Keep getting 'Error sending test message to Cloud PubSub...' with Google Cloud PubSub

Question

I'm trying to set up Google's push PubSub to my server to receive Gmail push notifications.

I'm getting the following scopes:

• https://mail.google.com/
• https://www.googleapis.com/auth/cloud-platform
• https://www.googleapis.com/auth/pubsub
• https://www.googleapis.com/auth/gmail.modify
• https://www.googleapis.com/auth/gmail.readonly

It works to create a topic, subscribe to that topic, grant access to the Gmail API on that topic but it fails when I'm trying to watch my inbox. I have followed this guide: https://developers.google.com/gmail/api/guides/push and this is the code I'm using to do the steps above:

var rp = require('request-promise');

// Step 1. Create a topic
rp({
   url: 'https://pubsub.googleapis.com/v1/projects/projectId/topics/mailSync',
   method: 'PUT',
   headers: {
     Authorization: 'Bearer accessToken'
   }
 }).then(function(response) {
   console.log(response);
   res.send(response);
 })
 .catch(function(error) {
   console.log(error.message);
   res.send(error.message);
 });

// Step 2. Create a subscription:
rp({
   url: 'https://pubsub.googleapis.com/v1/projects/projectId/subscriptions/mailSync',
   method: 'PUT',
   headers: {
     Authorization: 'Bearer accessToken'
   },
   json: {
     topic: 'projects/projectId/topics/mailSync',
     pushConfig: {
       pushEndpoint: 'https://developers.example.com/mailSyncHandler'
     }
   }
 }).then(function(response) {
   console.log(response);
   res.send(response);
 })
 .catch(function(err) {
   console.error(err);
   res.status(err.statusCode).send(err.error.error.message);
 });

// Step 3. Grant the Gmail API publish rights on our topic
rp({
   url: "https://pubsub.googleapis.com/v1beta2/projects/projectId/topics/mailSync:setIamPolicy",
   method: 'POST',
   headers: {
     Authorization: 'Bearer accessToken'
   },
   data: {
     policy: {
       bindings: [{
         role: "roles/pubsub.publisher",
         members: ["serviceAccount:[email protected]"]
       }]
     }
   },
   json: true
 }).then(function(response) {
   console.log(response);
   res.send(response);
 })
 .catch(function(error) {
   console.log(error.message);
   res.send(error.message);
 });

// Step 4. Watch my Inbox
rp({
  url: "https://www.googleapis.com/gmail/v1/users/me/watch",
  method: "POST",
  headers: {
    Authorization: 'Bearer accessToken'
  },
  json: {
    topicName: "projects/projectId/topics/mailSync",
    labelIds: ["INBOX"]
  }
}).then(function(response) {
  console.log(response);
  res.send(response);
})
.catch(function(error) {
  console.error(error);
  res.send(error.message);
});

Answer 1

Figured out why I got the error and it was because I didn't send the data as JSON in step 4.

The correct code in step 4 is (notice that I'm using json: instead of body: on row 8):

// Step 4. Watch my Inbox
rp({
  url: "https://www.googleapis.com/gmail/v1/users/me/watch",
  method: "POST",
  headers: {
    Authorization: 'Bearer accessToken'
  },
  json: {     <-----
    topicName: "projects/projectId/topics/mailSync",
    labelIds: ["INBOX"]
  }
}).then(function(response) {
  console.log(response);
  res.send(response);
})
.catch(function(error) {
  console.error(error);
  res.send(error.message);
});