class MachineName

class MachineName extends FieldPluginBase {
    
    /**
     * Stores the available options.
     *
     * @var array
     */
    protected $valueOptions;
    public function getValueOptions() {
        if (isset($this->valueOptions)) {
            return;
        }
        if (isset($this->definition['options callback']) && is_callable($this->definition['options callback'])) {
            if (isset($this->definition['options arguments']) && is_array($this->definition['options arguments'])) {
                $this->valueOptions = call_user_func_array($this->definition['options callback'], $this->definition['options arguments']);
            }
            else {
                $this->valueOptions = call_user_func($this->definition['options callback']);
            }
        }
        else {
            $this->valueOptions = [];
        }
    }
    
    /**
     * {@inheritdoc}
     */
    protected function defineOptions() {
        $options = parent::defineOptions();
        $options['machine_name'] = [
            'default' => FALSE,
        ];
        return $options;
    }
    
    /**
     * {@inheritdoc}
     */
    public function buildOptionsForm(&$form, FormStateInterface $form_state) {
        parent::buildOptionsForm($form, $form_state);
        $form['machine_name'] = [
            '#title' => $this->t('Output machine name'),
            '#description' => $this->t('Display field as machine name.'),
            '#type' => 'checkbox',
            '#default_value' => !empty($this->options['machine_name']),
        ];
    }
    
    /**
     * {@inheritdoc}
     */
    public function preRender(&$values) {
        $this->getValueOptions();
    }
    
    /**
     * {@inheritdoc}
     */
    public function render(ResultRow $values) {
        $value = $values->{$this->field_alias};
        if (!empty($this->options['machine_name']) || !isset($this->valueOptions[$value])) {
            $result = $this->sanitizeValue($value);
        }
        else {
            $result = $this->valueOptions[$value];
        }
        return $result;
    }

}