Persisting a side of 1:1 relationship using getReference to obtain id of another side - not working on 5.7.8

[merkator95]

Describe the bug

I've encountered an issue while trying to persist a new entity with one-to-one relationship with another, already persisted entity, using getReference() method to obtain reference to already-persisted side of 1:1 relationship.

I experienced this on update from 5.7.7 to 5.7.8.

To Reproduce

Repro repository link: https://github.com/merkator95/mikro-orm-entity-manager-get-reference-repro

Application manages two entities: Car and Driver. There is 1:1 relationship between those achieved via:

@Entity()
export class CarEntity extends CustomBaseEntity {
  @Property()
  brand: string;

  @OneToOne({ nullable: true, type: 'DriverEntity' })
  driver?: DriverEntity;
}

@Entity()
export class DriverEntity extends CustomBaseEntity {
  @OneToOne(() => CarEntity, (car) => car.driver, {
    orphanRemoval: true,
  })
  car: CarEntity;

  @Property()
  name: string;
}

a controller accepts Car brand and Car driver name as follows:

@Body() body: { brand: string; driverName: string },

A Car repository in its own class persists Car entity:

  async createCar(body: { brand: string; driverName: string }) {
    const record = new CarEntity();
    record.brand = body.brand;
    this.em.persist(record);
    await this.em.flush();
    const carId = record.id;
    return carId;
  }

and returns carId. A separate repository persists Driver entity and tries to create 1:1 relationship at that time:

  async persistDriverForCar(body: { driverName: string; carId: string }) {
   const record = new DriverEntity();
   record.name = body.driverName;
   const car = this.em.getReference(CarEntity, body.carId);
   record.car = car;
   this.em.persist(car);
   await this.em.flush();
 }

the getReference method successfully obtains reference to previously-persisted Car entity in both 5.7.7 and 5.7.8. The generated SQL, however, refers to the Car entity successfully in 5.7.7 but doesn't in 5.7.8.

Expected behavior

Persisting new entity with reference to another entity obtained via getReference method should allow for persistence of 1:1 relationship.

Additional context

Thank you so much for your amazing work on MikroORM!

Repro code is a bit of an example - I don't normally import domain modules to another modules in NestJS and use EventEmitter but I've done that here to simplify.

I do wonder if perhaps I was doing something against Mikro-ORM that I shouldn't have been but wanted to let you know in case this is an unintentional breaking change.

Versions

See package.json in repro.

Dependency	Version
node	20.1.0
typescript	5.1.3
mikro-orm	5.7.8 (works ?as intended on 5.7.7)
your-driver	postgresql

[B4nan]

Could you please turn this into a script instead of a nestjs app? Doesn't have to be a test case per se, but something I can just run and see it fail, instead of starting a web server and doing requests to it.

[merkator95]

Of course, thanks!
Scripted repro

Repro script works fine with SQLite but issue is reproduced with MikroORM 5.7.12 and postgres driver on pg15 (compose file in repo).

test('persisting 1:1 relation issue', async () => {
  const em = orm.em.fork();

  let car = em.create(CarEntity, { brand: 'skoda' });
  await em.persist(car).flush();

  const carReference = em.getReference(CarEntity, car.id);

  let driver = em.create(DriverEntity, { name: 'John Doe', car: carReference }); 
  const driverId = driver.id;
  await em.persist(driver).flush();

  const managedCar = car;
  expect(managedCar.driver).toBeDefined();
  expect(managedCar.driver.id).toStrictEqual(driverId); // Driver is defined and has an id in managed entity

  const foundCar = await em.findOneOrFail(CarEntity, { id: car.id });
  expect (foundCar).toBeDefined();
  expect (foundCar.driver).not.toBeNull(); // Fails, driver is null in found entity
});

What I got so far is:

1. Seems to be introduced with #7127ff6, #b5ab66bc works fine
2. If entity type doesn't have a version field, it works fine

  @Property({ version: true })
  version!: number; /// If this is commented out, issue is not reproduced

I've been looking into the internals of MikroORM and would love to try and offer a fix but I'm failing thus far - do let me know if there is anything else I can do.