src/net/http/roundtrip_js.go

   1 // Copyright 2018 The Go Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style
   3 // license that can be found in the LICENSE file.
   4
   5 // +build js,wasm
   6
   7 package http
   8
   9 import (
  10         "errors"
  11         "fmt"
  12         "io"
  13         "io/ioutil"
  14         "os"
  15         "strconv"
  16         "strings"
  17         "syscall/js"
  18 )
  19
  20 // jsFetchMode is a Request.Header map key that, if present,
  21 // signals that the map entry is actually an option to the Fetch API mode setting.
  22 // Valid values are: "cors", "no-cors", "same-origin", "navigate"
  23 // The default is "same-origin".
  24 //
  25 // Reference: https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch#Parameters
  26 const jsFetchMode = "js.fetch:mode"
  27
  28 // jsFetchCreds is a Request.Header map key that, if present,
  29 // signals that the map entry is actually an option to the Fetch API credentials setting.
  30 // Valid values are: "omit", "same-origin", "include"
  31 // The default is "same-origin".
  32 //
  33 // Reference: https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch#Parameters
  34 const jsFetchCreds = "js.fetch:credentials"
  35
  36 // RoundTrip implements the RoundTripper interface using the WHATWG Fetch API.
  37 func (t *Transport) RoundTrip(req *Request) (*Response, error) {
  38         if useFakeNetwork() {
  39                 return t.roundTrip(req)
  40         }
  41
  42         ac := js.Global().Get("AbortController")
  43         if ac != js.Undefined() {
  44                 // Some browsers that support WASM don't necessarily support
  45                 // the AbortController. See
  46                 // https://developer.mozilla.org/en-US/docs/Web/API/AbortController#Browser_compatibility.
  47                 ac = ac.New()
  48         }
  49
  50         opt := js.Global().Get("Object").New()
  51         // See https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch
  52         // for options available.
  53         opt.Set("method", req.Method)
  54         opt.Set("credentials", "same-origin")
  55         if h := req.Header.Get(jsFetchCreds); h != "" {
  56                 opt.Set("credentials", h)
  57                 req.Header.Del(jsFetchCreds)
  58         }
  59         if h := req.Header.Get(jsFetchMode); h != "" {
  60                 opt.Set("mode", h)
  61                 req.Header.Del(jsFetchMode)
  62         }
  63         if ac != js.Undefined() {
  64                 opt.Set("signal", ac.Get("signal"))
  65         }
  66         headers := js.Global().Get("Headers").New()
  67         for key, values := range req.Header {
  68                 for _, value := range values {
  69                         headers.Call("append", key, value)
  70                 }
  71         }
  72         opt.Set("headers", headers)
  73
  74         if req.Body != nil {
  75                 // TODO(johanbrandhorst): Stream request body when possible.
  76                 // See https://bugs.chromium.org/p/chromium/issues/detail?id=688906 for Blink issue.
  77                 // See https://bugzilla.mozilla.org/show_bug.cgi?id=1387483 for Firefox issue.
  78                 // See https://github.com/web-platform-tests/wpt/issues/7693 for WHATWG tests issue.
  79                 // See https://developer.mozilla.org/en-US/docs/Web/API/Streams_API for more details on the Streams API
  80                 // and browser support.
  81                 body, err := ioutil.ReadAll(req.Body)
  82                 if err != nil {
  83                         req.Body.Close() // RoundTrip must always close the body, including on errors.
  84                         return nil, err
  85                 }
  86                 req.Body.Close()
  87                 a := js.TypedArrayOf(body)
  88                 defer a.Release()
  89                 opt.Set("body", a)
  90         }
  91         respPromise := js.Global().Call("fetch", req.URL.String(), opt)
  92         var (
  93                 respCh = make(chan *Response, 1)
  94                 errCh  = make(chan error, 1)
  95         )
  96         success := js.NewCallback(func(args []js.Value) {
  97                 result := args[0]
  98                 header := Header{}
  99                 // https://developer.mozilla.org/en-US/docs/Web/API/Headers/entries
 100                 headersIt := result.Get("headers").Call("entries")
 101                 for {
 102                         n := headersIt.Call("next")
 103                         if n.Get("done").Bool() {
 104                                 break
 105                         }
 106                         pair := n.Get("value")
 107                         key, value := pair.Index(0).String(), pair.Index(1).String()
 108                         ck := CanonicalHeaderKey(key)
 109                         header[ck] = append(header[ck], value)
 110                 }
 111
 112                 contentLength := int64(0)
 113                 if cl, err := strconv.ParseInt(header.Get("Content-Length"), 10, 64); err == nil {
 114                         contentLength = cl
 115                 }
 116
 117                 b := result.Get("body")
 118                 var body io.ReadCloser
 119                 // The body is undefined when the browser does not support streaming response bodies (Firefox),
 120                 // and null in certain error cases, i.e. when the request is blocked because of CORS settings.
 121                 if b != js.Undefined() && b != js.Null() {
 122                         body = &streamReader{stream: b.Call("getReader")}
 123                 } else {
 124                         // Fall back to using ArrayBuffer
 125                         // https://developer.mozilla.org/en-US/docs/Web/API/Body/arrayBuffer
 126                         body = &arrayReader{arrayPromise: result.Call("arrayBuffer")}
 127                 }
 128
 129                 select {
 130                 case respCh <- &Response{
 131                         Status:        result.Get("status").String() + " " + StatusText(result.Get("status").Int()),
 132                         StatusCode:    result.Get("status").Int(),
 133                         Header:        header,
 134                         ContentLength: contentLength,
 135                         Body:          body,
 136                         Request:       req,
 137                 }:
 138                 case <-req.Context().Done():
 139                 }
 140         })
 141         defer success.Release()
 142         failure := js.NewCallback(func(args []js.Value) {
 143                 err := fmt.Errorf("net/http: fetch() failed: %s", args[0].String())
 144                 select {
 145                 case errCh <- err:
 146                 case <-req.Context().Done():
 147                 }
 148         })
 149         defer failure.Release()
 150         respPromise.Call("then", success, failure)
 151         select {
 152         case <-req.Context().Done():
 153                 if ac != js.Undefined() {
 154                         // Abort the Fetch request
 155                         ac.Call("abort")
 156                 }
 157                 return nil, req.Context().Err()
 158         case resp := <-respCh:
 159                 return resp, nil
 160         case err := <-errCh:
 161                 return nil, err
 162         }
 163 }
 164
 165 var errClosed = errors.New("net/http: reader is closed")
 166
 167 // useFakeNetwork is used to determine whether the request is made
 168 // by a test and should be made to use the fake in-memory network.
 169 func useFakeNetwork() bool {
 170         return len(os.Args) > 0 && strings.HasSuffix(os.Args[0], ".test")
 171 }
 172
 173 // streamReader implements an io.ReadCloser wrapper for ReadableStream.
 174 // See https://fetch.spec.whatwg.org/#readablestream for more information.
 175 type streamReader struct {
 176         pending []byte
 177         stream  js.Value
 178         err     error // sticky read error
 179 }
 180
 181 func (r *streamReader) Read(p []byte) (n int, err error) {
 182         if r.err != nil {
 183                 return 0, r.err
 184         }
 185         if len(r.pending) == 0 {
 186                 var (
 187                         bCh   = make(chan []byte, 1)
 188                         errCh = make(chan error, 1)
 189                 )
 190                 success := js.NewCallback(func(args []js.Value) {
 191                         result := args[0]
 192                         if result.Get("done").Bool() {
 193                                 errCh <- io.EOF
 194                                 return
 195                         }
 196                         value := make([]byte, result.Get("value").Get("byteLength").Int())
 197                         a := js.TypedArrayOf(value)
 198                         a.Call("set", result.Get("value"))
 199                         a.Release()
 200                         bCh <- value
 201                 })
 202                 defer success.Release()
 203                 failure := js.NewCallback(func(args []js.Value) {
 204                         // Assumes it's a TypeError. See
 205                         // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypeError
 206                         // for more information on this type. See
 207                         // https://streams.spec.whatwg.org/#byob-reader-read for the spec on
 208                         // the read method.
 209                         errCh <- errors.New(args[0].Get("message").String())
 210                 })
 211                 defer failure.Release()
 212                 r.stream.Call("read").Call("then", success, failure)
 213                 select {
 214                 case b := <-bCh:
 215                         r.pending = b
 216                 case err := <-errCh:
 217                         r.err = err
 218                         return 0, err
 219                 }
 220         }
 221         n = copy(p, r.pending)
 222         r.pending = r.pending[n:]
 223         return n, nil
 224 }
 225
 226 func (r *streamReader) Close() error {
 227         // This ignores any error returned from cancel method. So far, I did not encounter any concrete
 228         // situation where reporting the error is meaningful. Most users ignore error from resp.Body.Close().
 229         // If there's a need to report error here, it can be implemented and tested when that need comes up.
 230         r.stream.Call("cancel")
 231         if r.err == nil {
 232                 r.err = errClosed
 233         }
 234         return nil
 235 }
 236
 237 // arrayReader implements an io.ReadCloser wrapper for ArrayBuffer.
 238 // https://developer.mozilla.org/en-US/docs/Web/API/Body/arrayBuffer.
 239 type arrayReader struct {
 240         arrayPromise js.Value
 241         pending      []byte
 242         read         bool
 243         err          error // sticky read error
 244 }
 245
 246 func (r *arrayReader) Read(p []byte) (n int, err error) {
 247         if r.err != nil {
 248                 return 0, r.err
 249         }
 250         if !r.read {
 251                 r.read = true
 252                 var (
 253                         bCh   = make(chan []byte, 1)
 254                         errCh = make(chan error, 1)
 255                 )
 256                 success := js.NewCallback(func(args []js.Value) {
 257                         // Wrap the input ArrayBuffer with a Uint8Array
 258                         uint8arrayWrapper := js.Global().Get("Uint8Array").New(args[0])
 259                         value := make([]byte, uint8arrayWrapper.Get("byteLength").Int())
 260                         a := js.TypedArrayOf(value)
 261                         a.Call("set", uint8arrayWrapper)
 262                         a.Release()
 263                         bCh <- value
 264                 })
 265                 defer success.Release()
 266                 failure := js.NewCallback(func(args []js.Value) {
 267                         // Assumes it's a TypeError. See
 268                         // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypeError
 269                         // for more information on this type.
 270                         // See https://fetch.spec.whatwg.org/#concept-body-consume-body for reasons this might error.
 271                         errCh <- errors.New(args[0].Get("message").String())
 272                 })
 273                 defer failure.Release()
 274                 r.arrayPromise.Call("then", success, failure)
 275                 select {
 276                 case b := <-bCh:
 277                         r.pending = b
 278                 case err := <-errCh:
 279                         return 0, err
 280                 }
 281         }
 282         if len(r.pending) == 0 {
 283                 return 0, io.EOF
 284         }
 285         n = copy(p, r.pending)
 286         r.pending = r.pending[n:]
 287         return n, nil
 288 }
 289
 290 func (r *arrayReader) Close() error {
 291         if r.err == nil {
 292                 r.err = errClosed
 293         }
 294         return nil
 295 }