net/http: Make ReadResponse work with a nil Request parameter

Fixes #5583

R=golang-dev, dave, bradfitz
CC=golang-dev
https://golang.org/cl/9821043

src/pkg/net/http/response.go

@@ -98,18 +98,17 @@ func (r *Response) Location() (*url.URL, error) {
 	return url.Parse(lv)
 }
 
-// ReadResponse reads and returns an HTTP response from r.  The
-// req parameter specifies the Request that corresponds to
-// this Response.  Clients must call resp.Body.Close when finished
-// reading resp.Body.  After that call, clients can inspect
-// resp.Trailer to find key/value pairs included in the response
-// trailer.
-func ReadResponse(r *bufio.Reader, req *Request) (resp *Response, err error) {
-
+// ReadResponse reads and returns an HTTP response from r.
+// The req parameter optionally specifies the Request that corresponds
+// to this Response. If nil, a GET request is assumed.
+// Clients must call resp.Body.Close when finished reading resp.Body.
+// After that call, clients can inspect resp.Trailer to find key/value
+// pairs included in the response trailer.
+func ReadResponse(r *bufio.Reader, req *Request) (*Response, error) {
 	tp := textproto.NewReader(r)
-	resp = new(Response)
-
-	resp.Request = req
+	resp := &Response{
+		Request: req,
+	}
 
 	// Parse the first line of the response.
 	line, err := tp.ReadLine()

src/pkg/net/http/response_test.go

@@ -348,6 +348,29 @@ some body`,
 
 		"some body",
 	},
+
+	// Unchunked response without Content-Length, Request is nil
+	{
+		"HTTP/1.0 200 OK\r\n" +
+			"Connection: close\r\n" +
+			"\r\n" +
+			"Body here\n",
+
+		Response{
+			Status:     "200 OK",
+			StatusCode: 200,
+			Proto:      "HTTP/1.0",
+			ProtoMajor: 1,
+			ProtoMinor: 0,
+			Header: Header{
+				"Connection": {"close"}, // TODO(rsc): Delete?
+			},
+			Close:         true,
+			ContentLength: -1,
+		},
+
+		"Body here\n",
+	},
 }
 
 func TestReadResponse(t *testing.T) {

src/pkg/net/http/transfer.go

@@ -254,7 +254,7 @@ func bodyAllowedForStatus(status int) bool {
 
 // msg is *Request or *Response.
 func readTransfer(msg interface{}, r *bufio.Reader) (err error) {
-	t := &transferReader{}
+	t := &transferReader{RequestMethod: "GET"}
 
 	// Unify input
 	isResponse := false
@@ -262,11 +262,13 @@ func readTransfer(msg interface{}, r *bufio.Reader) (err error) {
 	case *Response:
 		t.Header = rr.Header
 		t.StatusCode = rr.StatusCode
-		t.RequestMethod = rr.Request.Method
 		t.ProtoMajor = rr.ProtoMajor
 		t.ProtoMinor = rr.ProtoMinor
 		t.Close = shouldClose(t.ProtoMajor, t.ProtoMinor, t.Header)
 		isResponse = true
+		if rr.Request != nil {
+			t.RequestMethod = rr.Request.Method
+		}
 	case *Request:
 		t.Header = rr.Header
 		t.ProtoMajor = rr.ProtoMajor
@@ -274,7 +276,6 @@ func readTransfer(msg interface{}, r *bufio.Reader) (err error) {
 		// Transfer semantics for Requests are exactly like those for
 		// Responses with status code 200, responding to a GET method
 		t.StatusCode = 200
-		t.RequestMethod = "GET"
 	default:
 		panic("unexpected type")
 	}