fix #1669 write empty body panic error

context/context.go

@@ -24,11 +24,13 @@ package context
 
 import (
 	"bufio"
+	"bytes"
 	"crypto/hmac"
 	"crypto/sha1"
 	"encoding/base64"
 	"errors"
 	"fmt"
+	"io"
 	"net"
 	"net/http"
 	"strconv"
@@ -184,6 +186,14 @@ func (w *Response) Write(p []byte) (int, error) {
 	return w.ResponseWriter.Write(p)
 }
 
+// Write writes the data to the connection as part of an HTTP reply,
+// and sets `started` to true.
+// started means the response has sent out.
+func (w *Response) Copy(buf *bytes.Buffer) (int64, error) {
+	w.Started = true
+	return io.Copy(w.ResponseWriter, buf)
+}
+
 // WriteHeader sends an HTTP response header with status code,
 // and sets `started` to true.
 func (w *Response) WriteHeader(code int) {

context/output.go

@@ -21,7 +21,6 @@ import (
 	"errors"
 	"fmt"
 	"html/template"
-	"io"
 	"mime"
 	"net/http"
 	"path/filepath"
@@ -75,7 +74,7 @@ func (output *BeegoOutput) Body(content []byte) {
 		output.Status = 0
 	}
 
-	io.Copy(output.Context.ResponseWriter, buf)
+	output.Context.ResponseWriter.Copy(buf)
 }
 
 // Cookie sets cookie value via given key.

router_test.go

@@ -65,6 +65,11 @@ func (tc *TestController) GetManyRouter() {
 	tc.Ctx.WriteString(tc.Ctx.Input.Query(":id") + tc.Ctx.Input.Query(":page"))
 }
 
+func (tc *TestController) GetEmptyBody() {
+	var res []byte
+	tc.Ctx.Output.Body(res)
+}
+
 type ResStatus struct {
 	Code int
 	Msg  string
@@ -239,6 +244,21 @@ func TestManyRoute(t *testing.T) {
 	}
 }
 
+// Test for issue #1669
+func TestEmptyResponse(t *testing.T) {
+
+	r, _ := http.NewRequest("GET", "/beego-empty.html", nil)
+	w := httptest.NewRecorder()
+
+	handler := NewControllerRegister()
+	handler.Add("/beego-empty.html", &TestController{}, "get:GetEmptyBody")
+	handler.ServeHTTP(w, r)
+
+	if body := w.Body.String(); body != "" {
+		t.Error("want empty body")
+	}
+}
+
 func TestNotFound(t *testing.T) {
 	r, _ := http.NewRequest("GET", "/", nil)
 	w := httptest.NewRecorder()