Request.headers is shared across Requests. Is it OK?

[yutakahirano]

const r1 = new Request('/');
const r2 = new Request(r1);

Because r2 is created without init argument, r2's associated request's header list is r1's associated request's header list. Hence modification is shared.

r1.headers.set('x', 'y');
r2.headers.get('x') // => returns 'y'.

Is it OK? Or should we clone the header list?

This was introduced at #560 I think.

@youennf @annevk @jakearchibald

[jakearchibald]

Hm, it does feel like cloning is better. Sorry if I caused this.

[annevk]

Agreed that this should clone and that's also what browsers do (r1.headers !== r2.headers in at least Firefox and Chrome).

[annevk]

I looked at https://fetch.spec.whatwg.org/#dom-request and it seems that step 13 always copies the underlying header list and step 31 always creates a new Headers object. What am I missing?

[yutakahirano]

Oh I see. I was looking at 33.1 and I thought the copy there was critical, which was wrong.

Sorry for the noise.

[annevk]

No problem, thanks for verifying!