minor #11813 [Cache] Make sure the chain cache configuration works (Nyholm)

This PR was submitted for the 4.3 branch but it was squashed and merged into the 3.4 branch instead (closes #11813).

Discussion
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[Cache] Make sure the chain cache configuration works

I just tried the configuration and noticed a few issues.

~~Im not 100% sure this actually works.~~ Lets wait for symfony/symfony#32139

Im sure now

Commits
-------

9fbebaf [Cache] Make sure the chain cache configuration works

Author: javiereguiluz

cache.rst

@@ -413,16 +413,22 @@ case the value needs to be recalculated.
             cache:
                 pools:
                     my_cache_pool:
-                        adapter: app.my_cache_chain_adapter
+                        adapter: cache.adapter.psr6
+                        provider: app.my_cache_chain_adapter
                     cache.my_redis:
                         adapter: cache.adapter.redis
                         provider: 'redis://user:[email protected]'
+                    cache.apcu:
+                        adapter: cache.adapter.apcu
+                    cache.array:
+                        adapter: cache.adapter.array
+
 
         services:
             app.my_cache_chain_adapter:
                 class: Symfony\Component\Cache\Adapter\ChainAdapter
                 arguments:
-                    - ['cache.adapter.array', 'cache.my_redis', 'cache.adapter.file']
+                    - ['@cache.array', '@cache.apcu', '@cache.my_redis']
                     - 31536000 # One year
 
     .. code-block:: xml
@@ -436,18 +442,20 @@ case the value needs to be recalculated.
                 https://symfony.com/schema/dic/services/services-1.0.xsd">
 
             <framework:config>
-                <framework:cache default_memcached_provider="memcached://localhost">
-                    <framework:pool name="my_cache_pool" adapter="app.my_cache_chain_adapter"/>
+                <framework:cache>
+                    <framework:pool name="my_cache_pool" adapter="cache.adapter.psr6" provider="app.my_cache_chain_adapter"/>
                     <framework:pool name="cache.my_redis" adapter="cache.adapter.redis" provider="redis://user:[email protected]"/>
+                    <framework:pool name="cache.apcu" adapter="cache.adapter.apcu"/>
+                    <framework:pool name="cache.array" adapter="cache.adapter.array"/>
                 </framework:cache>
             </framework:config>
 
             <services>
                 <service id="app.my_cache_chain_adapter" class="Symfony\Component\Cache\Adapter\ChainAdapter">
                     <argument type="collection">
-                        <argument type="service" value="cache.adapter.array"/>
+                        <argument type="service" value="cache.array"/>
+                        <argument type="service" value="cache.apcu"/>
                         <argument type="service" value="cache.my_redis"/>
-                        <argument type="service" value="cache.adapter.file"/>
                     </argument>
                     <argument>31536000</argument>
                 </service>
@@ -461,28 +469,37 @@ case the value needs to be recalculated.
             'cache' => [
                 'pools' => [
                     'my_cache_pool' => [
-                        'adapter' => 'app.my_cache_chain_adapter',
+                        'adapter' => 'cache.adapter.psr6',
+                        'provider' => 'app.my_cache_chain_adapter',
                     ],
                     'cache.my_redis' => [
                         'adapter' => 'cache.adapter.redis',
                         'provider' => 'redis://user:[email protected]',
                     ],
+                    'cache.apcu' => [
+                        'adapter' => 'cache.adapter.apcu',
+                    ],
+                    'cache.array' => [
+                        'adapter' => 'cache.adapter.array',
+                    ],
                 ],
             ],
         ]);
 
         $container->getDefinition('app.my_cache_chain_adapter', \Symfony\Component\Cache\Adapter\ChainAdapter::class)
             ->addArgument([
-                new Reference('cache.adapter.array'),
+                new Reference('cache.array'),
+                new Reference('cache.apcu'),
                 new Reference('cache.my_redis'),
-                new Reference('cache.adapter.file'),
             ])
             ->addArgument(31536000);
 
 .. note::
 
-    In this configuration there is a ``cache.my_redis`` pool that is used as an
-    adapter in the ``app.my_cache_chain_adapter``
+    In this configuration the ``my_cache_pool`` pool is using the ``cache.adapter.psr6``
+    adapter and the ``app.my_cache_chain_adapter`` service as a provider. That is
+    because ``ChainAdapter`` does not support the ``cache.pool`` tag. So it is decorated
+    with the ``ProxyAdapter``.
 
 
 Clearing the Cache