How do you use Google API getRequestHeaders() to get an OAuth2 access token?

Question

I'm using the googleapis npm library to authorize using OAuth2 to access my Gmail account to send emails. I am using the following code (TypeScript) to do that:

const oAuth2Client = new google.auth.OAuth2(
  googleConfig.clientId,
  googleConfig.clientSecret
);

oAuth2Client.setCredentials({
  refresh_token: googleConfig.refreshToken
});

const accessTokenRetVal = (await oAuth2Client.refreshAccessToken()).credentials.access_token;
const accessToken = accessTokenRetVal || '';

This code works, but I get the following message:

(node:8676) [google-auth-library:DEP007] DeprecationWarning: The `refreshAccessToken` method has been deprecated, and will be removed in the 3.0 release of google-auth-library. Please use the `getRequestHeaders` method instead.

I have searched on Google, on the GitHub for the googleapis module, on StackOverflow, and I haven't been able to find any documentation for what constitutes the getRequestHeaders method. I've tried calling getRequestHeaders, but it doesn't appear to return a credentials object with an access token.

Are there official docs for how getRequestHeaders should be used in this situation?

Accept

Answer 1

const accessToken=oAuth2Client.getAccessToken()

This worked for me

Galton

Answer 2

This new function directly gives you an 'Headers' object:

{ Authorization: 'Bearer xxxxxxxxx' }

So you can happend it directly use it as your header object:

const authHeaders = await this.auth.getRequestHeaders();
yourfetchlibrary.get('https://......', {
            headers: authHeaders,
        })

Or extract the Authorization part:

const authHeaders = await this.auth.getRequestHeaders();
yourfetchlibrary.get('https://......', {
            headers: {
                'Authorization': authHeaders.Authorization,
                'Content-Type': 'application/json',
            },
        })

Romansh

Is that the same as what one would get from credentials.access_token? Is there documentation for this? – Accept

Access token does not have the 'bearer ' string so it cannot be directly used in request headers. No doc but It was explained in release not: github.com/googleapis/google-auth-library-nodejs/releases/tag/… – Romansh

Excellent -- the documentation that you linked to mentions that you should use getAccessToken() instead, which is exactly what is needed (as opposed to the recommendation that the deprecation warning in my original post gives). Could you add getAccessToken() to the answer? Then I can accept it as the solution. – Accept

Yes, an access token can be used in HTTP headers. You build the header: header = 'authorization: Bearer ' + credentials.access_token – Jasik

Using @Accept suggestion, I am calling getAccessToken and it works great for me. Wish these things were documented. – Foment