node.js resolve promise and return value

Question

I use the Microsoft bot framework to come up with a "simple" PoC bot. I used a tutorial as a basis and extend it.

I've a couple of basic functions for differet intents (ie. greetings, goodbye, etc) and one with some more logic in it (reqstatus).

The simple ones (ie greeting.js) return the answer nicely but the more complex one doesn't (reqstatus.js). Running the main code of reqstatus.js (without the first "const getReqStatus = (entity) => {") in a standalone script works.

server.js (main) -> see call in "if (intent) {"...

const getFeelings = require('./intents/feelings.js')
const getGoodbyes = require('./intents/goodbyes.js')
const getGreetings = require('./intents/greetings.js')
const getHelp = require('./intents/help.js')
const getReqStatus = require('./intents/reqstatus.js')
... 
const bot = new builder.UniversalBot(connector)

// Intents based on definitions on recast
const INTENTS = {
  feelings: getFeelings,
  goodbyes: getGoodbyes,
  greetings: getGreetings,
  help: getHelp,
  reqstatus: getReqStatus,
}

// Event when Message received
bot.dialog('/', (session) => {
  recastClient.textRequest(session.message.text)
  .then(res => {
  const intent = res.intent()
  const entity = res.get('request_number')

  console.log(`UserName: ${session.message.user.name}`)
  console.log(`Msg: ${session.message.text}`)
  console.log(`Intent: ${intent.slug}`) 

  if (intent) {
    INTENTS[intent.slug](entity)
    .then(res => session.send(res)) 
    .catch(err => session.send(err))
  }
  })
  .catch(() => session.send('Sorry I didn\'t get that. '))
  })
  ...

greetings.js -> Returns the string ok

const getGreetings = () => {
  const answers = ['Hi, my name is SuperBot. Nice to meet you!', ] 
  return Promise.resolve((answers))
  }
module.exports = getGreetings

reqstatus.js -> Does not return anything

const getReqStatus = (entity) => {
  var request = require('request');
  var request_number = entity.toLowerCase()
  var output = [];


  // Processing
  var lineReader = require('readline').createInterface({
  input: fs.createReadStream('netreqs.csv')
  }); 

  lineReader.on('line', function (line) {
  var jsonFromLine = {};
  var lineSplit = line.split(';');
  jsonFromLine.req = lineSplit[0];
  jsonFromLine.req_count = lineSplit[1];
  jsonFromLine.req_type = lineSplit[2];
  //...
  var req_lowever = jsonFromLine.req.toLowerCase()
  if (req_lowever == request_number) {
     output.push( `Your request ${jsonFromLine.req} was received`);    
  // simplified
  }
  });

  // Output
  lineReader.on('close', function (line) {
  if (output == '') {
    output.push( `I was not able to find a request like ${request_number}.`);
    }
  console.log(output); // list output 
  return Promise.resolve(output); 
   });
  }
module.exports = getReqStatus

I also tried to put getReqStatus in a function but that also didn't work. After a lot of trying and googling I'm still stuck and wanted to ask the experts here. Thanks a lot in advance.

Answer 1

I think that the problem is that your getReqStatus isn't really returning anything. In your example getGreetings function you're actually returning Promise.resolve(answers) as the return value of that function.

However, in your getReqStatus function, you just set up a listener lineReader close event:

lineReader.on('close', function (line) {
if (output == '') {
    output.push( `I was not able to find a request like ${request_number}.`);
}
    console.log(output); // list output 
    return Promise.resolve(output); 
});

You're returning a Promise resolved inside the anonymous callback function you're passing to lineReader.on() as second parameter. That is not the return value from the getReqStatus function itself, so that getReqStatus is not returning anything, as expected.

The code of that function runs correctly as standalone code, as you say, just because it sets the listener properly and it does what it has to do. However, that code just doesn't return a Promise when wrapped in a function.

What you would need is to return a Promise that wraps the lineReader.on close handler, like:

function getReqStatus(){
//...code

return new Promise( function(resolve , reject ){
    lineReader.on('close', function (line) {
        if (output == '') {
            output.push( `I was not able to find a request like ${request_number}.`);
        }
        console.log(output); // list output
        return resolve(output);
        });
    });
}

I say would because I really don't know if this code will work, I don't have any kind of experience with the Microsoft Bot framework and not used at all with the readline module. However, even if this doesn't solve your problem, I hope it will help you a bit understanding why your function doesn't return a Promise and how could you fix it.