Cannot assign object to lazy relation (expects promise)

Issue type:

(I’m really not sure if this is an issue with the library, documentation, or just my understanding)

[ x ] question [ x ] bug report [ ] feature request [ x ] documentation issue

Database system/driver:

[ ] cordova [ ] mongodb [ ] mssql [ ] mysql / mariadb [ ] oracle [ x ] postgres [ ] sqlite [ ] sqljs [ ] react-native

TypeORM version:

[ x ] latest [ ] @next [ ] 0.x.x (or put your version here)

Steps to reproduce or a small repository showing the problem:

Entities

@Entity()
export class Role {

  @ManyToOne(type => Store, store => store.roles)
  store: Promise<Store>;
}

@Entity()
export class Store {

  @OneToMany(type => Role, role => role.store)
  roles: Promise<Role[]>;
}

This code fails because the types expect store to be a promise

  const r = roleRepository.create();
  r.store = await storeRepository.findOne();
  await roleRepository.save(r);

This code fails because the implementation expects an object (not a promise)

  const r = roleRepository.create();
  r.store = storeRepository.findOne();
  await roleRepository.save(r);

This code works, but is clearly ugly / hacky

  const r = roleRepository.create();
  r.store = <any>(await storeRepository.findOne());
  await roleRepository.save(r);

What is the correct way to achieve this?

[itslenny]

Another way to achieve this is to change the entity to…

@Entity()
export class Role {

  @ManyToOne(type => Store, store => store.roles)
  store: Promise<Store> | Store;
}

However, this isn’t explained in the documentation anywhere. The section about this says to just use store: Promise<Store> which would never work for assigning values as far as I can tell.

This solution seems dirty too. It allows me to bypass the compile time type check and do things that will break at run time due to invalid type (i.e. I could still pass a promise to role.store or try to read it as an object when querying).

Update:

After trying this I realized that with the entity typed like this If I do role.store it is undefined.

Unless I’m missing something this is a fatal flaw with the design of lazy relations which makes it entirely unusable.

[davidfrtala]

Hello I’m experiencing this issue. My code

// "type" here is async/awaited, so it's no longer a promise
const type = await typeRepo.findOneOrFail(typeId)

const entity = notificationRepo.create({
  name,
  eventId,
  type: Promise.resolve(type),
})

return notificationRepo.save(entity)

If I print an entity I get this, which is wrong and fails upon save

Notification {
  name: 'FooBar',
  eventId: 'ABC1',
  __type__: NotificationType {} 
}

Only workaround is manualy set property, like this

const entity = notificationRepo.create({
  ...
})

entity.type = Promise.resolve(type),

return notificationRepo.save(entity)

entity printed

Notification {
  name: 'FooBar',
  eventId: 'ABC1',
  __promise_type__:
   Promise {
     NotificationType {
     id: 1,
     prefix: 'ABC' 
    } 
  }
}

It’s working, but it’s it’s too ugly…