net/http: add Request.GetBody func for 307/308 redirects

Updates #10767

Change-Id: I197535f71bc2dc45e783f38d8031aa717d50fd80
Reviewed-on: https://go-review.googlesource.com/31733
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>

src/net/http/client.go

@@ -485,8 +485,15 @@ func (c *Client) doFollowingRedirects(req *Request, shouldRedirect func(int) boo
 				Cancel:   ireq.Cancel,
 				ctx:      ireq.ctx,
 			}
+			if ireq.GetBody != nil {
+				req.Body, err = ireq.GetBody()
+				if err != nil {
+					return nil, uerr(err)
+				}
+			}
 			if ireq.Method == "POST" || ireq.Method == "PUT" {
 				req.Method = "GET"
+				req.Body = nil // TODO: fix this when 307/308 support happens
 			}
 			// Copy the initial request's Header values
 			// (at least the safe ones).  Do this before

src/net/http/request.go

@@ -151,6 +151,14 @@ type Request struct {
 	// Handler does not need to.
 	Body io.ReadCloser
 
+	// GetBody defines an optional func to return a new copy of
+	// Body. It used for client requests when a redirect requires
+	// reading the body more than once. Use of GetBody still
+	// requires setting Body.
+	//
+	// For server requests it is unused.
+	GetBody func() (io.ReadCloser, error)
+
 	// ContentLength records the length of the associated content.
 	// The value -1 indicates that the length is unknown.
 	// Values >= 0 indicate that the given number of bytes may
@@ -738,10 +746,25 @@ func NewRequest(method, urlStr string, body io.Reader) (*Request, error) {
 		switch v := body.(type) {
 		case *bytes.Buffer:
 			req.ContentLength = int64(v.Len())
+			buf := v.Bytes()
+			req.GetBody = func() (io.ReadCloser, error) {
+				r := bytes.NewReader(buf)
+				return ioutil.NopCloser(r), nil
+			}
 		case *bytes.Reader:
 			req.ContentLength = int64(v.Len())
+			snapshot := *v
+			req.GetBody = func() (io.ReadCloser, error) {
+				r := snapshot
+				return ioutil.NopCloser(&r), nil
+			}
 		case *strings.Reader:
 			req.ContentLength = int64(v.Len())
+			snapshot := *v
+			req.GetBody = func() (io.ReadCloser, error) {
+				r := snapshot
+				return ioutil.NopCloser(&r), nil
+			}
 		default:
 			req.ContentLength = -1 // unknown
 		}
@@ -751,6 +774,7 @@ func NewRequest(method, urlStr string, body io.Reader) (*Request, error) {
 		// to set the Body to nil.
 		if req.ContentLength == 0 {
 			req.Body = nil
+			req.GetBody = nil
 		}
 	}
 

src/net/http/request_test.go

@@ -784,6 +784,47 @@ func TestMaxBytesReaderStickyError(t *testing.T) {
 	}
 }
 
+// verify that NewRequest sets Request.GetBody and that it works
+func TestNewRequestGetBody(t *testing.T) {
+	tests := []struct {
+		r io.Reader
+	}{
+		{r: strings.NewReader("hello")},
+		{r: bytes.NewReader([]byte("hello"))},
+		{r: bytes.NewBuffer([]byte("hello"))},
+	}
+	for i, tt := range tests {
+		req, err := NewRequest("POST", "http://foo.tld/", tt.r)
+		if err != nil {
+			t.Errorf("test[%d]: %v", i, err)
+			continue
+		}
+		if req.Body == nil {
+			t.Errorf("test[%d]: Body = nil", i)
+			continue
+		}
+		if req.GetBody == nil {
+			t.Errorf("test[%d]: GetBody = nil", i)
+			continue
+		}
+		slurp1, err := ioutil.ReadAll(req.Body)
+		if err != nil {
+			t.Errorf("test[%d]: ReadAll(Body) = %v", i, err)
+		}
+		newBody, err := req.GetBody()
+		if err != nil {
+			t.Errorf("test[%d]: GetBody = %v", i, err)
+		}
+		slurp2, err := ioutil.ReadAll(newBody)
+		if err != nil {
+			t.Errorf("test[%d]: ReadAll(GetBody()) = %v", i, err)
+		}
+		if string(slurp1) != string(slurp2) {
+			t.Errorf("test[%d]: Body %q != GetBody %q", i, slurp1, slurp2)
+		}
+	}
+}
+
 func testMissingFile(t *testing.T, req *Request) {
 	f, fh, err := req.FormFile("missing")
 	if f != nil {