[Serializer] Don't fallback to default serializer if tags specify a named one

Author: HypeMC

composer.json

@@ -55,6 +55,7 @@
         "symfony/polyfill-intl-normalizer": "~1.0",
         "symfony/polyfill-mbstring": "~1.0",
         "symfony/polyfill-php83": "^1.28",
+        "symfony/polyfill-php84": "^1.30",
         "symfony/polyfill-uuid": "^1.15"
     },
     "replace": {

src/Symfony/Component/Serializer/DependencyInjection/SerializerPass.php

@@ -89,6 +89,10 @@ private function createNamedSerializerTags(ContainerBuilder $container, string $
         foreach ($container->findTaggedServiceIds($tagName) as $serviceId => $tags) {
             $definition = $container->getDefinition($serviceId);
 
+            if (array_any($tags, $closure = fn (array $tag) => (bool) $tag)) {
+                $tags = array_filter($tags, $closure);
+            }
+
             foreach ($tags as $tag) {
                 $names = (array) ($tag['serializer'] ?? []);
 

src/Symfony/Component/Serializer/Tests/DependencyInjection/SerializerPassTest.php

@@ -381,6 +381,62 @@ public function testMultipleNamedSerializerTagsAreResolvedCorrectly()
         $this->assertCount(2, $encoderDefinition->getTag('serializer.encoder.api2'));
     }
 
+    /**
+     * @dataProvider provideEmptyTagsData
+     */
+    public function testEmptyTagsAreIgnoredWhenNonEmptyArePresent(
+        array $tagAttributesList,
+        array $expectedDefaultTags,
+        array $expectedApiTags,
+    ) {
+        $container = new ContainerBuilder();
+
+        $container->setParameter('kernel.debug', false);
+        $container->setParameter('.serializer.named_serializers', ['api' => []]);
+
+        $container->register('serializer')->setArguments([null, null]);
+        $container->register('n0')->addTag('serializer.normalizer', ['serializer' => ['default', 'api']]);
+        $container->register('e0')->addTag('serializer.encoder', ['serializer' => ['default', 'api']]);
+
+        $normalizerDefinition = $container->register('n1')->setTags(['serializer.normalizer' => $tagAttributesList]);
+        $encoderDefinition = $container->register('e1')->setTags(['serializer.encoder' => $tagAttributesList]);
+
+        $serializerPass = new SerializerPass();
+        $serializerPass->process($container);
+
+        $this->assertSame($expectedDefaultTags, $normalizerDefinition->getTag('serializer.normalizer.default'));
+        $this->assertSame($expectedApiTags, $normalizerDefinition->getTag('serializer.normalizer.api'));
+        $this->assertSame($expectedDefaultTags, $encoderDefinition->getTag('serializer.encoder.default'));
+        $this->assertSame($expectedApiTags, $encoderDefinition->getTag('serializer.encoder.api'));
+    }
+
+    public static function provideEmptyTagsData(): iterable
+    {
+        yield 'with default name' => [
+            [[], ['serializer' => 'default']],
+            [[]],
+            [],
+        ];
+
+        yield 'with non-default name' => [
+            [[], ['serializer' => 'api']],
+            [],
+            [[]],
+        ];
+
+        yield 'with wildcard' => [
+            [[], ['serializer' => '*']],
+            [[]],
+            [[]],
+        ];
+
+        yield 'with priority and no name' => [
+            [[], ['priority' => 100]],
+            [['priority' => 100]],
+            [],
+        ];
+    }
+
     public function testThrowExceptionWhenNoNormalizersForNamedSerializers()
     {
         $container = new ContainerBuilder();

src/Symfony/Component/Serializer/composer.json

@@ -18,7 +18,8 @@
     "require": {
         "php": ">=8.2",
         "symfony/deprecation-contracts": "^2.5|^3",
-        "symfony/polyfill-ctype": "~1.8"
+        "symfony/polyfill-ctype": "~1.8",
+        "symfony/polyfill-php84": "^1.30"
     },
     "require-dev": {
         "phpdocumentor/reflection-docblock": "^3.2|^4.0|^5.0",