fix fetch binding

cloudflare/fetch/bind.go

@@ -1,28 +1,31 @@
 package fetch
 
 import (
-	"errors"
 	"net/http"
 	"syscall/js"
 
 	"github.com/syumai/workers/internal/jshttp"
 	"github.com/syumai/workers/internal/jsutil"
 )
 
+var globalFetchFunc = js.Global().Get("fetch")
+
 // fetch is a function that reproduces cloudflare fetch.
 // Docs: https://developers.cloudflare.com/workers/runtime-apis/fetch/
 func fetch(namespace js.Value, req *http.Request, init *RequestInit) (*http.Response, error) {
-	if namespace.IsUndefined() {
-		return nil, errors.New("fetch function not found")
-	}
-	promise := namespace.Call("fetch",
-		// The Request object to fetch.
-		// Docs: https://developers.cloudflare.com/workers/runtime-apis/request
-		jshttp.ToJSRequest(req),
-		// The content of the request.
-		// Docs: https://developers.cloudflare.com/workers/runtime-apis/request#requestinit
-		init.ToJS(),
-	)
+	// The Request object to fetch.
+	// Docs: https://developers.cloudflare.com/workers/runtime-apis/request
+	reqValue := jshttp.ToJSRequest(req)
+	// The content of the request.
+	// Docs: https://developers.cloudflare.com/workers/runtime-apis/request#requestinit
+	initValue := init.ToJS()
+
+	promise := func() js.Value {
+		if namespace.IsUndefined() {
+			return globalFetchFunc.Invoke(reqValue, initValue)
+		}
+		return namespace.Call("fetch", reqValue, initValue)
+	}()
 
 	jsRes, err := jsutil.AwaitPromise(promise)
 	if err != nil {

cloudflare/fetch/client.go

@@ -7,7 +7,7 @@ import (
 
 // Client is an HTTP client.
 type Client struct {
-	// namespace - Objects that Fetch API belongs to. Default is Global
+	// namespace - Objects that Fetch API belongs to. Default is undefined
 	namespace js.Value
 }
 
@@ -42,7 +42,7 @@ func WithBinding(bind js.Value) ClientOption {
 // NewClient returns new Client
 func NewClient(opts ...ClientOption) *Client {
 	c := &Client{
-		namespace: js.Global(),
+		namespace: js.Undefined(),
 	}
 	c.applyOptions(opts)
 

cloudflare/fetch/transport.go

@@ -7,7 +7,7 @@ import (
 
 // transport is an implementation of http.RoundTripper
 type transport struct {
-	// namespace - Objects that Fetch API belongs to. Default is Global
+	// namespace - Objects that Fetch API belongs to. Default is undefined
 	namespace js.Value
 	redirect  RedirectMode
 }

internal/jshttp/request.go

@@ -1,7 +1,6 @@
 package jshttp
 
 import (
-	"bytes"
 	"io"
 	"net/http"
 	"net/url"
@@ -16,7 +15,7 @@ import (
 //   - ReadableStream: https://developer.mozilla.org/en-US/docs/Web/API/ReadableStream
 func ToBody(streamOrNull js.Value) io.ReadCloser {
 	if streamOrNull.IsNull() {
-		return io.NopCloser(bytes.NewReader([]byte{}))
+		return nil
 	}
 	return jsutil.ConvertReadableStreamToReadCloser(streamOrNull)
 }
@@ -32,6 +31,8 @@ func ToRequest(req js.Value) (*http.Request, error) {
 
 	contentLength, clErr := strconv.ParseInt(header.Get("Content-Length"), 10, 64)
 	bodyVal := req.Get("body")
+	// NOTE: `body` is ReadableStream or null. Therefore, `undefined` check may not be necessary.
+	// https://developer.mozilla.org/docs/Web/API/Request/body#value
 	if clErr != nil && !bodyVal.IsNull() && !bodyVal.IsUndefined() {
 		contentLength = -1
 	}