Fix header .Add functions

[erikdubbelboer]

These functions should take the headers that are handled differently into account.

Fixes #1033

After this change it is not possible to have multiple
Content-Type, Content-Length, Connection, Server, Set-Cookie, Transfer-Encoding and Date headers. Having other headers multiple times is still fine. For these headers it should never happen anyways and I don't think we have any users who do this. But if they do it would break for then.

[savsgio]

LGTM!

[Fenny]

Nice catch! Lgtm

[ReneWerner87]

old code:

	case HeaderTransferEncoding:
		// Transfer-Encoding is managed automatically.
	case HeaderDate:
		// Date is managed automatically.
	default:
		h.h = setArgBytes(h.h, key, value, argsHasValue)

new code:

	case 't':
		if caseInsensitiveCompare(strTransferEncoding, key) {
			// Transfer-Encoding is managed automatically.
			return true
		}
		.....
	case 'd':
		if caseInsensitiveCompare(strDate, key) {
			// Date is managed automatically.
			return true
		}
	}
	
	....

@erikdubbelboer
i think there is a mistake here, the return value should be false, outside of that you break if you have the value true and don't set a header

and if we don't change the return value, we have to set it inside, because somewhere the header value should be set

also think you should rebuild the adjustment with the encoding in the adapter test, because exactly that would have shown you this error

fasthttp/header.go

Line 1252 in 7bd43f6

if h.setSpecialHeader(key, value) {

fasthttp/header.go

Line 1296 in 7bd43f6

if h.setSpecialHeader(key, value) {

i saw this, because of our tests
https://github.com/gofiber/adaptor/pull/66/checks?check_run_id=2734201815

we expect
https://github.com/gofiber/adaptor/blob/master/main_test.go#L29
https://github.com/gofiber/adaptor/blob/master/main_test.go#L66
https://github.com/gofiber/adaptor/blob/master/main_test.go#L110

[ReneWerner87]

@erikdubbelboer

[erikdubbelboer]

To be honest I think your test is wrong. Transfer-Encoding can't just be set to something random like that. Transfer-Encoding control how the body is transferred between server and client which is something fasthttp controls itself. Otherwise you would be able to set Transfer-Encoding: chunked while fasthttp does an identity encoding and the whole thing fails.

[ReneWerner87]

ok, thanks

then I will adjust our tests times, just wanted to be sure

you had that also in your tests and I thought it should be settable

thx