DDC-1184 - Improve error handling in AssignedIdGenerator

lib/Doctrine/ORM/Id/AssignedGenerator.php

@@ -47,9 +47,13 @@ public function generate(EntityManager $em, $entity)
         if ($class->isIdentifierComposite) {
             $idFields = $class->getIdentifierFieldNames();
             foreach ($idFields as $idField) {
-                $value = $class->getReflectionProperty($idField)->getValue($entity);
+                $value = $class->reflFields[$idField]->getValue($entity);
                 if (isset($value)) {
                     if (is_object($value)) {
+                        if (!$em->getUnitOfWork()->isInIdentityMap($value)) {
+                            throw ORMException::entityMissingForeignAssignedId($entity, $value);
+                        }
+
                         // NOTE: Single Columns as associated identifiers only allowed - this constraint it is enforced.
                         $identifier[$idField] = current($em->getUnitOfWork()->getEntityIdentifier($value));
                     } else {
@@ -64,6 +68,10 @@ public function generate(EntityManager $em, $entity)
             $value = $class->reflFields[$idField]->getValue($entity);
             if (isset($value)) {
                 if (is_object($value)) {
+                    if (!$em->getUnitOfWork()->isInIdentityMap($value)) {
+                        throw ORMException::entityMissingForeignAssignedId($entity, $value);
+                    }
+
                     // NOTE: Single Columns as associated identifiers only allowed - this constraint it is enforced.
                     $identifier[$idField] = current($em->getUnitOfWork()->getEntityIdentifier($value));
                 } else {

lib/Doctrine/ORM/ORMException.php

@@ -34,10 +34,25 @@ public static function missingMappingDriverImpl()
         return new self("It's a requirement to specify a Metadata Driver and pass it ".
             "to Doctrine\ORM\Configuration::setMetadataDriverImpl().");
     }
+
+    public static function entityMissingForeignAssignedId($entity, $relatedEntity)
+    {
+        return new self(
+            "Entity of type " . get_class($entity) . " has identity through a foreign entity " . get_class($relatedEntityClass) . ", " .
+            "however this entity has no ientity itself. You have to call EntityManager#persist() on the related entity " .
+            "and make sure it an identifier was generated before trying to persist '" . get_class($entity) . "'. In case " .
+            "of Post Insert ID Generation (such as MySQL Auto-Increment or PostgreSQL SERIAL) this means you have to call " .
+            "EntityManager#flush() between both persist operations."
+        );
+    }
 
     public static function entityMissingAssignedId($entity)
     {
-        return new self("Entity of type " . get_class($entity) . " is missing an assigned ID.");
+        return new self("Entity of type " . get_class($entity) . " is missing an assigned ID. " .
+            "The identifier generation strategy for this entity requires the ID field to be populated before ".
+            "EntityManager#persist() is called. If you want automatically generated identifiers instead " . 
+            "you need to adjust the metadata mapping accordingly."
+        );
     }
 
     public static function unrecognizedField($field)