From cd81b337bc5a5e56b01551da5fa849e8898a93a1 Mon Sep 17 00:00:00 2001
From: Andrea Boriero <andrea@hibernate.org>
Date: Tue, 14 Nov 2023 11:59:27 +0100
Subject: [PATCH] HHH-17408 Unproxying leads to uninitialized one-to-one
 associations in some cases involving polymorphism

---
 .../internal/StatefulPersistenceContext.java    | 10 +++-------
 .../graph/entity/AbstractEntityInitializer.java | 17 ++++++++++-------
 2 files changed, 13 insertions(+), 14 deletions(-)

diff --git a/hibernate-core/src/main/java/org/hibernate/engine/internal/StatefulPersistenceContext.java b/hibernate-core/src/main/java/org/hibernate/engine/internal/StatefulPersistenceContext.java
index 9781c46e5c..0ed803d56c 100644
--- a/hibernate-core/src/main/java/org/hibernate/engine/internal/StatefulPersistenceContext.java
+++ b/hibernate-core/src/main/java/org/hibernate/engine/internal/StatefulPersistenceContext.java
@@ -895,14 +895,10 @@ public class StatefulPersistenceContext implements PersistenceContext {
 
 	@Override
 	public Object proxyFor(EntityHolder holder) throws HibernateException {
-		final Object entity = holder.getEntity();
-		final EntityEntry e = getEntry( entity );
-		final EntityPersister persister;
-		if ( e == null || !( persister = e.getPersister() ).hasProxy() ) {
-			return entity;
-		}
 		final Object proxy = holder.getProxy();
-		return proxy != null? narrowProxy( proxy, persister, e.getEntityKey(), entity ) : entity;
+		return proxy != null && holder.getDescriptor().hasProxy()
+				? narrowProxy( proxy, holder.getDescriptor(), holder.getEntityKey(), holder.getEntity() )
+				: holder.getEntity();
 	}
 
 	@Override
diff --git a/hibernate-core/src/main/java/org/hibernate/sql/results/graph/entity/AbstractEntityInitializer.java b/hibernate-core/src/main/java/org/hibernate/sql/results/graph/entity/AbstractEntityInitializer.java
index d0e407821e..4ee090ffde 100644
--- a/hibernate-core/src/main/java/org/hibernate/sql/results/graph/entity/AbstractEntityInitializer.java
+++ b/hibernate-core/src/main/java/org/hibernate/sql/results/graph/entity/AbstractEntityInitializer.java
@@ -398,6 +398,7 @@ public abstract class AbstractEntityInitializer extends AbstractFetchParentAcces
 					this
 			);
 			isOwningInitializer = holder.getEntityInitializer() == this;
+
 			if ( entityInstance == null ) {
 				resolveEntityInstance( rowProcessingState, holder, entityKey.getIdentifier() );
 			}
@@ -527,6 +528,12 @@ public abstract class AbstractEntityInitializer extends AbstractFetchParentAcces
 					}
 					this.isInitialized = true;
 				}
+				else if ( isOwningInitializer ) {
+					// Resolve the real entity instance for this proxy early so that potentially nested calls
+					// for eager association loading can leverage the real instance if needed
+					assert holder.getEntity() == null;
+					resolveEntityInstance( entityIdentifier, rowProcessingState );
+				}
 			}
 		}
 		else {
@@ -754,13 +761,9 @@ public abstract class AbstractEntityInitializer extends AbstractFetchParentAcces
 			final PersistenceContext persistenceContext = session.getPersistenceContextInternal();
 			if ( lazyInitializer != null ) {
 				final EntityHolder holder = persistenceContext.getEntityHolder( entityKey );
-				Object instance = holder.getEntity();
-				if ( instance == null ) {
-					instance = resolveInstance(
-							entityKey.getIdentifier(),
-							holder,
-							rowProcessingState
-					);
+				final Object instance = holder.getEntity();
+				assert instance != null : "The real entity instance must be resolved in the `resolveInstance()` phase";
+				if ( holder.getEntityInitializer() == this ) {
 					initializeEntity( instance, rowProcessingState );
 				}
 				lazyInitializer.setImplementation( instance );