Username.php

<?php

/**
 * @file
 * Definition of Drupal\comment\Plugin\views\field\Username.
 */
namespace Drupal\comment\Plugin\views\field;

use Drupal\views\ViewExecutable;
use Drupal\views\Plugin\views\display\DisplayPluginBase;
use Drupal\views\Plugin\views\field\FieldPluginBase;
use Drupal\Component\Annotation\PluginID;

/**
 * Field handler to allow linking to a user account or homepage.
 *
 * @ingroup views_field_handlers
 *
 * @PluginID("comment_username")
 */
class Username extends FieldPluginBase {

  /**
   * Overrides \Drupal\views\Plugin\views\field\FieldPluginBase::init().
   *
   * Add uid and homepage fields.
   */
  public function init(ViewExecutable $view, DisplayPluginBase $display, array &$options = NULL) {
    parent::init($view, $display, $options);
    $this->additional_fields['uid'] = 'uid';
    $this->additional_fields['homepage'] = 'homepage';
  }
  protected function defineOptions() {
    $options = parent::defineOptions();
    $options['link_to_user'] = array(
      'default' => TRUE,
      'bool' => TRUE,
    );
    return $options;
  }
  public function buildOptionsForm(&$form, &$form_state) {
    $form['link_to_user'] = array(
      '#title' => t("Link this field to its user or an author's homepage"),
      '#type' => 'checkbox',
      '#default_value' => $this->options['link_to_user'],
    );
    parent::buildOptionsForm($form, $form_state);
  }
  function render_link($data, $values) {
    if (!empty($this->options['link_to_user'])) {
      $account = entity_create('user', array());
      $account->uid = $this
        ->getValue($values, 'uid');
      $account->name = $this
        ->getValue($values);
      $account->homepage = $this
        ->getValue($values, 'homepage');
      return theme('username', array(
        'account' => $account,
      ));
    }
    else {
      return $data;
    }
  }
  function render($values) {
    $value = $this
      ->getValue($values);
    return $this
      ->render_link($this
      ->sanitizeValue($value), $values);
  }

}