Fix handling of HEAD requests for streaming responses

httpbin/handlers_test.go

@@ -1604,6 +1604,29 @@ func TestDrip(t *testing.T) {
 			assertStatusCode(t, w, test.code)
 		})
 	}
+
+	t.Run("ensure HEAD request works with streaming responses", func(t *testing.T) {
+		srv := httptest.NewServer(handler)
+		defer srv.Close()
+
+		resp, err := http.Head(srv.URL + "/drip?duration=900ms&delay=100ms")
+		if err != nil {
+			t.Fatalf("unexpected error: %s", err)
+		}
+		defer resp.Body.Close()
+
+		body, err := ioutil.ReadAll(resp.Body)
+		if err != nil {
+			t.Fatalf("error reading response body: %s", err)
+		}
+
+		if resp.StatusCode != http.StatusOK {
+			t.Fatalf("expected HTTP 200 OK rsponse, got %d", resp.StatusCode)
+		}
+		if bodySize := len(body); bodySize > 0 {
+			t.Fatalf("expected empty body from HEAD request, bot: %s", string(body))
+		}
+	})
 }
 
 func TestRange(t *testing.T) {

httpbin/middleware.go

@@ -61,7 +61,7 @@ func limitRequestSize(maxSize int64, h http.Handler) http.Handler {
 // headResponseWriter implements http.ResponseWriter in order to discard the
 // body of the response
 type headResponseWriter struct {
-	http.ResponseWriter
+	*metaResponseWriter
 }
 
 func (hw *headResponseWriter) Write(b []byte) (int, error) {
@@ -72,7 +72,7 @@ func (hw *headResponseWriter) Write(b []byte) (int, error) {
 func autohead(h http.Handler) http.Handler {
 	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		if r.Method == "HEAD" {
-			w = &headResponseWriter{w}
+			w = &headResponseWriter{&metaResponseWriter{w: w}}
 		}
 		h.ServeHTTP(w, r)
 	})