HHH-10842 - Entity graph attribute node is ignored if the entity is mapped by the Primary Key column

- Add test case to replicate the issue

hibernate-core/src/test/java/org/hibernate/jpa/test/graphs/mapped_by_id/LoadGraphFindByIdTest.java

@@ -0,0 +1,127 @@
+/*
+ * 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.jpa.test.graphs.mapped_by_id;
+
+import java.util.HashMap;
+import java.util.Map;
+import javax.persistence.Entity;
+import javax.persistence.EntityGraph;
+import javax.persistence.EntityManager;
+import javax.persistence.FetchType;
+import javax.persistence.Id;
+import javax.persistence.MapsId;
+import javax.persistence.OneToOne;
+import javax.persistence.TypedQuery;
+import javax.persistence.criteria.CriteriaBuilder;
+import javax.persistence.criteria.CriteriaQuery;
+import javax.persistence.criteria.Root;
+
+import org.hibernate.jpa.test.BaseEntityManagerFunctionalTestCase;
+
+import org.hibernate.testing.FailureExpected;
+import org.hibernate.testing.TestForIssue;
+import org.junit.Assert;
+import org.junit.FixMethodOrder;
+import org.junit.Test;
+import org.junit.runners.MethodSorters;
+
+import static org.hibernate.testing.transaction.TransactionUtil.doInJPA;
+
+/**
+ * @author Oliver Breidenbach
+ */
+@FixMethodOrder(MethodSorters.NAME_ASCENDING)
+public class LoadGraphFindByIdTest extends BaseEntityManagerFunctionalTestCase {
+
+	@Override
+	protected Class<?>[] getAnnotatedClasses() {
+		return new Class[] {User.class, UserStatistic.class};
+	}
+
+	@Override
+	protected void afterEntityManagerFactoryBuilt() {
+		doInJPA( this::entityManagerFactory, em -> {
+			UserStatistic statistic = new UserStatistic();
+			statistic.id = 1L;
+			statistic.commentCount = 7;
+			User user = new User();
+			user.id = 1L;
+			user.userStatistic = statistic;
+
+			em.persist( statistic );
+			em.persist( user );
+		} );
+	}
+
+	@Test
+	@TestForIssue(jiraKey = "HHH-10842")
+	@FailureExpected( jiraKey = "HHH-10842" )
+	public void findByPrimaryKeyWithId() {
+		doInJPA( this::entityManagerFactory, em -> {
+			User result = em.find( User.class, 1L, createProperties( em ) );
+			Assert.assertNotNull( result.userStatistic.commentCount );
+		} );
+	}
+
+	@Test
+	@TestForIssue(jiraKey = "HHH-10842")
+	public void findByPrimaryKeyWithQuery() {
+		doInJPA( this::entityManagerFactory, em -> {
+			User result = createTypedQuery( em ).getSingleResult();
+			Assert.assertNotNull( result.userStatistic.commentCount );
+		} );
+	}
+
+	private TypedQuery<User> createTypedQuery(EntityManager em) {
+		CriteriaBuilder cb = em.getCriteriaBuilder();
+		CriteriaQuery<User> cq = cb.createQuery( User.class );
+		Root<User> root = cq.from( User.class );
+
+		cq.where( cb.equal( root.get( "id" ), 1L ) );
+		TypedQuery<User> tq = em.createQuery( cq );
+		tq.setHint( "javax.persistence.loadgraph", createEntityGraph( em ) );
+		return tq;
+	}
+
+	private Map<String, Object> createProperties(EntityManager em) {
+		Map<String, Object> properties = new HashMap<String, Object>();
+		properties.put(
+				"javax.persistence.loadgraph",
+				createEntityGraph( em )
+		);
+		return properties;
+	}
+
+	private EntityGraph<User> createEntityGraph(EntityManager em) {
+		EntityGraph<User> entityGraph = em.createEntityGraph( User.class );
+		entityGraph.addAttributeNodes( "userStatistic" );
+		return entityGraph;
+	}
+
+	@Entity(name = "UserStatistic")
+	public static class UserStatistic {
+
+		@Id
+		private Long id;
+
+		private Integer commentCount;
+	}
+
+	@Entity(name = "User")
+	public static class User {
+
+		@Id
+		private Long id;
+
+		private String name;
+
+		@OneToOne(fetch = FetchType.LAZY, optional = false)
+		@MapsId
+		private UserStatistic userStatistic;
+
+	}
+}