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         respPromise := js.Global().Call("fetch", req.URL.String(), opt)
 106         var (
 107                 respCh = make(chan *Response, 1)
 108                 errCh  = make(chan error, 1)
 109         )
 110         success := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
 111                 result := args[0]
 112                 header := Header{}
 113                 // https://developer.mozilla.org/en-US/docs/Web/API/Headers/entries
 114                 headersIt := result.Get("headers").Call("entries")
 115                 for {
 116                         n := headersIt.Call("next")
 117                         if n.Get("done").Bool() {
 118                                 break
 119                         }
 120                         pair := n.Get("value")
 121                         key, value := pair.Index(0).String(), pair.Index(1).String()
 122                         ck := CanonicalHeaderKey(key)
 123                         header[ck] = append(header[ck], value)
 124                 }
 125
 126                 contentLength := int64(0)
 127                 if cl, err := strconv.ParseInt(header.Get("Content-Length"), 10, 64); err == nil {
 128                         contentLength = cl
 129                 }
 130
 131                 b := result.Get("body")
 132                 var body io.ReadCloser
 133                 // The body is undefined when the browser does not support streaming response bodies (Firefox),
 134                 // and null in certain error cases, i.e. when the request is blocked because of CORS settings.
 135                 if !b.IsUndefined() && !b.IsNull() {
 136                         body = &streamReader{stream: b.Call("getReader")}
 137                 } else {
 138                         // Fall back to using ArrayBuffer
 139                         // https://developer.mozilla.org/en-US/docs/Web/API/Body/arrayBuffer
 140                         body = &arrayReader{arrayPromise: result.Call("arrayBuffer")}
 141                 }
 142
 143                 code := result.Get("status").Int()
 144                 select {
 145                 case respCh <- &Response{
 146                         Status:        fmt.Sprintf("%d %s", code, StatusText(code)),
 147                         StatusCode:    code,
 148                         Header:        header,
 149                         ContentLength: contentLength,
 150                         Body:          body,
 151                         Request:       req,
 152                 }:
 153                 case <-req.Context().Done():
 154                 }
 155
 156                 return nil
 157         })
 158         defer success.Release()
 159         failure := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
 160                 err := fmt.Errorf("net/http: fetch() failed: %s", args[0].Get("message").String())
 161                 select {
 162                 case errCh <- err:
 163                 case <-req.Context().Done():
 164                 }
 165                 return nil
 166         })
 167         defer failure.Release()
 168         respPromise.Call("then", success, failure)
 169         select {
 170         case <-req.Context().Done():
 171                 if !ac.IsUndefined() {
 172                         // Abort the Fetch request
 173                         ac.Call("abort")
 174                 }
 175                 return nil, req.Context().Err()
 176         case resp := <-respCh:
 177                 return resp, nil
 178         case err := <-errCh:
 179                 return nil, err
 180         }
 181 }
 182
 183 var errClosed = errors.New("net/http: reader is closed")
 184
 185 // streamReader implements an io.ReadCloser wrapper for ReadableStream.
 186 // See https://fetch.spec.whatwg.org/#readablestream for more information.
 187 type streamReader struct {
 188         pending []byte
 189         stream  js.Value
 190         err     error // sticky read error
 191 }
 192
 193 func (r *streamReader) Read(p []byte) (n int, err error) {
 194         if r.err != nil {
 195                 return 0, r.err
 196         }
 197         if len(r.pending) == 0 {
 198                 var (
 199                         bCh   = make(chan []byte, 1)
 200                         errCh = make(chan error, 1)
 201                 )
 202                 success := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
 203                         result := args[0]
 204                         if result.Get("done").Bool() {
 205                                 errCh <- io.EOF
 206                                 return nil
 207                         }
 208                         value := make([]byte, result.Get("value").Get("byteLength").Int())
 209                         js.CopyBytesToGo(value, result.Get("value"))
 210                         bCh <- value
 211                         return nil
 212                 })
 213                 defer success.Release()
 214                 failure := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
 215                         // Assumes it's a TypeError. See
 216                         // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypeError
 217                         // for more information on this type. See
 218                         // https://streams.spec.whatwg.org/#byob-reader-read for the spec on
 219                         // the read method.
 220                         errCh <- errors.New(args[0].Get("message").String())
 221                         return nil
 222                 })
 223                 defer failure.Release()
 224                 r.stream.Call("read").Call("then", success, failure)
 225                 select {
 226                 case b := <-bCh:
 227                         r.pending = b
 228                 case err := <-errCh:
 229                         r.err = err
 230                         return 0, err
 231                 }
 232         }
 233         n = copy(p, r.pending)
 234         r.pending = r.pending[n:]
 235         return n, nil
 236 }
 237
 238 func (r *streamReader) Close() error {
 239         // This ignores any error returned from cancel method. So far, I did not encounter any concrete
 240         // situation where reporting the error is meaningful. Most users ignore error from resp.Body.Close().
 241         // If there's a need to report error here, it can be implemented and tested when that need comes up.
 242         r.stream.Call("cancel")
 243         if r.err == nil {
 244                 r.err = errClosed
 245         }
 246         return nil
 247 }
 248
 249 // arrayReader implements an io.ReadCloser wrapper for ArrayBuffer.
 250 // https://developer.mozilla.org/en-US/docs/Web/API/Body/arrayBuffer.
 251 type arrayReader struct {
 252         arrayPromise js.Value
 253         pending      []byte
 254         read         bool
 255         err          error // sticky read error
 256 }
 257
 258 func (r *arrayReader) Read(p []byte) (n int, err error) {
 259         if r.err != nil {
 260                 return 0, r.err
 261         }
 262         if !r.read {
 263                 r.read = true
 264                 var (
 265                         bCh   = make(chan []byte, 1)
 266                         errCh = make(chan error, 1)
 267                 )
 268                 success := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
 269                         // Wrap the input ArrayBuffer with a Uint8Array
 270                         uint8arrayWrapper := uint8Array.New(args[0])
 271                         value := make([]byte, uint8arrayWrapper.Get("byteLength").Int())
 272                         js.CopyBytesToGo(value, uint8arrayWrapper)
 273                         bCh <- value
 274                         return nil
 275                 })
 276                 defer success.Release()
 277                 failure := js.FuncOf(func(this js.Value, args []js.Value) interface{} {
 278                         // Assumes it's a TypeError. See
 279                         // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypeError
 280                         // for more information on this type.
 281                         // See https://fetch.spec.whatwg.org/#concept-body-consume-body for reasons this might error.
 282                         errCh <- errors.New(args[0].Get("message").String())
 283                         return nil
 284                 })
 285                 defer failure.Release()
 286                 r.arrayPromise.Call("then", success, failure)
 287                 select {
 288                 case b := <-bCh:
 289                         r.pending = b
 290                 case err := <-errCh:
 291                         return 0, err
 292                 }
 293         }
 294         if len(r.pending) == 0 {
 295                 return 0, io.EOF
 296         }
 297         n = copy(p, r.pending)
 298         r.pending = r.pending[n:]
 299         return n, nil
 300 }
 301
 302 func (r *arrayReader) Close() error {
 303         if r.err == nil {
 304                 r.err = errClosed
 305         }
 306         return nil
 307 }