Issue #3231996: Ensure file system is writeable

src/Validator/WritableFileSystemValidator.php

@@ -6,6 +6,8 @@ use Drupal\automatic_updates\AutomaticUpdatesEvents;
 use Drupal\automatic_updates\Event\UpdateEvent;
 use Drupal\automatic_updates\PathLocator;
 use Drupal\automatic_updates\Validation\ValidationResult;
+use Drupal\Core\File\Exception\FileException;
+use Drupal\Core\File\FileSystemInterface;
 use Drupal\Core\StringTranslation\StringTranslationTrait;
 use Drupal\Core\StringTranslation\TranslatableMarkup;
 use Symfony\Component\EventDispatcher\EventSubscriberInterface;
@@ -24,14 +26,24 @@ class WritableFileSystemValidator implements EventSubscriberInterface {
    */
   protected $pathLocator;
 
+  /**
+   * The file system service.
+   *
+   * @var \Drupal\Core\File\FileSystemInterface
+   */
+  protected $fileSystem;
+
   /**
    * Constructs a WriteableFileSystemValidator object.
    *
    * @param \Drupal\automatic_updates\PathLocator $path_locator
    *   The path locator service.
+   * @param \Drupal\Core\File\FileSystemInterface $file_system
+   *   The file system service.
    */
-  public function __construct(PathLocator $path_locator) {
+  public function __construct(PathLocator $path_locator, FileSystemInterface $file_system) {
     $this->pathLocator = $path_locator;
+    $this->fileSystem = $file_system;
   }
 
   /**
@@ -41,35 +53,49 @@ class WritableFileSystemValidator implements EventSubscriberInterface {
    *   The event object.
    */
   public function checkPermissions(UpdateEvent $event): void {
-    $dir = $this->pathLocator->getProjectRoot();
-    $message = $this->t('The project directory "@dir" is not writable.', [
+    $dir = $this->pathLocator->getWebRoot();
+    $message = $this->t('The Drupal directory "@dir" is not writable.', [
       '@dir' => $dir,
     ]);
-    $this->checkPath($dir, $event, $message);
+    $this->checkPath($dir, 'core/core.api.php', $event, $message);
 
     $dir = $this->pathLocator->getVendorDirectory();
     $message = $this->t('The vendor directory "@dir" is not writable.', [
       '@dir' => $dir,
     ]);
-    $this->checkPath($dir, $event, $message);
+    $this->checkPath($dir, 'composer/LICENSE', $event, $message);
   }
 
   /**
-   * Checks that a path is writable, and flags an error if it's not.
+   * Tests that a path is writable by writing and deleting a temporary file.
    *
-   * @param string $path
-   *   The path to check.
+   * @param string $path_to_check
+   *   The path (directory) to test.
+   * @param string $file_to_copy
+   *   The path of the file, relative to $path_to_check, which should be copied
+   *   temporarily.
    * @param \Drupal\automatic_updates\Event\UpdateEvent $event
    *   The event object.
    * @param \Drupal\Core\StringTranslation\TranslatableMarkup $error_message
-   *   The translated error message if the path is not writeable.
+   *   The error message to flag if the path is not writable.
    */
-  protected function checkPath(string $path, UpdateEvent $event, TranslatableMarkup $error_message): void {
-    if (is_writable($path)) {
-      return;
+  protected function checkPath(string $path_to_check, string $file_to_copy, UpdateEvent $event, TranslatableMarkup $error_message): void {
+    $source = $path_to_check . DIRECTORY_SEPARATOR . $file_to_copy;
+    $destination = uniqid($source);
+
+    try {
+      // If we can copy the file and then delete the copy, the file system is
+      // writable.
+      $this->fileSystem->copy($source, $destination, FileSystemInterface::EXISTS_REPLACE);
+      $this->fileSystem->delete($destination);
+    }
+    catch (FileException $e) {
+      $result = ValidationResult::createError([
+        $error_message,
+        $e->getMessage(),
+      ]);
+      $event->addValidationResult($result);
     }
-    $result = ValidationResult::createError([$error_message]);
-    $event->addValidationResult($result);
   }
 
   /**