net/http: fix handling of HEAD in ReadResponse and (*http.Response).Write

The test suite for ReadResponse was not checking the error return on the io.Copy
on the body. This was masking two errors: the handling of chunked responses to
HEAD requests and the handling of Content-Length > 0 to HEAD.

The former manifested itself as an 'unexpected EOF' when doing the io.Copy
because a chunked reader was assigned but there were no chunks to read. The
latter cause (*http.Response).Write to report an error on HEAD requests
because it saw a Content-Length > 0 and expected a body.

There was also a missing \r\n in one chunked test that meant that the chunked
encoding was malformed. This does not appear to have been intentional.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/7407046

src/pkg/net/http/response_test.go

@@ -157,7 +157,7 @@ var respTests = []respTest{
 			"Content-Length: 10\r\n" +
 			"\r\n" +
 			"0a\r\n" +
-			"Body here\n" +
+			"Body here\n\r\n" +
 			"0\r\n" +
 			"\r\n",
 
@@ -327,13 +327,10 @@ var respTests = []respTest{
 }
 
 func TestReadResponse(t *testing.T) {
-	for i := range respTests {
-		tt := &respTests[i]
-		var braw bytes.Buffer
-		braw.WriteString(tt.Raw)
-		resp, err := ReadResponse(bufio.NewReader(&braw), tt.Resp.Request)
+	for i, tt := range respTests {
+		resp, err := ReadResponse(bufio.NewReader(strings.NewReader(tt.Raw)), tt.Resp.Request)
 		if err != nil {
-			t.Errorf("#%d: %s", i, err)
+			t.Errorf("#%d: %v", i, err)
 			continue
 		}
 		rbody := resp.Body
@@ -341,7 +338,11 @@ func TestReadResponse(t *testing.T) {
 		diff(t, fmt.Sprintf("#%d Response", i), resp, &tt.Resp)
 		var bout bytes.Buffer
 		if rbody != nil {
-			io.Copy(&bout, rbody)
+			_, err = io.Copy(&bout, rbody)
+			if err != nil {
+				t.Errorf("#%d: %v", i, err)
+				continue
+			}
 			rbody.Close()
 		}
 		body := bout.String()
@@ -351,6 +352,22 @@ func TestReadResponse(t *testing.T) {
 	}
 }
 
+func TestWriteResponse(t *testing.T) {
+	for i, tt := range respTests {
+		resp, err := ReadResponse(bufio.NewReader(strings.NewReader(tt.Raw)), tt.Resp.Request)
+		if err != nil {
+			t.Errorf("#%d: %v", i, err)
+			continue
+		}
+		bout := bytes.NewBuffer(nil)
+		err = resp.Write(bout)
+		if err != nil {
+			t.Errorf("#%d: %v", i, err)
+			continue
+		}
+	}
+}
+
 var readResponseCloseInMiddleTests = []struct {
 	chunked, compressed bool
 }{

src/pkg/net/http/transfer.go

@@ -209,7 +209,7 @@ func (t *transferWriter) WriteBody(w io.Writer) (err error) {
 		}
 	}
 
-	if t.ContentLength != -1 && t.ContentLength != ncopy {
+	if !t.ResponseToHEAD && t.ContentLength != -1 && t.ContentLength != ncopy {
 		return fmt.Errorf("http: Request.ContentLength=%d with Body length %d",
 			t.ContentLength, ncopy)
 	}
@@ -327,7 +327,11 @@ func readTransfer(msg interface{}, r *bufio.Reader) (err error) {
 	// or close connection when finished, since multipart is not supported yet
 	switch {
 	case chunked(t.TransferEncoding):
+		if noBodyExpected(t.RequestMethod) {
+			t.Body = &body{Reader: io.LimitReader(r, 0), closing: t.Close}
+		} else {
 			t.Body = &body{Reader: newChunkedReader(r), hdr: msg, r: r, closing: t.Close}
+		}
 	case realLength >= 0:
 		// TODO: limit the Content-Length. This is an easy DoS vector.
 		t.Body = &body{Reader: io.LimitReader(r, realLength), closing: t.Close}