Nodejs Async/Await in api controller responds with unknown error - node.js

Question

export function getAllHost(req, res) {
function findAllHost() {
let query = {};
query.company = req.query && req.query.companyId ? req.query.companyId : res.locals.payload.companyId;
query.active = true;
if(req.query && req.query.name) {
let regexp = new RegExp('\\b' + req.query.name);
query['name'] = {$regex: regexp, $options: 'i'};
}
return Host.find(query);
}
async function sendRes() {
let allHost = [];
let hosts = [];
try {
hosts = await findAllHost();
} catch(err){
console.log(err)
}
for (let host of hosts) {
allHost.push(new Host_V1(host));
}
return allHost
}
sendRes().then(data => res.status(200).json(data)).catch(error => {
console.log("error is", error);
res.status(error.status || 500).json({
message: error.status ? error.message : 'Server Error'
});
});
}
I have been trying to adapt async/await into my code, so I converted one of the Promise based api controller to make use of async/await, but the thing that bothers me is that my server responds with 500, and the console.log inside my catch block doesn't print anything.
No error gets thrown.
I am using babel babel-plugin-syntax-async-functions to parse it.
What is it that I am doing wrong?

Answer 1

Your code is a bit overcomplicated, but judging by it you should receive an error in the console if one appears. It could instead be that you have a middleware producing an error? The main issue is that you're catching the error in the async function sendRes, so the .catch-method you call on the returned Promise will never be fired even if there is an error.
Like many others that are new to async/await, you've misunderstood and believe that you have to wrap every await expression in a try/catch-block. This is not the case. The error "trickles" up the call chain, and unless a particular function can provide a different return value, it's best to catch the error from the top-most callee. Take this simple example which shows a common anti-pattern: https://repl.it/repls/PunySafeInterfacestandard (await and async isn't even needed in these examples, but I added them for clarity)
But if you try to simplify your code, maybe something like the below snippet, you might be able to rule out if it's a middleware or not.
export async function getAllHosts (req, res) {
try {
let query = {
company: req.query && req.query.companyId ? req.query.companyId : res.locals.payload.companyId,
active: true
}
if (req.query && req.query.name) {
let regexp = new RegExp('\\b' + req.query.name)
query.name = {$regex: regexp, $options: 'i'}
}
let allHosts = (await Host.find(query)).map((host) => new Host_V1(host))
return res.json(allHosts)
} catch (e) {
console.log("error is", e)
res.status(error.status || 500).json({
message: error.status ? error.message : 'Server Error'
})
}
}
Take note of the (await Host.find(query)) line. If the Promise that's returned from Host.find() rejects, the .map()-method won't be executed on the data and execution will jump to the catch-block.
I also heavily discourage using Babel since async/await has been natively supported in Node since version 7.6.

Answer 2

EDIT : The value returned is indeed a promise
I think that the error is related to your 'SendRes.then' since what SendRes returns is not a promise but it's actually is the Array allHost
Your data argument is not an argument anymore it is the value returned from the sendRes function thanks to your async / await implementation.
const hosts = sendRes();
res.status(200).json(hosts);
if you want to handle an error you must return something from your catch block so that you can can handle it here.
if (!hosts) res.status(500);
To simplify your code you can also get rid of the sendRes function and make your getAllHost express middleware an async function
async getAllHost(req, res) { /*...*/ }
try {
let allHosts = await findAllHosts();
res.status(200).json(allHosts);
} catch (error) {
res.status(500).send({ error })
}