HHH-12712 add test showing issue resolved

Author: gavinking

hibernate-core/src/test/java/org/hibernate/orm/test/query/onetoone/QueryOneToOneIsNullTest.java

@@ -0,0 +1,102 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ * Copyright Red Hat Inc. and Hibernate Authors
+ */
+package org.hibernate.orm.test.query.onetoone;
+
+import jakarta.persistence.CascadeType;
+import jakarta.persistence.Entity;
+import jakarta.persistence.Id;
+import jakarta.persistence.OneToOne;
+import org.hibernate.testing.orm.junit.EntityManagerFactoryScope;
+import org.hibernate.testing.orm.junit.JiraKey;
+import org.hibernate.testing.orm.junit.Jpa;
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+@Jpa(annotatedClasses = {QueryOneToOneIsNullTest.Parent.class,
+						QueryOneToOneIsNullTest.Child.class})
+@JiraKey("HHH-12712")
+public class QueryOneToOneIsNullTest {
+	@Test
+	public void test(EntityManagerFactoryScope scope) {
+		scope.inTransaction(entityManager -> {
+			var parent1 = new Parent(1);
+			new Child(3, parent1);
+			entityManager.persist(parent1);
+			var parent2 = new Parent(2);
+			entityManager.persist(parent2);
+		});
+
+		scope.inTransaction(entityManager -> {
+			var query = entityManager.createQuery("from Parent p where p.child is null", Parent.class);
+			var parents = query.getResultList();
+			assertThat(parents).hasSize(1);
+			assertThat(parents).element(0).extracting(Parent::getId).isEqualTo(2L);
+		});
+	}
+
+	@Entity(name = "Parent")
+	static class Parent {
+		@Id
+		private long id;
+
+		@OneToOne(mappedBy = "parent", cascade = CascadeType.ALL)
+		private Child child;
+
+		Parent() {}
+
+		public Parent(long id) {
+			this.id = id;
+		}
+
+		public long getId() {
+			return id;
+		}
+
+		public Child getChild() {
+			return child;
+		}
+
+		void setChild(Child child) {
+			this.child = child;
+		}
+
+		@Override
+		public String toString() {
+			return "Parent [id=" + id + ", child=" + child + "]";
+		}
+	}
+
+
+	@Entity(name = "Child")
+	static class Child {
+		@Id
+		private long id;
+
+		@OneToOne
+		private Parent parent;
+
+		Child() {}
+
+		public Child(long id, Parent parent) {
+			this.id = id;
+			setParent(parent);
+		}
+
+		public Parent getParent() {
+			return parent;
+		}
+
+		public void setParent(Parent parent) {
+			this.parent = parent;
+			parent.setChild(this);
+		}
+
+		@Override
+		public String toString() {
+			return "Child [id=" + id + "]";
+		}
+	}
+}