Order by doesn’t work with embeddable fields inside populated entity

[olegkomendat]

Describe the bug

I'm trying to order data by embeddable fields inside the populated entity, and all the time I getting this error:

DriverException: Cannot read properties of null (reading 'toLowerCase')
    at PostgreSqlExceptionConverter.convertException (#Project/node_modules/@mikro-orm/core/platforms/ExceptionConverter.js:8:16)
    at PostgreSqlExceptionConverter.convertException (#Project/node_modules/@mikro-orm/postgresql/PostgreSqlExceptionConverter.js:48:22)
    at PostgreSqlDriver.convertException (#Project/node_modules/@mikro-orm/core/drivers/DatabaseDriver.js:331:54)
    at #Project/node_modules/@mikro-orm/core/drivers/DatabaseDriver.js:335:24
    at processTicksAndRejections (node:internal/process/task_queues:95:5)
    at PostgreSqlDriver.find (#Project/node_modules/@mikro-orm/knex/AbstractSqlDriver.js:68:24)
    at SqlEntityManager.find (#Project/node_modules/@mikro-orm/core/EntityManager.js:144:25)
    at PromotionalCodesService.getManyEntities (#Project/src/api-modules/common/snapshot-crud-service/snapshot-crud-service.service.ts:100:29)
    at PromotionalCodesService.getPromotionalCodesEntitiesList (#Project/src/api-modules/promotional-codes/promotional-codes.service.ts:171:19)

previous TypeError: Cannot read properties of null (reading 'toLowerCase')
    at PostgreSqlPlatform.getOrderByExpression (#Project/node_modules/@mikro-orm/knex/AbstractSqlPlatform.js:83:40)
    at QueryBuilderHelper.getQueryOrderFromObject (#Project/node_modules/@mikro-orm/knex/query/QueryBuilderHelper.js:514:47)
    at QueryBuilderHelper.getQueryOrder (#Project/node_modules/@mikro-orm/knex/query/QueryBuilderHelper.js:482:21)
    at #Project/node_modules/@mikro-orm/knex/query/QueryBuilderHelper.js:480:46
    at Array.flatMap (<anonymous>)
    at QueryBuilderHelper.getQueryOrder (#Project/node_modules/@mikro-orm/knex/query/QueryBuilderHelper.js:480:28)
    at #Project/node_modules/@mikro-orm/knex/query/QueryBuilder.js:474:44
    at Function.runIfNotEmpty (#Project/node_modules/@mikro-orm/core/utils/Utils.js:753:13)
    at QueryBuilder.getKnexQuery (#Project/node_modules/@mikro-orm/knex/query/QueryBuilder.js:473:22)
    at QueryBuilder.toQuery (#Project/node_modules/@mikro-orm/knex/query/QueryBuilder.js:514:26)

It works well if I use some other not embeddable fields like string, date, etc, but it doesn't work with embeddable (object).
In the old version 5, it works perfectly, but after the upgrade, it doesn't work as expected.

Reproduction

To reproduce, try to use order by for embeddable field inside the populated entity.

@Embeddable()
export class DateRangeEMM {
  @Property()
  startDate: Date;

  @Property()
  endDate: Date;
}

@Entity({ tableName: 'promotional_codes_snapshots' })
export class PromotionalCodeEM {
  @Embedded(() => DateRangeEMM)
  activeRange: DateRangeEMM;
}

@Entity({ tableName: 'actual_snapshots' })
export class ActualSnapshotEM extends CommonEM {
  @ManyToOne(() => PromotionalCodeEM, { nullable: true })
  actualPromotionalCode?: PromotionalCodeEM;
}

await this.actualSnapshotsService.repository.find(
  {},
  {
    populate: ['actualPromotionalCode'],
    orderBy: {
      actualPromotionalCode: {
        activeRange: { startDate: 'ASC' },
      },
    },
  }
);

What driver are you using?

@mikro-orm/postgresql

MikroORM version

6.1.12

Node.js version

v18.12.1

Operating system

macos

Validations

• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn't already an issue that reports the same bug to avoid creating a duplicate.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Slack.
• The provided reproduction is a minimal reproducible example of the bug.