A weird TypeScript error when lazy loading a related entity

[irshadahmad21]

Package version

21.5.1

Describe the bug

I have relations with the simplified version being this

import { BaseModel, belongsTo, column } from '@adonisjs/lucid/orm';
import type { BelongsTo } from '@adonisjs/lucid/types/relations';

class Client extends BaseModel {
	@column({ isPrimary: true })
	declare id: number;
}

class Project extends BaseModel {
	@column({ isPrimary: true })
	declare id: number;

	@column()
	declare name: string;

	@column()
	declare clientId: string;

	@belongsTo(() => Client)
	declare client: BelongsTo<typeof Client>;
}

class Task extends BaseModel {
	@column({ isPrimary: true })
	declare id: number;

	@column()
	declare projectId: string;

	@belongsTo(() => Project)
	declare project: BelongsTo<typeof Project>;

	async getProjectName(this: Task) {
		await this.load('project');
		return this.project.name;
	}
}

I see an error on that this.load('project') call.

No overload matches this call.
  Overload 1 of 2, '(callback: (preloader: PreloaderContract<Task>) => void): Promise<void>', gave the following error.
    Argument of type 'string' is not assignable to parameter of type '(preloader: PreloaderContract<Task>) => void'.
  Overload 2 of 2, '(relation: undefined, callback?: ((builder: never) => void) | undefined): Promise<void>', gave the following error.
    Argument of type '"project"' is not assignable to parameter of type 'undefined'.

It used to work fine in version 20.4.0. May be something changed in version 21.

Reproduction repo

No response

[RomainLanz]

Hey there! 👋🏻

This reminds me of an older TypeScript bug: microsoft/TypeScript#37778.

I'm not certain they're related, but does the issue persist if you downgrade Lucid or TypeScript? Also, could you create a minimal repository demonstrating the problem?

[thetutlage]

This reminds me of an older TypeScript bug: microsoft/TypeScript#37778.

Its the same issue, since it was never fixed in the first place by the TypeScript team

[irshadahmad21]

It may not be related to that bug because it works fine in Lucid v20 but breaks in v21.

Here are the minimal reproducible setups

With v20 (Build succeeds)
https://stackblitz.com/edit/vitejs-vite-8houbyjt?file=package.json

With v21 (Build fails)
https://stackblitz.com/edit/vitejs-vite-xcvgsb1y?file=package.json

[irshadahmad21]

I think the bug was introduced in 532b9cb.

If you change

extends ModelRelations<LucidModel, LucidModel>

to

extends ModelRelations<infer _, infer __>

in

type ExtractModelRelations<Model extends LucidRow> = {
    [Key in keyof Model]: Model[Key] extends ModelRelations<LucidModel, LucidModel> ? Key : never;
}[keyof Model];

That may fix the issue. I don't know if that can have any other implications.