fix: Serialize native PHP enums with their name and value instead of opaque 'Object' string

Enums were caught by the generic `is_object` branch in `serializeRecursively()`,
causing them to render as `Object ClassName` when `serializeAllObjects` was enabled.
This adds an early-return for `UnitEnum` before the object block and enhances the
output to include the backing value for `BackedEnum` instances.

Fixes #2037

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: jarstelfox

src/Serializer/AbstractSerializer.php

@@ -116,6 +116,10 @@ protected function serializeRecursively($value, int $_depth = 0)
                 return $serializedArray;
             }
 
+            if ($value instanceof \UnitEnum) {
+                return $this->serializeValue($value);
+            }
+
             if (\is_object($value)) {
                 $classSerializers = $this->resolveClassSerializers($value);
 
@@ -247,8 +251,13 @@ protected function serializeValue($value)
 
         if ($value instanceof \UnitEnum) {
             $reflection = new \ReflectionObject($value);
+            $enumValue = $reflection->getName() . '::' . $value->name;
+
+            if ($value instanceof \BackedEnum) {
+                return 'Enum ' . $enumValue . '(' . $value->value . ')';
+            }
 
-            return 'Enum ' . $reflection->getName() . '::' . $value->name;
+            return 'Enum ' . $enumValue;
         }
 
         if (\is_object($value)) {

tests/Serializer/AbstractSerializerTest.php

@@ -66,6 +66,54 @@ public function testEnumsAreNames(): void
         $this->assertSame('Enum Sentry\Tests\Serializer\SerializerTestEnum::CASE_NAME', $result);
     }
 
+    /**
+     * @requires PHP >= 8.1
+     */
+    public function testBackedEnumsIncludeValue(): void
+    {
+        $serializer = $this->createSerializer();
+        $input = SerializerTestBackedEnum::CASE_NAME;
+        $result = $this->invokeSerialization($serializer, $input);
+
+        $this->assertSame('Enum Sentry\Tests\Serializer\SerializerTestBackedEnum::CASE_NAME(case_value)', $result);
+    }
+
+    /**
+     * @requires PHP >= 8.1
+     * @dataProvider serializeAllObjectsDataProvider
+     */
+    public function testEnumsAreNotSerializedAsObjects(bool $serializeAllObjects): void
+    {
+        $serializer = $this->createSerializer();
+
+        if ($serializeAllObjects) {
+            $serializer->setSerializeAllObjects(true);
+        }
+
+        $input = SerializerTestEnum::CASE_NAME;
+        $result = $this->invokeSerialization($serializer, $input);
+
+        $this->assertSame('Enum Sentry\Tests\Serializer\SerializerTestEnum::CASE_NAME', $result);
+    }
+
+    /**
+     * @requires PHP >= 8.1
+     * @dataProvider serializeAllObjectsDataProvider
+     */
+    public function testBackedEnumsAreNotSerializedAsObjects(bool $serializeAllObjects): void
+    {
+        $serializer = $this->createSerializer();
+
+        if ($serializeAllObjects) {
+            $serializer->setSerializeAllObjects(true);
+        }
+
+        $input = SerializerTestBackedEnum::CASE_NAME;
+        $result = $this->invokeSerialization($serializer, $input);
+
+        $this->assertSame('Enum Sentry\Tests\Serializer\SerializerTestBackedEnum::CASE_NAME(case_value)', $result);
+    }
+
     public static function objectsWithIdPropertyDataProvider(): array
     {
         return [

tests/Serializer/SerializerTestBackedEnum.php

@@ -0,0 +1,10 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Sentry\Tests\Serializer;
+
+enum SerializerTestBackedEnum: string
+{
+    case CASE_NAME = 'case_value';
+}