Bug in handling binary files with Twilio serverless toolkit

[danh182]

The Twilio serverless toolkit is not able to correctly serve an mp3 file in a response. I'm following a guide in the docs here and I've got it working completely fine using the web services editor in the console. However when I try to replicate the code locally with serverless, it doesn't work.

The JS file at functions/handler.js is public and I have an mp3 file at assets/hello.mp3 which is private. The JS is:

const fs = require('fs');

exports.handler = function(context, event, callback) {
  var phrase = event.phrase;
  
  var filePath = Runtime.getAssets()[`/${phrase}.mp3`].path;
  var buffer = fs.readFileSync(filePath);
  var stat = fs.statSync(filePath);
  
  var response = new Twilio.Response();
  
  response.setBody(buffer);
  response.appendHeader('Content-Type', 'audio/mpeg');
  response.appendHeader('Content-Length', stat.size);
  
  return callback(null, response);
};

The only change from the docs is that phrase is a get parameter and allows the user to specify the filename. When I request http://localhost:3000/handler?phrase=hello Chrome detects that it's receiving an audio file (the headers are set correctly) but doesn't play it. The response is:

{type: "Buffer",…}
    data: [255, 243, 68, 196, 0, 17, 82, 130, 20, 0, 24, 68, 185, 52, 68, 74, 44, 234, 110, 238, 250, 23, 204,…]
    type: "Buffer"

This looks like the serverless toolkit is not encoding the binary data correctly. I've replicated the issue using Node v14 and v16, on Windows and CentOS.

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[makserik]

Hi!
Just use response.setBody(new AudioBuffer(buffer)); instead of response.setBody(buffer);.
Tested on node18 and latest chrome