symfony
diff --git a/‎src/Symfony/Component/Serializer/Normalizer/AbstractNormalizer.php
Copy file name to clipboardExpand all lines: src/Symfony/Component/Serializer/Normalizer/AbstractNormalizer.php
+5-1Lines changed: 5 additions & 1 deletion b/‎src/Symfony/Component/Serializer/Normalizer/AbstractNormalizer.php
Copy file name to clipboardExpand all lines: src/Symfony/Component/Serializer/Normalizer/AbstractNormalizer.php
+5-1Lines changed: 5 additions & 1 deletion
diff --git a/‎src/Symfony/Component/Serializer/Normalizer/AbstractObjectNormalizer.php
Copy file name to clipboardExpand all lines: src/Symfony/Component/Serializer/Normalizer/AbstractObjectNormalizer.php
+4-3Lines changed: 4 additions & 3 deletions b/‎src/Symfony/Component/Serializer/Normalizer/AbstractObjectNormalizer.php
Copy file name to clipboardExpand all lines: src/Symfony/Component/Serializer/Normalizer/AbstractObjectNormalizer.php
+4-3Lines changed: 4 additions & 3 deletions
@@ -486,8 +486,12 @@ protected function denormalizeParameter(\ReflectionClass $class, \ReflectionPara
      *
      * @internal
      */
-    protected function createChildContext(array $parentContext, $attribute/*, string $format = null */)
+    protected function createChildContext(array $parentContext, $attribute/*, ?string $format */)
     {
+        if (\func_num_args() < 3) {
+            @trigger_error(sprintf('Method %s::%s() will have a 3rd `?string $format` argument in version 5.0. Not defining it is deprecated since Symfony 4.3.', \get_class($this), __FUNCTION__), E_USER_DEPRECATED);
+            $format = null;
+        }
         if (isset($parentContext[self::ATTRIBUTES][$attribute])) {
             $parentContext[self::ATTRIBUTES] = $parentContext[self::ATTRIBUTES][$attribute];
         } else {
 
@@ -512,18 +512,19 @@ private function isMaxDepthReached(array $attributesMetadata, string $class, str
      * We must not mix up the attribute cache between parent and children.
      *
      * {@inheritdoc}
+     *
+     * @param string|null $format
      */
-    protected function createChildContext(array $parentContext, $attribute/*, string $format = null */)
+    protected function createChildContext(array $parentContext, $attribute/*, ?string $format */)
     {
         if (\func_num_args() >= 3) {
             $format = \func_get_arg(2);
         } else {
-            // will be deprecated in version 4
+            @trigger_error(sprintf('Method %s::%s() will have a 3rd `?string $format` argument in version 5.0. Not defining it is deprecated since Symfony 4.3.', \get_class($this), __FUNCTION__), E_USER_DEPRECATED);
             $format = null;
         }
 
         $context = parent::createChildContext($parentContext, $attribute, $format);
-        // format is already included in the cache_key of the parent.
         $context['cache_key'] = $this->getCacheKey($format, $context);
 
         return $context;