[SOLVED] How to extend passport.js module AuthenticateOptions interface

How to extend passport.js module AuthenticateOptions interface

Passport.js strategies can support additional options in the authenticate call:

    passport.authenticate('azuread-openidconnect', {
      // Default passport options
      failWithError: true,
      successReturnToOrRedirect: '/',
      // Custom option supported by the azure-ad plugin
      // Type error - 'tenantIdOrName' does not exist in type 'AuthenticateOptions'
      tenantIdOrName: 'common',
    });

Using an option that's supported by a custom strategy, eg tenantIdOrName above, results in a typescript error because it's not a part of passport's AuthenticateOptions interface found here and used in the authenticate signature here

I've tried a few things without success

module augmentation ie declare module 'passport' {...} seems to override the module's typings instead of extending them (anything not in my extension is treated as untyped)
merging interfaces ie declare namespace passport { interface AuthenticateOptions { ...new properties }}, this seems to have no effect on the authenticate method signature.

How can I support additional properties in the authenticate call without type-casting?

Solution

Turns out I needed to import the existing module for my module augmentation to extend the module's types.

The following in a .d.ts file* successfully extends the AuthenticateOptions interface:

import { AuthenticateOptions } from 'passport';

declare module 'passport' {
  // Extend acceptable authenticate options for Passport Azure AD
  // https://github.com/AzureAD/passport-azure-ad#513-options-available-for-passportauthenticate
  interface AuthenticateOptions {
    customState?: string;
    resourceURL?: string;
    tenantIdOrName?: string;
    domain_hint?: string;
    login_hint?: string;
    prompt?: string;
  }
}

*I found the file must not be named passport.d.ts, any other name worked fine