compiler/natives/src/net/http: Implement http.RoundTripper on Fetch API.

compiler/natives/src/net/http/fetch.go

@@ -0,0 +1,137 @@
+// +build js
+
+package http
+
+import (
+	"errors"
+	"io"
+	"io/ioutil"
+	"strconv"
+
+	"github.com/gopherjs/gopherjs/js"
+)
+
+// streamReader implements an io.ReadCloser wrapper for ReadableStream of https://fetch.spec.whatwg.org/.
+type streamReader struct {
+	pending []byte
+	stream  *js.Object
+}
+
+func (r *streamReader) Read(p []byte) (n int, err error) {
+	if len(r.pending) == 0 {
+		var (
+			bCh   = make(chan []byte)
+			errCh = make(chan error)
+		)
+		r.stream.Call("read").Call("then",
+			func(result *js.Object) {
+				if result.Get("done").Bool() {
+					errCh <- io.EOF
+					return
+				}
+				bCh <- result.Get("value").Interface().([]byte)
+			},
+			func(reason *js.Object) {
+				// Assumes it's a DOMException.
+				errCh <- errors.New(reason.Get("message").String())
+			},
+		)
+		select {
+		case b := <-bCh:
+			r.pending = b
+		case err := <-errCh:
+			return 0, err
+		}
+	}
+	n = copy(p, r.pending)
+	r.pending = r.pending[n:]
+	return n, nil
+}
+
+func (r *streamReader) Close() error {
+	// TOOD: Cannot do this because it's a blocking call, and Close() is often called
+	//       via `defer resp.Body.Close()`, but GopherJS currently has an issue with supporting that.
+	//       See https://github.com/gopherjs/gopherjs/issues/381 and https://github.com/gopherjs/gopherjs/issues/426.
+	/*ch := make(chan error)
+	r.stream.Call("cancel").Call("then",
+		func(result *js.Object) {
+			if result != js.Undefined {
+				ch <- errors.New(result.String()) // TODO: Verify this works, it probably doesn't and should be rewritten as result.Get("message").String() or something.
+				return
+			}
+			ch <- nil
+		},
+	)
+	return <-ch*/
+	r.stream.Call("cancel")
+	return nil
+}
+
+// fetchTransport is a RoundTripper that is implemented using Fetch API. It supports streaming
+// response bodies.
+type fetchTransport struct{}
+
+func (t *fetchTransport) RoundTrip(req *Request) (*Response, error) {
+	headers := js.Global.Get("Headers").New()
+	for key, values := range req.Header {
+		for _, value := range values {
+			headers.Call("append", key, value)
+		}
+	}
+	opt := map[string]interface{}{
+		"method":  req.Method,
+		"headers": headers,
+	}
+	if req.Body != nil {
+		// TODO: Find out if request body can be streamed into the fetch request rather than in advance here.
+		//       See BufferSource at https://fetch.spec.whatwg.org/#body-mixin.
+		body, err := ioutil.ReadAll(req.Body)
+		if err != nil {
+			req.Body.Close() // RoundTrip must always close the body, including on errors.
+			return nil, err
+		}
+		req.Body.Close()
+		opt["body"] = body
+	}
+	respPromise := js.Global.Call("fetch", req.URL.String(), opt)
+
+	var (
+		respCh = make(chan *Response)
+		errCh  = make(chan error)
+	)
+	respPromise.Call("then",
+		func(result *js.Object) {
+			header := Header{}
+			result.Get("headers").Call("forEach", func(value, key *js.Object) {
+				ck := CanonicalHeaderKey(key.String())
+				header[ck] = append(header[ck], value.String())
+			})
+
+			contentLength := int64(-1)
+			if cl, err := strconv.ParseInt(header.Get("Content-Length"), 10, 64); err == nil {
+				contentLength = cl
+			}
+
+			respCh <- &Response{
+				Status:        result.Get("status").String() + " " + StatusText(result.Get("status").Int()),
+				StatusCode:    result.Get("status").Int(),
+				Header:        header,
+				ContentLength: contentLength,
+				Body:          &streamReader{stream: result.Get("body").Call("getReader")},
+				Request:       req,
+			}
+		},
+		func(reason *js.Object) {
+			errCh <- errors.New("net/http: fetch() failed")
+		},
+	)
+	select {
+	case resp := <-respCh:
+		return resp, nil
+	case err := <-errCh:
+		return nil, err
+	case <-req.Cancel:
+		// TODO: Abort request if possible using Fetch API.
+		return nil, errors.New("net/http: request canceled")
+	}
+}

compiler/natives/src/net/http/http.go

@@ -13,18 +13,29 @@ import (
 	"github.com/gopherjs/gopherjs/js"
 )
 
-var DefaultTransport RoundTripper = &XHRTransport{}
+var DefaultTransport = func() RoundTripper {
+	if fetchAPI, streamsAPI := js.Global.Get("fetch"), js.Global.Get("ReadableStream"); fetchAPI != js.Undefined && streamsAPI != js.Undefined {
+		return &fetchTransport{}
+	}
+	if xhrAPI := js.Global.Get("XMLHttpRequest"); xhrAPI != js.Undefined {
+		return &XHRTransport{}
+	}
+	return noTransport{}
+}()
+
+// noTransport is used when neither Fetch API nor XMLHttpRequest API are available. It always fails.
+type noTransport struct{}
+
+func (noTransport) RoundTrip(req *Request) (*Response, error) {
+	return nil, errors.New("net/http: neither of Fetch nor XMLHttpRequest APIs is available")
+}
 
 type XHRTransport struct {
 	inflight map[*Request]*js.Object
 }
 
 func (t *XHRTransport) RoundTrip(req *Request) (*Response, error) {
-	xhrConstructor := js.Global.Get("XMLHttpRequest")
-	if xhrConstructor == js.Undefined {
-		return nil, errors.New("net/http: XMLHttpRequest not available")
-	}
-	xhr := xhrConstructor.New()
+	xhr := js.Global.Get("XMLHttpRequest").New()
 
 	if t.inflight == nil {
 		t.inflight = map[*Request]*js.Object{}
@@ -79,8 +90,10 @@ func (t *XHRTransport) RoundTrip(req *Request) (*Response, error) {
 		var err error
 		body, err = ioutil.ReadAll(req.Body)
 		if err != nil {
+			req.Body.Close() // RoundTrip must always close the body, including on errors.
 			return nil, err
 		}
+		req.Body.Close()
 	}
 	xhr.Call("send", body)