Review from @HeahDude

Author: mtarld

service_container/service_decoration.rst

@@ -316,9 +316,14 @@ The generated code will be the following::
 Control the Behavior When the Decorated Service Does Not Exist
 --------------------------------------------------------------
 
-Let's imagine you have a decorator that decorates a service defined by another bundle.
-If for some reasons, that bundle is missing, the ``decoration_on_invalid``
-option will allow you to handle the lack of the decorated service.
+When you decorate a service that doesn't exist, the ``decoration_on_invalid``
+option allows you to choose the behavior to adopt.
+
+Three different behaviors are available:
+
+* ``exception``: A ``ServiceNotFoundException`` will be thrown telling that decorator's dependency is missing. (default)
+* ``ignore``: The container will remove the decorator.
+* ``null``: The container will keep the decorator service and will set the decorated one to ``null``.
 
 .. configuration-block::
 
@@ -328,7 +333,6 @@ option will allow you to handle the lack of the decorated service.
         Foo: ~
 
         Bar:
-            public: false
             decorates: Foo
             decoration_on_invalid: ignore
             arguments: ['@Bar.inner']
@@ -365,62 +369,54 @@ option will allow you to handle the lack of the decorated service.
 
             $services->set(Bar::class)
                 ->decorate(Foo::class, null, 0, ContainerInterface::IGNORE_ON_INVALID_REFERENCE)
-                ->args([ref(Bar::class.'.inner')]);
-
-            $services->set(Baz::class)
-                ->private()
-                ->decorate(Foo::class, null, 1)
-                ->args([ref(Baz::class.'.inner')]);
+                ->args([ref(Bar::class.'.inner')])
+            ;
         };
 
-Three different behaviors are available:
+.. versionadded:: 4.4
 
-* ``exception``: When used, a ``ServiceNotFoundException``
-  will be thrown telling that decorator's dependency is missing. (default)
-* ``ignore``: Using that behavior, the container will remove either decorator
-  and decorated services.
-* ``null``: When used, the container will keep the decorator
-  service and will set the decorated one to ``null``.
+    The ``decoration_on_invalid`` option has been introduced in Symfony 4.4.
 
-.. tip::
+.. caution::
 
-    When using ``null``, you may update the decorator's constructor in
-    order to make decorated dependency nullable. In this way, you will be able to
-    check the presence of the decorated service in other methods.
+    When using ``null``, you may have to update the decorator constructor in
+    order to make decorated dependency nullable.
 
-    .. code-block:: yaml
+    .. configuration-block::
 
-        App\Service\DecoratorService:
-            decorates: Acme\OptionalBundle\Service\OptionalService
-            decoration_on_invalid: null
-            arguments: ['@App\Service\DecoratorService.inner']
+        .. code-block:: yaml
 
-    .. code-block: php
+            App\Service\DecoratorService:
+                decorates: Acme\OptionalBundle\Service\OptionalService
+                decoration_on_invalid: null
+                arguments: ['@App\Service\DecoratorService.inner']
 
-        namespace App\Service;
+        .. code-block:: php
 
-        use Acme\OptionalBundle\Service\OptionalService;
+            namespace App\Service;
 
-        class DecoratorService
-        {
-            private $decorated;
+            use Acme\OptionalBundle\Service\OptionalService;
 
-            public function __construct(?OptionalService $decorated)
+            class DecoratorService
             {
-                $this->decorated = $decorated;
-            }
+                private $decorated;
 
-            public function tellInterestingStuff(): string
-            {
-                if (!$this->decorated) {
-                    return 'Just one interesting thing';
+                public function __construct(?OptionalService $decorated)
+                {
+                    $this->decorated = $decorated;
                 }
 
-                return $this->decorated->tellInterestingStuff().' + one more interesting thing';
+                public function tellInterestingStuff(): string
+                {
+                    if (!$this->decorated) {
+                        return 'Just one interesting thing';
+                    }
+
+                    return $this->decorated->tellInterestingStuff().' + one more interesting thing';
+                }
             }
-        }
 
-.. tip::
+.. note::
 
     Sometimes, you may want to add a compiler pass that creates service
     definitions on the fly. If you want to decorate such a service,