Resolve #3408488 "Make unknownpathexcluder accept"

Closes #3408488

package_manager/src/PathExcluder/UnknownPathExcluder.php

@@ -74,18 +74,18 @@ final class UnknownPathExcluder implements EventSubscriberInterface {
     $known_paths[] = [$web_root];
 
     $project_root = $this->pathLocator->getProjectRoot();
-    // To determine the scaffold files to exclude, the installed packages must
-    // be known, and that requires Composer commands to be able to run. This
-    // intentionally does not catch exceptions: failed Composer validation in
-    // the project root implies that this excluder cannot function correctly.
+    // To determine the files to exclude, the installed packages must be known,
+    // and that requires Composer commands to be able to run. This intentionally
+    // does not catch exceptions: failed Composer validation in the project root
+    // implies that this excluder cannot function correctly.
     // Note: the call to ComposerInspector::getInstalledPackagesList() would
     // also have triggered this, but explicitness is preferred here.
     // @see \Drupal\package_manager\StatusCheckTrait::runStatusCheck()
     $this->composerInspector->validate($project_root);
 
-    // The vendor directory is always a known path.
+    // The vendor directory is always a known path, as are the `composer.json`
+    // and `composer.lock` files.
     $known_paths[] = $this->composerInspector->getConfig('vendor-dir', $project_root);
-    // So are the `composer.json` and `composer.lock` files.
     $known_paths[] = 'composer.json';
     $known_paths[] = 'composer.lock';
 
@@ -111,7 +111,10 @@ final class UnknownPathExcluder implements EventSubscriberInterface {
     // glob() flags aren't supported on all systems. We also can't use
     // \Drupal\Core\File\FileSystemInterface::scanDirectory(), because it
     // unconditionally ignores hidden files and directories.
-    $handle = opendir($project_root) ?: throw new \RuntimeException("Could not scan for files in the project root.");
+    $handle = opendir($project_root);
+    if (empty($handle)) {
+      throw new \RuntimeException("Could not scan for files in the project root.");
+    }
     while ($entry = readdir($handle)) {
       if ($entry === '.' || $entry === '..' || in_array($entry, $known_paths, TRUE)) {
         continue;