Draft: Issue #2707849 by Wim Leers, COBadger: Allow components to define asset libraries

Closes #2707849

src/Component/Discovery/DirectoryWithYamlDiscovery.php

+<?php
+
+namespace Drupal\components\Component\Discovery;
+
+use Drupal\Component\Discovery\YamlDirectoryDiscovery;
+
+/**
+ * Discovers directories each with one YAML file in a set of directories.
+ *
+ * @todo Move into Drupal\Component\Discovery namespace in core.
+ */
+class DirectoryWithYamlDiscovery extends YamlDirectoryDiscovery  {
+
+  /**
+   * The subdirectory to scan.
+   *
+   * @var string
+   */
+  protected $subdirectory;
+
+  /**
+   * Constructs a DirectoryWithYamlDiscovery object.
+   *
+   * @param array $directories
+   *   An array of directories to scan, keyed by the provider. The value can
+   *   either be a string or an array of strings. The string values should be
+   *   the path of a directory to scan.
+   * @param string $subdirectory
+   *   The subdirectory to scan in each of the passed $directories.
+   */
+  public function __construct(array $directories, $subdirectory) {
+    parent::__construct($directories, 'directory_with_yaml:' . $subdirectory);
+    $this->subdirectory = $subdirectory;
+  }
+
+  /**
+   * {@inheritdoc}
+   */
+  protected function getIdentifier($file, array $data) {
+    return basename($data[static::FILE_KEY], '.yml');
+  }
+
+  /**
+   * Returns an array of providers keyed by file path.
+   *
+   * @return array
+   *   An array of providers keyed by file path.
+   */
+  protected function findFiles() {
+    $file_list = [];
+    foreach ($this->directories as $provider => $directories) {
+      $directories = (array) $directories;
+      foreach ($directories as $directory) {
+        // Check if there is a subdirectory with the specified name.
+        if (is_dir($directory) && is_dir($directory . '/' . $this->subdirectory)) {
+          // Now iterate over all subdirectories below the specifically named
+          // subdirectory, and check if a .yml file exists with the same name.
+          // For example:
+          // - Assuming $this->subdirectory === 'fancy'
+          // - Then this checks for 'fancy/foo/foo.yml', 'fancy/bar/bar.yml'
+          $iterator = new \FilesystemIterator($directory . '/' . $this->subdirectory);
+          /** @var \SplFileInfo $file_info */
+          foreach ($iterator as $file_info) {
+            if ($file_info->isDir()) {
+              $this->findFile($file_info, $provider, $file_list);
+
+              // Allow for two levels.
+              $nested_iterator = new \FilesystemIterator($directory . '/' . $this->subdirectory . '/' . $file_info->getBasename());
+              foreach ($nested_iterator as $nested_file_info) {
+                if ($nested_file_info->isDir()) {
+                  $this->findFile($nested_file_info, $provider, $file_list);
+                }
+              }
+            }
+          }
+        }
+      }
+    }
+    return $file_list;
+  }
+
+  protected function findFile($file_info, $provider, array &$file_list) {
+    $yml_file_in_directory = $file_info->getPath() . '/' . $file_info->getBasename() . '/' . $file_info->getBasename() . '.yml';
+    if (is_file($yml_file_in_directory)) {
+      $file_list[$yml_file_in_directory] = $provider;
+    }
+  }
+
+}
\ No newline at end of file