rpcsrv: properly set content-type and CORS for all headers

Not only for successful ones. Close #3075.

Signed-off-by: Anna Shaleva <[email protected]>

pkg/services/rpcsrv/server.go

@@ -2861,16 +2861,16 @@ func (s *Server) writeHTTPServerResponse(r *params.Request, w http.ResponseWrite
 	resp.RunForErrors(func(jsonErr *neorpc.Error) {
 		s.logRequestError(r, jsonErr)
 	})
+	w.Header().Set("Content-Type", "application/json; charset=utf-8")
+	if s.config.EnableCORSWorkaround {
+		setCORSOriginHeaders(w.Header())
+	}
 	if r.In != nil {
 		resp := resp.(abstract)
 		if resp.Error != nil {
 			w.WriteHeader(getHTTPCodeForError(resp.Error))
 		}
 	}
-	w.Header().Set("Content-Type", "application/json; charset=utf-8")
-	if s.config.EnableCORSWorkaround {
-		setCORSOriginHeaders(w.Header())
-	}
 
 	encoder := json.NewEncoder(w)
 	err := encoder.Encode(resp)

pkg/services/rpcsrv/server_test.go

@@ -3350,3 +3350,20 @@ func TestFailedPreconditionShutdown(t *testing.T) {
 
 	require.Eventually(t, stopped.Load, 5*time.Second, 100*time.Millisecond, "Shutdown should return")
 }
+
+func TestErrorResponseContentType(t *testing.T) {
+	chain, rpcSrv, httpSrv := initClearServerWithServices(t, true, false, false)
+	defer chain.Close()
+	defer rpcSrv.Shutdown()
+
+	const (
+		expectedContentType = "application/json; charset=utf-8"
+		req                 = `{"jsonrpc":"2.0", "method":"unknown","params":[]}`
+	)
+
+	cl := http.Client{Timeout: time.Second}
+	resp, err := cl.Post(httpSrv.URL, "application/json", strings.NewReader(req))
+	require.NoErrorf(t, err, "could not make a POST request")
+	contentType := resp.Header.Get("Content-Type")
+	require.Equal(t, expectedContentType, contentType)
+}