TypeScript Error When Importing GCS Types to index.d.ts #70

In v5.2.0 we added Cloud Storage support to the Admin SDK. As a part of this we made a few changes to the index.d.ts file:

import {Bucket} from '@google-cloud/storage';

declare namespace admin.storage {
  interface Storage {
    app: admin.app.App;
    bucket(name?: string): Bucket;
  }
}

Turns out this is not supported properly in TypeScript. It triggers the following error in downstream apps:

node_modules/firebase-admin/lib/index.d.ts(396,3): error TS2666: Exports and export assignments are not permitted in module augmentations.
npm ERR! Test failed.  See above for more details.

Simply having the import statement at the top-level of the file is sufficient to trigger the error.

Possible Solutions

1. Not expose the GCS Bucket type in our API, and use any instead.
2. Change our module declaration as follows:

// index.d.ts
declare module 'firebase-admin' {
}

export = admin;

This fixes the error, but I don't know if it has other consequences.