8022: Uncaught Error: Call to a member function addItem() on array in app/code/Magento/Sales/Model/Order/Shipment.php(backport to 2.2)

Author: RomaKis

app/code/Magento/Sales/Model/Order/Shipment.php

@@ -93,6 +93,11 @@ class Shipment extends AbstractModel implements EntityInterface, ShipmentInterfa
      */
     protected $orderRepository;
 
+    /**
+     * @var \Magento\Sales\Model\ResourceModel\Order\Shipment\Track\Collection|null
+     */
+    private $tracksCollection = null;
+
     /**
      * @param \Magento\Framework\Model\Context $context
      * @param \Magento\Framework\Registry $registry
@@ -331,16 +336,11 @@ public function addItem(\Magento\Sales\Model\Order\Shipment\Item $item)
      */
     public function getTracksCollection()
     {
-        if (!$this->hasData(ShipmentInterface::TRACKS)) {
-            $this->setTracks($this->_trackCollectionFactory->create()->setShipmentFilter($this->getId()));
-
-            if ($this->getId()) {
-                foreach ($this->getTracks() as $track) {
-                    $track->setShipment($this);
-                }
-            }
+        if ($this->tracksCollection === null) {
+            $this->tracksCollection = $this->_trackCollectionFactory->create()->setShipmentFilter($this->getId());
         }
-        return $this->getTracks();
+
+        return $this->tracksCollection;
     }
 
     /**

app/code/Magento/Sales/Model/ResourceModel/Order/Shipment/Relation.php

@@ -62,8 +62,8 @@ public function processRelation(\Magento\Framework\Model\AbstractModel $object)
                 $this->shipmentItemResource->save($item);
             }
         }
-        if (null !== $object->getTracks()) {
-            foreach ($object->getTracks() as $track) {
+        if (null !== $object->getTracksCollection()) {
+            foreach ($object->getTracksCollection() as $track) {
                 $track->setParentId($object->getId());
                 $this->shipmentTrackResource->save($track);
             }

app/code/Magento/Sales/Test/Unit/Model/ResourceModel/Order/Shipment/RelationTest.php

@@ -86,7 +86,8 @@ protected function setUp()
                     'getId',
                     'getItems',
                     'getTracks',
-                    'getComments'
+                    'getComments',
+                    'getTracksCollection',
                 ]
             )
             ->getMock();
@@ -123,7 +124,7 @@ public function testProcessRelations()
             ->method('getComments')
             ->willReturn([$this->commentMock]);
         $this->shipmentMock->expects($this->exactly(2))
-            ->method('getTracks')
+            ->method('getTracksCollection')
             ->willReturn([$this->trackMock]);
         $this->itemMock->expects($this->once())
             ->method('setParentId')

dev/tests/integration/testsuite/Magento/Sales/Model/Order/ShipmentTest.php

@@ -3,6 +3,7 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+
 namespace Magento\Sales\Model\Order;
 
 /**
@@ -47,4 +48,35 @@ public function testPackages()
         $shipment->load($shipment->getId());
         $this->assertEquals($packages, $shipment->getPackages());
     }
+
+    /**
+     * Check that getTracksCollection() always return collection instance.
+     *
+     * @magentoDataFixture Magento/Sales/_files/order.php
+     */
+    public function testAddTrack()
+    {
+        $objectManager = \Magento\TestFramework\Helper\Bootstrap::getObjectManager();
+
+        $order = $objectManager->create(\Magento\Sales\Model\Order::class);
+        $order->loadByIncrementId('100000001');
+
+        /** @var \Magento\Sales\Model\Order\Shipment $shipment */
+        $shipment = $objectManager->create(\Magento\Sales\Model\Order\Shipment::class);
+        $shipment->setOrder($order);
+
+        $shipment->addItem($objectManager->create(\Magento\Sales\Model\Order\Shipment\Item::class));
+        $shipment->save();
+
+        /** @var $track \Magento\Sales\Model\Order\Shipment\Track */
+        $track = $objectManager->get(\Magento\Sales\Model\Order\Shipment\Track::class);
+        $track->setNumber('Test Number')->setTitle('Test Title')->setCarrierCode('Test CODE');
+
+        $this->assertEmpty($shipment->getTracks());
+        $shipment->addTrack($track)->save();
+
+        //to empty cache
+        $shipment->setTracks(null);
+        $this->assertNotEmpty($shipment->getTracks());
+    }
 }