Fix translations of category design theme not being applied

Author: cezary-zeglen

app/code/Magento/Catalog/Model/Design.php

@@ -5,6 +5,8 @@
  */
 namespace Magento\Catalog\Model;
 
+use \Magento\Framework\TranslateInterface;
+
 /**
  * Catalog Custom Category design Model
  *
@@ -31,6 +33,11 @@ class Design extends \Magento\Framework\Model\AbstractModel
      */
     protected $_localeDate;
 
+    /**
+     * @var TranslateInterface
+     */
+    private $translator;
+
     /**
      * @param \Magento\Framework\Model\Context $context
      * @param \Magento\Framework\Registry $registry
@@ -47,10 +54,13 @@ public function __construct(
         \Magento\Framework\View\DesignInterface $design,
         \Magento\Framework\Model\ResourceModel\AbstractResource $resource = null,
         \Magento\Framework\Data\Collection\AbstractDb $resourceCollection = null,
-        array $data = []
+        array $data = [],
+        TranslateInterface $translator = null
     ) {
         $this->_localeDate = $localeDate;
         $this->_design = $design;
+        $this->translator = $translator ?:
+            \Magento\Framework\App\ObjectManager::getInstance()->get(TranslateInterface::class);
         parent::__construct($context, $registry, $resource, $resourceCollection, $data);
     }
 
@@ -63,6 +73,7 @@ public function __construct(
     public function applyCustomDesign($design)
     {
         $this->_design->setDesignTheme($design);
+        $this->translator->loadData(null, true);
         return $this;
     }
 

dev/tests/integration/testsuite/Magento/Catalog/Model/DesignTest.php

@@ -32,8 +32,12 @@ public function testApplyCustomDesign($theme)
         $design = \Magento\TestFramework\Helper\Bootstrap::getObjectManager()->get(
             \Magento\Framework\View\DesignInterface::class
         );
+        $translate = \Magento\TestFramework\Helper\Bootstrap::getObjectManager()->get(
+            \Magento\Framework\TranslateInterface::class
+        );
         $this->assertEquals('package', $design->getDesignTheme()->getPackageCode());
         $this->assertEquals('theme', $design->getDesignTheme()->getThemeCode());
+        $this->assertEquals('themepackage/theme', $translate->getTheme());
     }
 
     /**