minor symfony#28451 [Messenger] Throw an exception when the serializer component is not loaded (sroze)

This PR was merged into the 4.2-dev branch.

Discussion
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[Messenger] Throw an exception when the serializer component is not loaded

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | ø
| License       | MIT
| Doc PR        | ø

This adds a sensible exception when trying to build the class without the Symfony Serializer component.

Commits
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c4415cf Throw an exception when the serializer component is not loaded

Author: fabpot

src/Symfony/Component/Messenger/Transport/Serialization/Serializer.php

@@ -13,6 +13,7 @@
 
 use Symfony\Component\Messenger\Envelope;
 use Symfony\Component\Messenger\Exception\InvalidArgumentException;
+use Symfony\Component\Messenger\Exception\RuntimeException;
 use Symfony\Component\Serializer\Encoder\JsonEncoder;
 use Symfony\Component\Serializer\Encoder\XmlEncoder;
 use Symfony\Component\Serializer\Normalizer\ObjectNormalizer;
@@ -37,6 +38,10 @@ public function __construct(SymfonySerializerInterface $serializer, string $form
 
     public static function create(): self
     {
+        if (!class_exists(SymfonySerializer::class)) {
+            throw new RuntimeException(sprintf('The default Messenger Serializer requires Symfony\'s Serializer component. Try running "composer require symfony/serializer".'));
+        }
+
         $encoders = array(new XmlEncoder(), new JsonEncoder());
         $normalizers = array(new ObjectNormalizer());
         $serializer = new SymfonySerializer($normalizers, $encoders);