Add a check to the builder class

Author: bigdevlarry

src/Server/Builder.php

@@ -46,6 +46,7 @@
 use Psr\Log\LoggerInterface;
 use Psr\Log\NullLogger;
 use Psr\SimpleCache\CacheInterface;
+use Symfony\Component\Finder\Finder;
 
 /**
  * @phpstan-import-type Handler from ElementReference
@@ -523,8 +524,12 @@ public function build(): Server
         );
 
         if (null !== $this->discoveryBasePath) {
-            $discoverer = $this->discoverer ?? $this->createDiscoverer($logger);
-            $loaders[] = new DiscoveryLoader($this->discoveryBasePath, $this->discoveryScanDirs, $this->discoveryExcludeDirs, $discoverer);
+            if (null !== $this->discoverer || class_exists(Finder::class)) {
+                $discoverer = $this->discoverer ?? $this->createDiscoverer($logger);
+                $loaders[] = new DiscoveryLoader($this->discoveryBasePath, $this->discoveryScanDirs, $this->discoveryExcludeDirs, $discoverer);
+            } else {
+                $logger->warning('File-based discovery requires symfony/finder. Skipping automatic discovery. Run: composer require symfony/finder');
+            }
         }
 
         foreach ($loaders as $loader) {