Cannot read properties of undefined (reading '__data') on entity creation with one-to-one relation

[denis-maiorov-brightsec]

Describe the bug
Creating and persisting entities with OneToOne relation on Entity that uses owning Entity primary key as their primary.
Worked with 5.5.0 version, fails with 5.6.16

Stack trace

/Users/domayorov/brightsec/mikro-orm-one-to-one-persist-bug/node_modules/@mikro-orm/core/entity/EntityHelper.js:174
            delete (0, wrap_1.helper)(other).__data[prop.name];
                                            ^

TypeError: Cannot read properties of undefined (reading '__data')
    at Function.propagateOneToOne (/Users/domayorov/brightsec/mikro-orm-one-to-one-persist-bug/node_modules/@mikro-orm/core/entity/EntityHelper.js:174:45)
    at Function.propagate (/Users/domayorov/brightsec/mikro-orm-one-to-one-persist-bug/node_modules/@mikro-orm/core/entity/EntityHelper.js:162:30)
    at OrderEntity.set [as summary] (/Users/domayorov/brightsec/mikro-orm-one-to-one-persist-bug/node_modules/@mikro-orm/core/entity/EntityHelper.js:145:30)
    at OrderEntity.set (/Users/domayorov/brightsec/mikro-orm-one-to-one-persist-bug/node_modules/@mikro-orm/core/entity/EntityHelper.js:81:41)
    at eval (eval at createFunction (/Users/domayorov/brightsec/mikro-orm-one-to-one-persist-bug/node_modules/@mikro-orm/core/utils/Utils.js:780:20), <anonymous>:13:22)
    at Function.callCompiledFunction (/Users/domayorov/brightsec/mikro-orm-one-to-one-persist-bug/node_modules/@mikro-orm/core/utils/Utils.js:791:20)
    at ObjectHydrator.hydrate (/Users/domayorov/brightsec/mikro-orm-one-to-one-persist-bug/node_modules/@mikro-orm/core/hydration/ObjectHydrator.js:26:23)
    at EntityFactory.hydrate (/Users/domayorov/brightsec/mikro-orm-one-to-one-persist-bug/node_modules/@mikro-orm/core/entity/EntityFactory.js:187:27)
    at EntityFactory.create (/Users/domayorov/brightsec/mikro-orm-one-to-one-persist-bug/node_modules/@mikro-orm/core/entity/EntityFactory.js:53:14)
    at SqlEntityManager.create (/Users/domayorov/brightsec/mikro-orm-one-to-one-persist-bug/node_modules/@mikro-orm/core/EntityManager.js:826:41)

To Reproduce
Steps to reproduce the behavior:

1. Create owning Entity and inverse Entity
2. Associate entities using OneToOne with inversed Entity using owning Entity id as primary key
3. Try to create new entity with prefilled primary keys and persist

Reproduction example: https://github.com/denis-maiorov-brightsec/mikro-orm-4254

Expected behavior
Both entities are persisted

Additional context
Runtime error shown in stack trace section

Versions

Dependency	Version
node	16
typescript	4.8.3
mikro-orm	5.6.16
your-driver	postgresql

[B4nan]

Please provide complete reproduction as code, I need to see what exactly are you doing, how your entities are defined as well as the ORM configuration.

[denis-maiorov-brightsec]

@B4nan updated original comment, here's repo with reproduction https://github.com/denis-maiorov-brightsec/mikro-orm-4254

[B4nan]

One quick note - you dont need to call em.persist, that's handled by em.create automatically, and you can use it to create the full entity graph in one step:

orm.em.create(OrderEntity, {
  id: 4,
  summary: {
    orderId: 4,
    prop: '123',
  },
});
await orm.em.flush();

I guess it will be caused by the mapToPk option.