net/http: document the behavior of %2F in url strings

[gopherbot]

by david.schmiddi.86:

What does 'go version' print?
go version go1.3 windows/amd64

What steps reproduce the problem?
http://play.golang.org/p/ZOqHmlFaU8

1. http.Get("https://example.com/search/Alive+%2F%2F+Well/true";)

What happened?
404

What should have happened instead?
200
The parameter is a string, it should not modify my provided url. I should care about
escaping myself or at least given an option or hint what is magically happening behind
the scenes.

Please provide any additional information below.

I stumbled across this on accident and after I finally found the flaw, I found a lot of
older issues and an updated note about this unexpected behavior in another package:
http://golang.org/pkg/net/url/#URL

It should be documented in net/http, that it uses net/url to parse, decode and reencode
the string url parameters and that %2F is going to be lost. I'd even document the
solution for users who need %2F support.

[jstemmer]

Comment 1:

I'm trying to work around a similar problem. Note that the string "Alice // Well" in
your example is technically part of the URL path (and not a query parameter) which means
the escaping should behave differently. A space for example should be represented as %20
instead of +, so using url.QueryEscape may not always lead to correct escaping.

[gopherbot]

Comment 2 by david.schmiddi.86:

But the "+" was the result of the encoder in http://golang.org/pkg/net/url/#URL .
http.Get(fmt.Sprintf("https://example.com/search/%s/true", url.QueryEscape(name)))

[mikioh]

Comment 3:

cf. issue #5684

[griesemer]

Comment 4:

Labels changed: added repo-main.

[rsc]

Isn't this already well documented?

[rsc]

(Original title mentioned RFC 3986.)