Issue #2532228: Use RecursiveCallbackFilterIterator instead of the $acceptTests parameter forwarding

core/lib/Drupal/Core/Extension/Discovery/RecursiveExtensionFilterCallback.php

+<?php
+
+namespace Drupal\Core\Extension\Discovery;
+
+/**
+ * Filters a RecursiveDirectoryIterator to discover extensions.
+ *
+ * To ensure the best possible performance for extension discovery, this
+ * filter implementation hard-codes a range of assumptions about directories
+ * in which Drupal extensions may appear and in which not. Every unnecessary
+ * subdirectory tree recursion is avoided.
+ *
+ * The list of globally ignored directory names is defined in the
+ * RecursiveExtensionFilterCallback::$skippedFolders property.
+ *
+ * In addition, all 'config' directories are skipped, unless the directory path
+ * ends with 'modules/config', to still find the config module provided by
+ * Drupal core and still allow that module to be overridden with a custom config
+ * module.
+ *
+ * Lastly, ExtensionDiscovery instructs this filter to additionally skip all
+ * 'tests' directories at regular runtime, since just with Drupal core only, the
+ * discovery process yields 4x more extensions when tests are not ignored.
+ *
+ * @see ExtensionDiscovery::scan()
+ * @see ExtensionDiscovery::scanDirectory()
+ *
+ * @internal
+ */
+class RecursiveExtensionFilterCallback {
+
+  /**
+   * List of base extension type directory names to scan.
+   *
+   * Only these directory names are considered when starting a filesystem
+   * recursion in a search path.
+   *
+   * @var string[]
+   */
+  protected array $allowedExtensionTypes = [
+    'profiles',
+    'modules',
+    'themes',
+  ];
+
+  /**
+   * List of directory names to skip when recursing.
+   *
+   * These directories are globally ignored in the recursive filesystem scan;
+   * i.e., extensions (of all types) are not able to use any of these names,
+   * because their directory names will be skipped.
+   *
+   * @var string[]
+   */
+  protected array $skippedFolders = [
+    // Object-oriented code subdirectories.
+    'src',
+    'lib',
+    'vendor',
+    // Front-end.
+    'assets',
+    'css',
+    'files',
+    'images',
+    'js',
+    'misc',
+    'templates',
+    // Legacy subdirectories.
+    'includes',
+    // Test subdirectories.
+    'fixtures',
+    // @todo ./tests/Drupal should be ./tests/src/Drupal
+    'Drupal',
+  ];
+
+  /**
+   * Construct a RecursiveExtensionFilterCallback.
+   *
+   * @param array $skipped_folders
+   *   (optional) Add to the list of directories that should be filtered out
+   *   during the iteration.
+   * @param bool $accept_tests
+   *   (optional) Pass FALSE to skip all test directories in the discovery. If
+   *   TRUE, extensions in test directories will be discovered and only the
+   *   global directory skip list in
+   *   RecursiveExtensionFilterCallback::$skippedFolders and $skipped_folders
+   *   are applied.
+   */
+  public function __construct(array $skipped_folders = [], bool $accept_tests = FALSE) {
+    $this->skippedFolders = array_merge($this->skippedFolders, $skipped_folders);
+    if (!$accept_tests) {
+      $this->skippedFolders[] = 'tests';
+    }
+  }
+
+  /**
+   * Checks whether a given filesystem directory is acceptable.
+   *
+   * @param \RecursiveDirectoryIterator $filesystem_directory
+   *   The filesystem directory to check.
+   *
+   * @return bool
+   *   TRUE if the given filesystem directory is acceptable, otherwise FALSE.
+   */
+  public function accept(\RecursiveDirectoryIterator $filesystem_directory): bool {
+    $name = $filesystem_directory->getFilename();
+    // FilesystemIterator::SKIP_DOTS only skips '.' and '..', but not hidden
+    // directories (like '.git').
+    if ($name[0] === '.') {
+      return FALSE;
+    }
+    if ($filesystem_directory->isDir()) {
+      // If this is a subdirectory of a base search path, only recurse into the
+      // fixed list of expected extension type directory names. Required for
+      // scanning the top-level/root directory; without this condition, we would
+      // recurse into the whole filesystem tree that possibly contains other
+      // files aside from Drupal.
+      if ($filesystem_directory->getSubPath() === '') {
+        return in_array($name, $this->allowedExtensionTypes, TRUE);
+      }
+      // 'config' directories are special-cased here, because every extension
+      // contains one. However, those default configuration directories cannot
+      // contain extensions. The directory name cannot be globally skipped,
+      // because core happens to have a directory of an actual module that is
+      // named 'config'. By explicitly testing for that case, we can skip all
+      // other config directories, and at the same time, still allow the core
+      // config module to be overridden/replaced in a profile/site directory
+      // (whereas it must be located directly in a modules directory).
+      if ($name === 'config') {
+        return str_ends_with($filesystem_directory->getPathname(), 'modules/config');
+      }
+      // Accept the directory unless the folder is skipped.
+      return !in_array($name, $this->skippedFolders, TRUE);
+    }
+    // Only accept extension info files.
+    return str_ends_with($name, '.info.yml');
+  }
+
+}