Use Custom types in a namespace that exports a function

Question

I like to write a index.d.ts file for https://github.com/LionC/express-basic-auth

But I am somehow stuck in how to declare the types for callbacks within the options object.

declare module "express-basic-auth" { 


  import {Handler, Request} from "express";

  function  ExpressBasicAuthorizer(username: string, password: string): boolean;
  function ExpressBasicAuthResponseHandler(req: Request): string|object;

  interface ExpressBasicAuthUsers {
    [username: string]: string;
  }

  interface ExpressBasicAuthOptions {
    challenge?: boolean;
    users?: ExpressBasicAuthUsers; // does not only allow string:string but other ex. string: number too
    authorizer?: ExpressBasicAuthorizer; // *does not work*
    authorizeAsync?: boolean;
    unauthorizedResponse?:  ExpressBasicAuthResponseHandler|string|object; // *does not work*
    realm?: ExpressBasicAuthResponseHandler|string; // *does not work*
  }

  function expressBasicAuth(options?:ExpressBasicAuthOptions): Handler;

  export = expressBasicAuth;

}

I get: error TS2304: Cannot find name 'ExpressBasicAuthorizer'

How can I declare ExpressBasicAuthorizer and ExpressBasicAuthResponseHandler so that it works?

Answer 1

The ExpressBasicAuthorizer and ExpressBasicAuthResponseHandler in this case needs to be declared as a "type" and not a "function". Try this:

declare module "express-basic-auth" {
    import { Handler, Request } from "express";

    type ExpressBasicAuthorizer = (username: string, password: string) => boolean;
    type ExpressBasicAuthResponseHandler = (req: Request) => string | object;

    interface ExpressBasicAuthUsers {
        [username: string]: string | number;
    }

    interface ExpressBasicAuthOptions {
        challenge?: boolean;
        users?: ExpressBasicAuthUsers;
        authorizer?: ExpressBasicAuthorizer;
        authorizeAsync?: boolean;
        unauthorizedResponse?: ExpressBasicAuthResponseHandler | string | object; 
        realm?: ExpressBasicAuthResponseHandler | string;
    }

    function expressBasicAuth(options?: ExpressBasicAuthOptions): Handler;

    export = expressBasicAuth;
}