a12s-1.0.0-beta7/modules/seo/a12s_seo.module

<?php

/**
 * @file
 * Contains a12s_seo.module.
 */

use Drupal\Core\Entity\EntityInterface;
use Drupal\Core\Url;
use Drupal\node\NodeInterface;

/**
 * Implements hook_preprocess_pager().
 *
 * Manage the "rel next" and "rel prev" head tags.
 *
 * @see https://www.drupal.org/project/drupal/issues/1567684#comment-12398066
 */
function a12s_seo_preprocess_pager(&$pager): void {
  if (!isset($pager['current']) || empty($pager['items'])) {
    return;
  }

  $currentPath = Url::fromRoute('<current>');
  $path = $currentPath->setAbsolute(TRUE)->toString();

  // Correct for first page actually being page 0.
  $currentPage = $pager['current'] - 1;

  // Use the base path if on page 2 otherwise `page={{current_page-1}}`.
  $prevHref = ($currentPage == 1 ? $path : (!empty($pager['items']['previous']['href']) ? $path . $pager['items']['previous']['href'] : NULL));
  $nextHref = (!empty($pager['items']['next']['href']) ? $path . $pager['items']['next']['href'] : NULL);

  // The $pager variable is never rendered, as the 'page', 'prev', or 'next'
  // keys.
  // So we need to attach the HTML head links to a dummy, element that have to
  // be displayed in the pager.html.twig template.
  // We could also transform the "text" key of the "prev" or "next element to
  // a renderable array, but it could lead to issue with other contrib modules
  // that want to alter the "text"...
  // Add The prev rel link.
  if ($prevHref) {
    $pager['items']['html_head']['#attached']['html_head_link'][] = [
      [
        'rel' => 'prev',
        'href' => $prevHref,
      ],
      TRUE,
    ];
  }

  // Add the next rel link.
  if ($nextHref) {
    $pager['items']['html_head']['#attached']['html_head_link'][] = [
      [
        'rel' => 'next',
        'href' => $nextHref,
      ],
      TRUE,
    ];
  }
}

/**
 * Implements hook_page_attachments_alter().
 */
function a12s_seo_page_attachments_alter(array &$attachments): void {
  // Remove some useless link tags (not SEO relevant, and may lead to 403).
  // @see \Drupal\a12s_seo\SeoManager::getUselessRelAttributes()
  $htmlHeadLink = $attachments['#attached']['html_head_link'];

  /** @var \Drupal\a12s_seo\SeoManager $seoManager */
  $seoManager = \Drupal::service('a12s_seo.manager');
  $uselessRelAttributes = $seoManager->getUselessRelAttributes();

  foreach ($htmlHeadLink as $key => $value) {
    if (isset($value[0]['rel']) && in_array($value[0]['rel'], $uselessRelAttributes, TRUE)) {
      unset($attachments['#attached']['html_head_link'][$key]);
    }
  }
}

/**
 * Implements hook_module_implements_alter().
 */
function a12s_seo_module_implements_alter(&$implementations, $hook): void {
  if ($hook === 'page_attachments_alter') {
    $group = $implementations['a12s_seo'];
    unset($implementations['a12s_seo']);
    $implementations['a12s_seo'] = $group;
  }
}

/**
 * Implements hook_entity_view_alter().
 *
 * Remove some useless link tags (not SEO relevant, and may lead to 403).
 *
 * @see \Drupal\a12s_seo\SeoManager::getUselessRelAttributes()
 */
function a12s_seo_entity_view_alter(array &$build, EntityInterface $entity): void {
  if ($build['#view_mode'] === 'full' && $entity instanceof NodeInterface) {
    if (!isset($build['#attached']['html_head_link'])) {
      return;
    }

    /** @var \Drupal\a12s_seo\SeoManager $seoManager */
    $seoManager = \Drupal::service('a12s_seo.manager');
    $uselessRelAttributes = $seoManager->getUselessRelAttributes();

    foreach ($build['#attached']['html_head_link'] as $key => $value) {
      if (isset($value[0]['rel']) && in_array($value[0]['rel'], $uselessRelAttributes, TRUE)) {
        unset($build['#attached']['html_head_link'][$key]);
      }
    }
  }
}