Error: No responses defined for platform: null when listing users google calendar events

Question

I'm trying to implement a reminders dialogflow agent in node js that reminds the user on his google calendar upcoming events. however I'm getting an No responses defined for platform: null error when calling the intent for listing the upcoming events.

This is my code:

const express = require('express');
const google = require('googleapis').google;
const jwt = require('jsonwebtoken');
const dfff = require('dialogflow-fulfillment')
const {googlec} = require('googleapis');

// Google's OAuth2 client
const OAuth2 = google.auth.OAuth2;
// Including our config file
const CONFIG = require('./config');
// Creating our express application
const app = express();
// Allowing ourselves to use cookies
const cookieParser = require('cookie-parser');
app.use(cookieParser());
// Setting up EJS Views
app.set('view engine', 'ejs');
app.set('views', __dirname);
console.log(dfff)

app.get('/', function (req, res) {
    // Create an OAuth2 client object from the credentials in our config file
    const oauth2Client = new OAuth2(CONFIG.oauth2Credentials.client_id, CONFIG.oauth2Credentials.client_secret, CONFIG.oauth2Credentials.redirect_uris[0]);
    // Obtain the google login link to which we'll send our users to give us access
    const loginLink = oauth2Client.generateAuthUrl({
      access_type: 'offline', // Indicates that we need to be able to access data continously without the user constantly giving us consent
      scope: CONFIG.oauth2Credentials.scopes // Using the access scopes from our config file
    });
    return res.render("index", { loginLink: loginLink });
  });


app.get('/auth_callback', function (req, res) {
    // Create an OAuth2 client object from the credentials in our config file
    const oauth2Client = new OAuth2(CONFIG.oauth2Credentials.client_id, CONFIG.oauth2Credentials.client_secret, CONFIG.oauth2Credentials.redirect_uris[0]);
    if (req.query.error) {
      // The user did not give us permission.
      return res.redirect('/error');
    } else {
      oauth2Client.getToken(req.query.code, function(err, token) {
        if (err)
          return res.redirect('/');
  
        // Store the credentials given by google into a jsonwebtoken in a cookie called 'jwt'
        res.cookie('jwt', jwt.sign(token, CONFIG.JWTsecret));
        return res.redirect('/');
      });
    }
  });

  app.post('/', express.json(),(req,res)=>{
    //if (!req.cookies.jwt) {
      // We haven't logged in
      //return res.redirect('/');
    //}
    const oauth2Client = new OAuth2(CONFIG.oauth2Credentials.client_id, CONFIG.oauth2Credentials.client_secret, CONFIG.oauth2Credentials.redirect_uris[0]);
    const calendar = google.calendar({version: 'v3' , auth:oauth2Client});
    const agent = new dfff.WebhookClient({
        request : req,
        response : res
      })
      function welcome(agent){
        agent.add("Hi")
      }
    
      function listEvents(agent){ 
        calendar.events.list({
        'calendarId': 'primary',
        'auth':oauth2Client,
        'timeMin': (new Date()).toISOString(),
        'showDeleted': false,
        'singleEvents': true,
        'maxResults': 10,
        'singleEvents': true,
        'orderBy': 'startTime'
     }).then((err,response)=> {
        let events = response.result.items;
        if (events.length > 0) {
          for (let i = 0; i < events.length; i++) {
            var event = events[i];
            var when = event.start.dateTime;
            if (!when) {
              when = event.start.date;
            }
             return agent.add('Be ready for '+ event.summary + ' event '+ 'at ' + when )
          }}
        else {
             return agent.add('You dont have any upcoming events.');
        }
      });   
         
      }
    
      let intenMap = new Map()
      intenMap.set('Default_Welcome_Intent',welcome)
      intenMap.set('Remind_me',listEvents)

      agent.handleRequest(intenMap)
   
  });

  // Listen on the port defined in the config file
app.listen(CONFIG.port, function () {
    console.log(`Listening on port ${CONFIG.port}`);
  });

Whenever listEvents function is processed I'm getting (Error: No responses defined for platform null) any idea why?

Answer 1

The issue is that listEvents() does an asynchronous operation that returns a Promise (the call to calendar.events.list()), which you handle through the .then() block, but you don't have a way for the agent.handleRequest() function to know this and to wait for the Promise to complete. To do this, you need to return a Promise.

Fortunately, in your case, the solution is straightforward, since the call and then() chain return a Promise, you can just return it. This would be done by adding the return keyword before calendar.events.list(). It might look something like this:

      function listEvents(agent){ 
        return calendar.events.list({
          // Parameters go here
        }).then((err,response)=> {
          // Code to handle response and return a message go here
        });   
      }