once())
             ->method('getConverter')
@@ -71,9 +75,11 @@ public function testGetCollection()
             [$linkedProductOneMock, ['name' => 'Product One', 'position' => 10]],
             [$linkedProductTwoMock, ['name' => 'Product Two', 'position' => 2]],
             [$linkedProductThreeMock, ['name' => 'Product Three', 'position' => 2]],
+            [$linkedProductFourMock, ['name' => 'Product Four', 'position' => null]],
+            [$linkedProductFiveMock, ['name' => 'Product Five']],
         ];
 
-        $this->converterMock->expects($this->exactly(3))->method('convert')->willReturnMap($map);
+        $this->converterMock->expects($this->exactly(5))->method('convert')->willReturnMap($map);
 
         $this->providerMock->expects($this->once())
             ->method('getLinkedProducts')
@@ -82,14 +88,18 @@ public function testGetCollection()
                 [
                     $linkedProductOneMock,
                     $linkedProductTwoMock,
-                    $linkedProductThreeMock
+                    $linkedProductThreeMock,
+                    $linkedProductFourMock,
+                    $linkedProductFiveMock,
                 ]
             );
 
         $expectedResult = [
-            2 => ['name' => 'Product Two', 'position' => 2],
-            3 => ['name' => 'Product Three', 'position' => 2],
-            10 => ['name' => 'Product One', 'position' => 10],
+            0 => ['name' => 'Product Four', 'position' => 0],
+            1 => ['name' => 'Product Five', 'position' => 0],
+            2 => ['name' => 'Product Three', 'position' => 2],
+            3 => ['name' => 'Product Two', 'position' => 2],
+            4 => ['name' => 'Product One', 'position' => 10],
         ];
 
         $actualResult = $this->model->getCollection($this->productMock, 'crosssell');