HHH-19688 add test for issue

Author: gavinking

hibernate-core/src/test/java/x/IdClassSingleOneToOneTest.java

@@ -0,0 +1,104 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package x;
+
+import jakarta.persistence.Entity;
+import jakarta.persistence.FetchType;
+import jakarta.persistence.Id;
+import jakarta.persistence.IdClass;
+import jakarta.persistence.OneToOne;
+import org.hibernate.testing.orm.junit.DomainModel;
+import org.hibernate.testing.orm.junit.SessionFactory;
+import org.hibernate.testing.orm.junit.SessionFactoryScope;
+import org.junit.jupiter.api.Test;
+
+import java.util.Objects;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+
+
+@DomainModel( annotatedClasses = {
+		IdClassSingleOneToOneTest.EntityA.class,
+		IdClassSingleOneToOneTest.EntityB.class,
+} )
+@SessionFactory
+public class IdClassSingleOneToOneTest {
+
+	@Test
+	public void test(SessionFactoryScope scope) {
+		scope.getSessionFactory();
+		scope.inTransaction( session -> {
+			EntityA entityA = new EntityA(3);
+			EntityB entityB = new EntityB( entityA );
+			entityA.entityB = entityB;
+			session.persist( entityA );
+			session.persist( entityB );
+			assertEquals( new EntityBId(3),
+					session.getIdentifier( entityB ) );
+		} );
+		scope.inTransaction( session -> {
+			EntityB entityB = session.find( EntityB.class, new EntityBId(3) );
+			assertNotNull( entityB );
+		} );
+	}
+
+	@Entity( name = "EntityA" )
+	static class EntityA {
+
+		@Id
+		private Integer id;
+
+		@OneToOne( mappedBy = "entityA", fetch = FetchType.LAZY )
+		private EntityB entityB;
+
+		public EntityA() {
+		}
+
+		public EntityA(Integer id) {
+			this.id = id;
+		}
+
+	}
+
+	@IdClass( EntityBId.class )
+	@Entity( name = "EntityB" )
+	static class EntityB {
+
+		@Id
+		@OneToOne( fetch = FetchType.LAZY )
+		private EntityA entityA;
+
+		public EntityB() {
+		}
+
+		public EntityB(EntityA entityA) {
+			this.entityA = entityA;
+		}
+
+	}
+
+	static class EntityBId {
+		private final Integer entityA;
+
+		EntityBId() {
+			entityA = null;
+		}
+		EntityBId(Integer entityA) {
+			this.entityA = entityA;
+		}
+
+		@Override
+		public boolean equals(Object o) {
+			return o instanceof EntityBId entityBId
+				&& Objects.equals( entityA, entityBId.entityA );
+		}
+
+		@Override
+		public int hashCode() {
+			return Objects.hashCode( entityA );
+		}
+	}
+}