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.