http: Change how HTTPResponseRecorder works

http/handler.go

@@ -236,6 +236,7 @@ func (this *Handler) serveDocument (
 	
 	// set up HTTP response recorder
 	recorder := HTTPResponseRecorder { }
+	defer recorder.Reset()
 	resetRecorder := func () {
 		recorder.Reset()
 		recorder.Head = res.Header().Clone()
@@ -272,6 +273,7 @@ func (this *Handler) serveDocument (
 	}
 	var httpRedirect Redirect
 	if errors.As(err, &httpRedirect) {
+		recorder.WriteHeaderValues(res)
 		http.Redirect(res, req, httpRedirect.Location, httpRedirect.Status)
 		return
 	}
@@ -283,9 +285,11 @@ func (this *Handler) serveDocument (
 	}
 
 	// play back recorded response
-	err = recorder.Play(res)
+	recorder.WriteHeaderStatus(res)
+	_, err = recorder.WriteBody(res)
 	if err != nil {
 		this.logErr(name, err)
+		return
 	}
 }
 

http/http.go

@@ -108,21 +108,35 @@ func (this *HTTPResponseRecorder) Write (buffer []byte) (int, error) {
 func (this *HTTPResponseRecorder) WriteHeader (statusCode int) {
 	this.Status = statusCode
 }
-// Play replays the response to the given http.ResponseWriter. This resets the
-// recorder.
+// Play replays the response in its entirety to res.
 func (this *HTTPResponseRecorder) Play (res http.ResponseWriter) error {
-	defer this.Reset()
-	status := this.Status
-	if status == 0 {
-		status = http.StatusOK
-	}
+	this.WriteHeaderValues(res)
+	this.WriteHeaderStatus(res)
+	_, err := this.WriteBody(res)
+	return err
+}
+
+// WriteHeaderValues adds all header values in the recorder to res, replacing
+// them if they exist already.
+func (this *HTTPResponseRecorder) WriteHeaderValues (res http.ResponseWriter) {
 	header := res.Header()
 	for name, value := range this.Head {
 		header[name] = value
 	}
+}
+
+// WriteHeaderStatus calls res.WriteHeader with the status code in the recorder.
+func (this *HTTPResponseRecorder) WriteHeaderStatus (res http.ResponseWriter) {
+	status := this.Status
+	if status == 0 {
+		status = http.StatusOK
+	}
 	res.WriteHeader(status)
-	_, err := io.Copy(res, &this.buffer)
-	return err
+}
+
+// WriteBody writes the body data within the recorder to res.
+func (this *HTTPResponseRecorder) WriteBody (res http.ResponseWriter) (int64, error) {
+	return io.Copy(res, &this.buffer)
 }
 
 // Reset resets this response recorder so it can be used again.