Sequelize-typescript: v2.0.0: compiler error when using stricter typing Model attributes signature

[spinlud]

It seems there are still problems when defining models with stricter typing syntax on attributes, as already reported here https://github.com/RobinBuschmann/sequelize-typescript/issues/844.
The following code does not compile:

import { Optional } from 'sequelize';
import { Sequelize, Model } from "sequelize-typescript";

interface PersonAttributes {
    id: number;
    name: string;
    country?: string;
}

interface PersonCreationAttributes extends Optional<PersonAttributes, 'country'> {}

class Person extends Model<PersonAttributes, PersonCreationAttributes> implements PersonAttributes {
    id!: number;
    name!: string;
    country?: string;
}


(async () => {
    const sequelize =  new Sequelize({
        dialect: 'mysql',
        host: 'localhost',
        port: 3306,
        database: 'testdb',
        username: 'admin',
        password: 'admin',
        logQueryParameters: true,
        logging: true,
    });

    await sequelize.authenticate();

    await sequelize.addModels([Person]); // <-- compiler complains

    await sequelize.close();
})();

See also:

• https://github.com/sequelize/sequelize/pull/12405
• https://github.com/RobinBuschmann/sequelize-typescript/pull/868

[RobinBuschmann]

Hey @spinlud, thanks for reporting.

This doesn't seem to be a sequelize-typescript (only) issue. Similar code also throws a compiler error with pure sequelize:

import {Model} from 'sequelize';

class Test extends Model<{test: string}> {}
class Test2 extends Model {}

Test2.findAll({
  include: [Test], // fails here
});

```
TS2322: Type 'typeof Test' is not assignable to type 'Includeable'.   
Type 'typeof Test' is not assignable to type 'typeof Model'.     
Types of construct signatures are incompatible.       
Type 'new (values?: { test: string; } | undefined, options?: BuildOptions | undefined) => Test' is not assignable to type 'new (values?: TCreationAttributes | undefined, options?: BuildOptions | undefined) => Model'.        
Types of parameters 'values' and 'values' are incompatible.           
Type 'TCreationAttributes | undefined' is not assignable to type '{ test: string; } | undefined'.             
Type 'TCreationAttributes' is not assignable to type '{ test: string; } | undefined'.               
Type '{}' is not assignable to type '{ test: string; }'.                 
Type 'TCreationAttributes' is not assignable to type '{ test: string; }'.                   
Property 'test' is missing in type '{}' but required in type '{ test: string; }'.

Can anyone confirm?

The source of the problem seems to be the default value of generic TCreationAttributes in the definition of `Model`(sequelize).

See following example:
```ts
class Model<TModelAttributes = any, TCreationAttributes = TModelAttributes> {
    constructor(values?: TCreationAttributes) {}
}

class Test extends Model<{test: string}> {}

const addModel = (model: typeof Model) => {};

addModel(Test);

(see in typescript playground)
If we change TCreationAttributes = TModelAttributes to TCreationAttributes = any the error disappears. Which is strange, since TCreationAttributes should be inferred to any anyway.

I'm considering to just use type ModelCtor<M extends Model = any> = (new (...args: any[]) => M) instead of export declare type ModelCtor<M extends Model = any> = (new () => M) & ModelType;(so omitting ModelType, which is an alias for typeof Model) in sequelize-typescriot. It fixes the problem and should give "enough" type safety, I think. But the IncludeOptions und the Includable type of sequelize need to be fixed as well: https://github.com/sequelize/sequelize/blob/main/types/lib/model.d.ts#L394

[RoelVB]

@RobinBuschmann I can confirm I'm seeing the same error with just sequelize.
Your playground example is very interesting 🤔

Found a related issue on the sequelize side:
https://github.com/sequelize/sequelize/issues/12842

[AlexanderProd]

It seems like, for now the only workaround is to use //@ts-ignore where this happens, right?

[RoelVB]

@AlexanderProd Yes, I've been ignoring the errors, didn't run into any problems yet.
But... I guess PR #900 would fix this.

-edit-
Looks like 2.1.0 was released a couple of hours ago, I will check it out tomorrow.

[AlexanderProd]

@RoelVB
The problem still happens in 2.1.0 for me.

[RoelVB]

@AlexanderProd I just tested [email protected] with [email protected] and the problem described in this issue disappeared.

I only noticed the typings issue is still there with includes. This is waiting for https://github.com/sequelize/sequelize/pull/13010

[KapitanOczywisty]

Issue should be fixed in sequelize 6.6.1, please verify. @Divlo

[spinlud]

Apologies for the delay.
Yes I can confirm that with the new versions the problem is solved.

I've also updated sequelize-typescript-generator to leverage the strict mode as well.