HHH-13815 - TransientObjectException when merging a bidirectional one-to-many with orphan delete

hibernate-core/src/main/java/org/hibernate/collection/spi/AbstractPersistentCollection.java

@@ -1295,8 +1295,8 @@ protected static <E> Collection<E> getOrphans(
 		// iterate over the *old* list
 		for ( E old : oldElements ) {
 			if ( !currentSaving.contains( old ) ) {
-				final Object oldId = ForeignKeys.getEntityIdentifierIfNotUnsaved( entityName, old, session );
-				if ( !currentIds.contains( useIdDirect ? oldId : new TypedValue( idType, oldId ) ) ) {
+				final Object oldId = ForeignKeys.getEntityIdentifier( entityName, old, session );
+				if ( oldId != null && !currentIds.contains( useIdDirect ? oldId : new TypedValue( idType, oldId ) ) ) {
 					res.add( old );
 				}
 			}

hibernate-core/src/test/java/org/hibernate/orm/test/merge/BidirectionalOneToManyMergeTest.java

@@ -0,0 +1,178 @@
+/*
+ * SPDX-License-Identifier: LGPL-2.1-or-later
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.orm.test.merge;
+
+import org.hibernate.testing.orm.junit.JiraKey;
+import org.junit.Before;
+import org.junit.Test;
+
+import jakarta.persistence.CascadeType;
+import jakarta.persistence.Entity;
+import jakarta.persistence.FetchType;
+import jakarta.persistence.GeneratedValue;
+import jakarta.persistence.GenerationType;
+import jakarta.persistence.Id;
+import jakarta.persistence.JoinColumn;
+import jakarta.persistence.ManyToOne;
+import jakarta.persistence.OneToMany;
+import java.util.ArrayList;
+import java.util.List;
+
+import static org.hibernate.testing.transaction.TransactionUtil.doInJPA;
+
+/**
+ * @author Lisandro Fernandez (kelechul at gmail dot com)
+ */
+@JiraKey("HHH-13815")
+public class BidirectionalOneToManyMergeTest extends org.hibernate.orm.test.jpa.BaseEntityManagerFunctionalTestCase {
+
+	@Override
+	protected Class<?>[] getAnnotatedClasses() {
+		return new Class<?>[]{
+				Post.class,
+				PostComment.class,
+		};
+	}
+
+	@Before
+	public void setUp() {
+		doInJPA(this::entityManagerFactory, entityManager -> {
+			entityManager.persist(
+					new Post("High-Performance Java Persistence").setId(1L)
+			);
+		});
+	}
+
+	@Test
+	public void testMerge() {
+		doInJPA(this::entityManagerFactory, entityManager -> {
+			Post post = entityManager.find(Post.class, 1L);
+			post.addComment(new PostComment("This post rocks!", post));
+			post.getComments().isEmpty();
+			entityManager.merge(post);
+		});
+	}
+
+	@Entity
+	public static class Post {
+
+		@Id
+		private Long id;
+
+		private String title;
+
+		@OneToMany(mappedBy = "post", cascade = CascadeType.ALL, orphanRemoval = true)
+		private List<PostComment> comments = new ArrayList<>();
+
+		public Post() {
+		}
+
+		public Post(String title) {
+			this.title = title;
+		}
+
+		public Long getId() {
+			return id;
+		}
+
+		public Post setId(Long id) {
+			this.id = id;
+			return this;
+		}
+
+		public String getTitle() {
+			return title;
+		}
+
+		public Post setTitle(String title) {
+			this.title = title;
+			return this;
+		}
+
+		public List<PostComment> getComments() {
+			return comments;
+		}
+
+		private Post setComments(List<PostComment> comments) {
+			this.comments = comments;
+			return this;
+		}
+
+		public Post addComment(PostComment comment) {
+			comments.add(comment);
+			comment.setPost(this);
+
+			return this;
+		}
+
+		public Post removeComment(PostComment comment) {
+			comments.remove(comment);
+			comment.setPost(null);
+
+			return this;
+		}
+	}
+
+	@Entity
+	public static class PostComment {
+
+		@Id
+		@GeneratedValue(strategy = GenerationType.IDENTITY)
+		private Long id;
+
+		private String review;
+
+		@ManyToOne(fetch = FetchType.LAZY)
+		@JoinColumn(name = "post_id")
+		private Post post;
+
+		public PostComment() {
+		}
+
+		public PostComment(String review, Post post) {
+			this.review = review;
+			this.post = post;
+		}
+
+		public Long getId() {
+			return id;
+		}
+
+		public PostComment setId(Long id) {
+			this.id = id;
+			return this;
+		}
+
+		public String getReview() {
+			return review;
+		}
+
+		public PostComment setReview(String review) {
+			this.review = review;
+			return this;
+		}
+
+		public Post getPost() {
+			return post;
+		}
+
+		public PostComment setPost(Post post) {
+			this.post = post;
+			return this;
+		}
+
+		@Override
+		public boolean equals(Object o) {
+			if (this == o) return true;
+			if (!(o instanceof PostComment)) return false;
+			return id != null && id.equals(((PostComment) o).getId());
+		}
+
+		@Override
+		public int hashCode() {
+			return 31;
+		}
+	}
+}