Issue #3486188: [Regression] Clean up temporary files created by XML data parser plugin

Closes #3486188

src/Plugin/migrate_plus/data_parser/Xml.php

@@ -87,6 +87,13 @@ class Xml extends DataParserPluginBase implements ContainerFactoryPluginInterfac
    */
   protected bool $prefixedName = FALSE;
 
+  /**
+   * The temporary file name of the XML, or FALSE.
+   *
+   * @var string|false
+   */
+  protected $temporaryFileName = FALSE;
+
   /**
    * Constructs a new XML data parser.
    *
@@ -137,6 +144,16 @@ class Xml extends DataParserPluginBase implements ContainerFactoryPluginInterfac
     }
   }
 
+  /**
+   * Destructs an XML data parser.
+   */
+  public function __destruct() {
+    if ($this->temporaryFileName !== FALSE) {
+      $this->fileSystem->unlink($this->temporaryFileName);
+      $this->temporaryFileName = FALSE;
+    }
+  }
+
   /**
    * {@inheritdoc}
    */
@@ -200,10 +217,12 @@ class Xml extends DataParserPluginBase implements ContainerFactoryPluginInterfac
     $this->reader->close();
 
     // Fetch the data and save it to a temporary file.
-    $xml_data = $this->getDataFetcherPlugin()->getResponseContent($url);
-    $url = $this->fileSystem->tempnam('temporary://', 'file');
-    if (file_put_contents($url, $xml_data) === FALSE) {
-      throw new MigrateException('Unable to save temporary XML');
+    if (!$this->temporaryFileName) {
+      $xml_data = $this->getDataFetcherPlugin()->getResponseContent($url);
+      $this->temporaryFileName = $this->fileSystem->tempnam('temporary://', 'file');
+      if (!$this->temporaryFileName || file_put_contents($this->temporaryFileName, $xml_data) === FALSE) {
+        throw new MigrateException('Unable to save temporary XML');
+      }
     }
 
     // Clear XML error buffer. Other Drupal code that executed during the
@@ -212,7 +231,7 @@ class Xml extends DataParserPluginBase implements ContainerFactoryPluginInterfac
     // that occur from attempting to load the XML string into an object here.
     libxml_clear_errors();
 
-    return $this->reader->open($url, NULL, \LIBXML_NOWARNING);
+    return $this->reader->open($this->temporaryFileName, NULL, \LIBXML_NOWARNING);
   }
 
   /**