modules/custom/d_product/src/Plugin/Block/ResetButton.php
public function blockSubmit($form, FormStateInterface $formState) {
    $this->configuration['button_text'] = $formState->getValue('button_text');
    $this->configuration['button_class'] = $formState->getValue('button_class');
    $this->configuration['button_target'] = '/' . ltrim(
        $formState->getValue('button_target'),
        '/'
      );
    $this->configuration['button_icon_class'] = $formState->getValue(
      'button_icon_class'
    );
  }
public function blockSubmit($form, FormStateInterface $formState) {
    $this->configuration['button_text'] = $formState->getValue('button_text');
    $this->configuration['button_class'] = $formState->getValue('button_class');
    $this->configuration['button_target'] = '/' . ltrim(
        $formState->getValue('button_target'),
        '/'
      );
    $this->configuration['button_icon_class'] = $formState->getValue(
      'button_icon_class'
    );
  }
{@inheritdoc}