loadRelationCountAndMap doesn't infer (Typescript)

[alielkhateeb]

Issue Description

If my entities look like this:

@Entity({ name: 'libraries' })
export class Library {
  @PrimaryGeneratedColumn('uuid')
  id: string;

  @OneToMany(() => Book, (book) => book.library)
  books: Book[];
}

@Entity({ name: 'books' })
export class Book {
  @PrimaryGeneratedColumn('uuid')
  id: string;

  @ManyToOne(() => Library, (lib) => lib.books)
  @JoinColumn({ name: 'library_id' })
  library: Library;
}

And my Library Dto looks like this:

export class LibraryDto {
  @IsUUID()
  id: string;

  @IsNumber()
  bookCount: number;
}

How can I make this function work with typescript?
async findLibraryById(libraryId: string): Promise<LibraryDto>

Running code like this:

    const library = await this.librariesRepository
      .createQueryBuilder('library')
      .loadRelationCountAndMap('library.bookCount', 'library.books')
      .where({ id })
      .getOne();

    console.log(library.bookCount); // This will not work, Typescript complains that bookCount doesn't exist on Library

Expected Behavior

I expect I'm able to reach the property I selected using loadRelationCountAndMap

Actual Behavior

There is absolutely no way I found to bypass the typescript issue:
Property 'bookCount' does not exist on type 'Library'

My Environment

Dependency	Version
Operating System
Node.js version	16.17.0
Typescript version	4.6.4
TypeORM version	0.3.9

Relevant Database Driver(s)

DB Type	Reproducible
aurora-mysql	I don't know
aurora-postgres	I don't know
better-sqlite3	I don't know
cockroachdb	I don't know
cordova	I don't know
expo	I don't know
mongodb	I don't know
mysql	I don't know
nativescript	I don't know
oracle	I don't know
postgres	YES
react-native	I don't know
sap	I don't know
spanner	I don't know
sqlite	I don't know
sqlite-abstract	I don't know
sqljs	I don't know
sqlserver	I don't know

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, but I can support (using donations) development.
• ✅ No, I don’t have the time and I’m okay to wait for the community / maintainers to resolve this issue.

[denysovvl]

+1

[NicolasPotierA]

+1