[LiveComponent] Throw exception for typed LiveProps as interfaces

src/LiveComponent/src/LiveComponentHydrator.php

@@ -496,6 +496,10 @@ private function dehydrateObjectValue(object $value, string $classType, ?string
             }
         }
 
+        if (interface_exists($classType)) {
+            throw new \LogicException(sprintf('Cannot dehydrate value typed as interface "%s" on component "%s". Change this to a concrete type that can be dehydrated. Or set the hydrateWith/dehydrateWith options in LiveProp or set "useSerializerForHydration: true" on the LiveProp to use the serializer.', get_debug_type($value), $parentObject::class));
+        }
+
         $dehydratedObjectValues = [];
         foreach ((new PropertyInfoExtractor([new ReflectionExtractor()]))->getProperties($classType) as $property) {
             $propertyValue = $this->propertyAccessor->getValue($value, $property);
@@ -540,6 +544,10 @@ private function hydrateObjectValue(mixed $value, string $className, bool $allow
             }
         }
 
+        if (interface_exists($className)) {
+            throw new \LogicException(sprintf('Cannot hydrate value typed as interface "%s" on component "%s". Change this to a concrete type that can be hydrated. Or set the hydrateWith/dehydrateWith options in LiveProp or set "useSerializerForHydration: true" on the LiveProp to use the serializer.', $className, $component::class));
+        }
+
         if (\is_array($value)) {
             $object = new $className();
             foreach ($value as $propertyName => $propertyValue) {

src/LiveComponent/tests/Fixtures/Dto/SimpleDto.php

@@ -0,0 +1,16 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\UX\LiveComponent\Tests\Fixtures\Dto;
+
+class SimpleDto implements SimpleDtoInterface
+{
+}

src/LiveComponent/tests/Fixtures/Dto/SimpleDtoInterface.php

@@ -0,0 +1,16 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\UX\LiveComponent\Tests\Fixtures\Dto;
+
+interface SimpleDtoInterface
+{
+}

src/LiveComponent/tests/Integration/LiveComponentHydratorTest.php

@@ -25,6 +25,8 @@
 use Symfony\UX\LiveComponent\Tests\Fixtures\Dto\Embeddable2;
 use Symfony\UX\LiveComponent\Tests\Fixtures\Dto\Money;
 use Symfony\UX\LiveComponent\Tests\Fixtures\Dto\ParentDTO;
+use Symfony\UX\LiveComponent\Tests\Fixtures\Dto\SimpleDto;
+use Symfony\UX\LiveComponent\Tests\Fixtures\Dto\SimpleDtoInterface;
 use Symfony\UX\LiveComponent\Tests\Fixtures\Dto\Temperature;
 use Symfony\UX\LiveComponent\Tests\Fixtures\Entity\CategoryFixtureEntity;
 use Symfony\UX\LiveComponent\Tests\Fixtures\Entity\Embeddable1;
@@ -1307,6 +1309,41 @@ public function __construct()
         );
     }
 
+    public function testInterfaceTypedLivePropCannotBeHydrated(): void
+    {
+        $componentClass = new class() {
+            #[LiveProp(writable: true)]
+            public ?SimpleDtoInterface $prop = null;
+        };
+
+        $this->expectException(\LogicException::class);
+        $this->expectExceptionMessageMatches('/Unable to hydrate value of type "Symfony\UX\LiveComponent\Tests\Fixtures\Dto\SimpleDto" for property "prop" typed as "Symfony\UX\LiveComponent\Tests\Fixtures\Dto\SimpleDtoInterface" on component/');
+        $this->expectExceptionMessageMatches('/ Change this to a concrete type that can be hydrate/');
+
+        $this->hydrator()->hydrate(
+            component: new $componentClass(),
+            props: $this->hydrator()->addChecksumToData(['prop' => 'foo']),
+            updatedProps: ['prop' => 'bar'],
+            componentMetadata: $this->createLiveMetadata($componentClass),
+        );
+    }
+
+    public function testInterfaceTypedLivePropCannotBeDehydrated(): void
+    {
+        $componentClass = new class() {
+            #[LiveProp(writable: true)]
+            public ?SimpleDtoInterface $prop = null;
+        };
+        $component = new $componentClass();
+        $component->prop = new SimpleDto();
+
+        $this->expectException(\LogicException::class);
+        $this->expectExceptionMessageMatches('/Cannot dehydrate value typed as interface "Symfony\UX\LiveComponent\Tests\Fixtures\Dto\SimpleDtoInterface" on component ');
+        $this->expectExceptionMessageMatches('/ Change this to a concrete type that can be dehydrated/');
+
+        $this->hydrator()->dehydrate($component, new ComponentAttributes([]), $this->createLiveMetadata($component));
+    }
+
     /**
      * @dataProvider provideInvalidHydrationTests
      */