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         "strconv"
  15         "syscall/js"
  16 )
  17
  18 var uint8Array = js.Global().Get("Uint8Array")
  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 // jsFetchRedirect is a Request.Header map key that, if present,
  37 // signals that the map entry is actually an option to the Fetch API redirect setting.
  38 // Valid values are: "follow", "error", "manual"
  39 // The default is "follow".
  40 //
  41 // Reference: https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch#Parameters
  42 const jsFetchRedirect = "js.fetch:redirect"
  43
  44 var useFakeNetwork = js.Global().Get("fetch").IsUndefined()
  45
  46 // RoundTrip implements the RoundTripper interface using the WHATWG Fetch API.
  47 func (t *Transport) RoundTrip(req *Request) (*Response, error) {
  48         if useFakeNetwork {
  49                 return t.roundTrip(req)
  50         }
  51
  52         ac := js.Global().Get("AbortController")
  53         if !ac.IsUndefined() {
  54                 // Some browsers that support WASM don't necessarily support
  55                 // the AbortController. See
  56                 // https://developer.mozilla.org/en-US/docs/Web/API/AbortController#Browser_compatibility.
  57                 ac = ac.New()
  58         }
  59
  60         opt := js.Global().Get("Object").New()
  61         // See https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch
  62         // for options available.
  63         opt.Set("method", req.Method)
  64         opt.Set("credentials", "same-origin")
  65         if h := req.Header.Get(jsFetchCreds); h != "" {
  66                 opt.Set("credentials", h)
  67                 req.Header.Del(jsFetchCreds)
  68         }
  69         if h := req.Header.Get(jsFetchMode); h != "" {
  70                 opt.Set("mode", h)
  71                 req.Header.Del(jsFetchMode)
  72         }
  73         if h := req.Header.Get(jsFetchRedirect); h != "" {
  74                 opt.Set("redirect", h)
  75                 req.Header.Del(jsFetchRedirect)
  76         }
  77         if !ac.IsUndefined() {
  78                 opt.Set("signal", ac.Get("signal"))
  79         }
  80         headers := js.Global().Get("Headers").New()
  81         for key, values := range req.Header {
  82                 for _, value := range values {
  83                         headers.Call("append", key, value)
  84                 }
  85         }
  86         opt.Set("headers", headers)
  87
  88         if req.Body != nil {
  89                 // TODO(johanbrandhorst): Stream request body when possible.
  90                 // See https://bugs.chromium.org/p/chromium/issues/detail?id=688906 for Blink issue.
  91                 // See https://bugzilla.mozilla.org/show_bug.cgi?id=1387483 for Firefox issue.
  92                 // See https://github.com/web-platform-tests/wpt/issues/7693 for WHATWG tests issue.
  93                 // See https://developer.mozilla.org/en-US/docs/Web/API/Streams_API for more details on the Streams API
  94                 // and browser support.
  95                 body, err := ioutil.ReadAll(req.Body)
  96                 if err != nil {
  97                         req.Body.Close() // RoundTrip must always close the body, including on errors.
  98                         return nil, err
  99                 }
 100                 req.Body.Close()
 101                 buf := uint8Array.New(len(body))
 102                 js.CopyBytesToJS(buf, body)
 103                 opt.Set("body", buf)
 104         }
 105
 106         fetchPromise := js.Global().Call("fetch", req.URL.String(), opt)
 107         var (
 108                 respCh           = make(chan *Response, 1)
 109                 errCh            = make(chan error, 1)
 110                 success, failure js.Func
 111         )
 112         success = js.FuncOf(func(this js.Value, args []js.Value) interface{} {
 113                 success.Release()
 114                 failure.Release()
 115
 116                 result := args[0]
 117                 header := Header{}
 118                 // https://developer.mozilla.org/en-US/docs/Web/API/Headers/entries
 119                 headersIt := result.Get("headers").Call("entries")
 120                 for {
 121                         n := headersIt.Call("next")
 122                         if n.Get("done").Bool() {
 123                                 break
 124                         }
 125                         pair := n.Get("value")
 126                         key, value := pair.Index(0).String(), pair.Index(1).String()
 127                         ck := CanonicalHeaderKey(key)
 128                         header[ck] = append(header[ck], value)
 129                 }
 130
 131                 contentLength := int64(0)
 132                 if cl, err := strconv.ParseInt(header.Get("Content-Length"), 10, 64); err == nil {
 133                         contentLength = cl
 134                 }
 135
 136                 b := result.Get("body")
 137                 var body io.ReadCloser
 138                 // The body is undefined when the browser does not support streaming response bodies (Firefox),
 139                 // and null in certain error cases, i.e. when the request is blocked because of CORS settings.
 140                 if !b.IsUndefined() && !b.IsNull() {
 141                         body = &streamReader{stream: b.Call("getReader")}
 142                 } else {
 143                         // Fall back to using ArrayBuffer
 144                         // https://developer.mozilla.org/en-US/docs/Web/API/Body/arrayBuffer
 145                         body = &arrayReader{arrayPromise: result.Call("arrayBuffer")}
 146                 }
 147
 148                 code := result.Get("status").Int()
 149                 respCh <- &Response{
 150                         Status:        fmt.Sprintf("%d %s", code, StatusText(code)),
 151                         StatusCode:    code,
 152                         Header:        header,
 153                         ContentLength: contentLength,
 154                         Body:          body,
 155                         Request:       req,
 156                 }
 157
 158                 return nil
 159         })
 160         failure = js.FuncOf(func(this js.Value, args []js.Value) interface{} {
 161                 success.Release()
 162                 failure.Release()
 163                 errCh <- fmt.Errorf("net/http: fetch() failed: %s", args[0].Get("message").String())
 164                 return nil
 165         })
 166
 167         fetchPromise.Call("then", success, failure)
 168         select {
 169         case <-req.Context().Done():
 170                 if !ac.IsUndefined() {
 171                         // Abort the Fetch request.
 172                         ac.Call("abort")
 173                 }
 174                 return nil, req.Context().Err()
 175         case resp := <-respCh:
 176                 return resp, nil
 177         case err := <-errCh:
 178                 return nil, err
 179         }
 180 }
 181
 182 var errClosed = errors.New("net/http: reader is closed")
 183
 184 // streamReader implements an io.ReadCloser wrapper for ReadableStream.
 185 // See https://fetch.spec.whatwg.org/#readablestream for more information.
 186 type streamReader struct {
 187         pending []byte
 188         stream  js.Value
 189         err     error // sticky read error
 190 }
 191
 192 func (r *streamReader) Read(p []byte) (n int, err error) {
 193         if r.err != nil {
 194                 return 0, r.err
 195         }
 196         if len(r.pending) == 0 {
 197                 var (
 198                         bCh   = make(chan []byte, 1)
 199                         errCh = make(chan error, 1)
 200                 )
 201                 success := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
 202                         result := args[0]
 203                         if result.Get("done").Bool() {
 204                                 errCh <- io.EOF
 205                                 return nil
 206                         }
 207                         value := make([]byte, result.Get("value").Get("byteLength").Int())
 208                         js.CopyBytesToGo(value, result.Get("value"))
 209                         bCh <- value
 210                         return nil
 211                 })
 212                 defer success.Release()
 213                 failure := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
 214                         // Assumes it's a TypeError. See
 215                         // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypeError
 216                         // for more information on this type. See
 217                         // https://streams.spec.whatwg.org/#byob-reader-read for the spec on
 218                         // the read method.
 219                         errCh <- errors.New(args[0].Get("message").String())
 220                         return nil
 221                 })
 222                 defer failure.Release()
 223                 r.stream.Call("read").Call("then", success, failure)
 224                 select {
 225                 case b := <-bCh:
 226                         r.pending = b
 227                 case err := <-errCh:
 228                         r.err = err
 229                         return 0, err
 230                 }
 231         }
 232         n = copy(p, r.pending)
 233         r.pending = r.pending[n:]
 234         return n, nil
 235 }
 236
 237 func (r *streamReader) Close() error {
 238         // This ignores any error returned from cancel method. So far, I did not encounter any concrete
 239         // situation where reporting the error is meaningful. Most users ignore error from resp.Body.Close().
 240         // If there's a need to report error here, it can be implemented and tested when that need comes up.
 241         r.stream.Call("cancel")
 242         if r.err == nil {
 243                 r.err = errClosed
 244         }
 245         return nil
 246 }
 247
 248 // arrayReader implements an io.ReadCloser wrapper for ArrayBuffer.
 249 // https://developer.mozilla.org/en-US/docs/Web/API/Body/arrayBuffer.
 250 type arrayReader struct {
 251         arrayPromise js.Value
 252         pending      []byte
 253         read         bool
 254         err          error // sticky read error
 255 }
 256
 257 func (r *arrayReader) Read(p []byte) (n int, err error) {
 258         if r.err != nil {
 259                 return 0, r.err
 260         }
 261         if !r.read {
 262                 r.read = true
 263                 var (
 264                         bCh   = make(chan []byte, 1)
 265                         errCh = make(chan error, 1)
 266                 )
 267                 success := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
 268                         // Wrap the input ArrayBuffer with a Uint8Array
 269                         uint8arrayWrapper := uint8Array.New(args[0])
 270                         value := make([]byte, uint8arrayWrapper.Get("byteLength").Int())
 271                         js.CopyBytesToGo(value, uint8arrayWrapper)
 272                         bCh <- value
 273                         return nil
 274                 })
 275                 defer success.Release()
 276                 failure := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
 277                         // Assumes it's a TypeError. See
 278                         // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypeError
 279                         // for more information on this type.
 280                         // See https://fetch.spec.whatwg.org/#concept-body-consume-body for reasons this might error.
 281                         errCh <- errors.New(args[0].Get("message").String())
 282                         return nil
 283                 })
 284                 defer failure.Release()
 285                 r.arrayPromise.Call("then", success, failure)
 286                 select {
 287                 case b := <-bCh:
 288                         r.pending = b
 289                 case err := <-errCh:
 290                         return 0, err
 291                 }
 292         }
 293         if len(r.pending) == 0 {
 294                 return 0, io.EOF
 295         }
 296         n = copy(p, r.pending)
 297         r.pending = r.pending[n:]
 298         return n, nil
 299 }
 300
 301 func (r *arrayReader) Close() error {
 302         if r.err == nil {
 303                 r.err = errClosed
 304         }
 305         return nil
 306 }