Issue #3363938: Package Manager should ignore default.settings.php and default.services.yml

package_manager/src/PathExcluder/SiteConfigurationExcluder.php

@@ -69,11 +69,26 @@ class SiteConfigurationExcluder implements EventSubscriberInterface {
   /**
    * Makes the staged `sites/default` directory world-writable.
    *
+   * This is done to allow the core scaffold plugin to make changes in
+   * `sites/default`, if necessary, without breaking if `sites/default` is not
+   * writable (this can happen because rsync perserves directory permissions,
+   * and Drupal will try to harden the site directory's permissions as much as
+   * possible). We specifically exclude the `default.settings.php` and
+   * `default.services.yml` files from Package Manager operations, so we want to
+   * allow the scaffold plugin to make whatever changes it wants to those files
+   * in the stage directory.
+   *
    * @param \Drupal\package_manager\Event\PostCreateEvent $event
    *   The event being handled.
+   *
+   * @see ::excludeSiteConfiguration()
    */
   public function makeDefaultSiteDirectoryWritable(PostCreateEvent $event): void {
     $dir = $this->getDefaultSiteDirectoryPath($event->stage->getStageDirectory());
+    // If the directory doesn't even exist, there's nothing to do here.
+    if (!is_dir($dir)) {
+      return;
+    }
     if (!$this->fileSystem->chmod($dir, 0777)) {
       throw new FileException("Could not change permissions on '$dir'.");
     }
@@ -86,25 +101,48 @@ class SiteConfigurationExcluder implements EventSubscriberInterface {
    *   The event being handled.
    *
    * @throws \Drupal\Core\File\Exception\FileException
-   *   If the permissions of the live `sites/default` cannot be determined, or
-   *   changed on the staged `sites/default`.
+   *   If the permissions of either the live or staged `sites/default` cannot
+   *   be determined, or cannot be changed on the staged `sites/default`.
    */
   public function syncDefaultSiteDirectoryPermissions(PreApplyEvent $event): void {
-    $live_dir = $this->getDefaultSiteDirectoryPath($this->pathLocator->getProjectRoot());
     $staged_dir = $this->getDefaultSiteDirectoryPath($event->stage->getStageDirectory());
-
-    $original_permissions = fileperms($live_dir);
-    if ($original_permissions === FALSE) {
-      throw new FileException("Could not determine permissions for '$live_dir'.");
+    // If the directory doesn't even exist, there's nothing to do here.
+    if (!is_dir($staged_dir)) {
+      return;
     }
+    $live_dir = $this->getDefaultSiteDirectoryPath($this->pathLocator->getProjectRoot());
 
-    // @see \Symfony\Component\Filesystem\Filesystem::copy() for another use
-    // of the 0111 bitmask.
-    if (!$this->fileSystem->chmod($staged_dir, $original_permissions & 0111)) {
+    // This is borrowed from \Symfony\Component\Filesystem\Filesystem::copy(),
+    // to ensure the correct permissions are preserved (chmod() requires
+    // permissions to be sent as an octal number, but fileperms() returns a
+    // decimal number, because PHP is just great).
+    $permissions = $this->getPermissions($staged_dir) | ($this->getPermissions($live_dir) & 0111);
+
+    if (!$this->fileSystem->chmod($staged_dir, $permissions)) {
       throw new FileException("Could not change permissions on '$staged_dir'.");
     }
   }
 
+  /**
+   * Gets the current file permissions of a path.
+   *
+   * @param string $path
+   *   The path to examine.
+   *
+   * @return int
+   *   The current permissions of the path.
+   *
+   * @throws \Drupal\Core\File\Exception\FileException
+   *   Thrown if the file permissions cannot be determined.
+   */
+  private function getPermissions(string $path): int {
+    $permissions = fileperms($path);
+    if ($permissions === FALSE) {
+      throw new FileException("Could not determine permissions for '$path'.");
+    }
+    return $permissions;
+  }
+
   /**
    * Returns the full path to `sites/default`, relative to a root directory.
    *
@@ -115,12 +153,12 @@ class SiteConfigurationExcluder implements EventSubscriberInterface {
    *   The full path to `sites/default` within the given root directory.
    */
   private function getDefaultSiteDirectoryPath(string $root_dir): string {
-    $dir = [$root_dir, 'sites', 'default'];
+    $dir = [$root_dir];
     $web_root = $this->pathLocator->getWebRoot();
     if ($web_root) {
-      array_splice($dir, 1, 0, $web_root);
+      $dir[] = $web_root;
     }
-    return implode(DIRECTORY_SEPARATOR, $dir);
+    return implode(DIRECTORY_SEPARATOR, [...$dir, 'sites', 'default']);
   }
 
   /**