drupal/core/modules/aggregator/aggregator.module

<?php

/**
 * @file
 * Used to aggregate syndicated content (RSS, RDF, and Atom).
 */

use Drupal\Core\Url;
use Drupal\aggregator\Entity\Feed;
use Drupal\Core\Routing\RouteMatchInterface;

/**
 * Implements hook_help().
 */
function aggregator_help($route_name, RouteMatchInterface $route_match) {
  switch ($route_name) {
    case 'help.page.aggregator':
      $path_validator = \Drupal::pathValidator();
      $output = '';
      $output .= '<h3>' . t('About') . '</h3>';
      $output .= '<p>' . t('The Aggregator module is an on-site syndicator and news reader that gathers and displays fresh content from RSS-, RDF-, and Atom-based feeds made available across the web. Thousands of sites (particularly news sites and blogs) publish their latest headlines in feeds, using a number of standardized XML-based formats. For more information, see the <a href=":aggregator-module">online documentation for the Aggregator module</a>.', [':aggregator-module' => 'https://www.drupal.org/documentation/modules/aggregator']) . '</p>';
      $output .= '<h3>' . t('Uses') . '</h3>';
      $output .= '<dl>';
      // Check if the aggregator sources View is enabled.
      if ($url = $path_validator->getUrlIfValid('aggregator/sources')) {
        $output .= '<dt>' . t('Viewing feeds') . '</dt>';
        $output .= '<dd>' . t('Users view feed content in the <a href=":aggregator">main aggregator display</a>, or by <a href=":aggregator-sources">their source</a> (usually via an RSS feed reader). The most recent content in a feed can be displayed as a block through the <a href=":admin-block">Blocks administration page</a>.', [':aggregator' => Url::fromRoute('aggregator.page_last')->toString(), ':aggregator-sources' => $url->toString(), ':admin-block' => (\Drupal::moduleHandler()->moduleExists('block')) ? Url::fromRoute('block.admin_display')->toString() : '#']) . '</dd>';
      }
      $output .= '<dt>' . t('Adding, editing, and deleting feeds') . '</dt>';
      $output .= '<dd>' . t('Administrators can add, edit, and delete feeds, and choose how often to check each feed for newly updated items on the <a href=":feededit">Aggregator administration page</a>.', [':feededit' => Url::fromRoute('aggregator.admin_overview')->toString()]) . '</dd>';
      $output .= '<dt>' . t('Configuring the display of feed items') . '</dt>';
      $output .= '<dd>' . t('Administrators can choose how many items are displayed in the listing pages, which HTML tags are allowed in the content of feed items, and whether they should be trimmed to a maximum number of characters on the <a href=":settings">Aggregator settings page</a>.', [':settings' => Url::fromRoute('aggregator.admin_settings')->toString()]) . '</dd>';
      $output .= '<dt>' . t('Discarding old feed items') . '</dt>';
      $output .= '<dd>' . t('Administrators can choose whether to discard feed items that are older than a specified period of time on the <a href=":settings">Aggregator settings page</a>. This requires a correctly configured cron maintenance task (see below).', [':settings' => Url::fromRoute('aggregator.admin_settings')->toString()]) . '<dd>';

      $output .= '<dt>' . t('<abbr title="Outline Processor Markup Language">OPML</abbr> integration') . '</dt>';
      // Check if the aggregator opml View is enabled.
      if ($url = $path_validator->getUrlIfValid('aggregator/opml')) {
        $output .= '<dd>' . t('A <a href=":aggregator-opml">machine-readable OPML file</a> of all feeds is available. OPML is an XML-based file format used to share outline-structured information such as a list of RSS feeds. Feeds can also be <a href=":import-opml">imported via an OPML file</a>.', [':aggregator-opml' => $url->toString(), ':import-opml' => Url::fromRoute('aggregator.opml_add')->toString()]) . '</dd>';
      }
      $output .= '<dt>' . t('Configuring cron') . '</dt>';
      $output .= '<dd>' . t('A working <a href=":cron">cron maintenance task</a> is required to update feeds automatically.', [':cron' => Url::fromRoute('system.cron_settings')->toString()]) . '</dd>';
      $output .= '</dl>';
      return $output;

    case 'aggregator.admin_overview':
      // Don't use placeholders for possibility to change URLs for translators.
      $output = '<p>' . t('Many sites publish their headlines and posts in feeds, using a number of standardized XML-based formats. The aggregator supports <a href="http://en.wikipedia.org/wiki/Rss">RSS</a>, <a href="http://en.wikipedia.org/wiki/Resource_Description_Framework">RDF</a>, and <a href="http://en.wikipedia.org/wiki/Atom_%28standard%29">Atom</a>.') . '</p>';
      $output .= '<p>' . t('Current feeds are listed below, and <a href=":addfeed">new feeds may be added</a>. For each feed, the <em>latest items</em> block may be enabled at the <a href=":block">blocks administration page</a>.', [':addfeed' => Url::fromRoute('aggregator.feed_add')->toString(), ':block' => (\Drupal::moduleHandler()->moduleExists('block')) ? Url::fromRoute('block.admin_display')->toString() : '#']) . '</p>';
      return $output;

    case 'aggregator.feed_add':
      return '<p>' . t('Add a feed in RSS, RDF or Atom format. A feed may only have one entry.') . '</p>';

    case 'aggregator.opml_add':
      return '<p>' . t('<abbr title="Outline Processor Markup Language">OPML</abbr> is an XML format for exchanging feeds between aggregators. A single OPML document may contain many feeds. Aggregator uses this file to import all feeds at once. Upload a file from your computer or enter a URL where the OPML file can be downloaded.') . '</p>';
  }
}

/**
 * Implements hook_theme().
 */
function aggregator_theme() {
  return [
    'aggregator_feed' => [
      'render element' => 'elements',
      'file' => 'aggregator.theme.inc',
    ],
    'aggregator_item' => [
      'render element' => 'elements',
      'file' => 'aggregator.theme.inc',
    ],
  ];
}

/**
 * Implements hook_entity_extra_field_info().
 *
 * By default this function creates pseudo-fields that mask the description and
 * image base fields. These pseudo-fields are omitted if:
 * - a module makes the field's display configurable via the field UI by means
 *   of BaseFieldDefinition::setDisplayConfigurable()
 * - AND the additional entity type property
 *   'enable_base_field_custom_preprocess_skipping' has been set using
 *   hook_entity_type_build().
 */
function aggregator_entity_extra_field_info() {
  $extra = [];
  $entity_type_manager = \Drupal::entityTypeManager();
  $entity_field_manager = \Drupal::service('entity_field.manager');

  $extra['aggregator_feed']['aggregator_feed'] = [
    'display' => [
      'items' => [
        'label' => t('Items'),
        'description' => t('Items associated with this feed'),
        'weight' => 0,
      ],
      'more_link' => [
        'label' => t('More link'),
        'description' => t('A more link to the feed detail page'),
        'weight' => 5,
      ],
      'feed_icon' => [
        'label' => t('Feed icon'),
        'description' => t('An icon that links to the feed URL'),
        'weight' => 6,
      ],
    ],
  ];

  // Create Feed image and description pseudo-fields. Skip this if the field
  // display is configurable and skipping has been enabled.
  // @todo https://www.drupal.org/project/drupal/issues/3015623
  //   Eventually delete this code and matching lines in FeedViewBuilder. Using
  //   field formatters is more flexible and consistent.
  $skip_custom_preprocessing = $entity_type_manager->getDefinition('aggregator_feed')->get('enable_base_field_custom_preprocess_skipping');
  $base_field_definitions = $entity_field_manager->getBaseFieldDefinitions('aggregator_feed');

  if (!$skip_custom_preprocessing || !$base_field_definitions['image']->isDisplayConfigurable('view')) {
    $extra['aggregator_feed']['aggregator_feed']['display']['image'] = [
      'label' => t('Image'),
      'description' => t('The feed image'),
      'weight' => 2,
    ];
  }

  if (!$skip_custom_preprocessing || !$base_field_definitions['description']->isDisplayConfigurable('view')) {
    $extra['aggregator_feed']['aggregator_feed']['display']['description'] = [
      'label' => t('Description'),
      'description' => t('The description of this feed'),
      'weight' => 3,
    ];
  }

  // Create Item description pseudo-field. Skip this if the field display is
  // configurable and skipping has been enabled.
  // @todo https://www.drupal.org/project/drupal/issues/3015623
  //   Eventually delete this code and matching lines in ItemViewBuilder. Using
  //   field formatters is more flexible and consistent.
  $skip_custom_preprocessing = $entity_type_manager->getDefinition('aggregator_item')->get('enable_base_field_custom_preprocess_skipping');
  $base_field_definitions = $entity_field_manager->getBaseFieldDefinitions('aggregator_item');

  if (!$skip_custom_preprocessing || !$base_field_definitions['description']->isDisplayConfigurable('view')) {
    $extra['aggregator_item']['aggregator_item']['display']['description'] = [
      'label' => t('Description'),
      'description' => t('The description of this feed item'),
      'weight' => 2,
    ];
  }

  return $extra;
}

/**
 * Implements hook_cron().
 *
 * Queues news feeds for updates once their refresh interval has elapsed.
 */
function aggregator_cron() {
  $queue = \Drupal::queue('aggregator_feeds');

  $ids = \Drupal::entityTypeManager()->getStorage('aggregator_feed')->getFeedIdsToRefresh();
  foreach (Feed::loadMultiple($ids) as $feed) {
    if ($queue->createItem($feed)) {
      // Add timestamp to avoid queueing item more than once.
      $feed->setQueuedTime(REQUEST_TIME);
      $feed->save();
    }
  }

  // Delete queued timestamp after 6 hours assuming the update has failed.
  $ids = \Drupal::entityQuery('aggregator_feed')
    ->condition('queued', REQUEST_TIME - (3600 * 6), '<')
    ->execute();

  if ($ids) {
    $feeds = Feed::loadMultiple($ids);
    foreach ($feeds as $feed) {
      $feed->setQueuedTime(0);
      $feed->save();
    }
  }
}

/**
 * Gets the list of allowed tags.
 *
 * @return array
 *   The list of allowed tags.
 *
 * @internal
 */
function _aggregator_allowed_tags() {
  return preg_split('/\s+|<|>/', \Drupal::config('aggregator.settings')->get('items.allowed_html'), -1, PREG_SPLIT_NO_EMPTY);
}

/**
 * Implements hook_preprocess_HOOK() for block templates.
 */
function aggregator_preprocess_block(&$variables) {
  if ($variables['configuration']['provider'] == 'aggregator') {
    $variables['attributes']['role'] = 'complementary';
  }
}