How to satisfy `Server.adapter()` with `typeof Adapter`?

[MickL]

Describe the bug
I am not sure if this is just a question or the typings are not correct, but it seems impossible for me to satisfy the Server.adapter() function which is defined as:

adapter(v: typeof Adapter): Server;

I tried:

createAdapter(): Adapter {}
createAdapter(): typeof Adapter {}
createAdapter(): ReturnType<Adapter> {}
createAdapter(): ReturnType<typeof Adapter> {}

Looking at socket.ioredis it just has no return type / returns any :/

[ironicbrew]

I think you may be importing Adapter from the wrong place, imported it improperly or it may be incorrectly declared wherever you are importing it from.

The exact type errors you are getting would be helpful here along with a more complete snippet/repo I could use to reproduce this error.

I figure this is the jist of what you are trying to accomplish except with your own custom Adapter class? The below throws no type issues on my end

import { Server } from "socket.io";
import {Adapter} from "socket.io-adapter";

function createAdapter(): typeof Adapter {
    return Adapter;
}

new Server(3333).adapter(createAdapter())

[darrachequesne]

@MickL I think you are right, the typings are not correct.

The adapter argument should be a function that takes a namespace and returns an Adapter instance. Example:

• the in-memory adapter: https://github.com/socketio/socket.io-adapter/blob/2.1.0/lib/index.ts#L30-L33
• the redis adapter: https://github.com/socketio/socket.io-redis/blob/6.0.1/lib/index.ts#L82-L84

[grubstarstar]

Isn't the problem that the types are using typeof Adapter instead of just using Adapter as it's already a type as it's a class.

e.g. If it change it to this:

adapter(): Adapter | undefined;
adapter(v: Adapter): this;
adapter(v?: Adapter): Adapter | undefined | this;

[darrachequesne]

@grubstarstar the adapter function does not take a Adapter instance, but a function that takes a namespace and returns an Adapter instance (there is one Adapter instance per namespace, created here), so I don't think this would work.

I guess we should rather have something like type AdapterConstructor = typeof Adapter | ((nsp: Namespace) => Adapter);, to match the current implementation, but the Typescript compiler does not agree.

[MickL]

IMO the existing adapters should have a return type. Then they would run in the same problem as I did or solve my question.

Currently they dont have any return type thats why they throw no error:
https://github.com/socketio/socket.io-redis/blob/4dae265a740129b0d86f16418319b902a0648a3c/lib/index.ts#L70

Also the docs are wrong. The function does not return a RedisAdapter, instead it returns a function that may create a RedisAdapter:
https://github.com/socketio/socket.io-redis/blob/4dae265a740129b0d86f16418319b902a0648a3c/lib/index.ts#L66

[darrachequesne]

This should be fixed by 891b187.

Please reopen if needed.