Well, they do parse as different URLs:

https://play.golang.org/p/7xC_QxjGyI

But maybe the (*URL).Query() method could return different values?

Additionally, url.Query().Encode() will percent-encode query parameters that were not previously encoded, which some servers don't like. One example:

http://www.dayonepatch.com/index.php?/topic/135060-data-saver-and-d1p/
http://www.dayonepatch.com/index.php?%2Ftopic%2F135060-data-saver-and-d1p%2F=

This may be fixable by adding url.Value.RawEncode()? Or again, this may just be something to document more clearly.

Maybe we should back up. What is the problem?

This bug is bordering on "Doctor, it hurts if I do this..."

That is, don't modify the RawQuery if the RawQuery was correct to begin with.

What is your use case?

The use case was adding/removing query params from a URL. We needed to do this without changing any of the existing query params. We're fixing this a different way, so I don't need a code change in the library, but I think the methods should document the behavior more clearly, particularly in the first example, which I think is surprising.

Gotcha, thanks.

I don't think there's anything to do here. url.Query() unfortunately only works for key=value query strings; isindex-style query strings have to be implemented using RawQuery.

I agree that a code change isn't needed, but I think the godoc could be clarified. URL.Query says that it "parses RawQuery" but doesn't say anything about formatting expectations. Something like:

// Query parses RawQuery and returns the corresponding values. It assumes
// RawQuery is a list of key=value pairs separated by '&' or ';'. If RawQuery
// has a different form, the return value is undefined.
func (u *URL) Query() Values

CL https://golang.org/cl/31331 mentions this issue.