PathBasedBreadcrumbBuilder::build

public PathBasedBreadcrumbBuilder::build(RouteMatchInterface $route_match)

public function build(RouteMatchInterface $route_match) {
  $breadcrumb = new Breadcrumb();
  $links = array();

  // General path-based breadcrumbs. Use the actual request path, prior to
  // resolving path aliases, so the breadcrumb can be defined by simply
  // creating a hierarchy of path aliases.
  $path = trim($this->context->getPathInfo(), '/');
  $path_elements = explode('/', $path);
  $exclude = array();
  // Don't show a link to the front-page path.
  $front = $this->config->get('page.front');
  $exclude[$front] = TRUE;
  // /user is just a redirect, so skip it.
  // @todo Find a better way to deal with /user.
  $exclude['/user'] = TRUE;
  // Add the url.path.parent cache context. This code ignores the last path
  // part so the result only depends on the path parents.
  $breadcrumb->addCacheContexts(['url.path.parent']);
  while (count($path_elements) > 1) {
    array_pop($path_elements);
    // Copy the path elements for up-casting.
    $route_request = $this->getRequestForPath('/' . implode('/', $path_elements), $exclude);
    if ($route_request) {
      $route_match = RouteMatch::createFromRequest($route_request);
      $access = $this->accessManager->check($route_match, $this->currentUser, NULL, TRUE);
      // The set of breadcrumb links depends on the access result, so merge
      // the access result's cacheability metadata.
      $breadcrumb = $breadcrumb->addCacheableDependency($access);
      if ($access->isAllowed()) {
        $title = $this->titleResolver->getTitle($route_request, $route_match->getRouteObject());
        if (!isset($title)) {
          // Fallback to using the raw path component as the title if the
          // route is missing a _title or _title_callback attribute.
          $title = str_replace(array('-', '_'), ' ', Unicode::ucfirst(end($path_elements)));
        }
        $url = Url::fromRouteMatch($route_match);
        $links[] = new Link($title, $url);
      }
    }

  }
  if ($path && '/' . $path != $front) {
    // Add the Home link, except for the front page.
    $links[] = Link::createFromRoute($this->t('Home'), '<front>');
  }

  return $breadcrumb->setLinks(array_reverse($links));
}