HHH-12439 : Merging of new entities can fail depending on cascade order

hibernate-core/src/main/java/org/hibernate/event/internal/MergeContext.java

@@ -231,17 +231,6 @@ class MergeContext implements Map {
 			throw new NullPointerException( "null merge and managed entities are not supported by " + getClass().getName() );
 		}
 
-		// Detect invalid 'managed entity' -> 'managed entity' mappings where key != value
-		if ( managedToMergeEntityXref.containsKey( mergeEntity ) ) {
-			if ( managedToMergeEntityXref.get( mergeEntity ) != mergeEntity ) {
-				throw new IllegalStateException(
-						"MergeContext#attempt to create managed -> managed mapping with different entities: "
-								+ printEntity( mergeEntity ) + "; " + printEntity(
-								managedEntity )
-				);
-			}
-		}
-
 		Object oldManagedEntity = mergeToManagedEntityXref.put( mergeEntity, managedEntity );
 		Boolean oldOperatedOn = mergeEntityToOperatedOnFlagMap.put( mergeEntity, isOperatedOn );
 		// If managedEntity already corresponds with a different merge entity, that means

hibernate-core/src/main/java/org/hibernate/type/EntityType.java

@@ -322,13 +322,6 @@ public abstract class EntityType extends AbstractType implements AssociationType
 			return null;
 		}
 		Object cached = copyCache.get( original );
-		if ( cached == null ) {
-			// Avoid creation of invalid managed -> managed mapping in copyCache when traversing
-			// cascade loop (@OneToMany(cascade=ALL) with associated @ManyToOne(cascade=ALL)) in entity graph
-			if ( copyCache.containsValue( original ) ) {
-				cached = original;
-			}
-		}
 		if ( cached != null ) {
 			return cached;
 		}
@@ -338,11 +331,20 @@ public abstract class EntityType extends AbstractType implements AssociationType
 			}
 			if ( session.getContextEntityIdentifier( original ) == null &&
 					ForeignKeys.isTransient( associatedEntityName, original, Boolean.FALSE, session ) ) {
+				// original is transient; it is possible that original is a "managed" entity that has
+				// not been made persistent yet, so check if copyCache contains original as a "managed" value
+				// that corresponds with some "merge" value.
+				if ( copyCache.containsValue( original ) ) {
+					return original;
+				}
+				else {
+					// the transient entity is not "managed"; add the merge/managed pair to copyCache
 					final Object copy = session.getEntityPersister( associatedEntityName, original )
 							.instantiate( null, session );
 					copyCache.put( original, copy );
 					return copy;
 				}
+			}
 			else {
 				Object id = getIdentifier( original, session );
 				if ( id == null ) {

hibernate-core/src/test/java/org/hibernate/test/ops/MergeManagedAndCopiesAllowedTest.java

@@ -0,0 +1,155 @@
+/*
+ * Hibernate, Relational Persistence for Idiomatic Java
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later.
+ * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
+ */
+package org.hibernate.test.ops;
+
+import java.util.HashSet;
+import java.util.Set;
+import javax.persistence.CascadeType;
+import javax.persistence.Entity;
+import javax.persistence.FetchType;
+import javax.persistence.GeneratedValue;
+import javax.persistence.Id;
+import javax.persistence.JoinColumn;
+import javax.persistence.OneToMany;
+import javax.persistence.OneToOne;
+
+import org.hibernate.cfg.Configuration;
+
+import org.hibernate.testing.junit4.BaseCoreFunctionalTestCase;
+import org.junit.Test;
+
+import static org.hibernate.testing.transaction.TransactionUtil.doInHibernate;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertSame;
+
+/**
+ * A  1 ------------> 1 B 1 ----------> 1 C
+ *                      1                 1
+ *                      |                 |
+ *                      |                 |
+ *                      V                 V
+ *                      1                 N
+ *                      D 1------------>N E
+ *
+ *
+ * @author Gail Badner
+ */
+public class MergeManagedAndCopiesAllowedTest extends BaseCoreFunctionalTestCase {
+
+	protected Class[] getAnnotatedClasses() {
+		return new Class[]{
+				A.class,
+				B.class,
+				C.class,
+				D.class,
+				E.class
+		};
+	}
+
+	protected void configure(Configuration cfg) {
+		super.configure( cfg );
+		cfg.setProperty( "hibernate.event.merge.entity_copy_observer", "allow"  );
+	}
+
+	@Test
+	public void testIt() {
+		A a = new A();
+		a.b = new B();
+		a.b.d = new D();
+		a.b.d.dEs.add( new E() );
+
+		doInHibernate(
+				this::sessionFactory, session -> {
+					session.persist( a );
+				}
+		);
+
+		doInHibernate(
+				this::sessionFactory, session -> {
+					A aGet= session.get( A.class, a.id );
+					aGet.b.c = new C();
+					Set<E> copies = new HashSet<>();
+					for ( E e : aGet.b.d.dEs ) {
+						copies.add ( new E( e.id, "description" ) );
+					}
+					aGet.b.c.cEs.addAll( copies );
+					session.merge( aGet );
+				}
+		);
+
+		doInHibernate(
+				this::sessionFactory, session -> {
+					A aGet= session.get( A.class, a.id );
+					E e = aGet.b.c.cEs.iterator().next();
+					assertSame( e, aGet.b.d.dEs.iterator().next() );
+					assertEquals( "description", e.description );
+				}
+		);
+	}
+
+	@Entity(name = "A")
+	public static class A {
+		@Id
+		@GeneratedValue
+		private int id;
+
+		@OneToOne(fetch=FetchType.EAGER, cascade = CascadeType.ALL)
+		private B b;
+	}
+
+	@Entity(name = "B")
+	public static class B {
+		@Id
+		@GeneratedValue
+		private int id;
+
+		@OneToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
+		private C c;
+
+		@OneToOne(fetch = FetchType.EAGER, cascade = CascadeType.ALL)
+		private D d;
+	}
+
+	@Entity(name = "C")
+	public static class C {
+		@Id
+		@GeneratedValue
+		private int id;
+
+		@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
+		@JoinColumn(nullable = true)
+		private Set<E> cEs = new HashSet<>();
+	}
+
+
+	@Entity(name = "D")
+	public static class D {
+		@Id
+		@GeneratedValue
+		private int id;
+
+		@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
+		@JoinColumn(nullable = false)
+		private Set<E> dEs = new HashSet<>();
+	}
+
+	@Entity(name = "E")
+	public static class E {
+		@Id
+		@GeneratedValue
+		private int id;
+
+		private String description;
+
+		E() {}
+
+		E(int id, String description) {
+			this.id = id;
+			this.description = description;
+		}
+	}
+}