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  //go:build js && wasm
     6  
     7  package http
     8  
     9  import (
    10  	"errors"
    11  	"fmt"
    12  	"io"
    13  	"net/http/internal/ascii"
    14  	"strconv"
    15  	"strings"
    16  	"syscall/js"
    17  )
    18  
    19  var uint8Array = js.Global().Get("Uint8Array")
    20  
    21  // jsFetchMode is a Request.Header map key that, if present,
    22  // signals that the map entry is actually an option to the Fetch API mode setting.
    23  // Valid values are: "cors", "no-cors", "same-origin", "navigate"
    24  // The default is "same-origin".
    25  //
    26  // Reference: https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch#Parameters
    27  const jsFetchMode = "js.fetch:mode"
    28  
    29  // jsFetchCreds is a Request.Header map key that, if present,
    30  // signals that the map entry is actually an option to the Fetch API credentials setting.
    31  // Valid values are: "omit", "same-origin", "include"
    32  // The default is "same-origin".
    33  //
    34  // Reference: https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch#Parameters
    35  const jsFetchCreds = "js.fetch:credentials"
    36  
    37  // jsFetchRedirect is a Request.Header map key that, if present,
    38  // signals that the map entry is actually an option to the Fetch API redirect setting.
    39  // Valid values are: "follow", "error", "manual"
    40  // The default is "follow".
    41  //
    42  // Reference: https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch#Parameters
    43  const jsFetchRedirect = "js.fetch:redirect"
    44  
    45  // jsFetchMissing will be true if the Fetch API is not present in
    46  // the browser globals.
    47  var jsFetchMissing = js.Global().Get("fetch").IsUndefined()
    48  
    49  // jsFetchDisabled controls whether the use of Fetch API is disabled.
    50  // It's set to true when we detect we're running in Node.js, so that
    51  // RoundTrip ends up talking over the same fake network the HTTP servers
    52  // currently use in various tests and examples. See go.dev/issue/57613.
    53  //
    54  // TODO(go.dev/issue/60810): See if it's viable to test the Fetch API
    55  // code path.
    56  var jsFetchDisabled = js.Global().Get("process").Type() == js.TypeObject &&
    57  	strings.HasPrefix(js.Global().Get("process").Get("argv0").String(), "node")
    58  
    59  // RoundTrip implements the [RoundTripper] interface using the WHATWG Fetch API.
    60  func (t *Transport) RoundTrip(req *Request) (*Response, error) {
    61  	// The Transport has a documented contract that states that if the DialContext or
    62  	// DialTLSContext functions are set, they will be used to set up the connections.
    63  	// If they aren't set then the documented contract is to use Dial or DialTLS, even
    64  	// though they are deprecated. Therefore, if any of these are set, we should obey
    65  	// the contract and dial using the regular round-trip instead. Otherwise, we'll try
    66  	// to fall back on the Fetch API, unless it's not available.
    67  	if t.Dial != nil || t.DialContext != nil || t.DialTLS != nil || t.DialTLSContext != nil || jsFetchMissing || jsFetchDisabled {
    68  		return t.roundTrip(req)
    69  	}
    70  
    71  	ac := js.Global().Get("AbortController")
    72  	if !ac.IsUndefined() {
    73  		// Some browsers that support WASM don't necessarily support
    74  		// the AbortController. See
    75  		// https://developer.mozilla.org/en-US/docs/Web/API/AbortController#Browser_compatibility.
    76  		ac = ac.New()
    77  	}
    78  
    79  	opt := js.Global().Get("Object").New()
    80  	// See https://developer.mozilla.org/en-US/docs/Web/API/WindowOrWorkerGlobalScope/fetch
    81  	// for options available.
    82  	opt.Set("method", req.Method)
    83  	opt.Set("credentials", "same-origin")
    84  	if h := req.Header.Get(jsFetchCreds); h != "" {
    85  		opt.Set("credentials", h)
    86  		req.Header.Del(jsFetchCreds)
    87  	}
    88  	if h := req.Header.Get(jsFetchMode); h != "" {
    89  		opt.Set("mode", h)
    90  		req.Header.Del(jsFetchMode)
    91  	}
    92  	if h := req.Header.Get(jsFetchRedirect); h != "" {
    93  		opt.Set("redirect", h)
    94  		req.Header.Del(jsFetchRedirect)
    95  	}
    96  	if !ac.IsUndefined() {
    97  		opt.Set("signal", ac.Get("signal"))
    98  	}
    99  	headers := js.Global().Get("Headers").New()
   100  	for key, values := range req.Header {
   101  		for _, value := range values {
   102  			headers.Call("append", key, value)
   103  		}
   104  	}
   105  	opt.Set("headers", headers)
   106  
   107  	if req.Body != nil {
   108  		// TODO(johanbrandhorst): Stream request body when possible.
   109  		// See https://bugs.chromium.org/p/chromium/issues/detail?id=688906 for Blink issue.
   110  		// See https://bugzilla.mozilla.org/show_bug.cgi?id=1387483 for Firefox issue.
   111  		// See https://github.com/web-platform-tests/wpt/issues/7693 for WHATWG tests issue.
   112  		// See https://developer.mozilla.org/en-US/docs/Web/API/Streams_API for more details on the Streams API
   113  		// and browser support.
   114  		// NOTE(haruyama480): Ensure HTTP/1 fallback exists.
   115  		// See https://go.dev/issue/61889 for discussion.
   116  		body, err := io.ReadAll(req.Body)
   117  		if err != nil {
   118  			req.Body.Close() // RoundTrip must always close the body, including on errors.
   119  			return nil, err
   120  		}
   121  		req.Body.Close()
   122  		if len(body) != 0 {
   123  			buf := uint8Array.New(len(body))
   124  			js.CopyBytesToJS(buf, body)
   125  			opt.Set("body", buf)
   126  		}
   127  	}
   128  
   129  	fetchPromise := js.Global().Call("fetch", req.URL.String(), opt)
   130  	var (
   131  		respCh           = make(chan *Response, 1)
   132  		errCh            = make(chan error, 1)
   133  		success, failure js.Func
   134  	)
   135  	success = js.FuncOf(func(this js.Value, args []js.Value) any {
   136  		success.Release()
   137  		failure.Release()
   138  
   139  		result := args[0]
   140  		header := Header{}
   141  		// https://developer.mozilla.org/en-US/docs/Web/API/Headers/entries
   142  		headersIt := result.Get("headers").Call("entries")
   143  		for {
   144  			n := headersIt.Call("next")
   145  			if n.Get("done").Bool() {
   146  				break
   147  			}
   148  			pair := n.Get("value")
   149  			key, value := pair.Index(0).String(), pair.Index(1).String()
   150  			ck := CanonicalHeaderKey(key)
   151  			header[ck] = append(header[ck], value)
   152  		}
   153  
   154  		contentLength := int64(0)
   155  		clHeader := header.Get("Content-Length")
   156  		switch {
   157  		case clHeader != "":
   158  			cl, err := strconv.ParseInt(clHeader, 10, 64)
   159  			if err != nil {
   160  				errCh <- fmt.Errorf("net/http: ill-formed Content-Length header: %v", err)
   161  				return nil
   162  			}
   163  			if cl < 0 {
   164  				// Content-Length values less than 0 are invalid.
   165  				// See: https://datatracker.ietf.org/doc/html/rfc2616/#section-14.13
   166  				errCh <- fmt.Errorf("net/http: invalid Content-Length header: %q", clHeader)
   167  				return nil
   168  			}
   169  			contentLength = cl
   170  		default:
   171  			// If the response length is not declared, set it to -1.
   172  			contentLength = -1
   173  		}
   174  
   175  		b := result.Get("body")
   176  		var body io.ReadCloser
   177  		// The body is undefined when the browser does not support streaming response bodies (Firefox),
   178  		// and null in certain error cases, i.e. when the request is blocked because of CORS settings.
   179  		if !b.IsUndefined() && !b.IsNull() {
   180  			body = &streamReader{stream: b.Call("getReader")}
   181  		} else {
   182  			// Fall back to using ArrayBuffer
   183  			// https://developer.mozilla.org/en-US/docs/Web/API/Body/arrayBuffer
   184  			body = &arrayReader{arrayPromise: result.Call("arrayBuffer")}
   185  		}
   186  
   187  		code := result.Get("status").Int()
   188  
   189  		uncompressed := false
   190  		if ascii.EqualFold(header.Get("Content-Encoding"), "gzip") {
   191  			// The fetch api will decode the gzip, but Content-Encoding not be deleted.
   192  			header.Del("Content-Encoding")
   193  			header.Del("Content-Length")
   194  			contentLength = -1
   195  			uncompressed = true
   196  		}
   197  
   198  		respCh <- &Response{
   199  			Status:        fmt.Sprintf("%d %s", code, StatusText(code)),
   200  			StatusCode:    code,
   201  			Header:        header,
   202  			ContentLength: contentLength,
   203  			Uncompressed:  uncompressed,
   204  			Body:          body,
   205  			Request:       req,
   206  		}
   207  
   208  		return nil
   209  	})
   210  	failure = js.FuncOf(func(this js.Value, args []js.Value) any {
   211  		success.Release()
   212  		failure.Release()
   213  
   214  		err := args[0]
   215  		// The error is a JS Error type
   216  		// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error
   217  		// We can use the toString() method to get a string representation of the error.
   218  		errMsg := err.Call("toString").String()
   219  		// Errors can optionally contain a cause.
   220  		if cause := err.Get("cause"); !cause.IsUndefined() {
   221  			// The exact type of the cause is not defined,
   222  			// but if it's another error, we can call toString() on it too.
   223  			if !cause.Get("toString").IsUndefined() {
   224  				errMsg += ": " + cause.Call("toString").String()
   225  			} else if cause.Type() == js.TypeString {
   226  				errMsg += ": " + cause.String()
   227  			}
   228  		}
   229  		errCh <- fmt.Errorf("net/http: fetch() failed: %s", errMsg)
   230  		return nil
   231  	})
   232  
   233  	fetchPromise.Call("then", success, failure)
   234  	select {
   235  	case <-req.Context().Done():
   236  		if !ac.IsUndefined() {
   237  			// Abort the Fetch request.
   238  			ac.Call("abort")
   239  		}
   240  		return nil, req.Context().Err()
   241  	case resp := <-respCh:
   242  		return resp, nil
   243  	case err := <-errCh:
   244  		return nil, err
   245  	}
   246  }
   247  
   248  var errClosed = errors.New("net/http: reader is closed")
   249  
   250  // streamReader implements an io.ReadCloser wrapper for ReadableStream.
   251  // See https://fetch.spec.whatwg.org/#readablestream for more information.
   252  type streamReader struct {
   253  	pending []byte
   254  	stream  js.Value
   255  	err     error // sticky read error
   256  }
   257  
   258  func (r *streamReader) Read(p []byte) (n int, err error) {
   259  	if r.err != nil {
   260  		return 0, r.err
   261  	}
   262  	if len(r.pending) == 0 {
   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) any {
   268  			result := args[0]
   269  			if result.Get("done").Bool() {
   270  				errCh <- io.EOF
   271  				return nil
   272  			}
   273  			value := make([]byte, result.Get("value").Get("byteLength").Int())
   274  			js.CopyBytesToGo(value, result.Get("value"))
   275  			bCh <- value
   276  			return nil
   277  		})
   278  		defer success.Release()
   279  		failure := js.FuncOf(func(this js.Value, args []js.Value) any {
   280  			// Assumes it's a TypeError. See
   281  			// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypeError
   282  			// for more information on this type. See
   283  			// https://streams.spec.whatwg.org/#byob-reader-read for the spec on
   284  			// the read method.
   285  			errCh <- errors.New(args[0].Get("message").String())
   286  			return nil
   287  		})
   288  		defer failure.Release()
   289  		r.stream.Call("read").Call("then", success, failure)
   290  		select {
   291  		case b := <-bCh:
   292  			r.pending = b
   293  		case err := <-errCh:
   294  			r.err = err
   295  			return 0, err
   296  		}
   297  	}
   298  	n = copy(p, r.pending)
   299  	r.pending = r.pending[n:]
   300  	return n, nil
   301  }
   302  
   303  func (r *streamReader) Close() error {
   304  	// This ignores any error returned from cancel method. So far, I did not encounter any concrete
   305  	// situation where reporting the error is meaningful. Most users ignore error from resp.Body.Close().
   306  	// If there's a need to report error here, it can be implemented and tested when that need comes up.
   307  	r.stream.Call("cancel")
   308  	if r.err == nil {
   309  		r.err = errClosed
   310  	}
   311  	return nil
   312  }
   313  
   314  // arrayReader implements an io.ReadCloser wrapper for ArrayBuffer.
   315  // https://developer.mozilla.org/en-US/docs/Web/API/Body/arrayBuffer.
   316  type arrayReader struct {
   317  	arrayPromise js.Value
   318  	pending      []byte
   319  	read         bool
   320  	err          error // sticky read error
   321  }
   322  
   323  func (r *arrayReader) Read(p []byte) (n int, err error) {
   324  	if r.err != nil {
   325  		return 0, r.err
   326  	}
   327  	if !r.read {
   328  		r.read = true
   329  		var (
   330  			bCh   = make(chan []byte, 1)
   331  			errCh = make(chan error, 1)
   332  		)
   333  		success := js.FuncOf(func(this js.Value, args []js.Value) any {
   334  			// Wrap the input ArrayBuffer with a Uint8Array
   335  			uint8arrayWrapper := uint8Array.New(args[0])
   336  			value := make([]byte, uint8arrayWrapper.Get("byteLength").Int())
   337  			js.CopyBytesToGo(value, uint8arrayWrapper)
   338  			bCh <- value
   339  			return nil
   340  		})
   341  		defer success.Release()
   342  		failure := js.FuncOf(func(this js.Value, args []js.Value) any {
   343  			// Assumes it's a TypeError. See
   344  			// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/TypeError
   345  			// for more information on this type.
   346  			// See https://fetch.spec.whatwg.org/#concept-body-consume-body for reasons this might error.
   347  			errCh <- errors.New(args[0].Get("message").String())
   348  			return nil
   349  		})
   350  		defer failure.Release()
   351  		r.arrayPromise.Call("then", success, failure)
   352  		select {
   353  		case b := <-bCh:
   354  			r.pending = b
   355  		case err := <-errCh:
   356  			return 0, err
   357  		}
   358  	}
   359  	if len(r.pending) == 0 {
   360  		return 0, io.EOF
   361  	}
   362  	n = copy(p, r.pending)
   363  	r.pending = r.pending[n:]
   364  	return n, nil
   365  }
   366  
   367  func (r *arrayReader) Close() error {
   368  	if r.err == nil {
   369  		r.err = errClosed
   370  	}
   371  	return nil
   372  }
   373
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