feature #36389 [DI] allow decorators to reference their decorated ser…

…vice using the special `.inner` id (nicolas-grekas)

This PR was merged into the 5.1-dev branch.

Discussion
----------

[DI] allow decorators to reference their decorated service using the special `.inner` id

| Q             | A
| ------------- | ---
| Branch?       | master
| Bug fix?      | no
| New feature?  | yes
| Deprecations? | no
| Tickets       | -
| License       | MIT
| Doc PR        | -

Right now, when one wants to decorate a service, one needs to reference the decorated service using `foo.inner`, where `foo` is the id of the decorating service.

There are two issues with this IMHO:
- it's weird to have to repeat the name of declaring service inside of it;
- it doesn't play well with child definitions.

In this PR, I propose to use `.inner` to fix both issues.

Before:
```yaml
services:
  decorating_service:
    arguments: [@decorating_service.inner]
    decorates: decorated_service
```

After:
```yaml
services:
  decorating_service:
    arguments: [@.inner]
    decorates: decorated_service
```

Commits
-------

7b6f767 [DI] allow decorators to reference their decorated service using the special `.inner` id

src/Symfony/Component/DependencyInjection/CHANGELOG.md

@@ -4,6 +4,7 @@ CHANGELOG
 5.1.0
 -----
 
+ * allow decorators to reference their decorated service using the special `.inner` id
  * added support to autowire public typed properties in php 7.4
  * added support for defining method calls, a configurator, and property setters in `InlineServiceConfigurator`
  * added possibility to define abstract service arguments

src/Symfony/Component/DependencyInjection/Compiler/DecoratorServicePass.php

@@ -24,8 +24,15 @@
  * @author Fabien Potencier <fabien@symfony.com>
  * @author Diego Saint Esteben <diego@saintesteben.me>
  */
-class DecoratorServicePass implements CompilerPassInterface
+class DecoratorServicePass extends AbstractRecursivePass
 {
+    private $innerId = '.inner';
+
+    public function __construct(?string $innerId = '.inner')
+    {
+        $this->innerId = $innerId;
+    }
+
     public function process(ContainerBuilder $container)
     {
         $definitions = new \SplPriorityQueue();
@@ -49,6 +56,10 @@ public function process(ContainerBuilder $container)
             if (!$renamedId) {
                 $renamedId = $id.'.inner';
             }
+
+            $this->currentId = $renamedId;
+            $this->processValue($definition);
+
             $definition->innerServiceId = $renamedId;
             $definition->decorationOnInvalid = $invalidBehavior;
 
@@ -96,4 +107,13 @@ public function process(ContainerBuilder $container)
             $container->setAlias($inner, $id)->setPublic($public)->setPrivate($private);
         }
     }
+
+    protected function processValue($value, bool $isRoot = false)
+    {
+        if ($value instanceof Reference && $this->innerId === (string) $value) {
+            return new Reference($this->currentId, $value->getInvalidBehavior());
+        }
+
+        return parent::processValue($value, $isRoot);
+    }
 }

src/Symfony/Component/DependencyInjection/Tests/Compiler/DecoratorServicePassTest.php

@@ -16,6 +16,7 @@
 use Symfony\Component\DependencyInjection\Compiler\DecoratorServicePass;
 use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\ContainerInterface;
+use Symfony\Component\DependencyInjection\Reference;
 
 class DecoratorServicePassTest extends TestCase
 {
@@ -242,6 +243,20 @@ public function testProcessLeavesServiceLocatorTagOnOriginalDefinition()
         $this->assertEquals(['bar' => ['attr' => 'baz'], 'foobar' => ['attr' => 'bar']], $container->getDefinition('baz')->getTags());
     }
 
+    public function testGenericInnerReference()
+    {
+        $container = new ContainerBuilder();
+        $container->register('foo');
+
+        $container->register('bar')
+            ->setDecoratedService('foo')
+            ->setProperty('prop', new Reference('.inner'));
+
+        $this->process($container);
+
+        $this->assertEquals(['prop' => new Reference('bar.inner')], $container->getDefinition('bar')->getProperties());
+    }
+
     protected function process(ContainerBuilder $container)
     {
         $pass = new DecoratorServicePass();