Issue #3368855: Admin theme not active when using batch export method and a...

src/Plugin/views/display/DataExport.php

@@ -931,13 +931,19 @@ class DataExport extends RestExport {
    */
   protected function getRoute($view_id, $display_id) {
     $route = parent::getRoute($view_id, $display_id);
-    $view = Views::getView($view_id);
-    $view->setDisplay($display_id);
 
     // If this display is going to perform a redirect to the batch url
     // make sure thr redirect response is never cached.
-    if ($view->display_handler->getOption('export_method') == 'batch') {
+    if ($this->getOption('export_method') == 'batch') {
       $route->setOption('no_cache', TRUE);
+
+      // Additionally if the path is an admin path we need to set the
+      // _admin_route option to TRUE so the batch process is executed in the
+      // same theme as we'd normally expect for the path even though this is
+      // not an HTML route.
+      if (str_starts_with($this->getOption('path') ?? '', 'admin/')) {
+        $route->setOption('_admin_route', TRUE);
+      }
     }
     return $route;
   }