Netlify server functions unable to handle multipart/form-data - pdf

Question

I’m working on a Netlify Function where we take form data for a job application (including a file upload) and pass the data on to a third-party API for use in their system. I was following along with this handy post (thanks!) —
https://www.netlify.com/blog/2021/07/29/how-to-process-multipart-form-data-with-a-netlify-function/
— but seem to have run into a situation where the data in the file is not handled properly (for example, PDFs turn up with blank content, though ASCII metadata appears to be at least partly intact), at least when using the Netlify CLI; I have yet to try on a deploy preview. Writing to a local directory confirms that the issue isn’t with the third party API. Is there something I’m missing when working with these files? Example code below (note that I’ve also attempted to work with the Buffer data, with identical results).
Fetch function to call the Netlify Function:
const data = new FormData(form);
fetch('/.netlify/functions/apply', {
method: 'POST',
body: data,
}).then(res => {
if (!res.ok && res.status !== 406) {
throw new Error('oh no');
}
return res.json();
}).then(data => {
if (Array.isArray(data.missingRequiredFields) && data.missingRequiredFields.length > 0) {
console.log(data);
showMissingFields(data.missingRequiredFields);
} else {
showConfirmationMessage(data.message);
}
}).catch(err => {
showWarningMessage('Something went wrong; please try again.');
}).finally(() => {
submitButton.removeAttribute('disabled');
});
And here’s our Netlify Function:
const Busboy = require("busboy");
const FormData = require("form-data");
const fetch = require("node-fetch");
function parseMultipartForm(event) {
// source: https://www.netlify.com/blog/2021/07/29/how-to-process-multipart-form-data-with-a-netlify-function/
return new Promise(resolve => {
const fields = {};
const busboy = new Busboy({
// uses request headers to extract the form boundary value
headers: event.headers,
});
// before parsing anything, we need to set up some handlers.
// whenever busboy comes across a file ...
const f = [];
busboy.on("file", (fieldname, filestream, filename, transferEncoding, mimeType) => {
// ... we take a look at the file's data ...
filestream.on("data", data => {
fields[fieldname] = {
filename,
type: mimeType,
content: data,
transferEncoding,
};
});
});
// whenever busboy comes across a normal field ...
busboy.on("field", (fieldName, value) => {
// ... we write its value into `fields`.
fields[fieldName] = value;
});
// once busboy is finished, we resolve the promise with the resulted fields.
busboy.on("finish", () => {
resolve(fields);
});
// now that all handlers are set up, we can finally start processing our request!
busboy.write(event.body);
});
}
/** ***************************************************************************
* Serverless function
**************************************************************************** */
exports.handler = async function(event, context) {
// parse the incoming multipart/form-data data into fields object
const fields = await parseMultipartForm(event);
// create new formdata object to be send to Lever
const form = new FormData();
for (const [key, value] of Object.entries(fields)) {
if (key === "resume") {
// append "resume" with the file buffer and add the file name
form.append("resume", value.content, { filename: value.filename });
} else {
form.append(key, value);
}
}
};
Any guidance you might have would be greatly appreciated.