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) {
    }

}