interface DiscoveryInterface

interface DiscoveryInterface {
    
    /**
     * Gets a specific plugin definition.
     *
     * @param string $plugin_id
     *   A plugin id.
     * @param bool $exception_on_invalid
     *   (optional) If TRUE, an invalid plugin ID will throw an exception.
     *
     * @return mixed
     *   A plugin definition, or NULL if the plugin ID is invalid and
     *   $exception_on_invalid is FALSE.
     *
     * @throws \Drupal\Component\Plugin\Exception\PluginNotFoundException
     *   Thrown if $plugin_id is invalid and $exception_on_invalid is TRUE.
     */
    public function getDefinition($plugin_id, $exception_on_invalid = TRUE);
    
    /**
     * Gets the definition of all plugins for this type.
     *
     * @return mixed[]
     *   An array of plugin definitions (empty array if no definitions were
     *   found). Keys are plugin IDs.
     *
     * @see \Drupal\Core\Plugin\FilteredPluginManagerInterface::getFilteredDefinitions()
     */
    public function getDefinitions();
    
    /**
     * Indicates if a specific plugin definition exists.
     *
     * @param string $plugin_id
     *   A plugin ID.
     *
     * @return bool
     *   TRUE if the definition exists, FALSE otherwise.
     */
    public function hasDefinition($plugin_id);

}