Embeddables: fieldName option is ignored

[edorgeville]

Describe the bug
Now that #1948 is implemented and merged (thank you so much 🙌) I am trying to migrate some code that was previously using ObjectIds to embeddables + m:1.
It seems that the fieldName parameter in ManyToOne is ignored.

To Reproduce

Code

import { Embeddable, Embedded, Entity, ManyToOne, MikroORM, PrimaryKey, Property } from '@mikro-orm/core';
import type { SqliteDriver } from '@mikro-orm/sqlite';

@Entity()
export class User {

  @PrimaryKey()
  id!: number;

  @Property()
  name: string = '';

  constructor(name: string) {
    this.name = name;
  }

}

@Embeddable()
export class FamilyMember {

  @Property()
  relation: string = 'brother';

  @ManyToOne(() => User, { eager: true, fieldName: 'user_id' }) // we want to save our relationship inside a `user_id` field
  user!: User;

}

@Entity()
export class Family {

  @PrimaryKey()
  id!: number;

  @Embedded(() => FamilyMember, { array: true })
  members: FamilyMember[] = [];

}

describe('GH issue 1003', () => {

  let orm: MikroORM<SqliteDriver>;

  beforeAll(async () => {
    orm = await MikroORM.init({
      entities: [FamilyMember, User, Family],
      dbName: ':memory:',
      type: 'sqlite',
    });
    await orm.getSchemaGenerator().createSchema();
  });

  afterAll(async () => {
    await orm.close(true);
  });

  test(`GH issue 2165`, async () => {
    const family = new Family();

    const dad = new FamilyMember();
    dad.relation = 'dad';
    dad.user = new User('John');
    family.members.push(dad);

    const mom = new FamilyMember();
    mom.relation = 'mom';
    mom.user = new User('Jane');
    family.members.push(mom);

    console.log(family);

    await orm.em.persistAndFlush(family);

    const nativeResults: Family[] = await orm.em.createQueryBuilder(Family).execute();

    // Relationship is saved in `user` field instead of `user_id`
    console.log(nativeResults[0].members);
  });

});

Also available in repro-repo here: https://github.com/edorgeville/mikro-orm-embeddable-m1-fieldName

Expected behavior
Expected relationships to be saved according to fieldName property. Instead, it uses the class property name.

Versions

Dependency	Version
node	v14.17.3
typescript	v10.0.0
@mikro-orm/core	^5.0.0-dev.250
@mikro-orm/mongodb	^5.0.0-dev.250

[B4nan]

I've been struggling with fixing this for quite some time unfortunately, almost got it fixed but it would break em.create() as it is also using hydrator :/

Need to move to other things now as I can't stall v5 release for one bug. Will try to get back to it later.

[edorgeville]

Not a showstopper for me, our current ObjectId workaround will do in the meantime. Thanks for the update, good luck for 5.0 release 🙏

[titivuk]

Hello
Any updates on this?

[B4nan]

Closing as fixed in v6 via #4866