net/http: send cookies in jar on redirect

Until a RFC 6265 jar lands, Request.AddCookie() will work incorrectly.

Fixes #2692

R=bradfitz, rsc
CC=golang-dev, r
https://golang.org/cl/5544069

src/pkg/net/http/client.go

@@ -213,11 +213,11 @@ func (c *Client) doFollowingRedirects(ireq *Request) (r *Response, err error) {
 					break
 				}
 			}
+		}
+
 		for _, cookie := range jar.Cookies(req.URL) {
 			req.AddCookie(cookie)
 		}
-		}
-
 		urlStr = req.URL.String()
 		if r, err = send(req, c.Transport); err != nil {
 			break

src/pkg/net/http/client_test.go

@@ -18,6 +18,7 @@ import (
 	"net/url"
 	"strconv"
 	"strings"
+	"sync"
 	"testing"
 )
 
@@ -236,6 +237,92 @@ func TestRedirects(t *testing.T) {
 	}
 }
 
+var expectedCookies = []*Cookie{
+	&Cookie{Name: "ChocolateChip", Value: "tasty"},
+	&Cookie{Name: "First", Value: "Hit"},
+	&Cookie{Name: "Second", Value: "Hit"},
+}
+
+var echoCookiesRedirectHandler = HandlerFunc(func(w ResponseWriter, r *Request) {
+	for _, cookie := range r.Cookies() {
+		SetCookie(w, cookie)
+	}
+	if r.URL.Path == "/" {
+		SetCookie(w, expectedCookies[1])
+		Redirect(w, r, "/second", StatusMovedPermanently)
+	} else {
+		SetCookie(w, expectedCookies[2])
+		w.Write([]byte("hello"))
+	}
+})
+
+// Just enough correctness for our redirect tests. Uses the URL.Host as the
+// scope of all cookies.
+type TestJar struct {
+	m      sync.Mutex
+	perURL map[string][]*Cookie
+}
+
+func (j *TestJar) SetCookies(u *url.URL, cookies []*Cookie) {
+	j.m.Lock()
+	defer j.m.Unlock()
+	j.perURL[u.Host] = cookies
+}
+
+func (j *TestJar) Cookies(u *url.URL) []*Cookie {
+	j.m.Lock()
+	defer j.m.Unlock()
+	return j.perURL[u.Host]
+}
+
+func TestRedirectCookiesOnRequest(t *testing.T) {
+	var ts *httptest.Server
+	ts = httptest.NewServer(echoCookiesRedirectHandler)
+	defer ts.Close()
+	c := &Client{}
+	req, _ := NewRequest("GET", ts.URL, nil)
+	req.AddCookie(expectedCookies[0])
+	// TODO: Uncomment when an implementation of a RFC6265 cookie jar lands.
+	_ = c
+	// resp, _ := c.Do(req)
+	// matchReturnedCookies(t, expectedCookies, resp.Cookies())
+
+	req, _ = NewRequest("GET", ts.URL, nil)
+	// resp, _ = c.Do(req)
+	// matchReturnedCookies(t, expectedCookies[1:], resp.Cookies())
+}
+
+func TestRedirectCookiesJar(t *testing.T) {
+	var ts *httptest.Server
+	ts = httptest.NewServer(echoCookiesRedirectHandler)
+	defer ts.Close()
+	c := &Client{}
+	c.Jar = &TestJar{perURL: make(map[string][]*Cookie)}
+	u, _ := url.Parse(ts.URL)
+	c.Jar.SetCookies(u, []*Cookie{expectedCookies[0]})
+	resp, _ := c.Get(ts.URL)
+	matchReturnedCookies(t, expectedCookies, resp.Cookies())
+}
+
+func matchReturnedCookies(t *testing.T, expected, given []*Cookie) {
+	t.Logf("Received cookies: %v", given)
+	if len(given) != len(expected) {
+		t.Errorf("Expected %d cookies, got %d", len(expected), len(given))
+	}
+	for _, ec := range expected {
+		foundC := false
+		for _, c := range given {
+			if ec.Name == c.Name && ec.Value == c.Value {
+				foundC = true
+				break
+			}
+		}
+		if !foundC {
+			t.Errorf("Missing cookie %v", ec)
+		}
+	}
+}
+
 func TestStreamingGet(t *testing.T) {
 	say := make(chan string)
 	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {