Include extended JsonLD data if DTO outputs original object

In `ApiPlatform\Core\DataTransformer\DataTransformerInterface` there is a comment that states that DTOs should be allowed to return the same original object if no transformation is done. This resulted in missing LD data. (No @id, @context etc.).
```php
     /**
     * Transforms the given object to something else, usually another object.
     * This must return the original object if no transformation has been done.
     *
     * @param object $object
     *
     * @return object
     */
    public function transform($object, string $to, array $context = []);
```
This update checks if the output class is the same as the original, and if so populated the extended metadata in the JsonLd\ItemNormalizer as it would not be added using the JsonLd\ObjectNormalizer

Author: silverbackdan

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 * GraphQL: Do not allow empty cursor values on `before` or `after`
 * Filter: Improve the RangeFilter query in case the values are equals using the between operator
+* Bug fix: Allow Data Transformers to return the original class if no transformation has been made, or the transformation was to the original object
 
 ## 2.5.4
 

src/JsonLd/Serializer/ItemNormalizer.php

@@ -65,7 +65,9 @@ public function supportsNormalization($data, $format = null): bool
      */
     public function normalize($object, $format = null, array $context = [])
     {
-        if (null !== $this->getOutputClass($this->getObjectClass($object), $context)) {
+        $objectClass = $this->getObjectClass($object);
+        $outputClass = $this->getOutputClass($objectClass, $context);
+        if (null !== $outputClass && !isset($context[self::IS_TRANSFORMED_TO_SAME_CLASS_CONTEXT_KEY])) {
             return parent::normalize($object, $format, $context);
         }
 

src/Serializer/AbstractItemNormalizer.php

@@ -51,6 +51,8 @@ abstract class AbstractItemNormalizer extends AbstractObjectNormalizer
     use ContextTrait;
     use InputOutputMetadataTrait;
 
+    public const IS_TRANSFORMED_TO_SAME_CLASS_CONTEXT_KEY = 'is_transformed_to_same_class';
+
     protected $propertyNameCollectionFactory;
     protected $propertyMetadataFactory;
     protected $iriConverter;
@@ -112,18 +114,24 @@ public function hasCacheableSupportsMethod(): bool
      */
     public function normalize($object, $format = null, array $context = [])
     {
-        if ($object !== $transformed = $this->transformOutput($object, $context)) {
+        if (!($isTransformed = isset($context[self::IS_TRANSFORMED_TO_SAME_CLASS_CONTEXT_KEY])) && $outputClass = $this->getOutputClass($this->getObjectClass($object), $context)) {
             if (!$this->serializer instanceof NormalizerInterface) {
                 throw new LogicException('Cannot normalize the output because the injected serializer is not a normalizer');
             }
 
-            $context['api_normalize'] = true;
-            $context['api_resource'] = $object;
-            unset($context['output']);
-            unset($context['resource_class']);
+            if ($object !== $transformed = $this->transformOutput($object, $context, $outputClass)) {
+                $context['api_normalize'] = true;
+                $context['api_resource'] = $object;
+                unset($context['output'], $context['resource_class']);
+            } else {
+                $context[self::IS_TRANSFORMED_TO_SAME_CLASS_CONTEXT_KEY] = true;
+            }
 
             return $this->serializer->normalize($transformed, $format, $context);
         }
+        if ($isTransformed) {
+            unset($context[self::IS_TRANSFORMED_TO_SAME_CLASS_CONTEXT_KEY]);
+        }
 
         $resourceClass = $this->resourceClassResolver->getResourceClass($object, $context['resource_class'] ?? null);
         $context = $this->initContext($resourceClass, $context);
@@ -637,9 +645,12 @@ protected function getDataTransformer($data, string $to, array $context = []): ?
      * For a given resource, it returns an output representation if any
      * If not, the resource is returned.
      */
-    protected function transformOutput($object, array $context = [])
+    protected function transformOutput($object, array $context = [], string $outputClass = null)
     {
-        $outputClass = $this->getOutputClass($this->getObjectClass($object), $context);
+        if (null === $outputClass) {
+            $outputClass = $this->getOutputClass($this->getObjectClass($object), $context);
+        }
+
         if (null !== $outputClass && null !== $dataTransformer = $this->getDataTransformer($object, $outputClass, $context)) {
             return $dataTransformer->transform($object, $outputClass, $context);
         }