feat: Support Instantiating OAuth2Client with Credentials (#1652)

src/auth/oauth2client.ts

@@ -404,12 +404,6 @@ export interface VerifyIdTokenOptions {
   maxExpiry?: number;
 }
 
-export interface OAuth2ClientOptions extends RefreshOptions {
-  clientId?: string;
-  clientSecret?: string;
-  redirectUri?: string;
-}
-
 export interface RefreshOptions {
   // Eagerly refresh unexpired tokens when they are within this many
   // milliseconds from expiring".
@@ -423,6 +417,13 @@ export interface RefreshOptions {
   forceRefreshOnFailure?: boolean;
 }
 
+export interface OAuth2ClientOptions extends RefreshOptions {
+  clientId?: string;
+  clientSecret?: string;
+  redirectUri?: string;
+  credentials?: Credentials;
+}
+
 export class OAuth2Client extends AuthClient {
   private redirectUri?: string;
   private certificateCache: Certificates = {};
@@ -474,6 +475,7 @@ export class OAuth2Client extends AuthClient {
     this.eagerRefreshThresholdMillis =
       opts.eagerRefreshThresholdMillis || 5 * 60 * 1000;
     this.forceRefreshOnFailure = !!opts.forceRefreshOnFailure;
+    this.credentials = opts.credentials || {};
   }
 
   protected static readonly GOOGLE_TOKEN_INFO_URL =

test/test.oauth2.ts

@@ -23,7 +23,7 @@ import * as path from 'path';
 import * as qs from 'querystring';
 import * as sinon from 'sinon';
 
-import {CodeChallengeMethod, OAuth2Client} from '../src';
+import {CodeChallengeMethod, Credentials, OAuth2Client} from '../src';
 import {LoginTicket} from '../src/auth/loginticket';
 
 nock.disableNetConnect();
@@ -1593,5 +1593,32 @@ describe('oauth2', () => {
         /No access token is returned by the refreshHandler callback./
       );
     });
+
+    it('should accept and attempt to use an `access_token`', async () => {
+      const credentials: Credentials = {access_token: 'my-access-token'};
+      const url = 'http://example.com';
+
+      const client = new OAuth2Client({credentials});
+
+      const scope = nock(url, {
+        reqheaders: {
+          Authorization: `Bearer ${credentials.access_token}`,
+        },
+      })
+        .get('/')
+        .reply(200);
+
+      // We want the credentials object to be reference equal
+      assert.strict.equal(client.credentials, credentials);
+
+      await client.request({url});
+
+      scope.done();
+
+      // The access token should still be available after use
+      assert.strict.deepEqual(await client.getAccessToken(), {
+        token: credentials.access_token,
+      });
+    });
   });
 });