Starting over

Author: Mathieu

controller/value_resolver.rst

@@ -204,6 +204,27 @@ PSR-7 Objects Resolver:
     :class:`Psr\\Http\\Message\\RequestInterface` or :class:`Psr\\Http\\Message\\MessageInterface`.
     It requires installing :doc:`the PSR-7 Bridge </components/psr7>` component.
 
+Managing Value Resolvers
+------------------------
+
+For each argument, every available resolver will be called until one provides a value.
+The order in which they are called depends on their priority.
+For example, the ``SessionValueResolver`` (priority 50) will be called before the
+``DefaultValueResolver`` (priority -100) which allows to write e.g.
+``SessionInterface $session = null`` to get the session if there is one, or ``null``
+if there is none.
+
+But what if you *know* there will be a session? In that case every resolver running
+before ``SessionValueResolver`` is useless. Worse, some other resolver could actually
+provide a value before ``SessionValueResolver`` has a chance to (don't worry though,
+this won't happen with built-in resolvers). Since Symfony 6.3, you can leverage the
+:class:`Symfony\\Component\\HttpKernel\\Attribute\\ValueResolver` to avoid this kind of
+issue.
+
+    .. versionadded:: 6.3
+
+        The ``ValueResolver`` attribute was introduced in Symfony 6.3.
+
 Adding a Custom Value Resolver
 ------------------------------