Adding upstream version 1.16.10.upstream/1.16.10upstream

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 2084 insertions, 0 deletions

diff --git a/src/net/http/client_test.go b/src/net/http/client_test.go
new file mode 100644
index 0000000..d90b484
--- /dev/null
+++ b/src/net/http/client_test.go
@@ -0,0 +1,2084 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Tests for client.go
+
+package http_test
+
+import (
+	"bytes"
+	"context"
+	"crypto/tls"
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"io"
+	"log"
+	"net"
+	. "net/http"
+	"net/http/cookiejar"
+	"net/http/httptest"
+	"net/url"
+	"reflect"
+	"strconv"
+	"strings"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+var robotsTxtHandler = HandlerFunc(func(w ResponseWriter, r *Request) {
+	w.Header().Set("Last-Modified", "sometime")
+	fmt.Fprintf(w, "User-agent: go\nDisallow: /something/")
+})
+
+// pedanticReadAll works like io.ReadAll but additionally
+// verifies that r obeys the documented io.Reader contract.
+func pedanticReadAll(r io.Reader) (b []byte, err error) {
+	var bufa [64]byte
+	buf := bufa[:]
+	for {
+		n, err := r.Read(buf)
+		if n == 0 && err == nil {
+			return nil, fmt.Errorf("Read: n=0 with err=nil")
+		}
+		b = append(b, buf[:n]...)
+		if err == io.EOF {
+			n, err := r.Read(buf)
+			if n != 0 || err != io.EOF {
+				return nil, fmt.Errorf("Read: n=%d err=%#v after EOF", n, err)
+			}
+			return b, nil
+		}
+		if err != nil {
+			return b, err
+		}
+	}
+}
+
+type chanWriter chan string
+
+func (w chanWriter) Write(p []byte) (n int, err error) {
+	w <- string(p)
+	return len(p), nil
+}
+
+func TestClient(t *testing.T) {
+	setParallel(t)
+	defer afterTest(t)
+	ts := httptest.NewServer(robotsTxtHandler)
+	defer ts.Close()
+
+	c := ts.Client()
+	r, err := c.Get(ts.URL)
+	var b []byte
+	if err == nil {
+		b, err = pedanticReadAll(r.Body)
+		r.Body.Close()
+	}
+	if err != nil {
+		t.Error(err)
+	} else if s := string(b); !strings.HasPrefix(s, "User-agent:") {
+		t.Errorf("Incorrect page body (did not begin with User-agent): %q", s)
+	}
+}
+
+func TestClientHead_h1(t *testing.T) { testClientHead(t, h1Mode) }
+func TestClientHead_h2(t *testing.T) { testClientHead(t, h2Mode) }
+
+func testClientHead(t *testing.T, h2 bool) {
+	defer afterTest(t)
+	cst := newClientServerTest(t, h2, robotsTxtHandler)
+	defer cst.close()
+
+	r, err := cst.c.Head(cst.ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, ok := r.Header["Last-Modified"]; !ok {
+		t.Error("Last-Modified header not found.")
+	}
+}
+
+type recordingTransport struct {
+	req *Request
+}
+
+func (t *recordingTransport) RoundTrip(req *Request) (resp *Response, err error) {
+	t.req = req
+	return nil, errors.New("dummy impl")
+}
+
+func TestGetRequestFormat(t *testing.T) {
+	setParallel(t)
+	defer afterTest(t)
+	tr := &recordingTransport{}
+	client := &Client{Transport: tr}
+	url := "http://dummy.faketld/"
+	client.Get(url) // Note: doesn't hit network
+	if tr.req.Method != "GET" {
+		t.Errorf("expected method %q; got %q", "GET", tr.req.Method)
+	}
+	if tr.req.URL.String() != url {
+		t.Errorf("expected URL %q; got %q", url, tr.req.URL.String())
+	}
+	if tr.req.Header == nil {
+		t.Errorf("expected non-nil request Header")
+	}
+}
+
+func TestPostRequestFormat(t *testing.T) {
+	defer afterTest(t)
+	tr := &recordingTransport{}
+	client := &Client{Transport: tr}
+
+	url := "http://dummy.faketld/"
+	json := `{"key":"value"}`
+	b := strings.NewReader(json)
+	client.Post(url, "application/json", b) // Note: doesn't hit network
+
+	if tr.req.Method != "POST" {
+		t.Errorf("got method %q, want %q", tr.req.Method, "POST")
+	}
+	if tr.req.URL.String() != url {
+		t.Errorf("got URL %q, want %q", tr.req.URL.String(), url)
+	}
+	if tr.req.Header == nil {
+		t.Fatalf("expected non-nil request Header")
+	}
+	if tr.req.Close {
+		t.Error("got Close true, want false")
+	}
+	if g, e := tr.req.ContentLength, int64(len(json)); g != e {
+		t.Errorf("got ContentLength %d, want %d", g, e)
+	}
+}
+
+func TestPostFormRequestFormat(t *testing.T) {
+	defer afterTest(t)
+	tr := &recordingTransport{}
+	client := &Client{Transport: tr}
+
+	urlStr := "http://dummy.faketld/"
+	form := make(url.Values)
+	form.Set("foo", "bar")
+	form.Add("foo", "bar2")
+	form.Set("bar", "baz")
+	client.PostForm(urlStr, form) // Note: doesn't hit network
+
+	if tr.req.Method != "POST" {
+		t.Errorf("got method %q, want %q", tr.req.Method, "POST")
+	}
+	if tr.req.URL.String() != urlStr {
+		t.Errorf("got URL %q, want %q", tr.req.URL.String(), urlStr)
+	}
+	if tr.req.Header == nil {
+		t.Fatalf("expected non-nil request Header")
+	}
+	if g, e := tr.req.Header.Get("Content-Type"), "application/x-www-form-urlencoded"; g != e {
+		t.Errorf("got Content-Type %q, want %q", g, e)
+	}
+	if tr.req.Close {
+		t.Error("got Close true, want false")
+	}
+	// Depending on map iteration, body can be either of these.
+	expectedBody := "foo=bar&foo=bar2&bar=baz"
+	expectedBody1 := "bar=baz&foo=bar&foo=bar2"
+	if g, e := tr.req.ContentLength, int64(len(expectedBody)); g != e {
+		t.Errorf("got ContentLength %d, want %d", g, e)
+	}
+	bodyb, err := io.ReadAll(tr.req.Body)
+	if err != nil {
+		t.Fatalf("ReadAll on req.Body: %v", err)
+	}
+	if g := string(bodyb); g != expectedBody && g != expectedBody1 {
+		t.Errorf("got body %q, want %q or %q", g, expectedBody, expectedBody1)
+	}
+}
+
+func TestClientRedirects(t *testing.T) {
+	setParallel(t)
+	defer afterTest(t)
+	var ts *httptest.Server
+	ts = httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		n, _ := strconv.Atoi(r.FormValue("n"))
+		// Test Referer header. (7 is arbitrary position to test at)
+		if n == 7 {
+			if g, e := r.Referer(), ts.URL+"/?n=6"; e != g {
+				t.Errorf("on request ?n=7, expected referer of %q; got %q", e, g)
+			}
+		}
+		if n < 15 {
+			Redirect(w, r, fmt.Sprintf("/?n=%d", n+1), StatusTemporaryRedirect)
+			return
+		}
+		fmt.Fprintf(w, "n=%d", n)
+	}))
+	defer ts.Close()
+
+	c := ts.Client()
+	_, err := c.Get(ts.URL)
+	if e, g := `Get "/?n=10": stopped after 10 redirects`, fmt.Sprintf("%v", err); e != g {
+		t.Errorf("with default client Get, expected error %q, got %q", e, g)
+	}
+
+	// HEAD request should also have the ability to follow redirects.
+	_, err = c.Head(ts.URL)
+	if e, g := `Head "/?n=10": stopped after 10 redirects`, fmt.Sprintf("%v", err); e != g {
+		t.Errorf("with default client Head, expected error %q, got %q", e, g)
+	}
+
+	// Do should also follow redirects.
+	greq, _ := NewRequest("GET", ts.URL, nil)
+	_, err = c.Do(greq)
+	if e, g := `Get "/?n=10": stopped after 10 redirects`, fmt.Sprintf("%v", err); e != g {
+		t.Errorf("with default client Do, expected error %q, got %q", e, g)
+	}
+
+	// Requests with an empty Method should also redirect (Issue 12705)
+	greq.Method = ""
+	_, err = c.Do(greq)
+	if e, g := `Get "/?n=10": stopped after 10 redirects`, fmt.Sprintf("%v", err); e != g {
+		t.Errorf("with default client Do and empty Method, expected error %q, got %q", e, g)
+	}
+
+	var checkErr error
+	var lastVia []*Request
+	var lastReq *Request
+	c.CheckRedirect = func(req *Request, via []*Request) error {
+		lastReq = req
+		lastVia = via
+		return checkErr
+	}
+	res, err := c.Get(ts.URL)
+	if err != nil {
+		t.Fatalf("Get error: %v", err)
+	}
+	res.Body.Close()
+	finalUrl := res.Request.URL.String()
+	if e, g := "<nil>", fmt.Sprintf("%v", err); e != g {
+		t.Errorf("with custom client, expected error %q, got %q", e, g)
+	}
+	if !strings.HasSuffix(finalUrl, "/?n=15") {
+		t.Errorf("expected final url to end in /?n=15; got url %q", finalUrl)
+	}
+	if e, g := 15, len(lastVia); e != g {
+		t.Errorf("expected lastVia to have contained %d elements; got %d", e, g)
+	}
+
+	// Test that Request.Cancel is propagated between requests (Issue 14053)
+	creq, _ := NewRequest("HEAD", ts.URL, nil)
+	cancel := make(chan struct{})
+	creq.Cancel = cancel
+	if _, err := c.Do(creq); err != nil {
+		t.Fatal(err)
+	}
+	if lastReq == nil {
+		t.Fatal("didn't see redirect")
+	}
+	if lastReq.Cancel != cancel {
+		t.Errorf("expected lastReq to have the cancel channel set on the initial req")
+	}
+
+	checkErr = errors.New("no redirects allowed")
+	res, err = c.Get(ts.URL)
+	if urlError, ok := err.(*url.Error); !ok || urlError.Err != checkErr {
+		t.Errorf("with redirects forbidden, expected a *url.Error with our 'no redirects allowed' error inside; got %#v (%q)", err, err)
+	}
+	if res == nil {
+		t.Fatalf("Expected a non-nil Response on CheckRedirect failure (https://golang.org/issue/3795)")
+	}
+	res.Body.Close()
+	if res.Header.Get("Location") == "" {
+		t.Errorf("no Location header in Response")
+	}
+}
+
+// Tests that Client redirects' contexts are derived from the original request's context.
+func TestClientRedirectContext(t *testing.T) {
+	setParallel(t)
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		Redirect(w, r, "/", StatusTemporaryRedirect)
+	}))
+	defer ts.Close()
+
+	ctx, cancel := context.WithCancel(context.Background())
+	c := ts.Client()
+	c.CheckRedirect = func(req *Request, via []*Request) error {
+		cancel()
+		select {
+		case <-req.Context().Done():
+			return nil
+		case <-time.After(5 * time.Second):
+			return errors.New("redirected request's context never expired after root request canceled")
+		}
+	}
+	req, _ := NewRequestWithContext(ctx, "GET", ts.URL, nil)
+	_, err := c.Do(req)
+	ue, ok := err.(*url.Error)
+	if !ok {
+		t.Fatalf("got error %T; want *url.Error", err)
+	}
+	if ue.Err != context.Canceled {
+		t.Errorf("url.Error.Err = %v; want %v", ue.Err, context.Canceled)
+	}
+}
+
+type redirectTest struct {
+	suffix       string
+	want         int // response code
+	redirectBody string
+}
+
+func TestPostRedirects(t *testing.T) {
+	postRedirectTests := []redirectTest{
+		{"/", 200, "first"},
+		{"/?code=301&next=302", 200, "c301"},
+		{"/?code=302&next=302", 200, "c302"},
+		{"/?code=303&next=301", 200, "c303wc301"}, // Issue 9348
+		{"/?code=304", 304, "c304"},
+		{"/?code=305", 305, "c305"},
+		{"/?code=307&next=303,308,302", 200, "c307"},
+		{"/?code=308&next=302,301", 200, "c308"},
+		{"/?code=404", 404, "c404"},
+	}
+
+	wantSegments := []string{
+		`POST / "first"`,
+		`POST /?code=301&next=302 "c301"`,
+		`GET /?code=302 ""`,
+		`GET / ""`,
+		`POST /?code=302&next=302 "c302"`,
+		`GET /?code=302 ""`,
+		`GET / ""`,
+		`POST /?code=303&next=301 "c303wc301"`,
+		`GET /?code=301 ""`,
+		`GET / ""`,
+		`POST /?code=304 "c304"`,
+		`POST /?code=305 "c305"`,
+		`POST /?code=307&next=303,308,302 "c307"`,
+		`POST /?code=303&next=308,302 "c307"`,
+		`GET /?code=308&next=302 ""`,
+		`GET /?code=302 "c307"`,
+		`GET / ""`,
+		`POST /?code=308&next=302,301 "c308"`,
+		`POST /?code=302&next=301 "c308"`,
+		`GET /?code=301 ""`,
+		`GET / ""`,
+		`POST /?code=404 "c404"`,
+	}
+	want := strings.Join(wantSegments, "\n")
+	testRedirectsByMethod(t, "POST", postRedirectTests, want)
+}
+
+func TestDeleteRedirects(t *testing.T) {
+	deleteRedirectTests := []redirectTest{
+		{"/", 200, "first"},
+		{"/?code=301&next=302,308", 200, "c301"},
+		{"/?code=302&next=302", 200, "c302"},
+		{"/?code=303", 200, "c303"},
+		{"/?code=307&next=301,308,303,302,304", 304, "c307"},
+		{"/?code=308&next=307", 200, "c308"},
+		{"/?code=404", 404, "c404"},
+	}
+
+	wantSegments := []string{
+		`DELETE / "first"`,
+		`DELETE /?code=301&next=302,308 "c301"`,
+		`GET /?code=302&next=308 ""`,
+		`GET /?code=308 ""`,
+		`GET / "c301"`,
+		`DELETE /?code=302&next=302 "c302"`,
+		`GET /?code=302 ""`,
+		`GET / ""`,
+		`DELETE /?code=303 "c303"`,
+		`GET / ""`,
+		`DELETE /?code=307&next=301,308,303,302,304 "c307"`,
+		`DELETE /?code=301&next=308,303,302,304 "c307"`,
+		`GET /?code=308&next=303,302,304 ""`,
+		`GET /?code=303&next=302,304 "c307"`,
+		`GET /?code=302&next=304 ""`,
+		`GET /?code=304 ""`,
+		`DELETE /?code=308&next=307 "c308"`,
+		`DELETE /?code=307 "c308"`,
+		`DELETE / "c308"`,
+		`DELETE /?code=404 "c404"`,
+	}
+	want := strings.Join(wantSegments, "\n")
+	testRedirectsByMethod(t, "DELETE", deleteRedirectTests, want)
+}
+
+func testRedirectsByMethod(t *testing.T, method string, table []redirectTest, want string) {
+	defer afterTest(t)
+	var log struct {
+		sync.Mutex
+		bytes.Buffer
+	}
+	var ts *httptest.Server
+	ts = httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		log.Lock()
+		slurp, _ := io.ReadAll(r.Body)
+		fmt.Fprintf(&log.Buffer, "%s %s %q", r.Method, r.RequestURI, slurp)
+		if cl := r.Header.Get("Content-Length"); r.Method == "GET" && len(slurp) == 0 && (r.ContentLength != 0 || cl != "") {
+			fmt.Fprintf(&log.Buffer, " (but with body=%T, content-length = %v, %q)", r.Body, r.ContentLength, cl)
+		}
+		log.WriteByte('\n')
+		log.Unlock()
+		urlQuery := r.URL.Query()
+		if v := urlQuery.Get("code"); v != "" {
+			location := ts.URL
+			if final := urlQuery.Get("next"); final != "" {
+				splits := strings.Split(final, ",")
+				first, rest := splits[0], splits[1:]
+				location = fmt.Sprintf("%s?code=%s", location, first)
+				if len(rest) > 0 {
+					location = fmt.Sprintf("%s&next=%s", location, strings.Join(rest, ","))
+				}
+			}
+			code, _ := strconv.Atoi(v)
+			if code/100 == 3 {
+				w.Header().Set("Location", location)
+			}
+			w.WriteHeader(code)
+		}
+	}))
+	defer ts.Close()
+
+	c := ts.Client()
+	for _, tt := range table {
+		content := tt.redirectBody
+		req, _ := NewRequest(method, ts.URL+tt.suffix, strings.NewReader(content))
+		req.GetBody = func() (io.ReadCloser, error) { return io.NopCloser(strings.NewReader(content)), nil }
+		res, err := c.Do(req)
+
+		if err != nil {
+			t.Fatal(err)
+		}
+		if res.StatusCode != tt.want {
+			t.Errorf("POST %s: status code = %d; want %d", tt.suffix, res.StatusCode, tt.want)
+		}
+	}
+	log.Lock()
+	got := log.String()
+	log.Unlock()
+
+	got = strings.TrimSpace(got)
+	want = strings.TrimSpace(want)
+
+	if got != want {
+		got, want, lines := removeCommonLines(got, want)
+		t.Errorf("Log differs after %d common lines.\n\nGot:\n%s\n\nWant:\n%s\n", lines, got, want)
+	}
+}
+
+func removeCommonLines(a, b string) (asuffix, bsuffix string, commonLines int) {
+	for {
+		nl := strings.IndexByte(a, '\n')
+		if nl < 0 {
+			return a, b, commonLines
+		}
+		line := a[:nl+1]
+		if !strings.HasPrefix(b, line) {
+			return a, b, commonLines
+		}
+		commonLines++
+		a = a[len(line):]
+		b = b[len(line):]
+	}
+}
+
+func TestClientRedirectUseResponse(t *testing.T) {
+	setParallel(t)
+	defer afterTest(t)
+	const body = "Hello, world."
+	var ts *httptest.Server
+	ts = httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		if strings.Contains(r.URL.Path, "/other") {
+			io.WriteString(w, "wrong body")
+		} else {
+			w.Header().Set("Location", ts.URL+"/other")
+			w.WriteHeader(StatusFound)
+			io.WriteString(w, body)
+		}
+	}))
+	defer ts.Close()
+
+	c := ts.Client()
+	c.CheckRedirect = func(req *Request, via []*Request) error {
+		if req.Response == nil {
+			t.Error("expected non-nil Request.Response")
+		}
+		return ErrUseLastResponse
+	}
+	res, err := c.Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if res.StatusCode != StatusFound {
+		t.Errorf("status = %d; want %d", res.StatusCode, StatusFound)
+	}
+	defer res.Body.Close()
+	slurp, err := io.ReadAll(res.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(slurp) != body {
+		t.Errorf("body = %q; want %q", slurp, body)
+	}
+}
+
+// Issue 17773: don't follow a 308 (or 307) if the response doesn't
+// have a Location header.
+func TestClientRedirect308NoLocation(t *testing.T) {
+	setParallel(t)
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Header().Set("Foo", "Bar")
+		w.WriteHeader(308)
+	}))
+	defer ts.Close()
+	c := ts.Client()
+	res, err := c.Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	res.Body.Close()
+	if res.StatusCode != 308 {
+		t.Errorf("status = %d; want %d", res.StatusCode, 308)
+	}
+	if got := res.Header.Get("Foo"); got != "Bar" {
+		t.Errorf("Foo header = %q; want Bar", got)
+	}
+}
+
+// Don't follow a 307/308 if we can't resent the request body.
+func TestClientRedirect308NoGetBody(t *testing.T) {
+	setParallel(t)
+	defer afterTest(t)
+	const fakeURL = "https://localhost:1234/" // won't be hit
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Header().Set("Location", fakeURL)
+		w.WriteHeader(308)
+	}))
+	defer ts.Close()
+	req, err := NewRequest("POST", ts.URL, strings.NewReader("some body"))
+	if err != nil {
+		t.Fatal(err)
+	}
+	c := ts.Client()
+	req.GetBody = nil // so it can't rewind.
+	res, err := c.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	res.Body.Close()
+	if res.StatusCode != 308 {
+		t.Errorf("status = %d; want %d", res.StatusCode, 308)
+	}
+	if got := res.Header.Get("Location"); got != fakeURL {
+		t.Errorf("Location header = %q; want %q", got, fakeURL)
+	}
+}
+
+var expectedCookies = []*Cookie{
+	{Name: "ChocolateChip", Value: "tasty"},
+	{Name: "First", Value: "Hit"},
+	{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"))
+	}
+})
+
+func TestClientSendsCookieFromJar(t *testing.T) {
+	defer afterTest(t)
+	tr := &recordingTransport{}
+	client := &Client{Transport: tr}
+	client.Jar = &TestJar{perURL: make(map[string][]*Cookie)}
+	us := "http://dummy.faketld/"
+	u, _ := url.Parse(us)
+	client.Jar.SetCookies(u, expectedCookies)
+
+	client.Get(us) // Note: doesn't hit network
+	matchReturnedCookies(t, expectedCookies, tr.req.Cookies())
+
+	client.Head(us) // Note: doesn't hit network
+	matchReturnedCookies(t, expectedCookies, tr.req.Cookies())
+
+	client.Post(us, "text/plain", strings.NewReader("body")) // Note: doesn't hit network
+	matchReturnedCookies(t, expectedCookies, tr.req.Cookies())
+
+	client.PostForm(us, url.Values{}) // Note: doesn't hit network
+	matchReturnedCookies(t, expectedCookies, tr.req.Cookies())
+
+	req, _ := NewRequest("GET", us, nil)
+	client.Do(req) // Note: doesn't hit network
+	matchReturnedCookies(t, expectedCookies, tr.req.Cookies())
+
+	req, _ = NewRequest("POST", us, nil)
+	client.Do(req) // Note: doesn't hit network
+	matchReturnedCookies(t, expectedCookies, tr.req.Cookies())
+}
+
+// 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()
+	if j.perURL == nil {
+		j.perURL = make(map[string][]*Cookie)
+	}
+	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 TestRedirectCookiesJar(t *testing.T) {
+	setParallel(t)
+	defer afterTest(t)
+	var ts *httptest.Server
+	ts = httptest.NewServer(echoCookiesRedirectHandler)
+	defer ts.Close()
+	c := ts.Client()
+	c.Jar = new(TestJar)
+	u, _ := url.Parse(ts.URL)
+	c.Jar.SetCookies(u, []*Cookie{expectedCookies[0]})
+	resp, err := c.Get(ts.URL)
+	if err != nil {
+		t.Fatalf("Get: %v", err)
+	}
+	resp.Body.Close()
+	matchReturnedCookies(t, expectedCookies, resp.Cookies())
+}
+
+func matchReturnedCookies(t *testing.T, expected, given []*Cookie) {
+	if len(given) != len(expected) {
+		t.Logf("Received cookies: %v", given)
+		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 TestJarCalls(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		pathSuffix := r.RequestURI[1:]
+		if r.RequestURI == "/nosetcookie" {
+			return // don't set cookies for this path
+		}
+		SetCookie(w, &Cookie{Name: "name" + pathSuffix, Value: "val" + pathSuffix})
+		if r.RequestURI == "/" {
+			Redirect(w, r, "http://secondhost.fake/secondpath", 302)
+		}
+	}))
+	defer ts.Close()
+	jar := new(RecordingJar)
+	c := ts.Client()
+	c.Jar = jar
+	c.Transport.(*Transport).Dial = func(_ string, _ string) (net.Conn, error) {
+		return net.Dial("tcp", ts.Listener.Addr().String())
+	}
+	_, err := c.Get("http://firsthost.fake/")
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = c.Get("http://firsthost.fake/nosetcookie")
+	if err != nil {
+		t.Fatal(err)
+	}
+	got := jar.log.String()
+	want := `Cookies("http://firsthost.fake/")
+SetCookie("http://firsthost.fake/", [name=val])
+Cookies("http://secondhost.fake/secondpath")
+SetCookie("http://secondhost.fake/secondpath", [namesecondpath=valsecondpath])
+Cookies("http://firsthost.fake/nosetcookie")
+`
+	if got != want {
+		t.Errorf("Got Jar calls:\n%s\nWant:\n%s", got, want)
+	}
+}
+
+// RecordingJar keeps a log of calls made to it, without
+// tracking any cookies.
+type RecordingJar struct {
+	mu  sync.Mutex
+	log bytes.Buffer
+}
+
+func (j *RecordingJar) SetCookies(u *url.URL, cookies []*Cookie) {
+	j.logf("SetCookie(%q, %v)\n", u, cookies)
+}
+
+func (j *RecordingJar) Cookies(u *url.URL) []*Cookie {
+	j.logf("Cookies(%q)\n", u)
+	return nil
+}
+
+func (j *RecordingJar) logf(format string, args ...interface{}) {
+	j.mu.Lock()
+	defer j.mu.Unlock()
+	fmt.Fprintf(&j.log, format, args...)
+}
+
+func TestStreamingGet_h1(t *testing.T) { testStreamingGet(t, h1Mode) }
+func TestStreamingGet_h2(t *testing.T) { testStreamingGet(t, h2Mode) }
+
+func testStreamingGet(t *testing.T, h2 bool) {
+	defer afterTest(t)
+	say := make(chan string)
+	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.(Flusher).Flush()
+		for str := range say {
+			w.Write([]byte(str))
+			w.(Flusher).Flush()
+		}
+	}))
+	defer cst.close()
+
+	c := cst.c
+	res, err := c.Get(cst.ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var buf [10]byte
+	for _, str := range []string{"i", "am", "also", "known", "as", "comet"} {
+		say <- str
+		n, err := io.ReadFull(res.Body, buf[0:len(str)])
+		if err != nil {
+			t.Fatalf("ReadFull on %q: %v", str, err)
+		}
+		if n != len(str) {
+			t.Fatalf("Receiving %q, only read %d bytes", str, n)
+		}
+		got := string(buf[0:n])
+		if got != str {
+			t.Fatalf("Expected %q, got %q", str, got)
+		}
+	}
+	close(say)
+	_, err = io.ReadFull(res.Body, buf[0:1])
+	if err != io.EOF {
+		t.Fatalf("at end expected EOF, got %v", err)
+	}
+}
+
+type writeCountingConn struct {
+	net.Conn
+	count *int
+}
+
+func (c *writeCountingConn) Write(p []byte) (int, error) {
+	*c.count++
+	return c.Conn.Write(p)
+}
+
+// TestClientWrites verifies that client requests are buffered and we
+// don't send a TCP packet per line of the http request + body.
+func TestClientWrites(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+	}))
+	defer ts.Close()
+
+	writes := 0
+	dialer := func(netz string, addr string) (net.Conn, error) {
+		c, err := net.Dial(netz, addr)
+		if err == nil {
+			c = &writeCountingConn{c, &writes}
+		}
+		return c, err
+	}
+	c := ts.Client()
+	c.Transport.(*Transport).Dial = dialer
+
+	_, err := c.Get(ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if writes != 1 {
+		t.Errorf("Get request did %d Write calls, want 1", writes)
+	}
+
+	writes = 0
+	_, err = c.PostForm(ts.URL, url.Values{"foo": {"bar"}})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if writes != 1 {
+		t.Errorf("Post request did %d Write calls, want 1", writes)
+	}
+}
+
+func TestClientInsecureTransport(t *testing.T) {
+	setParallel(t)
+	defer afterTest(t)
+	ts := httptest.NewTLSServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Write([]byte("Hello"))
+	}))
+	errc := make(chanWriter, 10) // but only expecting 1
+	ts.Config.ErrorLog = log.New(errc, "", 0)
+	defer ts.Close()
+
+	// TODO(bradfitz): add tests for skipping hostname checks too?
+	// would require a new cert for testing, and probably
+	// redundant with these tests.
+	c := ts.Client()
+	for _, insecure := range []bool{true, false} {
+		c.Transport.(*Transport).TLSClientConfig = &tls.Config{
+			InsecureSkipVerify: insecure,
+		}
+		res, err := c.Get(ts.URL)
+		if (err == nil) != insecure {
+			t.Errorf("insecure=%v: got unexpected err=%v", insecure, err)
+		}
+		if res != nil {
+			res.Body.Close()
+		}
+	}
+
+	select {
+	case v := <-errc:
+		if !strings.Contains(v, "TLS handshake error") {
+			t.Errorf("expected an error log message containing 'TLS handshake error'; got %q", v)
+		}
+	case <-time.After(5 * time.Second):
+		t.Errorf("timeout waiting for logged error")
+	}
+
+}
+
+func TestClientErrorWithRequestURI(t *testing.T) {
+	defer afterTest(t)
+	req, _ := NewRequest("GET", "http://localhost:1234/", nil)
+	req.RequestURI = "/this/field/is/illegal/and/should/error/"
+	_, err := DefaultClient.Do(req)
+	if err == nil {
+		t.Fatalf("expected an error")
+	}
+	if !strings.Contains(err.Error(), "RequestURI") {
+		t.Errorf("wanted error mentioning RequestURI; got error: %v", err)
+	}
+}
+
+func TestClientWithCorrectTLSServerName(t *testing.T) {
+	defer afterTest(t)
+
+	const serverName = "example.com"
+	ts := httptest.NewTLSServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		if r.TLS.ServerName != serverName {
+			t.Errorf("expected client to set ServerName %q, got: %q", serverName, r.TLS.ServerName)
+		}
+	}))
+	defer ts.Close()
+
+	c := ts.Client()
+	c.Transport.(*Transport).TLSClientConfig.ServerName = serverName
+	if _, err := c.Get(ts.URL); err != nil {
+		t.Fatalf("expected successful TLS connection, got error: %v", err)
+	}
+}
+
+func TestClientWithIncorrectTLSServerName(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewTLSServer(HandlerFunc(func(w ResponseWriter, r *Request) {}))
+	defer ts.Close()
+	errc := make(chanWriter, 10) // but only expecting 1
+	ts.Config.ErrorLog = log.New(errc, "", 0)
+
+	c := ts.Client()
+	c.Transport.(*Transport).TLSClientConfig.ServerName = "badserver"
+	_, err := c.Get(ts.URL)
+	if err == nil {
+		t.Fatalf("expected an error")
+	}
+	if !strings.Contains(err.Error(), "127.0.0.1") || !strings.Contains(err.Error(), "badserver") {
+		t.Errorf("wanted error mentioning 127.0.0.1 and badserver; got error: %v", err)
+	}
+	select {
+	case v := <-errc:
+		if !strings.Contains(v, "TLS handshake error") {
+			t.Errorf("expected an error log message containing 'TLS handshake error'; got %q", v)
+		}
+	case <-time.After(5 * time.Second):
+		t.Errorf("timeout waiting for logged error")
+	}
+}
+
+// Test for golang.org/issue/5829; the Transport should respect TLSClientConfig.ServerName
+// when not empty.
+//
+// tls.Config.ServerName (non-empty, set to "example.com") takes
+// precedence over "some-other-host.tld" which previously incorrectly
+// took precedence. We don't actually connect to (or even resolve)
+// "some-other-host.tld", though, because of the Transport.Dial hook.
+//
+// The httptest.Server has a cert with "example.com" as its name.
+func TestTransportUsesTLSConfigServerName(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewTLSServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Write([]byte("Hello"))
+	}))
+	defer ts.Close()
+
+	c := ts.Client()
+	tr := c.Transport.(*Transport)
+	tr.TLSClientConfig.ServerName = "example.com" // one of httptest's Server cert names
+	tr.Dial = func(netw, addr string) (net.Conn, error) {
+		return net.Dial(netw, ts.Listener.Addr().String())
+	}
+	res, err := c.Get("https://some-other-host.tld/")
+	if err != nil {
+		t.Fatal(err)
+	}
+	res.Body.Close()
+}
+
+func TestResponseSetsTLSConnectionState(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewTLSServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Write([]byte("Hello"))
+	}))
+	defer ts.Close()
+
+	c := ts.Client()
+	tr := c.Transport.(*Transport)
+	tr.TLSClientConfig.CipherSuites = []uint16{tls.TLS_RSA_WITH_3DES_EDE_CBC_SHA}
+	tr.TLSClientConfig.MaxVersion = tls.VersionTLS12 // to get to pick the cipher suite
+	tr.Dial = func(netw, addr string) (net.Conn, error) {
+		return net.Dial(netw, ts.Listener.Addr().String())
+	}
+	res, err := c.Get("https://example.com/")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer res.Body.Close()
+	if res.TLS == nil {
+		t.Fatal("Response didn't set TLS Connection State.")
+	}
+	if got, want := res.TLS.CipherSuite, tls.TLS_RSA_WITH_3DES_EDE_CBC_SHA; got != want {
+		t.Errorf("TLS Cipher Suite = %d; want %d", got, want)
+	}
+}
+
+// Check that an HTTPS client can interpret a particular TLS error
+// to determine that the server is speaking HTTP.
+// See golang.org/issue/11111.
+func TestHTTPSClientDetectsHTTPServer(t *testing.T) {
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {}))
+	ts.Config.ErrorLog = quietLog
+	defer ts.Close()
+
+	_, err := Get(strings.Replace(ts.URL, "http", "https", 1))
+	if got := err.Error(); !strings.Contains(got, "HTTP response to HTTPS client") {
+		t.Fatalf("error = %q; want error indicating HTTP response to HTTPS request", got)
+	}
+}
+
+// Verify Response.ContentLength is populated. https://golang.org/issue/4126
+func TestClientHeadContentLength_h1(t *testing.T) {
+	testClientHeadContentLength(t, h1Mode)
+}
+
+func TestClientHeadContentLength_h2(t *testing.T) {
+	testClientHeadContentLength(t, h2Mode)
+}
+
+func testClientHeadContentLength(t *testing.T, h2 bool) {
+	defer afterTest(t)
+	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
+		if v := r.FormValue("cl"); v != "" {
+			w.Header().Set("Content-Length", v)
+		}
+	}))
+	defer cst.close()
+	tests := []struct {
+		suffix string
+		want   int64
+	}{
+		{"/?cl=1234", 1234},
+		{"/?cl=0", 0},
+		{"", -1},
+	}
+	for _, tt := range tests {
+		req, _ := NewRequest("HEAD", cst.ts.URL+tt.suffix, nil)
+		res, err := cst.c.Do(req)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if res.ContentLength != tt.want {
+			t.Errorf("Content-Length = %d; want %d", res.ContentLength, tt.want)
+		}
+		bs, err := io.ReadAll(res.Body)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if len(bs) != 0 {
+			t.Errorf("Unexpected content: %q", bs)
+		}
+	}
+}
+
+func TestEmptyPasswordAuth(t *testing.T) {
+	setParallel(t)
+	defer afterTest(t)
+	gopher := "gopher"
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		auth := r.Header.Get("Authorization")
+		if strings.HasPrefix(auth, "Basic ") {
+			encoded := auth[6:]
+			decoded, err := base64.StdEncoding.DecodeString(encoded)
+			if err != nil {
+				t.Fatal(err)
+			}
+			expected := gopher + ":"
+			s := string(decoded)
+			if expected != s {
+				t.Errorf("Invalid Authorization header. Got %q, wanted %q", s, expected)
+			}
+		} else {
+			t.Errorf("Invalid auth %q", auth)
+		}
+	}))
+	defer ts.Close()
+	req, err := NewRequest("GET", ts.URL, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	req.URL.User = url.User(gopher)
+	c := ts.Client()
+	resp, err := c.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+}
+
+func TestBasicAuth(t *testing.T) {
+	defer afterTest(t)
+	tr := &recordingTransport{}
+	client := &Client{Transport: tr}
+
+	url := "http://My%20User:My%20Pass@dummy.faketld/"
+	expected := "My User:My Pass"
+	client.Get(url)
+
+	if tr.req.Method != "GET" {
+		t.Errorf("got method %q, want %q", tr.req.Method, "GET")
+	}
+	if tr.req.URL.String() != url {
+		t.Errorf("got URL %q, want %q", tr.req.URL.String(), url)
+	}
+	if tr.req.Header == nil {
+		t.Fatalf("expected non-nil request Header")
+	}
+	auth := tr.req.Header.Get("Authorization")
+	if strings.HasPrefix(auth, "Basic ") {
+		encoded := auth[6:]
+		decoded, err := base64.StdEncoding.DecodeString(encoded)
+		if err != nil {
+			t.Fatal(err)
+		}
+		s := string(decoded)
+		if expected != s {
+			t.Errorf("Invalid Authorization header. Got %q, wanted %q", s, expected)
+		}
+	} else {
+		t.Errorf("Invalid auth %q", auth)
+	}
+}
+
+func TestBasicAuthHeadersPreserved(t *testing.T) {
+	defer afterTest(t)
+	tr := &recordingTransport{}
+	client := &Client{Transport: tr}
+
+	// If Authorization header is provided, username in URL should not override it
+	url := "http://My%20User@dummy.faketld/"
+	req, err := NewRequest("GET", url, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	req.SetBasicAuth("My User", "My Pass")
+	expected := "My User:My Pass"
+	client.Do(req)
+
+	if tr.req.Method != "GET" {
+		t.Errorf("got method %q, want %q", tr.req.Method, "GET")
+	}
+	if tr.req.URL.String() != url {
+		t.Errorf("got URL %q, want %q", tr.req.URL.String(), url)
+	}
+	if tr.req.Header == nil {
+		t.Fatalf("expected non-nil request Header")
+	}
+	auth := tr.req.Header.Get("Authorization")
+	if strings.HasPrefix(auth, "Basic ") {
+		encoded := auth[6:]
+		decoded, err := base64.StdEncoding.DecodeString(encoded)
+		if err != nil {
+			t.Fatal(err)
+		}
+		s := string(decoded)
+		if expected != s {
+			t.Errorf("Invalid Authorization header. Got %q, wanted %q", s, expected)
+		}
+	} else {
+		t.Errorf("Invalid auth %q", auth)
+	}
+
+}
+
+func TestStripPasswordFromError(t *testing.T) {
+	client := &Client{Transport: &recordingTransport{}}
+	testCases := []struct {
+		desc string
+		in   string
+		out  string
+	}{
+		{
+			desc: "Strip password from error message",
+			in:   "http://user:password@dummy.faketld/",
+			out:  `Get "http://user:***@dummy.faketld/": dummy impl`,
+		},
+		{
+			desc: "Don't Strip password from domain name",
+			in:   "http://user:password@password.faketld/",
+			out:  `Get "http://user:***@password.faketld/": dummy impl`,
+		},
+		{
+			desc: "Don't Strip password from path",
+			in:   "http://user:password@dummy.faketld/password",
+			out:  `Get "http://user:***@dummy.faketld/password": dummy impl`,
+		},
+		{
+			desc: "Strip escaped password",
+			in:   "http://user:pa%2Fssword@dummy.faketld/",
+			out:  `Get "http://user:***@dummy.faketld/": dummy impl`,
+		},
+	}
+	for _, tC := range testCases {
+		t.Run(tC.desc, func(t *testing.T) {
+			_, err := client.Get(tC.in)
+			if err.Error() != tC.out {
+				t.Errorf("Unexpected output for %q: expected %q, actual %q",
+					tC.in, tC.out, err.Error())
+			}
+		})
+	}
+}
+
+func TestClientTimeout_h1(t *testing.T) { testClientTimeout(t, h1Mode) }
+func TestClientTimeout_h2(t *testing.T) { testClientTimeout(t, h2Mode) }
+
+func testClientTimeout(t *testing.T, h2 bool) {
+	setParallel(t)
+	defer afterTest(t)
+	testDone := make(chan struct{}) // closed in defer below
+
+	sawRoot := make(chan bool, 1)
+	sawSlow := make(chan bool, 1)
+	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
+		if r.URL.Path == "/" {
+			sawRoot <- true
+			Redirect(w, r, "/slow", StatusFound)
+			return
+		}
+		if r.URL.Path == "/slow" {
+			sawSlow <- true
+			w.Write([]byte("Hello"))
+			w.(Flusher).Flush()
+			<-testDone
+			return
+		}
+	}))
+	defer cst.close()
+	defer close(testDone) // before cst.close, to unblock /slow handler
+
+	// 200ms should be long enough to get a normal request (the /
+	// handler), but not so long that it makes the test slow.
+	const timeout = 200 * time.Millisecond
+	cst.c.Timeout = timeout
+
+	res, err := cst.c.Get(cst.ts.URL)
+	if err != nil {
+		if strings.Contains(err.Error(), "Client.Timeout") {
+			t.Skipf("host too slow to get fast resource in %v", timeout)
+		}
+		t.Fatal(err)
+	}
+
+	select {
+	case <-sawRoot:
+		// good.
+	default:
+		t.Fatal("handler never got / request")
+	}
+
+	select {
+	case <-sawSlow:
+		// good.
+	default:
+		t.Fatal("handler never got /slow request")
+	}
+
+	errc := make(chan error, 1)
+	go func() {
+		_, err := io.ReadAll(res.Body)
+		errc <- err
+		res.Body.Close()
+	}()
+
+	const failTime = 5 * time.Second
+	select {
+	case err := <-errc:
+		if err == nil {
+			t.Fatal("expected error from ReadAll")
+		}
+		ne, ok := err.(net.Error)
+		if !ok {
+			t.Errorf("error value from ReadAll was %T; expected some net.Error", err)
+		} else if !ne.Timeout() {
+			t.Errorf("net.Error.Timeout = false; want true")
+		}
+		if got := ne.Error(); !strings.Contains(got, "(Client.Timeout") {
+			t.Errorf("error string = %q; missing timeout substring", got)
+		}
+	case <-time.After(failTime):
+		t.Errorf("timeout after %v waiting for timeout of %v", failTime, timeout)
+	}
+}
+
+func TestClientTimeout_Headers_h1(t *testing.T) { testClientTimeout_Headers(t, h1Mode) }
+func TestClientTimeout_Headers_h2(t *testing.T) { testClientTimeout_Headers(t, h2Mode) }
+
+// Client.Timeout firing before getting to the body
+func testClientTimeout_Headers(t *testing.T, h2 bool) {
+	setParallel(t)
+	defer afterTest(t)
+	donec := make(chan bool, 1)
+	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
+		<-donec
+	}), optQuietLog)
+	defer cst.close()
+	// Note that we use a channel send here and not a close.
+	// The race detector doesn't know that we're waiting for a timeout
+	// and thinks that the waitgroup inside httptest.Server is added to concurrently
+	// with us closing it. If we timed out immediately, we could close the testserver
+	// before we entered the handler. We're not timing out immediately and there's
+	// no way we would be done before we entered the handler, but the race detector
+	// doesn't know this, so synchronize explicitly.
+	defer func() { donec <- true }()
+
+	cst.c.Timeout = 5 * time.Millisecond
+	res, err := cst.c.Get(cst.ts.URL)
+	if err == nil {
+		res.Body.Close()
+		t.Fatal("got response from Get; expected error")
+	}
+	if _, ok := err.(*url.Error); !ok {
+		t.Fatalf("Got error of type %T; want *url.Error", err)
+	}
+	ne, ok := err.(net.Error)
+	if !ok {
+		t.Fatalf("Got error of type %T; want some net.Error", err)
+	}
+	if !ne.Timeout() {
+		t.Error("net.Error.Timeout = false; want true")
+	}
+	if got := ne.Error(); !strings.Contains(got, "Client.Timeout exceeded") {
+		t.Errorf("error string = %q; missing timeout substring", got)
+	}
+}
+
+// Issue 16094: if Client.Timeout is set but not hit, a Timeout error shouldn't be
+// returned.
+func TestClientTimeoutCancel(t *testing.T) {
+	setParallel(t)
+	defer afterTest(t)
+
+	testDone := make(chan struct{})
+	ctx, cancel := context.WithCancel(context.Background())
+
+	cst := newClientServerTest(t, h1Mode, HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.(Flusher).Flush()
+		<-testDone
+	}))
+	defer cst.close()
+	defer close(testDone)
+
+	cst.c.Timeout = 1 * time.Hour
+	req, _ := NewRequest("GET", cst.ts.URL, nil)
+	req.Cancel = ctx.Done()
+	res, err := cst.c.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	cancel()
+	_, err = io.Copy(io.Discard, res.Body)
+	if err != ExportErrRequestCanceled {
+		t.Fatalf("error = %v; want errRequestCanceled", err)
+	}
+}
+
+func TestClientRedirectEatsBody_h1(t *testing.T) { testClientRedirectEatsBody(t, h1Mode) }
+func TestClientRedirectEatsBody_h2(t *testing.T) { testClientRedirectEatsBody(t, h2Mode) }
+func testClientRedirectEatsBody(t *testing.T, h2 bool) {
+	setParallel(t)
+	defer afterTest(t)
+	saw := make(chan string, 2)
+	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
+		saw <- r.RemoteAddr
+		if r.URL.Path == "/" {
+			Redirect(w, r, "/foo", StatusFound) // which includes a body
+		}
+	}))
+	defer cst.close()
+
+	res, err := cst.c.Get(cst.ts.URL)
+	if err != nil {
+		t.Fatal(err)
+	}
+	_, err = io.ReadAll(res.Body)
+	res.Body.Close()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	var first string
+	select {
+	case first = <-saw:
+	default:
+		t.Fatal("server didn't see a request")
+	}
+
+	var second string
+	select {
+	case second = <-saw:
+	default:
+		t.Fatal("server didn't see a second request")
+	}
+
+	if first != second {
+		t.Fatal("server saw different client ports before & after the redirect")
+	}
+}
+
+// eofReaderFunc is an io.Reader that runs itself, and then returns io.EOF.
+type eofReaderFunc func()
+
+func (f eofReaderFunc) Read(p []byte) (n int, err error) {
+	f()
+	return 0, io.EOF
+}
+
+func TestReferer(t *testing.T) {
+	tests := []struct {
+		lastReq, newReq string // from -> to URLs
+		want            string
+	}{
+		// don't send user:
+		{"http://gopher@test.com", "http://link.com", "http://test.com"},
+		{"https://gopher@test.com", "https://link.com", "https://test.com"},
+
+		// don't send a user and password:
+		{"http://gopher:go@test.com", "http://link.com", "http://test.com"},
+		{"https://gopher:go@test.com", "https://link.com", "https://test.com"},
+
+		// nothing to do:
+		{"http://test.com", "http://link.com", "http://test.com"},
+		{"https://test.com", "https://link.com", "https://test.com"},
+
+		// https to http doesn't send a referer:
+		{"https://test.com", "http://link.com", ""},
+		{"https://gopher:go@test.com", "http://link.com", ""},
+	}
+	for _, tt := range tests {
+		l, err := url.Parse(tt.lastReq)
+		if err != nil {
+			t.Fatal(err)
+		}
+		n, err := url.Parse(tt.newReq)
+		if err != nil {
+			t.Fatal(err)
+		}
+		r := ExportRefererForURL(l, n)
+		if r != tt.want {
+			t.Errorf("refererForURL(%q, %q) = %q; want %q", tt.lastReq, tt.newReq, r, tt.want)
+		}
+	}
+}
+
+// issue15577Tripper returns a Response with a redirect response
+// header and doesn't populate its Response.Request field.
+type issue15577Tripper struct{}
+
+func (issue15577Tripper) RoundTrip(*Request) (*Response, error) {
+	resp := &Response{
+		StatusCode: 303,
+		Header:     map[string][]string{"Location": {"http://www.example.com/"}},
+		Body:       io.NopCloser(strings.NewReader("")),
+	}
+	return resp, nil
+}
+
+// Issue 15577: don't assume the roundtripper's response populates its Request field.
+func TestClientRedirectResponseWithoutRequest(t *testing.T) {
+	c := &Client{
+		CheckRedirect: func(*Request, []*Request) error { return fmt.Errorf("no redirects!") },
+		Transport:     issue15577Tripper{},
+	}
+	// Check that this doesn't crash:
+	c.Get("http://dummy.tld")
+}
+
+// Issue 4800: copy (some) headers when Client follows a redirect.
+func TestClientCopyHeadersOnRedirect(t *testing.T) {
+	const (
+		ua   = "some-agent/1.2"
+		xfoo = "foo-val"
+	)
+	var ts2URL string
+	ts1 := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		want := Header{
+			"User-Agent":      []string{ua},
+			"X-Foo":           []string{xfoo},
+			"Referer":         []string{ts2URL},
+			"Accept-Encoding": []string{"gzip"},
+		}
+		if !reflect.DeepEqual(r.Header, want) {
+			t.Errorf("Request.Header = %#v; want %#v", r.Header, want)
+		}
+		if t.Failed() {
+			w.Header().Set("Result", "got errors")
+		} else {
+			w.Header().Set("Result", "ok")
+		}
+	}))
+	defer ts1.Close()
+	ts2 := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		Redirect(w, r, ts1.URL, StatusFound)
+	}))
+	defer ts2.Close()
+	ts2URL = ts2.URL
+
+	c := ts1.Client()
+	c.CheckRedirect = func(r *Request, via []*Request) error {
+		want := Header{
+			"User-Agent": []string{ua},
+			"X-Foo":      []string{xfoo},
+			"Referer":    []string{ts2URL},
+		}
+		if !reflect.DeepEqual(r.Header, want) {
+			t.Errorf("CheckRedirect Request.Header = %#v; want %#v", r.Header, want)
+		}
+		return nil
+	}
+
+	req, _ := NewRequest("GET", ts2.URL, nil)
+	req.Header.Add("User-Agent", ua)
+	req.Header.Add("X-Foo", xfoo)
+	req.Header.Add("Cookie", "foo=bar")
+	req.Header.Add("Authorization", "secretpassword")
+	res, err := c.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer res.Body.Close()
+	if res.StatusCode != 200 {
+		t.Fatal(res.Status)
+	}
+	if got := res.Header.Get("Result"); got != "ok" {
+		t.Errorf("result = %q; want ok", got)
+	}
+}
+
+// Issue 22233: copy host when Client follows a relative redirect.
+func TestClientCopyHostOnRedirect(t *testing.T) {
+	// Virtual hostname: should not receive any request.
+	virtual := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		t.Errorf("Virtual host received request %v", r.URL)
+		w.WriteHeader(403)
+		io.WriteString(w, "should not see this response")
+	}))
+	defer virtual.Close()
+	virtualHost := strings.TrimPrefix(virtual.URL, "http://")
+	t.Logf("Virtual host is %v", virtualHost)
+
+	// Actual hostname: should not receive any request.
+	const wantBody = "response body"
+	var tsURL string
+	var tsHost string
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		switch r.URL.Path {
+		case "/":
+			// Relative redirect.
+			if r.Host != virtualHost {
+				t.Errorf("Serving /: Request.Host = %#v; want %#v", r.Host, virtualHost)
+				w.WriteHeader(404)
+				return
+			}
+			w.Header().Set("Location", "/hop")
+			w.WriteHeader(302)
+		case "/hop":
+			// Absolute redirect.
+			if r.Host != virtualHost {
+				t.Errorf("Serving /hop: Request.Host = %#v; want %#v", r.Host, virtualHost)
+				w.WriteHeader(404)
+				return
+			}
+			w.Header().Set("Location", tsURL+"/final")
+			w.WriteHeader(302)
+		case "/final":
+			if r.Host != tsHost {
+				t.Errorf("Serving /final: Request.Host = %#v; want %#v", r.Host, tsHost)
+				w.WriteHeader(404)
+				return
+			}
+			w.WriteHeader(200)
+			io.WriteString(w, wantBody)
+		default:
+			t.Errorf("Serving unexpected path %q", r.URL.Path)
+			w.WriteHeader(404)
+		}
+	}))
+	defer ts.Close()
+	tsURL = ts.URL
+	tsHost = strings.TrimPrefix(ts.URL, "http://")
+	t.Logf("Server host is %v", tsHost)
+
+	c := ts.Client()
+	req, _ := NewRequest("GET", ts.URL, nil)
+	req.Host = virtualHost
+	resp, err := c.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer resp.Body.Close()
+	if resp.StatusCode != 200 {
+		t.Fatal(resp.Status)
+	}
+	if got, err := io.ReadAll(resp.Body); err != nil || string(got) != wantBody {
+		t.Errorf("body = %q; want %q", got, wantBody)
+	}
+}
+
+// Issue 17494: cookies should be altered when Client follows redirects.
+func TestClientAltersCookiesOnRedirect(t *testing.T) {
+	cookieMap := func(cs []*Cookie) map[string][]string {
+		m := make(map[string][]string)
+		for _, c := range cs {
+			m[c.Name] = append(m[c.Name], c.Value)
+		}
+		return m
+	}
+
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		var want map[string][]string
+		got := cookieMap(r.Cookies())
+
+		c, _ := r.Cookie("Cycle")
+		switch c.Value {
+		case "0":
+			want = map[string][]string{
+				"Cookie1": {"OldValue1a", "OldValue1b"},
+				"Cookie2": {"OldValue2"},
+				"Cookie3": {"OldValue3a", "OldValue3b"},
+				"Cookie4": {"OldValue4"},
+				"Cycle":   {"0"},
+			}
+			SetCookie(w, &Cookie{Name: "Cycle", Value: "1", Path: "/"})
+			SetCookie(w, &Cookie{Name: "Cookie2", Path: "/", MaxAge: -1}) // Delete cookie from Header
+			Redirect(w, r, "/", StatusFound)
+		case "1":
+			want = map[string][]string{
+				"Cookie1": {"OldValue1a", "OldValue1b"},
+				"Cookie3": {"OldValue3a", "OldValue3b"},
+				"Cookie4": {"OldValue4"},
+				"Cycle":   {"1"},
+			}
+			SetCookie(w, &Cookie{Name: "Cycle", Value: "2", Path: "/"})
+			SetCookie(w, &Cookie{Name: "Cookie3", Value: "NewValue3", Path: "/"}) // Modify cookie in Header
+			SetCookie(w, &Cookie{Name: "Cookie4", Value: "NewValue4", Path: "/"}) // Modify cookie in Jar
+			Redirect(w, r, "/", StatusFound)
+		case "2":
+			want = map[string][]string{
+				"Cookie1": {"OldValue1a", "OldValue1b"},
+				"Cookie3": {"NewValue3"},
+				"Cookie4": {"NewValue4"},
+				"Cycle":   {"2"},
+			}
+			SetCookie(w, &Cookie{Name: "Cycle", Value: "3", Path: "/"})
+			SetCookie(w, &Cookie{Name: "Cookie5", Value: "NewValue5", Path: "/"}) // Insert cookie into Jar
+			Redirect(w, r, "/", StatusFound)
+		case "3":
+			want = map[string][]string{
+				"Cookie1": {"OldValue1a", "OldValue1b"},
+				"Cookie3": {"NewValue3"},
+				"Cookie4": {"NewValue4"},
+				"Cookie5": {"NewValue5"},
+				"Cycle":   {"3"},
+			}
+			// Don't redirect to ensure the loop ends.
+		default:
+			t.Errorf("unexpected redirect cycle")
+			return
+		}
+
+		if !reflect.DeepEqual(got, want) {
+			t.Errorf("redirect %s, Cookie = %v, want %v", c.Value, got, want)
+		}
+	}))
+	defer ts.Close()
+
+	jar, _ := cookiejar.New(nil)
+	c := ts.Client()
+	c.Jar = jar
+
+	u, _ := url.Parse(ts.URL)
+	req, _ := NewRequest("GET", ts.URL, nil)
+	req.AddCookie(&Cookie{Name: "Cookie1", Value: "OldValue1a"})
+	req.AddCookie(&Cookie{Name: "Cookie1", Value: "OldValue1b"})
+	req.AddCookie(&Cookie{Name: "Cookie2", Value: "OldValue2"})
+	req.AddCookie(&Cookie{Name: "Cookie3", Value: "OldValue3a"})
+	req.AddCookie(&Cookie{Name: "Cookie3", Value: "OldValue3b"})
+	jar.SetCookies(u, []*Cookie{{Name: "Cookie4", Value: "OldValue4", Path: "/"}})
+	jar.SetCookies(u, []*Cookie{{Name: "Cycle", Value: "0", Path: "/"}})
+	res, err := c.Do(req)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer res.Body.Close()
+	if res.StatusCode != 200 {
+		t.Fatal(res.Status)
+	}
+}
+
+// Part of Issue 4800
+func TestShouldCopyHeaderOnRedirect(t *testing.T) {
+	tests := []struct {
+		header     string
+		initialURL string
+		destURL    string
+		want       bool
+	}{
+		{"User-Agent", "http://foo.com/", "http://bar.com/", true},
+		{"X-Foo", "http://foo.com/", "http://bar.com/", true},
+
+		// Sensitive headers:
+		{"cookie", "http://foo.com/", "http://bar.com/", false},
+		{"cookie2", "http://foo.com/", "http://bar.com/", false},
+		{"authorization", "http://foo.com/", "http://bar.com/", false},
+		{"www-authenticate", "http://foo.com/", "http://bar.com/", false},
+
+		// But subdomains should work:
+		{"www-authenticate", "http://foo.com/", "http://foo.com/", true},
+		{"www-authenticate", "http://foo.com/", "http://sub.foo.com/", true},
+		{"www-authenticate", "http://foo.com/", "http://notfoo.com/", false},
+		{"www-authenticate", "http://foo.com/", "https://foo.com/", false},
+		{"www-authenticate", "http://foo.com:80/", "http://foo.com/", true},
+		{"www-authenticate", "http://foo.com:80/", "http://sub.foo.com/", true},
+		{"www-authenticate", "http://foo.com:443/", "https://foo.com/", true},
+		{"www-authenticate", "http://foo.com:443/", "https://sub.foo.com/", true},
+		{"www-authenticate", "http://foo.com:1234/", "http://foo.com/", false},
+	}
+	for i, tt := range tests {
+		u0, err := url.Parse(tt.initialURL)
+		if err != nil {
+			t.Errorf("%d. initial URL %q parse error: %v", i, tt.initialURL, err)
+			continue
+		}
+		u1, err := url.Parse(tt.destURL)
+		if err != nil {
+			t.Errorf("%d. dest URL %q parse error: %v", i, tt.destURL, err)
+			continue
+		}
+		got := Export_shouldCopyHeaderOnRedirect(tt.header, u0, u1)
+		if got != tt.want {
+			t.Errorf("%d. shouldCopyHeaderOnRedirect(%q, %q => %q) = %v; want %v",
+				i, tt.header, tt.initialURL, tt.destURL, got, tt.want)
+		}
+	}
+}
+
+func TestClientRedirectTypes(t *testing.T) {
+	setParallel(t)
+	defer afterTest(t)
+
+	tests := [...]struct {
+		method       string
+		serverStatus int
+		wantMethod   string // desired subsequent client method
+	}{
+		0: {method: "POST", serverStatus: 301, wantMethod: "GET"},
+		1: {method: "POST", serverStatus: 302, wantMethod: "GET"},
+		2: {method: "POST", serverStatus: 303, wantMethod: "GET"},
+		3: {method: "POST", serverStatus: 307, wantMethod: "POST"},
+		4: {method: "POST", serverStatus: 308, wantMethod: "POST"},
+
+		5: {method: "HEAD", serverStatus: 301, wantMethod: "HEAD"},
+		6: {method: "HEAD", serverStatus: 302, wantMethod: "HEAD"},
+		7: {method: "HEAD", serverStatus: 303, wantMethod: "HEAD"},
+		8: {method: "HEAD", serverStatus: 307, wantMethod: "HEAD"},
+		9: {method: "HEAD", serverStatus: 308, wantMethod: "HEAD"},
+
+		10: {method: "GET", serverStatus: 301, wantMethod: "GET"},
+		11: {method: "GET", serverStatus: 302, wantMethod: "GET"},
+		12: {method: "GET", serverStatus: 303, wantMethod: "GET"},
+		13: {method: "GET", serverStatus: 307, wantMethod: "GET"},
+		14: {method: "GET", serverStatus: 308, wantMethod: "GET"},
+
+		15: {method: "DELETE", serverStatus: 301, wantMethod: "GET"},
+		16: {method: "DELETE", serverStatus: 302, wantMethod: "GET"},
+		17: {method: "DELETE", serverStatus: 303, wantMethod: "GET"},
+		18: {method: "DELETE", serverStatus: 307, wantMethod: "DELETE"},
+		19: {method: "DELETE", serverStatus: 308, wantMethod: "DELETE"},
+
+		20: {method: "PUT", serverStatus: 301, wantMethod: "GET"},
+		21: {method: "PUT", serverStatus: 302, wantMethod: "GET"},
+		22: {method: "PUT", serverStatus: 303, wantMethod: "GET"},
+		23: {method: "PUT", serverStatus: 307, wantMethod: "PUT"},
+		24: {method: "PUT", serverStatus: 308, wantMethod: "PUT"},
+
+		25: {method: "MADEUPMETHOD", serverStatus: 301, wantMethod: "GET"},
+		26: {method: "MADEUPMETHOD", serverStatus: 302, wantMethod: "GET"},
+		27: {method: "MADEUPMETHOD", serverStatus: 303, wantMethod: "GET"},
+		28: {method: "MADEUPMETHOD", serverStatus: 307, wantMethod: "MADEUPMETHOD"},
+		29: {method: "MADEUPMETHOD", serverStatus: 308, wantMethod: "MADEUPMETHOD"},
+	}
+
+	handlerc := make(chan HandlerFunc, 1)
+
+	ts := httptest.NewServer(HandlerFunc(func(rw ResponseWriter, req *Request) {
+		h := <-handlerc
+		h(rw, req)
+	}))
+	defer ts.Close()
+
+	c := ts.Client()
+	for i, tt := range tests {
+		handlerc <- func(w ResponseWriter, r *Request) {
+			w.Header().Set("Location", ts.URL)
+			w.WriteHeader(tt.serverStatus)
+		}
+
+		req, err := NewRequest(tt.method, ts.URL, nil)
+		if err != nil {
+			t.Errorf("#%d: NewRequest: %v", i, err)
+			continue
+		}
+
+		c.CheckRedirect = func(req *Request, via []*Request) error {
+			if got, want := req.Method, tt.wantMethod; got != want {
+				return fmt.Errorf("#%d: got next method %q; want %q", i, got, want)
+			}
+			handlerc <- func(rw ResponseWriter, req *Request) {
+				// TODO: Check that the body is valid when we do 307 and 308 support
+			}
+			return nil
+		}
+
+		res, err := c.Do(req)
+		if err != nil {
+			t.Errorf("#%d: Response: %v", i, err)
+			continue
+		}
+
+		res.Body.Close()
+	}
+}
+
+// issue18239Body is an io.ReadCloser for TestTransportBodyReadError.
+// Its Read returns readErr and increments *readCalls atomically.
+// Its Close returns nil and increments *closeCalls atomically.
+type issue18239Body struct {
+	readCalls  *int32
+	closeCalls *int32
+	readErr    error
+}
+
+func (b issue18239Body) Read([]byte) (int, error) {
+	atomic.AddInt32(b.readCalls, 1)
+	return 0, b.readErr
+}
+
+func (b issue18239Body) Close() error {
+	atomic.AddInt32(b.closeCalls, 1)
+	return nil
+}
+
+// Issue 18239: make sure the Transport doesn't retry requests with bodies
+// if Request.GetBody is not defined.
+func TestTransportBodyReadError(t *testing.T) {
+	setParallel(t)
+	defer afterTest(t)
+	ts := httptest.NewServer(HandlerFunc(func(w ResponseWriter, r *Request) {
+		if r.URL.Path == "/ping" {
+			return
+		}
+		buf := make([]byte, 1)
+		n, err := r.Body.Read(buf)
+		w.Header().Set("X-Body-Read", fmt.Sprintf("%v, %v", n, err))
+	}))
+	defer ts.Close()
+	c := ts.Client()
+	tr := c.Transport.(*Transport)
+
+	// Do one initial successful request to create an idle TCP connection
+	// for the subsequent request to reuse. (The Transport only retries
+	// requests on reused connections.)
+	res, err := c.Get(ts.URL + "/ping")
+	if err != nil {
+		t.Fatal(err)
+	}
+	res.Body.Close()
+
+	var readCallsAtomic int32
+	var closeCallsAtomic int32 // atomic
+	someErr := errors.New("some body read error")
+	body := issue18239Body{&readCallsAtomic, &closeCallsAtomic, someErr}
+
+	req, err := NewRequest("POST", ts.URL, body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	req = req.WithT(t)
+	_, err = tr.RoundTrip(req)
+	if err != someErr {
+		t.Errorf("Got error: %v; want Request.Body read error: %v", err, someErr)
+	}
+
+	// And verify that our Body wasn't used multiple times, which
+	// would indicate retries. (as it buggily was during part of
+	// Go 1.8's dev cycle)
+	readCalls := atomic.LoadInt32(&readCallsAtomic)
+	closeCalls := atomic.LoadInt32(&closeCallsAtomic)
+	if readCalls != 1 {
+		t.Errorf("read calls = %d; want 1", readCalls)
+	}
+	if closeCalls != 1 {
+		t.Errorf("close calls = %d; want 1", closeCalls)
+	}
+}
+
+type roundTripperWithoutCloseIdle struct{}
+
+func (roundTripperWithoutCloseIdle) RoundTrip(*Request) (*Response, error) { panic("unused") }
+
+type roundTripperWithCloseIdle func() // underlying func is CloseIdleConnections func
+
+func (roundTripperWithCloseIdle) RoundTrip(*Request) (*Response, error) { panic("unused") }
+func (f roundTripperWithCloseIdle) CloseIdleConnections()               { f() }
+
+func TestClientCloseIdleConnections(t *testing.T) {
+	c := &Client{Transport: roundTripperWithoutCloseIdle{}}
+	c.CloseIdleConnections() // verify we don't crash at least
+
+	closed := false
+	var tr RoundTripper = roundTripperWithCloseIdle(func() {
+		closed = true
+	})
+	c = &Client{Transport: tr}
+	c.CloseIdleConnections()
+	if !closed {
+		t.Error("not closed")
+	}
+}
+
+func TestClientPropagatesTimeoutToContext(t *testing.T) {
+	errDial := errors.New("not actually dialing")
+	c := &Client{
+		Timeout: 5 * time.Second,
+		Transport: &Transport{
+			DialContext: func(ctx context.Context, netw, addr string) (net.Conn, error) {
+				deadline, ok := ctx.Deadline()
+				if !ok {
+					t.Error("no deadline")
+				} else {
+					t.Logf("deadline in %v", deadline.Sub(time.Now()).Round(time.Second/10))
+				}
+				return nil, errDial
+			},
+		},
+	}
+	c.Get("https://example.tld/")
+}
+
+func TestClientDoCanceledVsTimeout_h1(t *testing.T) {
+	testClientDoCanceledVsTimeout(t, h1Mode)
+}
+
+func TestClientDoCanceledVsTimeout_h2(t *testing.T) {
+	testClientDoCanceledVsTimeout(t, h2Mode)
+}
+
+// Issue 33545: lock-in the behavior promised by Client.Do's
+// docs about request cancelation vs timing out.
+func testClientDoCanceledVsTimeout(t *testing.T, h2 bool) {
+	defer afterTest(t)
+	cst := newClientServerTest(t, h2, HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.Write([]byte("Hello, World!"))
+	}))
+	defer cst.close()
+
+	cases := []string{"timeout", "canceled"}
+
+	for _, name := range cases {
+		t.Run(name, func(t *testing.T) {
+			var ctx context.Context
+			var cancel func()
+			if name == "timeout" {
+				ctx, cancel = context.WithTimeout(context.Background(), -time.Nanosecond)
+			} else {
+				ctx, cancel = context.WithCancel(context.Background())
+				cancel()
+			}
+			defer cancel()
+
+			req, _ := NewRequestWithContext(ctx, "GET", cst.ts.URL, nil)
+			_, err := cst.c.Do(req)
+			if err == nil {
+				t.Fatal("Unexpectedly got a nil error")
+			}
+
+			ue := err.(*url.Error)
+
+			var wantIsTimeout bool
+			var wantErr error = context.Canceled
+			if name == "timeout" {
+				wantErr = context.DeadlineExceeded
+				wantIsTimeout = true
+			}
+			if g, w := ue.Timeout(), wantIsTimeout; g != w {
+				t.Fatalf("url.Timeout() = %t, want %t", g, w)
+			}
+			if g, w := ue.Err, wantErr; g != w {
+				t.Errorf("url.Error.Err = %v; want %v", g, w)
+			}
+		})
+	}
+}
+
+type nilBodyRoundTripper struct{}
+
+func (nilBodyRoundTripper) RoundTrip(req *Request) (*Response, error) {
+	return &Response{
+		StatusCode: StatusOK,
+		Status:     StatusText(StatusOK),
+		Body:       nil,
+		Request:    req,
+	}, nil
+}
+
+func TestClientPopulatesNilResponseBody(t *testing.T) {
+	c := &Client{Transport: nilBodyRoundTripper{}}
+
+	resp, err := c.Get("http://localhost/anything")
+	if err != nil {
+		t.Fatalf("Client.Get rejected Response with nil Body: %v", err)
+	}
+
+	if resp.Body == nil {
+		t.Fatalf("Client failed to provide a non-nil Body as documented")
+	}
+	defer func() {
+		if err := resp.Body.Close(); err != nil {
+			t.Fatalf("error from Close on substitute Response.Body: %v", err)
+		}
+	}()
+
+	if b, err := io.ReadAll(resp.Body); err != nil {
+		t.Errorf("read error from substitute Response.Body: %v", err)
+	} else if len(b) != 0 {
+		t.Errorf("substitute Response.Body was unexpectedly non-empty: %q", b)
+	}
+}
+
+// Issue 40382: Client calls Close multiple times on Request.Body.
+func TestClientCallsCloseOnlyOnce(t *testing.T) {
+	setParallel(t)
+	defer afterTest(t)
+	cst := newClientServerTest(t, h1Mode, HandlerFunc(func(w ResponseWriter, r *Request) {
+		w.WriteHeader(StatusNoContent)
+	}))
+	defer cst.close()
+
+	// Issue occurred non-deterministically: needed to occur after a successful
+	// write (into TCP buffer) but before end of body.
+	for i := 0; i < 50 && !t.Failed(); i++ {
+		body := &issue40382Body{t: t, n: 300000}
+		req, err := NewRequest(MethodPost, cst.ts.URL, body)
+		if err != nil {
+			t.Fatal(err)
+		}
+		resp, err := cst.tr.RoundTrip(req)
+		if err != nil {
+			t.Fatal(err)
+		}
+		resp.Body.Close()
+	}
+}
+
+// issue40382Body is an io.ReadCloser for TestClientCallsCloseOnlyOnce.
+// Its Read reads n bytes before returning io.EOF.
+// Its Close returns nil but fails the test if called more than once.
+type issue40382Body struct {
+	t                *testing.T
+	n                int
+	closeCallsAtomic int32
+}
+
+func (b *issue40382Body) Read(p []byte) (int, error) {
+	switch {
+	case b.n == 0:
+		return 0, io.EOF
+	case b.n < len(p):
+		p = p[:b.n]
+		fallthrough
+	default:
+		for i := range p {
+			p[i] = 'x'
+		}
+		b.n -= len(p)
+		return len(p), nil
+	}
+}
+
+func (b *issue40382Body) Close() error {
+	if atomic.AddInt32(&b.closeCallsAtomic, 1) == 2 {
+		b.t.Error("Body closed more than once")
+	}
+	return nil
+}