Add missing @id property

Author: dunglas

src/Hydra/Serializer/CollectionNormalizer.php

@@ -90,7 +90,7 @@ public function normalize($object, $format = null, array $context = [])
         $data['hydra:member'] = [];
         $iriOnly = $context[self::IRI_ONLY] ?? $this->defaultContext[self::IRI_ONLY];
         foreach ($object as $obj) {
-            $data['hydra:member'][] = $iriOnly ? $this->iriConverter->getIriFromItem($obj) : $this->normalizer->normalize($obj, $format, $context);
+            $data['hydra:member'][] = $iriOnly ? ['@id' => $this->iriConverter->getIriFromItem($obj)] : $this->normalizer->normalize($obj, $format, $context);
         }
 
         $paginated = null;

tests/Hydra/Serializer/CollectionNormalizerTest.php

@@ -368,8 +368,8 @@ public function testNormalizeIriOnlyResourceCollection(): void
             '@id' => '/foos',
             '@type' => 'hydra:Collection',
             'hydra:member' => [
-                '/foos/1',
-                '/foos/3',
+                ['@id' => '/foos/1'],
+                ['@id' => '/foos/3'],
             ],
             'hydra:totalItems' => 2,
         ], $actual);