bug symfony#27633 [Messenger] Fixed MessengerPass::guessHandledClasses return type (massimilianobraglia)

This PR was squashed before being merged into the 4.2-dev branch (closes symfony#27633).

Discussion
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[Messenger] Fixed MessengerPass::guessHandledClasses return type

| Q             | A
| ------------- | ---
| Branch?       | 4.1
| Bug fix?      | yes
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| License       | MIT

Good evening! Thanks for this amazing project.
I've searched over issues and PRs and I didn't find anything about this bug I found. Excuse me if this is a duplicate.

If you create an implementation of `MessageSubscriberInterface` and yield results from `getHandledMessages` method, a TypeError (like the following) will be raised:

```TypeError: Return value of Symfony\Component\Messenger\DependencyInjection\MessengerPass::guessHandledClasses() must be of the type array, object returned```

`MessengerPass::guessHandledClasses` return type declared is `array`, when `MessageSubscriberInterface::guessHandledClasses()`'s return type is `iterable`.

In this PR I have fixed the return type and wrote a simple test for it.

I am looking forward your review. Thank you.
Massimiliano

Commits
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0b1c825 [Messenger] Fixed MessengerPass::guessHandledClasses return type

Author: nicolas-grekas

src/Symfony/Component/Messenger/DependencyInjection/MessengerPass.php

@@ -185,7 +185,7 @@ private function registerHandlers(ContainerBuilder $container, array $busIds)
         }
     }
 
-    private function guessHandledClasses(\ReflectionClass $handlerClass, string $serviceId): array
+    private function guessHandledClasses(\ReflectionClass $handlerClass, string $serviceId): iterable
     {
         if ($handlerClass->implementsInterface(MessageSubscriberInterface::class)) {
             if (!$handledMessages = $handlerClass->getName()::getHandledMessages()) {

src/Symfony/Component/Messenger/Tests/DependencyInjection/MessengerPassTest.php

@@ -274,6 +274,23 @@ public function testItRegistersSenderWithoutTagName()
         $this->assertEquals(array(AmqpSender::class => new Reference(AmqpSender::class)), $container->getDefinition('messenger.sender_locator')->getArgument(0));
     }
 
+    public function testItShouldNotThrowIfGeneratorIsReturnedInsteadOfArray()
+    {
+        $container = $this->getContainerBuilder($busId = 'message_bus');
+        $container
+            ->register(HandlerWithGenerators::class, HandlerWithGenerators::class)
+            ->addTag('messenger.message_handler')
+        ;
+
+        (new MessengerPass())->process($container);
+
+        $handlerLocatorDefinition = $container->getDefinition($container->getDefinition("$busId.messenger.handler_resolver")->getArgument(0));
+        $handlerMapping = $handlerLocatorDefinition->getArgument(0);
+
+        $this->assertArrayHasKey('handler.'.DummyMessage::class, $handlerMapping);
+        $this->assertArrayHasKey('handler.'.SecondMessage::class, $handlerMapping);
+    }
+
     /**
      * @expectedException \Symfony\Component\DependencyInjection\Exception\RuntimeException
      * @expectedExceptionMessage Invalid sender "app.messenger.sender": class "Symfony\Component\Messenger\Tests\DependencyInjection\InvalidSender" must implement interface "Symfony\Component\Messenger\Transport\SenderInterface".
@@ -685,6 +702,23 @@ public function __invoke()
     }
 }
 
+class HandlerWithGenerators implements MessageSubscriberInterface
+{
+    public static function getHandledMessages(): iterable
+    {
+        yield DummyMessage::class => 'dummyMethod';
+        yield SecondMessage::class => 'secondMessage';
+    }
+
+    public function dummyMethod()
+    {
+    }
+
+    public function secondMessage()
+    {
+    }
+}
+
 class UselessMiddleware implements MiddlewareInterface
 {
     public function handle($message, callable $next)