class SelectionPluginBase

abstract class SelectionPluginBase extends PluginBase implements SelectionInterface, ConfigurableInterface, DependentPluginInterface {
  
  /**
   * Constructs a new selection object.
   *
   * @param array $configuration
   *   A configuration array containing information about the plugin instance.
   * @param string $plugin_id
   *   The plugin_id for the plugin instance.
   * @param mixed $plugin_definition
   *   The plugin implementation definition.
   */
  public function __construct(array $configuration, $plugin_id, $plugin_definition) {
    parent::__construct($configuration, $plugin_id, $plugin_definition);
    $this->setConfiguration($configuration);
  }
  
  /**
   * {@inheritdoc}
   */
  public function defaultConfiguration() {
    return [
      'target_type' => NULL,
      'entity' => NULL,
    ];
  }
  
  /**
   * {@inheritdoc}
   */
  public function getConfiguration() {
    return $this->configuration;
  }
  
  /**
   * {@inheritdoc}
   */
  public function setConfiguration(array $configuration) {
    // Merge in defaults.
    $this->configuration = NestedArray::mergeDeep($this->defaultConfiguration(), $configuration);
  }
  
  /**
   * {@inheritdoc}
   */
  public function calculateDependencies() {
    return [];
  }
  
  /**
   * {@inheritdoc}
   */
  public function buildConfigurationForm(array $form, FormStateInterface $form_state) {
    return $form;
  }
  
  /**
   * {@inheritdoc}
   */
  public function validateConfigurationForm(array &$form, FormStateInterface $form_state) {
  }
  
  /**
   * {@inheritdoc}
   */
  public function submitConfigurationForm(array &$form, FormStateInterface $form_state) {
  }
  
  /**
   * {@inheritdoc}
   */
  public function entityQueryAlter(SelectInterface $query) {
  }

}