net/http: add knobs for which headers Client forwards on redirect?

[zachgersh]

Please answer these questions before submitting your issue. Thanks!

What version of Go are you using (go version)?

1.8.1

What operating system and processor architecture are you using (go env)?

amd64/darwin

What did you do?

Making a request to upload a file that is setting the content-type of application/x-compressed which results in a successful 302 redirect to a task monitoring endpoint.

What did you expect to see?

The request succeeds and the task monitoring endpoint returns a 200.

What did you see instead?

The endpoint fails due to the fact that it has received the additional header.

I know I can implement a CheckRedirect function that would allow me to strip out the headers but it seems like the go 1.7.X behavior was more desirable (providing the function to forward the headers).

It actually might be nice to make this a flag on the client (so headers can be optionally be forwarded or not). Having to implement CheckRedirect just to not send along headers feels a tad bit heavy handed but I am open to it.

I also know that the API server, which I have no control over, could be modified to ignore additional headers but the code I have talking to this server worked in 1.7.X and now doesn't work in 1.8.1 (slightly surprising).

[bradfitz]

For 8 releases people complained about the lack of header forwarding and we kept putting it off and thinking about it. And then we did it, and... this. :)

I'll entertain proposals but I don't have the resources to think about this more and design the API myself.

[zachgersh]

@bradfitz I almost dreaded putting this in because it felt like a "damned if you do, damned if you don't" sort of behavior. I'd be glad to take this on and rough it out, of course as long as you are willing to provide feedback 😄

Easiest solution:

Client now takes a bool for RedirectHeaders.

I'd love to see if anyone else has run into this and/or cares. Also, thanks for all you do and even being open to the idea.

[bradfitz]

We're not going to make the behavior off in 1.0-1.7, on in 1.8, and off again in 1.9. It's going to be on by default now. So any bool would need to turn it off, so would need a different name.

But a bool might not be flexible enough. A func(string) bool might be better. A per-key policy func or something. And then there could be predefined funcs/vars for AllowAll or AllNone. And a nil func (the default) would be a Go-defined policy, like we have in 1.8.

[gopherbot]

Change https://golang.org/cl/95895 mentions this issue: net/http: optionally add headers on redirect

[zachgersh]

I am also closing this issue. Seems like the default behavior is fine as @bradfitz originally stated.