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
  *
@@ -31,26 +33,44 @@ class Design extends \Magento\Framework\Model\AbstractModel
      */
     protected $_localeDate;
 
+    /**
+     * @var \Magento\Framework\View\Design\ThemeInterfaceFactory
+     */
+    protected $_themeFactory;
+
+    /**
+     * @var TranslateInterface
+     */
+    private $translator;
+
     /**
      * @param \Magento\Framework\Model\Context $context
      * @param \Magento\Framework\Registry $registry
      * @param \Magento\Framework\Stdlib\DateTime\TimezoneInterface $localeDate
      * @param \Magento\Framework\View\DesignInterface $design
+     * @param \Magento\Framework\View\Design\ThemeInterfaceFactory $themeFactory
      * @param \Magento\Framework\Model\ResourceModel\AbstractResource $resource
      * @param \Magento\Framework\Data\Collection\AbstractDb $resourceCollection
+     * @param TranslateInterface $translator
      * @param array $data
      */
     public function __construct(
         \Magento\Framework\Model\Context $context,
         \Magento\Framework\Registry $registry,
         \Magento\Framework\Stdlib\DateTime\TimezoneInterface $localeDate,
         \Magento\Framework\View\DesignInterface $design,
+        \Magento\Framework\View\Design\ThemeInterfaceFactory $themeFactory,
         \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->_themeFactory = $themeFactory;
+        $this->translator = $translator ?:
+            \Magento\Framework\App\ObjectManager::getInstance()->get(TranslateInterface::class);
+
         parent::__construct($context, $registry, $resource, $resourceCollection, $data);
     }
 
@@ -63,6 +83,20 @@ public function __construct(
     public function applyCustomDesign($design)
     {
         $this->_design->setDesignTheme($design);
+        $this->applyCustomDesingTranslations($design);
+        return $this;
+    }
+
+    /**
+     * Apply custom design translations
+     *
+     * @param string $design
+     * @return $this
+     */
+    private function applyCustomDesingTranslations($design)
+    {
+        $theme = $this->_themeFactory->create()->load($design)->getThemePath();
+        $this->translator->setTheme($theme)->loadData(null, true);
         return $this;
     }
 

lib/internal/Magento/Framework/Test/Unit/TranslateTest.php

@@ -313,6 +313,12 @@ public function testGetTheme()
         $this->assertEquals('themeTheme Title', $this->translate->getTheme());
     }
 
+    public function testSetTheme()
+    {
+        $this->translate->setTheme('Magento/blank');
+        $this->assertEquals('themeMagento/blank', $this->translate->getTheme());
+    }
+
     public function testLoadDataNoTheme()
     {
         $forceReload = true;

lib/internal/Magento/Framework/Translate.php

@@ -460,6 +460,18 @@ public function getTheme()
         return self::CONFIG_THEME_KEY . $theme['theme_title'];
     }
 
+    /**
+     * Set theme
+     *
+     * @param string $theme
+     * @return \Magento\Framework\TranslateInterface
+     */
+    public function setTheme($theme)
+    {
+        $this->_config[self::CONFIG_THEME_KEY] = $theme;
+        return $this;
+    }
+
     /**
      * Retrieve cache identifier
      *

lib/internal/Magento/Framework/TranslateInterface.php

@@ -52,4 +52,12 @@ public function setLocale($locale);
      * @return string
      */
     public function getTheme();
+
+    /**
+     * Set theme
+     *
+     * @param string $theme
+     * @return \Magento\Framework\TranslateInterface
+     */
+    public function setTheme($theme);
 }