How can I type the OAuthClient from googleapis?

I am working on nodemailer app with gmail OAuth2 in TypeScript, with "noImplicitAny": true,"noImplicitReturns": true. This requires me to explicitly specify return types.

I have this snippet

import { google } from 'googleapis';

export const getOAuth2Client = (): OAuth2Client => { // 2. So I set the return type as OAuth2Client  
  const { OAuth2 } = google.auth;

  const auth2Client = new OAuth2(
    process.env.G_OAUTH_CLIENT_ID,
    process.env.G_OAUTH_CLIENT_SECRET,
    process.env.G_OAUTH_REDIRECT_URL
  );

  auth2Client.setCredentials({
    /* eslint-disable @typescript-eslint/camelcase */
    refresh_token: process.env.G_OAUTH_REFRESH_TOKEN,
  });

  return auth2Client; // 1. Inspecting auth2Client shows its of type OAuth2Client
};

I got the OAuth2Client type on inspecting the type of the returned auth2Client. The problem though is where to import it from and use it in the project.

I tried the following...

import { google, OAuth2Client } from 'googleapis';

That fails as googleapis has no such named export.

I also saw this approach from @corolla answer where he imports the types from google-auth-library

import { OAuth2Client } from 'google-auth-library';

I would wish to use the type without having to add another library as a dependency just for a single type for an already typed library (Much as googleapis uses types from google-auth-library under the hood, the project linter requires me to list it as a project dependency, which I wouldn't wish to do for now). Is there any other way I can go about this please.

Thank you.

Solution

I settled with just disabling the eslint warning for no-extraneous-dependencies.

// eslint-disable-next-line import/no-extraneous-dependencies
import { OAuth2Client } from 'google-auth-library';
import { google } from 'googleapis';

I couldn't specifically specify google-auth-library as a project dependency just to pick one type, yet under the hood, the googleapis package was also importing the types for the same package. So I wouldn't be breaking anything I guess.