TypeORM import of Relation fails

Question

I am using typeorm in a nodejs project with esm. I need to use the Relation wrapper to avoid circular dependencies.

I get this error when i try to use the relation wrapper:

import { Column, Entity, OneToOne, PrimaryGeneratedColumn, Relation } from 'typeorm';
                                                           ^^^^^^^^
SyntaxError: The requested module 'typeorm' does not provide an export named 'Relation'

The code file:

import { Column, Entity, OneToOne, PrimaryGeneratedColumn, Relation } from 'typeorm';
import { Vehicle } from './vehicle';

@Entity({ name: 'vehicle_default_values' })
export class VehicleDefaultValues {
    @PrimaryGeneratedColumn({ unsigned: true })
    id: number;

    @Column({ type: 'int', unsigned: true, unique: true })
    model: number;

    @Column({ type: 'float', default: 550 })
    maxFuel: number;

    @Column({ type: 'boolean', default: false })
    isElectric: boolean;

    @Column({ type: 'float', default: 0.008 })
    fuelConsumption: number;

    @Column({ type: 'mediumint', unsigned: true, default: 200 })
    maxSpeed: number;

    @Column({ type: 'mediumint', unsigned: true, default: 50 })
    trunkVolume: number;

    @Column({ type: 'text', nullable: true })
    vehicleExtras: string;

    @OneToOne(() => Vehicle, (vehicle) => vehicle.vehicleDefaultValues)
    vehicle: Relation<Vehicle>;
}

Used version of typeorm: 0.3.7

Answer 1

This is probably happening because the types are not included when converting the file to javascript. The imports Column, Entity, OneToOne, PrimaryGeneratedColumn are all functions, while the import Relation is a type.

With typescript 3.8 or newer you can explicitly tell that you are importing types like this:

import { Column, Entity, OneToOne, PrimaryGeneratedColumn } from 'typeorm';
import type { Relation } from 'typeorm';

or with typescript 4.5 or newer you can do the same like this:

import { Column, Entity, OneToOne, PrimaryGeneratedColumn, type Relation } from 'typeorm';