multipartBodyParser crash if mapping files array

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• Title adequately and concisely reflects the feature or the bug

Bug Report

Restify Version

8.5.1

Node.js Version

v10.15.1

Expected behaviour

No crash

Actual behaviour

Crash stack:
NodeError: The "path" argument must be one of type string, Buffer, or URL. Received type undefined
at Object.readFile (fs.js:297:3)
at forEach (/Users/guoyi/git/testServer/node_modules/restify/lib/plugins/multipartBodyParser.js:120:28)
at Array.forEach ()
at parse (/Users/guoyi/git/testServer/node_modules/restify/lib/plugins/multipartBodyParser.js:115:40)
at IncomingForm. (/Users/guoyi/git/testServer/node_modules/formidable/lib/incoming_form.js:107:9)
at IncomingForm.emit (events.js:189:13)
at IncomingForm._maybeEnd (/Users/guoyi/git/testServer/node_modules/formidable/lib/incoming_form.js:557:8)
at /Users/guoyi/git/testServer/node_modules/formidable/lib/incoming_form.js:238:12
at WriteStream. (/Users/guoyi/git/testServer/node_modules/formidable/lib/file.js:79:5)
at Object.onceWrapper (events.js:277:13)

Repro case

server side:

const restify = require('restify');

const server = restify.createServer({
name: 'Test Server',
maxParamLength: 1024,
});

server.use(restify.plugins.queryParser({ mapParams: false }));
server.use(restify.plugins.bodyParser({
mapParams: true,
mapFiles: true,
multiples: true,
}));

server.post("/files/upload", async (request, response) => {
return response.status(200).send(requst.url);
});

server.listen(3000, () => console.log(Server started on port 3000));

client side:

async function addAttachment(folder, files) {
const url = http://localhost:3000/files/upload;

const headers = {
host: hostname,
'contentType': 'multipart/form-data',
};

const formData = {
folder,
files: files.map((file) => fs.createReadStream(file)),
};

return new Promise((resolve, reject) => {
request.post({
url,
headers,
formData,
}, (err, httpResponse, body) => {
if (err) {
return reject(err);
}
if (httpResponse.statusCode === 200){
return resolve(body);
}
return reject(new Error('Unkown error'));
});
});
}

Cause

https://github.com/restify/node-restify/blob/master/lib/plugins/multipartBodyParser.js
line 120, not check array

Are you willing and able to fix this?

No

Start in lib/plugins/multipartBodyParser.js at the reported line 120, then run the supplied server and client reproduction with bodyParser configured for mapParams, mapFiles, and multiples. Check how the files array is handled and verify that uploading multiple files completes without the reported undefined-path crash.