HHH-19892 signature of Session.merge() accepting EntityGraph

hibernate-core/src/main/java/org/hibernate/Session.java

@@ -706,18 +706,21 @@ public interface Session extends SharedSessionContract, EntityManager {
 	/**
 	 * Copy the state of the given object onto the persistent object with the same
 	 * identifier. If there is no persistent instance currently associated with
-	 * the session, it will be loaded. Return the persistent instance. If the
-	 * given instance is unsaved, save a copy and return it as a newly persistent
-	 * instance. The given instance does not become associated with the session.
-	 * This operation cascades to associated instances if the association is mapped
-	 * with {@link jakarta.persistence.CascadeType#MERGE}.
+	 * the session, it is loaded using the given {@link EntityGraph}, which is
+	 * interpreted as a load graph. Return the persistent instance. If the given
+	 * instance is unsaved, save a copy and return it as a newly persistent instance.
+	 * The given instance does not become associated with the session. This operation
+	 * cascades to associated instances if the association is mapped with
+	 * {@link jakarta.persistence.CascadeType#MERGE}.
 	 *
 	 * @param object a detached instance with state to be copied
-	 * @param loadGraph entity graph interpreted as a load graph
+	 * @param loadGraph an entity graph interpreted as a load graph
 	 *
 	 * @return an updated persistent instance
+	 *
+	 * @since 7.0
 	 */
-	<T> T merge( T object, EntityGraph<?> loadGraph);
+	<T> T merge(T object, EntityGraph<? super T> loadGraph);
 
 	/**
 	 * Make a transient instance persistent and mark it for later insertion in the

hibernate-core/src/main/java/org/hibernate/engine/spi/SessionDelegatorBaseImpl.java

@@ -846,7 +846,7 @@ public <T> T merge(String entityName, T object) {
 	}
 
 	@Override
-	public <T> T merge(T object, EntityGraph<?> loadGraph) {
+	public <T> T merge(T object, EntityGraph<? super T> loadGraph) {
 		return delegate.merge( object, loadGraph );
 	}
 

hibernate-core/src/main/java/org/hibernate/engine/spi/SessionLazyDelegator.java

@@ -213,7 +213,7 @@ public <T> T merge(String entityName, T object) {
 	}
 
 	@Override
-	public <T> T merge(T object, EntityGraph<?> loadGraph) {
+	public <T> T merge(T object, EntityGraph<? super T> loadGraph) {
 		return this.lazySession.get().merge( object, loadGraph );
 	}
 

hibernate-core/src/main/java/org/hibernate/internal/SessionImpl.java

@@ -758,7 +758,7 @@ public <T> T merge(String entityName, T object) {
 	}
 
 	@Override
-	public <T> T merge(T object, EntityGraph<?> loadGraph) {
+	public <T> T merge(T object, EntityGraph<? super T> loadGraph) {
 		final var effectiveEntityGraph = loadQueryInfluencers.getEffectiveEntityGraph();
 		try {
 			effectiveEntityGraph.applyGraph( (RootGraphImplementor<?>) loadGraph, GraphSemantic.LOAD );

hibernate-core/src/test/java/org/hibernate/orm/test/entitygraph/LoadGraphMergeTest.java

@@ -19,9 +19,7 @@
 import org.junit.jupiter.api.BeforeAll;
 import org.junit.jupiter.api.Test;
 
-import java.util.Collections;
 
-import static org.hibernate.jpa.SpecHints.HINT_SPEC_LOAD_GRAPH;
 import static org.junit.jupiter.api.Assertions.assertFalse;
 import static org.junit.jupiter.api.Assertions.assertTrue;
 
@@ -58,21 +56,11 @@ public static void init(EntityManagerFactoryScope scope) {
 	@Test
 	public void testGrandChildHasNotBeenInitializedByMerge(EntityManagerFactoryScope scope) {
 		Parent parent = scope.fromTransaction( entityManager ->
-				entityManager.find(
-						Parent.class,
-						PARENT_ID_1,
-						Collections.singletonMap(
-								HINT_SPEC_LOAD_GRAPH,
-								entityManager.getEntityGraph( "parent.child" ) ) )
+				entityManager.find( LoadGraphMergeTest_.Parent_._parent_child, PARENT_ID_1 )
 		);
 
 		Parent parent2 = scope.fromTransaction( entityManager ->
-				entityManager.find(
-						Parent.class,
-						PARENT_ID_2,
-						Collections.singletonMap(
-								HINT_SPEC_LOAD_GRAPH,
-								entityManager.getEntityGraph( "parent.child" ) ) )
+				entityManager.find( LoadGraphMergeTest_.Parent_._parent_child, PARENT_ID_2)
 		);
 
 		scope.inTransaction( entityManager -> {
@@ -81,8 +69,7 @@ public void testGrandChildHasNotBeenInitializedByMerge(EntityManagerFactoryScope
 
 			Session session = entityManager.unwrap( Session.class );
 
-			Parent mergedParent = session.merge( parent,
-					entityManager.getEntityGraph( "parent.child" ) );
+			Parent mergedParent = session.merge( parent, LoadGraphMergeTest_.Parent_._parent_child );
 
 			Child child = mergedParent.getChild();
 			assertTrue( Hibernate.isInitialized( child ) );
@@ -113,7 +100,7 @@ public void testChildHasNotBeenInitializedByMerge(EntityManagerFactoryScope scop
 			assertFalse( Hibernate.isInitialized( child1 ) );
 
 			Session session = entityManager.unwrap( Session.class );
-			Parent mergedParent = session.merge( parent, session.createEntityGraph( "parent" ) );
+			Parent mergedParent = session.merge( parent, LoadGraphMergeTest_.Parent_._parent );
 
 			Child child = mergedParent.getChild();
 			assertFalse( Hibernate.isInitialized( child ),