Catch superagent request error before piping - node.js

Question

I'm trying to pipe a file from service A trough service B into my Postman cliente. Service A builds an delivers a CSV file, and service B (nodejs) has to pipe into my client.
After researching a lot I have managed to successfully pipe the files into service B and then into Postman. Now I want to handle the ugly cases: what if the request token is invalid? What if I can't find the file?
As of this moment, I have found zero documentation or examples on how successfully handle errors while piping a request using superagent.
This is what I have so far
router.post("/csv", (req, res) => {
download_csv(req.get("Authorization"), req.body.ids)
.then((response) => {
res.sendFile(path.resolve(response));
})
.catch((err) => {
res.status(error.status).json(error.response.body);
})
});
function download_csv(token, ids) {
const stream = fs.createWriteStream("filters.csv")
let request = agent
.post(`${profiles}/api/documents/csv`)
.set("authorization", token)
.send({
ids: ids,
action: DOWNLOAD_CSV_PROFILES
})
request.on("response", res => {
// Maybe I can use abort to handle this thing, but can't figure out how!
// if (res.status !== 200) request.abort()
console.log(res.status)
})
request.on("abort", () => {
console.log("aborted")
return new Promise((resolve, reject) => {
resolve("request aborted")
})
})
request.pipe(stream)
return streamToPromise(stream);
}
function streamToPromise(stream) {
return new Promise((resolve, reject) => {
stream.on("error", (err) => {
console.log("error in error")
})
stream.on("finish", () => {
console.log("File saved")
resolve(stream.path);
});
});
}
This code handles the creation of the files correctly. When I fake the token or misspell the Authorization header, I get a correct 401 response, but a file gets written anyway with its contents being the authentication error.
Can anyway give me a hint on how to:
actually catch and manage the request when fails
in such case, how to escape the piping by going back to the express context and just returning a failed express request?
Many thanks!

Answer 1

If I understand you correctly, simply create the fs write stream in on('response') and make a small fix on the resultion.
function download_csv(token, ids) {
return new Promise((resolve, reject) => {
let request = agent
.post(`${profiles}/api/documents/csv`)
.set("authorization", token)
.send({
ids: ids,
action: DOWNLOAD_CSV_PROFILES
})
request.on("response", res => {
// Maybe I can use abort to handle this thing, but can't figure out how!
if (res.status === 200) {
res
.on("end", resolve)
.pipe(fs.createWriteStream("filters.csv"));
} else {
reject();
}
})
request.on("abort", reject);
});
}
I'm not sure what is the "request" you're using - but assuming it's actually the request npm module that will help.
Ideally, upload the file to a temporary directory and move it when the promise is resolved, delete on rejected. This way you'll solve the issue of partial downloads.
If you want to make any on-the-fly transforms, check out my "scramjet". It'll make everything easier with promises.