[DependencyInjection] Add support of PHP enumerations

Author: alexandre-daubois

Inline.php

@@ -127,6 +127,8 @@ public static function dump($value, int $flags = 0): string
                 return self::dumpNull($flags);
             case $value instanceof \DateTimeInterface:
                 return $value->format('c');
+            case $value instanceof \UnitEnum:
+                return sprintf('!php/const %s::%s', \get_class($value), $value->name);
             case \is_object($value):
                 if ($value instanceof TaggedValue) {
                     return '!'.$value->getTag().' '.self::dump($value->getValue(), $flags);

Tests/Fixtures/FooUnitEnum.php

@@ -0,0 +1,8 @@
+<?php
+
+namespace Symfony\Component\Yaml\Tests\Fixtures;
+
+enum FooUnitEnum
+{
+    case BAR;
+}

Tests/InlineTest.php

@@ -15,6 +15,7 @@
 use Symfony\Component\Yaml\Exception\ParseException;
 use Symfony\Component\Yaml\Inline;
 use Symfony\Component\Yaml\Tag\TaggedValue;
+use Symfony\Component\Yaml\Tests\Fixtures\FooUnitEnum;
 use Symfony\Component\Yaml\Yaml;
 
 class InlineTest extends TestCase
@@ -577,6 +578,14 @@ public function testDumpDateTime($dateTime, $expected)
         $this->assertSame($expected, Inline::dump($dateTime));
     }
 
+    /**
+     * @requires PHP 8.1
+     */
+    public function testDumpUnitEnum()
+    {
+        $this->assertSame("!php/const Symfony\Component\Yaml\Tests\Fixtures\FooUnitEnum::BAR", Inline::dump(FooUnitEnum::BAR));
+    }
+
     public function getDateTimeDumpTests()
     {
         $tests = [];