Error when setting unsafe headers

[jeremymeng]

We have code that works in live mode using xhr, but fails using mock.

https://github.com/sinonjs/nise/blob/805200b70084b1c19569ad0c04158da7bf5eed0c/lib/fake-xhr/index.js#L590

according to the spec, setting/deleting a forbidden header should be a no-op

Otherwise, if this’s guard is "request" and name is a forbidden header name, return.

[mroderick]

according to the spec, setting/deleting a forbidden header should be a no-op

That's the spec for fetch. This library does not deal with fetch.

What is expected to happend for XHR?

[fatso83]

@mroderick The spec for XHR says pretty much the same thing.

1. If this’s state is not opened, then throw an "InvalidStateError" DOMException.

2. If this’s send() flag is set, then throw an "InvalidStateError" DOMException.

3. Normalize value.

4. If name is not a name or value is not a value, then throw a "SyntaxError" DOMException.

   An empty byte sequence represents an empty header value.

5. If name is a forbidden header name, then return.

6. Combine name/value in this’s author request headers.

[stale[bot]]

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