[Feature Request]: Migrate to ES module syntax

[juliusmarminge]

Description

Would be better if Lucia supported module augmentation through ES module syntax:

declare module "lucia" {
  type Auth = OurAuth;
  interface DatabaseUserAttributes {
    github_username: string;
  }
}

This would improve monorepo support as we could put this declaration in a .ts file (.d.ts files kinda suck in monorepos) and better align with what other repos are doing:

• NextAuth:

declare module "next-auth" {
  interface Session {
    user: {
      id: string;
    } & DefaultSession["user"];
  }
}

• Tanstack Router:

export function createRouter() {
  const router = new Router( ... )

  return router;
}

declare module '@tanstack/router' {
  interface Register {
    router: ReturnType<typeof createRouter>
  }
}

As of now, I can't seem to get this to properly work in a monorepo as declaring types in .d.ts files don't propagate well through multiple packages

[hdwatts]

+1 - It would also be following Microsoft's recommendations

It is also worth noting that, for Node.js applications, modules are the default and we recommended modules over namespaces in modern code.

To note, @juliusmarminge I was able to get this working in a create-t3-turbo repo. I'm continuing to play around, but let me know if there's anything I'm potentially missing. The need for an additional .d.ts file isn't ideal, but I haven't been able to avoid it.

1. Create app.d.ts in packages/auth and follow the lucia recommendation

// File: /packages/auth/app.d.ts

/// <reference types="lucia" />
declare namespace Lucia {
  export type Auth = import("./src/lucia").Auth;
  // export type DatabaseUserAttributes =
  // import("./types").DatabaseUserAttributes;
  export interface DatabaseUserAttributes {
    username: string;
  }
  export interface DatabaseSessionAttributes {}
}

2. Confirm it works in the local auth package by creating an invalid database user attributes call
   File: /packages/auth/src/lucia.ts

3. In my nextjs app create an app.d.ts and reference one in @acme/auth

// File: /apps/nextjs/app.d.ts

/// <reference types="@acme/auth/app.d.ts" />

4. Create an invalid createUser call in my nextjs app
   File: /apps/nextjs/src/app/api/auth/signup/route.ts

[juliusmarminge]

Step 3 is a workaround around the problem though. Using modules it just works

[hdwatts]

Step 3 is a workaround around the problem though. Using modules it just works

Yup, definitely agreed modules are the way to go, hence my +1. Was just offering a workaround to help with your comment:

As of now, I can't seem to get this to properly work in a monorepo as declaring types in .d.ts files don't propagate well through multiple packages

[pilcrowOnPaper]

Hi, sorry for the late response. I tried it out and it looks to work fine. My only issue is that I'm not sure if I can support both namespaces and modules, in which case the change has to be part of v3.

[tobiasdiez]

Another idea would be to completely drop the augmentation and simply specify the types as generics to the adapter (if needed, e.g. prisma should be able to extract the type from the model).

[pilcrowOnPaper]

I've been playing around with this for a while, and yeah, I can't support Lucia namespace while making it optional (tsc will throw a Cannot find namespace error if you don't have it defined). It has to part of the next major release.

[hobo1618]

@hdwatts Any chance you could link to a working t3-turbo + lucia example please? It seems like I have everything set up properly (the types propagate across packages, as per your example) but I get a 500 error whenever I try to create a user as per the nextJS + app directory tutorial on the site. I am pretty new to this, so a working example to look over would be great. I would also be happy to write it up as a guide if you're interested, @pilcrowOnPaper

[pilcrowOnPaper]

Addressed in v3 (beta)