[Serializer] add note on Custom Normalizer page about cacheable performance

Author: maxhelias

components/serializer.rst

@@ -1499,31 +1499,7 @@ Once configured, the serializer uses the mapping to pick the correct class::
     $repository = $serializer->deserialize($serialized, CodeRepository::class, 'json');
     // instanceof GitHubCodeRepository
 
-Performance
------------
-
-To figure which normalizer (or denormalizer) must be used to handle an object,
-the :class:`Symfony\\Component\\Serializer\\Serializer` class will call the
-:method:`Symfony\\Component\\Serializer\\Normalizer\\NormalizerInterface::supportsNormalization`
-(or :method:`Symfony\\Component\\Serializer\\Normalizer\\DenormalizerInterface::supportsDenormalization`)
-of all registered normalizers (or denormalizers) in a loop.
-
-The result of these methods can vary depending on the object to serialize, the
-format and the context. That's why the result **is not cached** by default and
-can result in a significant performance bottleneck.
-
-However, most normalizers (and denormalizers) always return the same result when
-the object's type and the format are the same, so the result can be cached. To
-do so, make those normalizers (and denormalizers) implement the
-:class:`Symfony\\Component\\Serializer\\Normalizer\\CacheableSupportsMethodInterface`
-and return ``true`` when
-:method:`Symfony\\Component\\Serializer\\Normalizer\\CacheableSupportsMethodInterface::hasCacheableSupportsMethod`
-is called.
-
-.. note::
-
-    All built-in :ref:`normalizers and denormalizers <component-serializer-normalizers>`
-    as well the ones included in `API Platform`_ natively implement this interface.
+.. include:: /serializer/_performance_tip.rst.inc
 
 Learn more
 ----------

serializer/_performance_tip.rst.inc

@@ -0,0 +1,25 @@
+Performance
+-----------
+
+To figure which normalizer (or denormalizer) must be used to handle an object,
+the :class:`Symfony\\Component\\Serializer\\Serializer` class will call the
+:method:`Symfony\\Component\\Serializer\\Normalizer\\NormalizerInterface::supportsNormalization`
+(or :method:`Symfony\\Component\\Serializer\\Normalizer\\DenormalizerInterface::supportsDenormalization`)
+of all registered normalizers (or denormalizers) in a loop.
+
+The result of these methods can vary depending on the object to serialize, the
+format and the context. That's why the result **is not cached** by default and
+can result in a significant performance bottleneck.
+
+However, most normalizers (and denormalizers) always return the same result when
+the object's type and the format are the same, so the result can be cached. To
+do so, make those normalizers (and denormalizers) implement the
+:class:`Symfony\\Component\\Serializer\\Normalizer\\CacheableSupportsMethodInterface`
+and return ``true`` when
+:method:`Symfony\\Component\\Serializer\\Normalizer\\CacheableSupportsMethodInterface::hasCacheableSupportsMethod`
+is called.
+
+.. note::
+
+    All built-in :ref:`normalizers and denormalizers <component-serializer-normalizers>`
+    as well the ones included in `API Platform`_ natively implement this interface.

serializer/custom_normalizer.rst

@@ -60,3 +60,5 @@ Before using this normalizer in a Symfony application it must be registered as
 a service and :doc:`tagged </service_container/tags>` with ``serializer.normalizer``.
 If you're using the :ref:`default services.yaml configuration <service-container-services-load-example>`,
 this is done automatically!
+
+.. include:: /serializer/_performance_tip.rst.inc