Fix error when generating urn catalog for empty misc.xml

app/code/Magento/Developer/Model/XmlCatalog/Format/PhpStorm.php

@@ -6,11 +6,12 @@
 
 namespace Magento\Developer\Model\XmlCatalog\Format;
 
+use Magento\Framework\App\ObjectManager;
+use Magento\Framework\DomDocument\DomDocumentFactory;
 use Magento\Framework\Exception\FileSystemException;
 use Magento\Framework\Filesystem\Directory\ReadFactory;
 use Magento\Framework\Filesystem\Directory\ReadInterface;
-use Magento\Framework\Filesystem\Directory\WriteFactory;
-use Magento\Framework\Filesystem\Directory\WriteInterface;
+use Magento\Framework\Filesystem\File\WriteFactory;
 
 /**
  * Class PhpStorm generates URN catalog for PhpStorm 9
@@ -23,20 +24,28 @@ class PhpStorm implements FormatInterface
     private $currentDirRead;
 
     /**
-     * @var \Magento\Framework\Filesystem\File\WriteFactory
+     * @var WriteFactory
      */
     private $fileWriteFactory;
 
+    /**
+     * @var DomDocumentFactory
+     */
+    private $domDocumentFactory;
+
     /**
      * @param ReadFactory $readFactory
-     * @param \Magento\Framework\Filesystem\File\WriteFactory $fileWriteFactory
+     * @param WriteFactory $fileWriteFactory
+     * @param DomDocumentFactory $domDocumentFactory
      */
     public function __construct(
         ReadFactory $readFactory,
-        \Magento\Framework\Filesystem\File\WriteFactory $fileWriteFactory
+        WriteFactory $fileWriteFactory,
+        DomDocumentFactory $domDocumentFactory = null
     ) {
         $this->currentDirRead = $readFactory->create(getcwd());
         $this->fileWriteFactory = $fileWriteFactory;
+        $this->domDocumentFactory = $domDocumentFactory ?: ObjectManager::getInstance()->get(DomDocumentFactory::class);
     }
 
     /**
@@ -57,26 +66,21 @@ public function generateCatalog(array $dictionary, $configFilePath)
                 \Magento\Framework\Filesystem\DriverPool::FILE,
                 'r'
             );
-            $dom = new \DOMDocument();
-            $dom->loadXML($file->readAll());
+            $dom = $this->domDocumentFactory->create();
+            $fileContent = $file->readAll();
+            if (!empty($fileContent)) {
+                $dom->loadXML($fileContent);
+            } else {
+                $this->initEmptyFile($dom);
+            }
             $xpath = new \DOMXPath($dom);
             $nodeList = $xpath->query('/project');
             $projectNode = $nodeList->item(0);
             $file->close();
         } catch (FileSystemException $f) {
             //create file if does not exists
-            $dom = new \DOMDocument();
-            $projectNode = $dom->createElement('project');
-
-            //PhpStorm 9 version for component is "4"
-            $projectNode->setAttribute('version', '4');
-            $dom->appendChild($projectNode);
-            $rootComponentNode = $dom->createElement('component');
-
-            //PhpStorm 9 version for ProjectRootManager is "2"
-            $rootComponentNode->setAttribute('version', '2');
-            $rootComponentNode->setAttribute('name', 'ProjectRootManager');
-            $projectNode->appendChild($rootComponentNode);
+            $dom = $this->domDocumentFactory->create();
+            $projectNode = $this->initEmptyFile($dom);
         }
 
         $xpath = new \DOMXPath($dom);
@@ -103,4 +107,26 @@ public function generateCatalog(array $dictionary, $configFilePath)
         $file->write($dom->saveXML());
         $file->close();
     }
+
+    /**
+     * Setup basic empty dom elements
+     *
+     * @param \DOMDocument $dom
+     * @return \DOMElement
+     */
+    private function initEmptyFile(\DOMDocument $dom)
+    {
+        $projectNode = $dom->createElement('project');
+
+        //PhpStorm 9 version for component is "4"
+        $projectNode->setAttribute('version', '4');
+        $dom->appendChild($projectNode);
+        $rootComponentNode = $dom->createElement('component');
+
+        //PhpStorm 9 version for ProjectRootManager is "2"
+        $rootComponentNode->setAttribute('version', '2');
+        $rootComponentNode->setAttribute('name', 'ProjectRootManager');
+        $projectNode->appendChild($rootComponentNode);
+        return $projectNode;
+    }
 }

lib/internal/Magento/Framework/DomDocument/DomDocumentFactory.php

@@ -3,6 +3,7 @@
  * Copyright © Magento, Inc. All rights reserved.
  * See COPYING.txt for license details.
  */
+
 namespace Magento\Framework\DomDocument;
 
 /**

lib/internal/Magento/Framework/Test/Unit/DomDocument/DomDocumentFactoryTest.php

@@ -0,0 +1,21 @@
+<?php
+/**
+ * Copyright © Magento, Inc. All rights reserved.
+ * See COPYING.txt for license details.
+ */
+
+namespace Magento\Framework\Test\Unit\DomDocument;
+
+use Magento\Framework\DomDocument\DomDocumentFactory;
+
+class DomDocumentFactoryTest extends \PHPUnit\Framework\TestCase
+{
+    public function testCreateReturnsDomDocument()
+    {
+        $domDocumentFactory = new DomDocumentFactory();
+        $this->assertInstanceOf(
+            \DOMDocument::class,
+            $domDocumentFactory->create()
+        );
+    }
+}