bgenc.net/content/posts/2022.12.17.firefox-xml-parsing-error-no-root-element.md

title	date	toc	images	tags
Solving "XML Parsing Error: no root element found" in Firefox	2022-12-17T21:27:37-05:00	false		dev web

I've been seeing this error a lot while working on my project Bulgur Cloud. It seems to show up only on Firefox:

What is curious was that I was not actually loading the file mentioned in the error message. I tried looking up what the error might mean, but all that came up was very specific issues regarding some web frameworks, unrelated to what I'm using.

I later realized however, while I wasn't loading the file in the error message, I was actually sending a DELETE request. The Bulgur Cloud server then responds to this request with an empty 200 OK response. Turns out, if you send an empty response to Firefox, it tries to parse the body of the response even though it's empty and gives you this error.

To quiet this error, I started just sending an empty JSON response even for requests that don't actually need it. Here's some rust code to illustrate the solution:

#[derive(Debug, Serialize)]
pub struct EmptySuccess {
    status: &'static str,
}

// Using actix-web
fn empty_ok_response() -> HttpResponse {
    HttpResponse::Ok().json(EmptySuccess { status: "ok"})
}

This adds a {"status": "ok"} json to the response, which seems to be enough to make Firefox happy.