LogicException: The controller must return a response (Object(Drupal\Core\Render\Markup) given)

Question

I'm getting this error:

LogicException: The controller must return a response (Object(Drupal\Core\Render\Markup) given). in Symfony\Component\HttpKernel\HttpKernel->handleRaw() (line 157 of C:\xampp\htdocs\drupal-8.1.10\vendor\symfony\http-kernel\HttpKernel.php).

Below is the code that I'm trying to execute:

<?php
/**
 * @file
 * Contains \Drupal\my_module\Controller\DefaultController.
 */

namespace Drupal\my_module\Controller;

use Drupal\Core\Controller\ControllerBase;

/**
 * Default controller for the my_module module.
 */
class DefaultController extends ControllerBase {

  public function my_module(\Drupal\user\UserInterface $user = NULL) {
    $name = $mail = $roles = $picture = "";

    if (!$user->getUsername() && $user->getUsername()) {
      $name = $user->getUsername();
    }

    if (!$user->getEmail() && $user->getEmail())->get('my_module_user_email_display_status')) {
      $mail = $user->getEmail();
    }

    foreach ($user->getRoles() as $value) {
      $roles = $value;
    }

    $user_data = [
      'name' => \Drupal\Component\Utility\SafeMarkup::checkPlain($name),
      'mail' => \Drupal\Component\Utility\SafeMarkup::checkPlain($mail),
      'roles' => \Drupal\Component\Utility\SafeMarkup::checkPlain($roles),
    ];

    $my_module_template_build = array(
      '#theme' => 'my_module_template',
      '#details' => $user_data,
    );

    $my_module_template = drupal_render($my_module_template_build);

    return $my_module_template;
  }
}

Answer 1

You can return $my_module_template_build, e.g.:

$my_module_template = \Drupal::service('renderer')->renderRoot($my_module_template_build);

Answer 2

You've to return a response using Response Object, instead of returning rendered HTML as string, check code snippet provided here.

Answer 3

Try

return array(
  '#markup' => $my_module_template
);

Instead of

return $my_module_template;