class ConstraintManager

class ConstraintManager extends DefaultPluginManager {
    
    /**
     * Overrides \Drupal\Component\Plugin\PluginManagerBase::__construct().
     *
     * @param \Traversable $namespaces
     *   An object that implements \Traversable which contains the root paths
     *   keyed by the corresponding namespace to look for plugin implementations.
     * @param \Drupal\Core\Cache\CacheBackendInterface $cache_backend
     *   Cache backend instance to use.
     * @param \Drupal\Core\Extension\ModuleHandlerInterface $module_handler
     *   The module handler to invoke the alter hook with.
     */
    public function __construct(\Traversable $namespaces, CacheBackendInterface $cache_backend, ModuleHandlerInterface $module_handler) {
        $this->factory = new ConstraintFactory($this);
        parent::__construct('Plugin/Validation/Constraint', $namespaces, $module_handler, NULL, 'Drupal\\Core\\Validation\\Annotation\\Constraint');
        $this->alterInfo('validation_constraint');
        $this->setCacheBackend($cache_backend, 'validation_constraint_plugins');
    }
    
    /**
     * {@inheritdoc}
     */
    protected function getDiscovery() {
        if (!isset($this->discovery)) {
            $this->discovery = parent::getDiscovery();
            $this->discovery = new StaticDiscoveryDecorator($this->discovery, [
                $this,
                'registerDefinitions',
            ]);
        }
        return $this->discovery;
    }
    
    /**
     * Creates a validation constraint.
     *
     * @param string $name
     *   The name or plugin id of the constraint.
     * @param mixed $options
     *   The options to pass to the constraint class. Required and supported
     *   options depend on the constraint class.
     *
     * @return \Symfony\Component\Validator\Constraint
     *   A validation constraint plugin.
     */
    public function create($name, $options) {
        if (!is_array($options)) {
            // Plugins need an array as configuration, so make sure we have one.
            // The constraint classes support passing the options as part of the
            // 'value' key also.
            $options = isset($options) ? [
                'value' => $options,
            ] : [];
        }
        return $this->createInstance($name, $options);
    }
    
    /**
     * Callback for registering definitions for constraints shipped with Symfony.
     *
     * @see ConstraintManager::__construct()
     */
    public function registerDefinitions() {
        $this->getDiscovery()
            ->setDefinition('Callback', [
            'label' => new TranslatableMarkup('Callback'),
            'class' => '\\Symfony\\Component\\Validator\\Constraints\\Callback',
            'type' => FALSE,
        ]);
        $this->getDiscovery()
            ->setDefinition('Blank', [
            'label' => new TranslatableMarkup('Blank'),
            'class' => '\\Symfony\\Component\\Validator\\Constraints\\Blank',
            'type' => FALSE,
        ]);
        $this->getDiscovery()
            ->setDefinition('NotBlank', [
            'label' => new TranslatableMarkup('Not blank'),
            'class' => '\\Symfony\\Component\\Validator\\Constraints\\NotBlank',
            'type' => FALSE,
        ]);
        $this->getDiscovery()
            ->setDefinition('Email', [
            'label' => new TranslatableMarkup('Email'),
            'class' => '\\Drupal\\Core\\Validation\\Plugin\\Validation\\Constraint\\EmailConstraint',
            'type' => [
                'string',
            ],
        ]);
    }
    
    /**
     * {@inheritdoc}
     */
    public function processDefinition(&$definition, $plugin_id) {
        // Make sure 'type' is set and either an array or FALSE.
        if ($definition['type'] !== FALSE && !is_array($definition['type'])) {
            $definition['type'] = [
                $definition['type'],
            ];
        }
    }
    
    /**
     * Returns a list of constraints that support the given type.
     *
     * @param string $type
     *   The type to filter on.
     *
     * @return array
     *   An array of constraint plugin definitions supporting the given type,
     *   keyed by constraint name (plugin ID).
     */
    public function getDefinitionsByType($type) {
        $definitions = [];
        foreach ($this->getDefinitions() as $plugin_id => $definition) {
            if ($definition['type'] === FALSE || in_array($type, $definition['type'])) {
                $definitions[$plugin_id] = $definition;
            }
        }
        return $definitions;
    }

}