Lose database relations when use "loadRelationIds"

Lose database relations when use loadRelationIds

Steps to Reproduce

UserEntity:

@Entity({ name: 'users' })
export class User extends BaseEntity {
  @PrimaryGeneratedColumn('uuid')
  id!: string;

 @Column({ type: 'simple-json', default: {} })
  properties!: IProperties;

  @ManyToMany(() => Department, (department) => department.users)
  departments!: Department[] | string[];
}

DepartmentEntity:

@Entity({ name: 'departments', schema: config.database.schema.department })
export class Department extends BaseEntity {
  @PrimaryGeneratedColumn('uuid')
  id!: string;

  @Column()
  name!: string;

  @Column({ type: 'simple-json', default: {} })
  properties!: IProperties;

  // ----- Relations -----
  @ManyToMany(() => User, (user) => user.departments)
  @JoinTable({ name: 'user_has_departments' })
  users!: User[] | string[];
}

Controller:

 const user = await User.findOneOrFail({ where: { id: req.body.id }, loadRelationIds: true });

 if (req.body.points !== undefined) {
   user.properties.points = req.body.points;
 }

 const _user = await user.save();

Expected Behavior

When a model is loaded with loadRelationIds, all relations should be kept when saving without overwriting them.

Actual Behavior

If I save the user model as in the example, all department relations will be deleted.

My Environment

Dependency	Version
Operating System	docker (macOS)
Node.js version	v14.17.3
Typescript version	typescript@4.3.4
TypeORM version	typeorm@0.2.34

Additional Context

Should this behavior be correct, is there a workaround or a better way? I actually only work with relation ids.

Relevant Database Driver(s)

[ ] aurora-data-api
[ ] aurora-data-api-pg
[ ] better-sqlite3
[ ] cockroachdb
[ ] cordova
[ ] expo
[ ] mongodb
[ ] mysql
[ ] nativescript
[ ] oracle
[x] postgres
[ ] react-native
[ ] sap
[ ] sqlite
[ ] sqlite-abstract
[ ] sqljs
[ ] sqlserver

Are you willing to resolve this issue by submitting a Pull Request?

[ ] Yes, I have the time, and I know how to start.
[ ] Yes, I have the time, but I don't know how to start. I would need guidance.
[ ] No, I don't have the time, although I believe I could do it if I had the time...
[x] No, I don't have the time and I wouldn't even know how to start.

@imnotjames let's discuss loadRelationIds feature:

it feels like loadRelationIds is a weird feature to have. It's very old (came from 0.1.x era).
in order to make this feature work you must define your relations as: users!: User[] | string[]; - not the best UX, and everywhere it used user needs to put type guard checks
we have @RelationId decorator, but it's abandoned, I don't even know if still properly work

However I think sometimes it's useful feature, we just have ugly implementation. Right now I have 3 options in my mind:

fix current @RelationId state and make loadRelationIds to accept @RelationId-marked properties (and map to them):

Department.find({
   loadRelationIds: {
      userIds: true,
      photos: {
          albumIds: true
      }
   }
})

(same as ["userIds", "photos.albumIds"])

forget about relation ids - deprecate and remove this feature, user can simply load relation with "only user id":

DepartmentRepo.find({
   select: {
      users: {
         id: true
      }
   }
})

The result will contain the full "department" (by @future design all columns are selected until at least one column (not relation) isn't specified in the selection) + "users" property with only "id" inside.

I'm more thinking towards #2 because it doesn't bring any new functionality / complexity and does solve the problem of having only relation ids. Plus we don't need to add extra properties into the model.

typeorm / typeorm