PluginExistsConstraintValidator.php

<?php

declare (strict_types=1);
namespace Drupal\Core\Plugin\Plugin\Validation\Constraint;

use Drupal\Component\Plugin\Factory\DefaultFactory;
use Drupal\Component\Plugin\FallbackPluginManagerInterface;
use Symfony\Component\Validator\Constraint;
use Symfony\Component\Validator\ConstraintValidator;

/**
 * Validates the PluginExists constraint.
 */
class PluginExistsConstraintValidator extends ConstraintValidator {
    
    /**
     * {@inheritdoc}
     */
    public function validate(mixed $plugin_id, Constraint $constraint) : void {
        assert($constraint instanceof PluginExistsConstraint);
        if ($plugin_id === NULL) {
            return;
        }
        $definition = $constraint->pluginManager
            ->getDefinition($plugin_id, FALSE);
        // Some plugin managers provide fallbacks. In most cases, the use of a
        // fallback plugin ID suggests that the given plugin ID is invalid in some
        // way, so by default, we don't consider fallback plugin IDs as valid,
        // although that can be overridden by the `allowFallback` option if needed.
        if ($constraint->pluginManager instanceof FallbackPluginManagerInterface && $constraint->allowFallback) {
            $fallback_plugin_id = $constraint->pluginManager
                ->getFallbackPluginId($plugin_id);
            $definition = $constraint->pluginManager
                ->getDefinition($fallback_plugin_id, FALSE);
        }
        if (empty($definition)) {
            $this->context
                ->addViolation($constraint->unknownPluginMessage, [
                '@plugin_id' => $plugin_id,
            ]);
            return;
        }
        // If we don't need to validate the plugin class's interface, we're done.
        if (empty($constraint->interface)) {
            return;
        }
        if (!is_a(DefaultFactory::getPluginClass($plugin_id, $definition), $constraint->interface, TRUE)) {
            $this->context
                ->addViolation($constraint->invalidInterfaceMessage, [
                '@plugin_id' => $plugin_id,
                '@interface' => $constraint->interface,
            ]);
        }
    }

}