feature symfony#54346 [Serializer] Fix: Report Xml warning/error instead of silently returning a wrong xml (VincentLanglet)

This PR was squashed before being merged into the 7.1 branch.

Discussion
----------

[Serializer] Fix: Report Xml warning/error instead of silently returning a wrong xml

| Q             | A
| ------------- | ---
| Branch?       | 7.1
| Bug fix?      | yes
| New feature?  | no
| Deprecations? | no
| Issues        | Fix #... <!-- prefix each issue number with "Fix #", no need to create an issue if none exists, explain below instead -->
| License       | MIT

When `DomDocument::saveXML` encounter an error/warning, for example
```
DOMDocument::saveXML(): xmlEscapeEntities : char out of range
```
the method will return false or an empty/incomplete XML.

In case of `false`, since symfony doesn't use strict type, it will be cast into `string` (for 6.4+ version with native typehint) so the `encode` method will return an empty string.
In case of empty/incomplete XML, symfony returns it as if, without any notice about the error/warning.

I think Symfony should not silently ignore such XML error when decoding.

Or should it be an option ?

Commits
-------

70e74dd [Serializer] Fix: Report Xml warning/error instead of silently returning a wrong xml

Author: fabpot

src/Symfony/Component/Serializer/Encoder/XmlEncoder.php

@@ -82,7 +82,7 @@ public function encode(mixed $data, string $format, array $context = []): string
         $encoderIgnoredNodeTypes = $context[self::ENCODER_IGNORED_NODE_TYPES] ?? $this->defaultContext[self::ENCODER_IGNORED_NODE_TYPES];
         $ignorePiNode = \in_array(\XML_PI_NODE, $encoderIgnoredNodeTypes, true);
         if ($data instanceof \DOMDocument) {
-            return $data->saveXML($ignorePiNode ? $data->documentElement : null);
+            return $this->saveXml($data, $ignorePiNode ? $data->documentElement : null);
         }
 
         $xmlRootNodeName = $context[self::ROOT_NODE_NAME] ?? $this->defaultContext[self::ROOT_NODE_NAME];
@@ -97,7 +97,7 @@ public function encode(mixed $data, string $format, array $context = []): string
             $this->appendNode($dom, $data, $format, $context, $xmlRootNodeName);
         }
 
-        return $dom->saveXML($ignorePiNode ? $dom->documentElement : null, $context[self::SAVE_OPTIONS] ?? $this->defaultContext[self::SAVE_OPTIONS]);
+        return $this->saveXml($dom, $ignorePiNode ? $dom->documentElement : null, $context[self::SAVE_OPTIONS] ?? $this->defaultContext[self::SAVE_OPTIONS]);
     }
 
     public function decode(string $data, string $format, array $context = []): mixed
@@ -498,4 +498,23 @@ private function createDomDocument(array $context): \DOMDocument
 
         return $document;
     }
+
+    /**
+     * @throws NotEncodableValueException
+     */
+    private function saveXml(\DOMDocument $document, ?\DOMNode $node = null, ?int $options = null): string
+    {
+        $prevErrorHandler = set_error_handler(static function ($type, $message, $file, $line, $context = []) use (&$prevErrorHandler) {
+            if (\E_ERROR === $type || \E_WARNING === $type) {
+                throw new NotEncodableValueException($message);
+            }
+
+            return $prevErrorHandler ? $prevErrorHandler($type, $message, $file, $line, $context) : false;
+        });
+        try {
+            return $document->saveXML($node, $options);
+        } finally {
+            restore_error_handler();
+        }
+    }
 }

src/Symfony/Component/Serializer/Tests/Encoder/XmlEncoderTest.php

@@ -433,6 +433,12 @@ public function testEncodeTraversableWhenNormalizable()
         $this->assertEquals($expected, $serializer->serialize(new NormalizableTraversableDummy(), 'xml'));
     }
 
+    public function testEncodeException()
+    {
+        $this->expectException(NotEncodableValueException::class);
+        $this->encoder->encode('Invalid character: '.\chr(7), 'xml');
+    }
+
     public function testDecode()
     {
         $source = $this->getXmlSource();