http: send full URL in proxy requests

Fixes #53.  (again)

R=agl1
CC=golang-dev
https://golang.org/cl/4167054

src/pkg/http/client.go

@@ -92,19 +92,25 @@ func send(req *Request) (resp *Response, err os.Error) {
 
 	var proxyURL *URL
 	proxyAuth := ""
-	proxy := os.Getenv("HTTP_PROXY")
+	proxy := ""
+	if !matchNoProxy(addr) {
+		proxy = os.Getenv("HTTP_PROXY")
 		if proxy == "" {
 			proxy = os.Getenv("http_proxy")
 		}
-	if matchNoProxy(addr) {
-		proxy = ""
 	}
 
 	if proxy != "" {
-		proxyURL, err = ParseURL(proxy)
+		proxyURL, err = ParseRequestURL(proxy)
 		if err != nil {
 			return nil, os.ErrorString("invalid proxy address")
 		}
+		if proxyURL.Host == "" {
+			proxyURL, err = ParseRequestURL("http://" + proxy)
+			if err != nil {
+				return nil, os.ErrorString("invalid proxy address")
+			}
+		}
 		addr = proxyURL.Host
 		proxyInfo := proxyURL.RawUserinfo
 		if proxyInfo != "" {

src/pkg/http/request.go

@@ -184,6 +184,17 @@ const defaultUserAgent = "Go http package"
 // If Body is present, Write forces "Transfer-Encoding: chunked" as a header
 // and then closes Body when finished sending it.
 func (req *Request) Write(w io.Writer) os.Error {
+	return req.write(w, false)
+}
+
+// WriteProxy is like Write but writes the request in the form
+// expected by an HTTP proxy.  It includes the scheme and host
+// name in the URI instead of using a separate Host: header line.
+func (req *Request) WriteProxy(w io.Writer) os.Error {
+	return req.write(w, true)
+}
+
+func (req *Request) write(w io.Writer, usingProxy bool) os.Error {
 	host := req.Host
 	if host == "" {
 		host = req.URL.Host
@@ -197,10 +208,19 @@ func (req *Request) Write(w io.Writer) os.Error {
 		}
 	}
 
+	if usingProxy {
+		if uri == "" || uri[0] != '/' {
+			uri = "/" + uri
+		}
+		uri = req.URL.Scheme + "://" + host + uri
+	}
+
 	fmt.Fprintf(w, "%s %s HTTP/1.1\r\n", valueOrDefault(req.Method, "GET"), uri)
 
 	// Header lines
+	if !usingProxy {
 		fmt.Fprintf(w, "Host: %s\r\n", host)
+	}
 	fmt.Fprintf(w, "User-Agent: %s\r\n", valueOrDefault(req.UserAgent, defaultUserAgent))
 	if req.Referer != "" {
 		fmt.Fprintf(w, "Referer: %s\r\n", req.Referer)