Fix CharsetValidator with string encoding

Author: alamirault

src/Symfony/Component/Validator/Constraints/CharsetValidator.php

@@ -38,7 +38,7 @@ public function validate(mixed $value, Constraint $constraint): void
         if (!\in_array(mb_detect_encoding($value, $constraint->encodings, true), (array) $constraint->encodings, true)) {
             $this->context->buildViolation($constraint->message)
                 ->setParameter('{{ detected }}', mb_detect_encoding($value, strict: true))
-                ->setParameter('{{ encodings }}', implode(', ', $constraint->encodings))
+                ->setParameter('{{ encodings }}', implode(', ', (array) $constraint->encodings))
                 ->setCode(Charset::BAD_ENCODING_ERROR)
                 ->addViolation();
         }

src/Symfony/Component/Validator/Tests/Constraints/CharsetValidatorTest.php

@@ -37,13 +37,13 @@ public function testEncodingIsValid(string|\Stringable $value, array|string $enc
     /**
      * @dataProvider provideInvalidValues
      */
-    public function testInvalidValues(string $value, array $encodings)
+    public function testInvalidValues(string $value, array|string $encodings)
     {
         $this->validator->validate($value, new Charset(encodings: $encodings));
 
         $this->buildViolation('The detected character encoding is invalid ({{ detected }}). Allowed encodings are {{ encodings }}.')
             ->setParameter('{{ detected }}', 'UTF-8')
-            ->setParameter('{{ encodings }}', implode(', ', $encodings))
+            ->setParameter('{{ encodings }}', implode(', ', (array) $encodings))
             ->setCode(Charset::BAD_ENCODING_ERROR)
             ->assertRaised();
     }
@@ -73,6 +73,7 @@ public static function provideValidValues()
 
     public static function provideInvalidValues()
     {
+        yield ['my non-Äscîi string', 'ASCII'];
         yield ['my non-Äscîi string', ['ASCII']];
         yield ['😊', ['7bit']];
     }