Issue with PubSub client using provided JWTAccess

[salrashid123]

JWTAccess clients not used with pubsub

The following snippet constructs a jwtaccess token client and then tries to apply that as an authClient to pubsub

const {GoogleAuth, JWTAccess, OAuth2Client} =  require('google-auth-library');
const {PubSub} = require('@google-cloud/pubsub');

key = require("/path/to/svc_account.json");
const projectId = yourproject';
const aud = "https://pubsub.googleapis.com/google.pubsub.v1.Publisher";
const jwtClient = new JWTAccess();
jwtClient.fromJSON(key);
const md = jwtClient.getRequestHeaders(aud);
console.log(md);

const pubsub = new PubSub({
  projectId: projectId,
  authClient: jwtClient,
});
pubsub.getTopics((err, topic) => {
	if (err) {
		console.log(err);
		return;
	}
	topic.forEach(function(entry) {
    console.log(entry.name);
	});
});

however, it seems the provided client is ignored. the error thrown:

}
Error: 16 UNAUTHENTICATED: Failed to retrieve auth metadata with error: getHeaders.then is not a function
    at Object.callErrorFromStatus (/jwt_access_token/node/node_modules/@grpc/grpc-js/build/src/call.js:31:26)
    at Object.onReceiveStatus (/jwt_access_token/node/node_modules/@grpc/grpc-js/build/src/client.js:180:52)
    at Object.onReceiveStatus (/jwt_access_token/node/node_modules/@grpc/grpc-js/build/src/client-interceptors.js:365:141)
    at Object.onReceiveStatus (/jwt_access_token/node/node_modules/@grpc/grpc-js/build/src/client-interceptors.js:328:181)
    at /jwt_access_token/node/node_modules/@grpc/grpc-js/build/src/call-stream.js:187:78
    at processTicksAndRejections (node:internal/process/task_queues:78:11) {
  code: 16,
  details: 'Failed to retrieve auth metadata with error: getHeaders.then is not a function',
  metadata: Metadata { internalRepr: Map(0) {}, options: {} },
  note: 'Exception occurred in retry method that was not classified as transient'
}

i maynot be specifying the client correctly but i think you should be able to set an authClient:

new PubSub(options?: ClientConfig): PubSub 
   --> constructor(options?: ClientConfig); 
       -->  
       export interface ClientConfig extends gax.GrpcClientOptions {
        apiEndpoint?: string;
        servicePath?: string;
        port?: string | number;
        sslCreds?: gax.grpc.ChannelCredentials;}
            --> 
            export interface GrpcClientOptions extends GoogleAuthOptions {
                auth?: GoogleAuth;
                grpc?: GrpcModule;
            }
            -->
            export interface GoogleAuthOptions<T extends AuthClient = JSONClient> {
              /**
               * An `AuthClient` to use
               */
              authClient?: T;

---

using

• "@google-cloud/pubsub": "^2.19.0",
• "google-auth-library": "^7.14.1",