Hide block on 4xx pages - Drupal

We can develop a new visibility condition for it, It will add a new visibility condition to the block configuration form with our custom configuration. Later we can use those configuration values inside our "evaluate" function to evaluate the condition.

1.  Develop a condition plugin by using @Condition annotation. Full plugin code is added below.

   namespace Drupal\drupaljournal_base\Plugin\Condition;
   
   use Drupal\Core\Condition\ConditionPluginBase;
   use Drupal\Core\Form\FormStateInterface;
   use Drupal\Core\Plugin\ContainerFactoryPluginInterface;
   use Symfony\Component\DependencyInjection\ContainerInterface;
   use Symfony\Component\HttpFoundation\RequestStack;
   
   /**
    * Provides 'HTTP 4XX Requests' condition.
    *
    * @Condition(
    *   id = "http_4xx_request",
    *   label = @Translation("HTTP 4XX Requests"),
    * )
    */
   class Http4xxRequestCondition extends ConditionPluginBase implements ContainerFactoryPluginInterface {
   
     /**
      * The request stack.
      *
      * @var \Symfony\Component\HttpFoundation\RequestStack
      */
     protected $requestStack;
   
     /**
      * {@inheritdoc}
      */
     public static function create(ContainerInterface $container, array $configuration, $plugin_id, $plugin_definition) {
       return new static(
         $container->get('request_stack'),
         $configuration,
         $plugin_id,
         $plugin_definition);
     }
   
     /**
      * {@inheritdoc}
      */
     public function defaultConfiguration() {
       return [
         'http_401' => 0,
         'http_403' => 0,
         'http_404' => 0,
       ] + parent::defaultConfiguration();
     }
   
     /**
      * {@inheritdoc}
      */
     public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
   
       $form['prefix'] = ['#markup' => '<h5>HTTP 4XX Requests</h5>'];
       $form['http_401'] = [
         '#type' => 'checkbox',
         '#title' => $this->t('Show on 401 pages'),
         '#default_value' => $this->configuration['http_401'],
       ];
       $form['http_403'] = [
         '#type' => 'checkbox',
         '#title' => $this->t('Show on 403 pages'),
         '#default_value' => $this->configuration['http_403'],
       ];
       $form['http_404'] = [
         '#type' => 'checkbox',
         '#title' => $this->t('Show on 404 pages'),
         '#default_value' => $this->configuration['http_404'],
       ];
       return $form + parent::buildConfigurationForm($form, $form_state);
   
     }
   
     /**
      * {@inheritdoc}
      */
     public function submitConfigurationForm(array &$form, FormStateInterface $form_state) {
       $this->configuration['http_401'] = $form_state->getValue('http_401');
       $this->configuration['http_403'] = $form_state->getValue('http_403');
       $this->configuration['http_404'] = $form_state->getValue('http_404');
       parent::submitConfigurationForm($form, $form_state);
     }
   
     /**
      * Constructs "HTTP 4XX Requests" condition plugin.
      *
      * @param \Symfony\Component\HttpFoundation\RequestStack $request_stack
      *   The request stack.
      * @param array $configuration
      *   A configuration array containing information about the plugin instance.
      * @param string $plugin_id
      *   The plugin_id for the plugin instance.
      * @param array $plugin_definition
      *   The plugin implementation definition.
      */
     public function __construct(RequestStack $request_stack, array $configuration, $plugin_id, array $plugin_definition) {
       parent::__construct($configuration, $plugin_id, $plugin_definition);
       $this->requestStack = $request_stack;
     }
   
     /**
      * Evaluates the condition and returns TRUE or FALSE accordingly.
      *
      * @return bool
      *   TRUE if the condition has been met, FALSE otherwise.
      */
     public function evaluate() {
       $exception = $this->requestStack->getCurrentRequest()->attributes->get('exception');
       if (!is_null($exception)) {
         $code = $exception->getStatusCode();
         $value = $this->configuration["http_{$code}"];
         if ($value == 1) {
           return TRUE;
         }
         else {
           return FALSE;
         }
       }
       else {
         $this->configuration["negate"] = FALSE;
         return TRUE;
       }
     }
   
     /**
      * Provides a human readable summary of the condition's configuration.
      */
     public function summary() {
       if (!empty($this->configuration['negate'])) {
         return $this->t('Do not return true on HTTP 4XX Requests.');
       }
       return $this->t('Return true on HTTP 4XX Requests.');
   
     }
   
     /**
      * {@inheritdoc}
      */
     public function getCacheContexts() {
       $contexts = parent::getCacheContexts();
       $contexts[] = 'url.path';
       return $contexts;
     }
   
   }
   

2. Above plugin will add a new condition to the block configuration form. See added screenshot.

3. Select the error page for which you want to hide the block. check negate checkbox and save the block configuration.