context/ctxhttp: add a specialized minimal version for Go 1.7

Change-Id: Ib174b984184191d803364c684070346a105ef4b5
Reviewed-on: https://go-review.googlesource.com/24620
Reviewed-by: Chris Broadfoot <cbro@golang.org>
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
Reviewed-by: Dave Day <djd@golang.org>

context/ctxhttp/ctxhttp.go

@@ -1,7 +1,9 @@
-// Copyright 2015 The Go Authors. All rights reserved.
+// Copyright 2016 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.
 
+// +build go1.7
+
 // Package ctxhttp provides helper functions for performing context-aware HTTP requests.
 package ctxhttp // import "golang.org/x/net/context/ctxhttp"
 
@@ -14,77 +16,18 @@ import (
 	"golang.org/x/net/context"
 )
 
-func nop() {}
-
-var (
-	testHookContextDoneBeforeHeaders = nop
-	testHookDoReturned               = nop
-	testHookDidBodyClose             = nop
-)
-
-// Do sends an HTTP request with the provided http.Client and returns an HTTP response.
+// Do sends an HTTP request with the provided http.Client and returns
+// an HTTP response.
+//
 // If the client is nil, http.DefaultClient is used.
-// If the context is canceled or times out, ctx.Err() will be returned.
+//
+// The provided ctx must be non-nil. If it is canceled or times out,
+// ctx.Err() will be returned.
 func Do(ctx context.Context, client *http.Client, req *http.Request) (*http.Response, error) {
 	if client == nil {
 		client = http.DefaultClient
 	}
-
-	// TODO(djd): Respect any existing value of req.Cancel.
-	cancel := make(chan struct{})
-	req.Cancel = cancel
-
-	type responseAndError struct {
-		resp *http.Response
-		err  error
-	}
-	result := make(chan responseAndError, 1)
-
-	// Make local copies of test hooks closed over by goroutines below.
-	// Prevents data races in tests.
-	testHookDoReturned := testHookDoReturned
-	testHookDidBodyClose := testHookDidBodyClose
-
-	go func() {
-		resp, err := client.Do(req)
-		testHookDoReturned()
-		result <- responseAndError{resp, err}
-	}()
-
-	var resp *http.Response
-
-	select {
-	case <-ctx.Done():
-		testHookContextDoneBeforeHeaders()
-		close(cancel)
-		// Clean up after the goroutine calling client.Do:
-		go func() {
-			if r := <-result; r.resp != nil {
-				testHookDidBodyClose()
-				r.resp.Body.Close()
-			}
-		}()
-		return nil, ctx.Err()
-	case r := <-result:
-		var err error
-		resp, err = r.resp, r.err
-		if err != nil {
-			return resp, err
-		}
-	}
-
-	c := make(chan struct{})
-	go func() {
-		select {
-		case <-ctx.Done():
-			close(cancel)
-		case <-c:
-			// The response's Body is closed.
-		}
-	}()
-	resp.Body = &notifyingReader{resp.Body, c}
-
-	return resp, nil
+	return client.Do(req.WithContext(ctx))
 }
 
 // Get issues a GET request via the Do function.
@@ -119,28 +62,3 @@ func Post(ctx context.Context, client *http.Client, url string, bodyType string,
 func PostForm(ctx context.Context, client *http.Client, url string, data url.Values) (*http.Response, error) {
 	return Post(ctx, client, url, "application/x-www-form-urlencoded", strings.NewReader(data.Encode()))
 }
-
-// notifyingReader is an io.ReadCloser that closes the notify channel after
-// Close is called or a Read fails on the underlying ReadCloser.
-type notifyingReader struct {
-	io.ReadCloser
-	notify chan<- struct{}
-}
-
-func (r *notifyingReader) Read(p []byte) (int, error) {
-	n, err := r.ReadCloser.Read(p)
-	if err != nil && r.notify != nil {
-		close(r.notify)
-		r.notify = nil
-	}
-	return n, err
-}
-
-func (r *notifyingReader) Close() error {
-	err := r.ReadCloser.Close()
-	if r.notify != nil {
-		close(r.notify)
-		r.notify = nil
-	}
-	return err
-}

context/ctxhttp/ctxhttp_17_test.go

@@ -0,0 +1,28 @@
+// Copyright 2015 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.
+
+// +build !plan9,go1.7
+
+package ctxhttp
+
+import (
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"context"
+)
+
+func TestGo17Context(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		io.WriteString(w, "ok")
+	}))
+	ctx := context.Background()
+	resp, err := Get(ctx, http.DefaultClient, ts.URL)
+	if resp == nil || err != nil {
+		t.Fatalf("error received from client: %v %v", err, resp)
+	}
+	resp.Body.Close()
+}

context/ctxhttp/ctxhttp_pre17.go

@@ -0,0 +1,147 @@
+// Copyright 2015 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.
+
+// +build !go1.7
+
+package ctxhttp // import "golang.org/x/net/context/ctxhttp"
+
+import (
+	"io"
+	"net/http"
+	"net/url"
+	"strings"
+
+	"golang.org/x/net/context"
+)
+
+func nop() {}
+
+var (
+	testHookContextDoneBeforeHeaders = nop
+	testHookDoReturned               = nop
+	testHookDidBodyClose             = nop
+)
+
+// Do sends an HTTP request with the provided http.Client and returns an HTTP response.
+// If the client is nil, http.DefaultClient is used.
+// If the context is canceled or times out, ctx.Err() will be returned.
+func Do(ctx context.Context, client *http.Client, req *http.Request) (*http.Response, error) {
+	if client == nil {
+		client = http.DefaultClient
+	}
+
+	// TODO(djd): Respect any existing value of req.Cancel.
+	cancel := make(chan struct{})
+	req.Cancel = cancel
+
+	type responseAndError struct {
+		resp *http.Response
+		err  error
+	}
+	result := make(chan responseAndError, 1)
+
+	// Make local copies of test hooks closed over by goroutines below.
+	// Prevents data races in tests.
+	testHookDoReturned := testHookDoReturned
+	testHookDidBodyClose := testHookDidBodyClose
+
+	go func() {
+		resp, err := client.Do(req)
+		testHookDoReturned()
+		result <- responseAndError{resp, err}
+	}()
+
+	var resp *http.Response
+
+	select {
+	case <-ctx.Done():
+		testHookContextDoneBeforeHeaders()
+		close(cancel)
+		// Clean up after the goroutine calling client.Do:
+		go func() {
+			if r := <-result; r.resp != nil {
+				testHookDidBodyClose()
+				r.resp.Body.Close()
+			}
+		}()
+		return nil, ctx.Err()
+	case r := <-result:
+		var err error
+		resp, err = r.resp, r.err
+		if err != nil {
+			return resp, err
+		}
+	}
+
+	c := make(chan struct{})
+	go func() {
+		select {
+		case <-ctx.Done():
+			close(cancel)
+		case <-c:
+			// The response's Body is closed.
+		}
+	}()
+	resp.Body = &notifyingReader{resp.Body, c}
+
+	return resp, nil
+}
+
+// Get issues a GET request via the Do function.
+func Get(ctx context.Context, client *http.Client, url string) (*http.Response, error) {
+	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		return nil, err
+	}
+	return Do(ctx, client, req)
+}
+
+// Head issues a HEAD request via the Do function.
+func Head(ctx context.Context, client *http.Client, url string) (*http.Response, error) {
+	req, err := http.NewRequest("HEAD", url, nil)
+	if err != nil {
+		return nil, err
+	}
+	return Do(ctx, client, req)
+}
+
+// Post issues a POST request via the Do function.
+func Post(ctx context.Context, client *http.Client, url string, bodyType string, body io.Reader) (*http.Response, error) {
+	req, err := http.NewRequest("POST", url, body)
+	if err != nil {
+		return nil, err
+	}
+	req.Header.Set("Content-Type", bodyType)
+	return Do(ctx, client, req)
+}
+
+// PostForm issues a POST request via the Do function.
+func PostForm(ctx context.Context, client *http.Client, url string, data url.Values) (*http.Response, error) {
+	return Post(ctx, client, url, "application/x-www-form-urlencoded", strings.NewReader(data.Encode()))
+}
+
+// notifyingReader is an io.ReadCloser that closes the notify channel after
+// Close is called or a Read fails on the underlying ReadCloser.
+type notifyingReader struct {
+	io.ReadCloser
+	notify chan<- struct{}
+}
+
+func (r *notifyingReader) Read(p []byte) (int, error) {
+	n, err := r.ReadCloser.Read(p)
+	if err != nil && r.notify != nil {
+		close(r.notify)
+		r.notify = nil
+	}
+	return n, err
+}
+
+func (r *notifyingReader) Close() error {
+	err := r.ReadCloser.Close()
+	if r.notify != nil {
+		close(r.notify)
+		r.notify = nil
+	}
+	return err
+}

context/ctxhttp/ctxhttp_pre17_test.go

@@ -0,0 +1,79 @@
+// Copyright 2015 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.
+
+// +build !plan9,!go1.7
+
+package ctxhttp
+
+import (
+	"net"
+	"net/http"
+	"net/http/httptest"
+	"sync"
+	"testing"
+	"time"
+
+	"golang.org/x/net/context"
+)
+
+// golang.org/issue/14065
+func TestClosesResponseBodyOnCancel(t *testing.T) {
+	defer func() { testHookContextDoneBeforeHeaders = nop }()
+	defer func() { testHookDoReturned = nop }()
+	defer func() { testHookDidBodyClose = nop }()
+
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {}))
+	defer ts.Close()
+
+	ctx, cancel := context.WithCancel(context.Background())
+
+	// closed when Do enters select case <-ctx.Done()
+	enteredDonePath := make(chan struct{})
+
+	testHookContextDoneBeforeHeaders = func() {
+		close(enteredDonePath)
+	}
+
+	testHookDoReturned = func() {
+		// We now have the result (the Flush'd headers) at least,
+		// so we can cancel the request.
+		cancel()
+
+		// But block the client.Do goroutine from sending
+		// until Do enters into the <-ctx.Done() path, since
+		// otherwise if both channels are readable, select
+		// picks a random one.
+		<-enteredDonePath
+	}
+
+	sawBodyClose := make(chan struct{})
+	testHookDidBodyClose = func() { close(sawBodyClose) }
+
+	tr := &http.Transport{}
+	defer tr.CloseIdleConnections()
+	c := &http.Client{Transport: tr}
+	req, _ := http.NewRequest("GET", ts.URL, nil)
+	_, doErr := Do(ctx, c, req)
+
+	select {
+	case <-sawBodyClose:
+	case <-time.After(5 * time.Second):
+		t.Fatal("timeout waiting for body to close")
+	}
+
+	if doErr != ctx.Err() {
+		t.Errorf("Do error = %v; want %v", doErr, ctx.Err())
+	}
+}
+
+type noteCloseConn struct {
+	net.Conn
+	onceClose sync.Once
+	closefn   func()
+}
+
+func (c *noteCloseConn) Close() error {
+	c.onceClose.Do(c.closefn)
+	return c.Conn.Close()
+}

context/ctxhttp/ctxhttp_test.go

@@ -7,11 +7,11 @@
 package ctxhttp
 
 import (
+	"io"
 	"io/ioutil"
-	"net"
 	"net/http"
 	"net/http/httptest"
-	"sync"
+	"strings"
 	"testing"
 	"time"
 
@@ -23,59 +23,62 @@ const (
 	requestBody     = "ok"
 )
 
-func TestNoTimeout(t *testing.T) {
-	ctx := context.Background()
-	resp, err := doRequest(ctx)
-
-	if resp == nil || err != nil {
-		t.Fatalf("error received from client: %v %v", err, resp)
-	}
+func okHandler(w http.ResponseWriter, r *http.Request) {
+	time.Sleep(requestDuration)
+	io.WriteString(w, requestBody)
 }
 
-func TestCancel(t *testing.T) {
-	ctx, cancel := context.WithCancel(context.Background())
-	go func() {
-		time.Sleep(requestDuration / 2)
-		cancel()
-	}()
-
-	resp, err := doRequest(ctx)
+func TestNoTimeout(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(okHandler))
+	defer ts.Close()
 
-	if resp != nil || err == nil {
-		t.Fatalf("expected error, didn't get one. resp: %v", resp)
+	ctx := context.Background()
+	res, err := Get(ctx, nil, ts.URL)
+	if err != nil {
+		t.Fatal(err)
 	}
-	if err != ctx.Err() {
-		t.Fatalf("expected error from context but got: %v", err)
+	defer res.Body.Close()
+	slurp, err := ioutil.ReadAll(res.Body)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(slurp) != requestBody {
+		t.Errorf("body = %q; want %q", slurp, requestBody)
 	}
 }
 
-func TestCancelAfterRequest(t *testing.T) {
+func TestCancelBeforeHeaders(t *testing.T) {
 	ctx, cancel := context.WithCancel(context.Background())
 
-	resp, err := doRequest(ctx)
-
-	// Cancel before reading the body.
-	// Request.Body should still be readable after the context is canceled.
-	cancel()
+	blockServer := make(chan struct{})
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		cancel()
+		<-blockServer
+		io.WriteString(w, requestBody)
+	}))
+	defer ts.Close()
+	defer close(blockServer)
 
-	b, err := ioutil.ReadAll(resp.Body)
-	if err != nil || string(b) != requestBody {
-		t.Fatalf("could not read body: %q %v", b, err)
+	res, err := Get(ctx, nil, ts.URL)
+	if err == nil {
+		res.Body.Close()
+		t.Fatal("Get returned unexpected nil error")
+	}
+	if !strings.Contains(err.Error(), "canceled") {
+		t.Errorf("err = %v; want something with \"canceled\"", err)
 	}
 }
 
 func TestCancelAfterHangingRequest(t *testing.T) {
-	handler := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		w.WriteHeader(http.StatusOK)
 		w.(http.Flusher).Flush()
 		<-w.(http.CloseNotifier).CloseNotify()
-	})
-
-	serv := httptest.NewServer(handler)
-	defer serv.Close()
+	}))
+	defer ts.Close()
 
 	ctx, cancel := context.WithCancel(context.Background())
-	resp, err := Get(ctx, nil, serv.URL)
+	resp, err := Get(ctx, nil, ts.URL)
 	if err != nil {
 		t.Fatalf("unexpected error in Get: %v", err)
 	}
@@ -101,76 +104,3 @@ func TestCancelAfterHangingRequest(t *testing.T) {
 	case <-done:
 	}
 }
-
-func doRequest(ctx context.Context) (*http.Response, error) {
-	var okHandler = http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		time.Sleep(requestDuration)
-		w.Write([]byte(requestBody))
-	})
-
-	serv := httptest.NewServer(okHandler)
-	defer serv.Close()
-
-	return Get(ctx, nil, serv.URL)
-}
-
-// golang.org/issue/14065
-func TestClosesResponseBodyOnCancel(t *testing.T) {
-	defer func() { testHookContextDoneBeforeHeaders = nop }()
-	defer func() { testHookDoReturned = nop }()
-	defer func() { testHookDidBodyClose = nop }()
-
-	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {}))
-	defer ts.Close()
-
-	ctx, cancel := context.WithCancel(context.Background())
-
-	// closed when Do enters select case <-ctx.Done()
-	enteredDonePath := make(chan struct{})
-
-	testHookContextDoneBeforeHeaders = func() {
-		close(enteredDonePath)
-	}
-
-	testHookDoReturned = func() {
-		// We now have the result (the Flush'd headers) at least,
-		// so we can cancel the request.
-		cancel()
-
-		// But block the client.Do goroutine from sending
-		// until Do enters into the <-ctx.Done() path, since
-		// otherwise if both channels are readable, select
-		// picks a random one.
-		<-enteredDonePath
-	}
-
-	sawBodyClose := make(chan struct{})
-	testHookDidBodyClose = func() { close(sawBodyClose) }
-
-	tr := &http.Transport{}
-	defer tr.CloseIdleConnections()
-	c := &http.Client{Transport: tr}
-	req, _ := http.NewRequest("GET", ts.URL, nil)
-	_, doErr := Do(ctx, c, req)
-
-	select {
-	case <-sawBodyClose:
-	case <-time.After(5 * time.Second):
-		t.Fatal("timeout waiting for body to close")
-	}
-
-	if doErr != ctx.Err() {
-		t.Errorf("Do error = %v; want %v", doErr, ctx.Err())
-	}
-}
-
-type noteCloseConn struct {
-	net.Conn
-	onceClose sync.Once
-	closefn   func()
-}
-
-func (c *noteCloseConn) Close() error {
-	c.onceClose.Do(c.closefn)
-	return c.Conn.Close()
-}