Cascade on bidirectional @OneToOne with @MapsId

I work on spring boot 2.1.1.RELEASE, hibernate 5.3.7.FINAL

Rules are, that user can have no phone (phone is nullable in user) but, phone can't exist without a user (user is not null in phone).

Entities:

@Entity
public class Phone {
    
   @Id
   private Long id;
    
   @OneToOne
   @MapsId
   @JoinColumn(name = "id")
   private User user;
    
   public Long getId() {
       return id;
   }
   public void setId(final Long id) {
       this.id = id;
   }
    
   public User getUser() {
      return user;
   }
   public void setUser(final User user) {
      this.user = user;
   }
}
        
@Entity
public class User {

   @Id
   @GeneratedValue(strategy = GenerationType.IDENTITY)
   private Long id;
    
   @OneToOne(mappedBy = "user", cascade = CascadeType.ALL, orphanRemoval = true)
   private Phone phone;
    
   public Long getId() {
       return id;
   }
   public void setId(final Long id) {
       this.id = id;
   }
    
   public Phone getPhone() {
       return phone;
   }
   public void setPhone(final Phone phone) {
       this.phone = phone;
   }
}

Controller:

@RestController
@RequestMapping
public class UserController {
    
   private final UserService userService;
    
   public UserController(final UserService userService) {
       this.userService = userService;
   }
    
   @GetMapping("/demo")
   public void createUserAndAddPhone() {
       final User user = new User();
       userService.save(user);
       final Phone phone = new Phone();
    
       phone.setUser(user);
       user.setPhone(phone);
       userService.update(user);
   }
}

Repository:

public interface UserRepository  extends PagingAndSortingRepository<User, Long> {
}

Serivce:

@Service
public class UserService {
    
   private final UserRepository userRepository;
    
   public UserService(final UserRepository userRepository) {
       this.userRepository = userRepository;
   }
    
   @Transactional
   public void save(final User user) {
       userRepository.save(user);
   }
    
   @Transactional
   public void update(final User user) {
       userRepository.save(user);
   }
}

Tables:

CREATE TABLE `phone` (
   `id` bigint(20) NOT NULL,
   PRIMARY KEY (`id`)
);
    
CREATE TABLE `user` (
   `id` bigint(20) NOT NULL AUTO_INCREMENT,
   PRIMARY KEY (`id`)
)

application yml:

spring:
   datasource:
      url: jdbc:mysql://localhost:3308/demo?characterEncoding=utf8&useSSL=false&serverTimezone=UTC&useLegacyDatetimeCode=false&allowPublicKeyRetrieval=true
      username: root
      password: 123456
      driver-class-name: com.mysql.jdbc.Driver
   jpa:
      database-platform: org.hibernate.dialect.MySQL5Dialect
      hibernate:
         ddl-auto: validate

pom xml:

<?xml version="1.0" encoding="UTF-8"?>
    <project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  	<modelVersion>4.0.0</modelVersion>
   	<parent>
   		<groupId>org.springframework.boot</groupId>
   		<artifactId>spring-boot-starter-parent</artifactId>
   		<version>2.1.1.RELEASE</version>
   		<relativePath/> <!-- lookup parent from repository -->
   	</parent>

   	<groupId>com.example</groupId>
   	<artifactId>demo</artifactId>
   	<version>0.0.1-SNAPSHOT</version>
   	<name>demo</name>
   	<description>Demo project for Spring Boot</description>
    
   	<properties>
   		<java.version>1.8</java.version>
   	</properties>
    
   	<dependencies>
   		<dependency>
   			<groupId>org.springframework.boot</groupId>
   			<artifactId>spring-boot-starter</artifactId>
   		</dependency>
   		<dependency>
   			<groupId>org.springframework.boot</groupId>
   			<artifactId>spring-boot-starter-data-jpa</artifactId>
   		</dependency>
   		<dependency>
   			<groupId>org.springframework.boot</groupId>
   			<artifactId>spring-boot-starter-web</artifactId>
   		</dependency>
   		<dependency>
   			<groupId>com.google.code.findbugs</groupId>
   			<artifactId>jsr305</artifactId>
   			<version>2.0.1</version>
   		</dependency>
   		<dependency>
   			<groupId>mysql</groupId>
   			<artifactId>mysql-connector-java</artifactId>
   			<version>5.1.46</version>
  			<scope>runtime</scope>
   		</dependency>
   	</dependencies>
    
   	<build>
   		<plugins>
   			<plugin>
   				<groupId>org.springframework.boot</groupId>
   				<artifactId>spring-boot-maven-plugin</artifactId>
   			</plugin>
   		</plugins>
   	</build>
</project>

Call GET http://localhost:8080/demo gives me an error:

> org.hibernate.id.IdentifierGenerationException: attempted to assign id
> from null one-to-one property [com.example.demo.Phone.user]

When I comment out userService.save(user);, it works and generates:

insert into `user` 
values ( )

-- Generated identifier: 13, using strategy: org.hibernate.id.ForeignGenerator
                
insert into `phone` (`id`)  values (?)
-- Binding parameter [1] as [BIGINT] - [13]

but if the user is persisted and then updated, it doesn't work (raises the above exception)

Ah, in the end, this is a hibernate bug (HHH-12436).

It is reproducible in a pure hibernate application by the following use case:

Session session = sessionFactory.openSession();

Transaction tr1 = session.beginTransaction();
User user = new User();
session.persist(user);
tr1.commit();

Transaction tr2 = session.beginTransaction();
Phone newPhone = new Phone();
user.setPhone(newPhone);
newPhone.setUser(user);
session.merge(user);
tr2.commit();

session.close();

As you can see from the above link it is fixed in hibernate 5.4 branch.

P.S. I was able to reproduce the problem in the latest 5.3 version (5.3.18.Final)