Better error handling with Promises?

Question

I am currently experimenting Google Firebase functions to access Google APIs. It's running fine, but I am a little bit lost in trying to manage the errors that could be detected ...

In the .HTTPS getGoogleUsers functions , I would like to return an HTTP status code ( 200 or error code ) , and the data ( or error message )

As far as I can see , I can get errors:

from the connect() function ( 500: Internal server error or 401 Unauthorized )
from the listUsers() function ( 500: Internal server error or 400 Bad Request )

Am I totally or partially wrong ? what should be my strategy in this case ? thanks for feedback ..

const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();

const {google} = require('googleapis');
const KEY = require('./service-key.json');

 // Create JSON Web Token Client
 function connect () {
  return new Promise((resolve, reject) => {
    const jwtClient = new google.auth.JWT(
      KEY.client_email,
      null,
      KEY.private_key,
      ['https://www.googleapis.com/auth/admin.directory.user'],
      'adminuser@mydomain.com'
    );
    jwtClient.authorize((err) => {
      if(err) {
        reject(err);
      } else {
        resolve(jwtClient);
      }
    });
  });
}

function listUsers (client) {
  return new Promise((resolve, reject) => {
    google.admin('directory_v1').users.list({
      auth: client,
      domain: 'mydomain.com',
    }, (err, response) => {
      if (err) {
        reject(err);
      }
      resolve(response.data.users);
    });
  });
}

function getAllUsers () {
  connect()
    .then(client => {
      return listUsers(client);
    })
    .catch(error => {
      return error;
    })
}
exports.getGoogleUsers = functions.https.onRequest((req, res) => {
  const users = getAllUsers();
  if (error) {
     status = error.status;
     data = error.message;
  } else {
    status = 200;
    data = users;
  }
  res.send({ status: status, datas: data })
});

The part `const users = getAllUsers(); if (error) { …` can't work — Bergi, May 16 '18 at 15:06

score 0 · Accepted Answer · answered May 16 '18 at 15:09

0

I think you are looking for

function getAllUsers () {
  return connect().then(listUsers);
//^^^^^^
}

exports.getGoogleUsers = functions.https.onRequest((req, res) => {
  getAllUsers().then(users => {
    return {status: 200, datas: users};
  }, error => {
    return {status: error.status, datas: error.message};
  }).then(response => {
    res.send(response);
  });
});

This uses the .then(…, …) method with two callbacks to distinguish between success and error case, and to wait for the result of the promise.

answered May 16 '18 at 15:09

Bergi

630,263
148
957
1,375

yes ,good point .. however I get a lint error in libe : getAllUsers().then(users => {... 53:3 error Expected catch() or return promise/catch-or-return – May 16 '18 at 16:44
If any of the three callbacks (especially `res.send`) throws an error, it'll cause an unhandled rejection. You can add another `.catch(console.error)` at the end if you want. – Bergi May 16 '18 at 17:34

Better error handling with Promises?

1 Answers1