From 7befd1d4d0475bf80da4f97491504a58084f8373 Mon Sep 17 00:00:00 2001
From: Michael Babker <michael@happydog.digital>
Date: Tue, 27 Jun 2023 10:51:00 -0400
Subject: [PATCH] Only add the YamlDriver to the chain when symfony/yaml is
 installed

---
 src/Builder/DefaultDriverFactory.php | 25 +++++++++++++++++--------
 1 file changed, 17 insertions(+), 8 deletions(-)

diff --git a/src/Builder/DefaultDriverFactory.php b/src/Builder/DefaultDriverFactory.php
index 5b53daf68..041ca4a71 100644
--- a/src/Builder/DefaultDriverFactory.php
+++ b/src/Builder/DefaultDriverFactory.php
@@ -19,6 +19,7 @@
 use Metadata\Driver\DriverChain;
 use Metadata\Driver\DriverInterface;
 use Metadata\Driver\FileLocator;
+use Symfony\Component\Yaml\Yaml;
 
 final class DefaultDriverFactory implements DriverFactoryInterface
 {
@@ -56,19 +57,27 @@ public function enableEnumSupport(bool $enableEnumSupport = true): void
 
     public function createDriver(array $metadataDirs, Reader $annotationReader): DriverInterface
     {
-        $driver = new DriverChain([
-            new AnnotationOrAttributeDriver($this->propertyNamingStrategy, $this->typeParser, $this->expressionEvaluator, $annotationReader),
-        ]);
+        /*
+         * Build the sorted list of metadata drivers based on the environment. The final order should be:
+         *
+         * - YAML Driver
+         * - XML Driver
+         * - Annotations/Attributes Driver
+         * - Null (Fallback) Driver
+         */
+        $metadataDrivers = [new AnnotationOrAttributeDriver($this->propertyNamingStrategy, $this->typeParser, $this->expressionEvaluator, $annotationReader)];
 
         if (!empty($metadataDirs)) {
             $fileLocator = new FileLocator($metadataDirs);
-            $driver = new DriverChain([
-                new YamlDriver($fileLocator, $this->propertyNamingStrategy, $this->typeParser, $this->expressionEvaluator),
-                new XmlDriver($fileLocator, $this->propertyNamingStrategy, $this->typeParser, $this->expressionEvaluator),
-                $driver,
-            ]);
+
+            array_unshift($metadataDrivers, new XmlDriver($fileLocator, $this->propertyNamingStrategy, $this->typeParser, $this->expressionEvaluator));
+
+            if (class_exists(Yaml::class)) {
+                array_unshift($metadataDrivers, new YamlDriver($fileLocator, $this->propertyNamingStrategy, $this->typeParser, $this->expressionEvaluator));
+            }
         }
 
+        $driver = new DriverChain($metadataDrivers);
         $driver->addDriver(new NullDriver($this->propertyNamingStrategy));
 
         if ($this->enableEnumSupport) {