Allow updating request's RequestURI and Host header via Request.URI()

http.go

@@ -896,7 +896,7 @@ func (req *Request) onlyMultipartForm() bool {
 //
 // See also WriteTo.
 func (req *Request) Write(w *bufio.Writer) error {
-	if len(req.Header.Host()) == 0 {
+	if len(req.Header.Host()) == 0 || req.parsedURI {
 		uri := req.URI()
 		host := uri.Host()
 		if len(host) == 0 {

http_test.go

@@ -11,6 +11,28 @@ import (
 	"testing"
 )
 
+func TestRequestUpdateURI(t *testing.T) {
+	var r Request
+	r.Header.SetHost("aaa.bbb")
+	r.SetRequestURI("/lkjkl/kjl")
+
+	// Modify request uri and host via URI() object and make sure
+	// the requestURI and Host header are properly updated
+	u := r.URI()
+	u.SetPath("/123/432.html")
+	u.SetHost("foobar.com")
+	a := u.QueryArgs()
+	a.Set("aaa", "bcse")
+
+	s := r.String()
+	if !strings.HasPrefix(s, "GET /123/432.html?aaa=bcse") {
+		t.Fatalf("cannot find %q in %q", "GET /123/432.html?aaa=bcse", s)
+	}
+	if strings.Index(s, "\r\nHost: foobar.com\r\n") < 0 {
+		t.Fatalf("cannot find %q in %q", "\r\nHost: foobar.com\r\n", s)
+	}
+}
+
 func TestRequestBodyStreamMultipleBodyCalls(t *testing.T) {
 	var r Request
 

uri.go

@@ -122,7 +122,7 @@ func (u *URI) Path() []byte {
 
 // SetPath sets URI path.
 func (u *URI) SetPath(path string) {
-	u.pathOriginal = append(u.pathOriginal, path...)
+	u.pathOriginal = append(u.pathOriginal[:0], path...)
 	u.path = normalizePath(u.path, u.pathOriginal)
 }