net/http/httptest: ResponseRecorder does not implement http.ResponseWriter spec correctly

[srinathh]

The documentation for http.ResponseWriter specifies certain behaviors for the Header() Header and the Write([]byte) (int, error) functions that are not being implemented by httptest.ResponseRecorder currently. Specifically -

• in Write() If the Header does not contain a Content-Type line, Write adds a Content-Type set to the result of passing the initial 512 bytes of written data to DetectContentType.
• Changing the header after a call to WriteHeader (or Write) has no effect unless the modified headers were declared as trailers by setting the "Trailer" header before the call to WriteHeader

I ran into this issue when looking for Content-Type header from ResponseRecorder and looking at the code for ResponseRecorder, did not see an implementation for the spec.

[nodirt]

I will take this one

[gopherbot]

CL https://golang.org/cl/16096 mentions this issue.

[nodirt]

I think ResponseRecorder already has enough to check trailers.

// trailers returns only trailer headers.
func trailers(h http.Header) http.Header {
    res := http.Header{}
    for _, keyString := range h["Trailer"] {
        for _, key := range strings.Split(keyString, ",") {
            key = http.CanonicalHeaderKey(strings.TrimSpace(key))
            res[key] = h[key]
        }
    }
    return res
}

This will return only trailers. https://play.golang.org/p/348R0WDFOM

[nodirt]

I think this can be closed.