Disallow lifecycle callbacks on embedded classes

UPGRADE.md

@@ -1,5 +1,10 @@
 # Upgrade to 3.0
 
+## BC BREAK: Lifecycle callback mapping on embedded classes is now explicitly forbidden
+
+Lifecycle callback mapping on embedded classes produced no effect, and is now
+explicitly forbidden to point out mistakes.
+
 ## BC BREAK: The `NOTIFY` change tracking policy is removed
 
 You should use `DEFERRED_EXPLICIT` instead.

lib/Doctrine/ORM/Mapping/ClassMetadata.php

@@ -2044,13 +2044,7 @@ public function getLifecycleCallbacks(string $event): array
     public function addLifecycleCallback(string $callback, string $event): void
     {
         if ($this->isEmbeddedClass) {
-            Deprecation::trigger(
-                'doctrine/orm',
-                'https://github.com/doctrine/orm/pull/8381',
-                'Registering lifecycle callback %s on Embedded class %s is not doing anything and will throw exception in 3.0',
-                $event,
-                $this->name,
-            );
+            throw MappingException::illegalLifecycleCallbackOnEmbeddedClass($callback, $this->name);
         }
 
         if (isset($this->lifecycleCallbacks[$event]) && in_array($callback, $this->lifecycleCallbacks[$event], true)) {

lib/Doctrine/ORM/Mapping/MappingException.php

@@ -498,6 +498,19 @@ public static function lifecycleCallbackMethodNotFound(string $className, string
         return new self("Entity '" . $className . "' has no method '" . $methodName . "' to be registered as lifecycle callback.");
     }
 
+    /** @param class-string $className */
+    public static function illegalLifecycleCallbackOnEmbeddedClass(string $event, string $className): self
+    {
+        return new self(sprintf(
+            <<<'EXCEPTION'
+            Context: Attempt to register lifecycle callback "%s" on embedded class "%s".
+            Problem: Registering lifecycle callbacks on embedded classes is not allowed.
+            EXCEPTION,
+            $event,
+            $className,
+        ));
+    }
+
     public static function entityListenerClassNotFound(string $listenerName, string $className): self
     {
         return new self(sprintf('Entity Listener "%s" declared on "%s" not found.', $listenerName, $className));

tests/Doctrine/Tests/ORM/Mapping/ClassMetadataTest.php

@@ -1014,6 +1014,20 @@ public function testRejectsEmbeddableWithoutValidClassName(): void
             'columnPrefix' => false,
         ]);
     }
+
+    public function testItAddingLifecycleCallbackOnEmbeddedClassIsIllegal(): void
+    {
+        $metadata                  = new ClassMetadata(self::class);
+        $metadata->isEmbeddedClass = true;
+
+        $this->expectException(MappingException::class);
+        $this->expectExceptionMessage(<<<'EXCEPTION'
+            Context: Attempt to register lifecycle callback "foo" on embedded class "Doctrine\Tests\ORM\Mapping\ClassMetadataTest".
+            Problem: Registering lifecycle callbacks on embedded classes is not allowed.
+            EXCEPTION);
+
+        $metadata->addLifecycleCallback('foo', 'bar');
+    }
 }
 
 #[MappedSuperclass]