[ESP8266HTTPUpdateServer library] [WebUpdate example] false "Update Success" response if no file selected

[rejnok93]

Basic Infos

• This issue complies with the issue POLICY doc.
• I have read the documentation at readthedocs and the issue is not addressed there.
• I have tested that the issue is present in current master branch (aka latest git).
• I have searched the issue tracker for a similar issue.
• If there is a stack dump, I have decoded it.
• I have filled out all fields below.

Platform

• Hardware: ESP-01
• Core Version: 2 Aug 2020 (2.7.4)
• Development Env: Platformio
• Operating System: MacOS

Settings in IDE

• Module: Generic ESP8266 Module
• Flash Mode: qio
• Flash Size: 1MB
• lwip Variant: ?
• Reset Method: ?
• Flash Frequency: 40Mhz
• CPU Frequency: ?
• Upload Using: OTA
• Upload Speed: -

Problem Description

Steps to reproduce + Actual behaviour:
When user not select any file for FileSystem, and click update filesystem, server respond message that update is succesfull - not true.
Expected behaviour:
Server respond that update fails, because no file is sent!

MCVE Sketch

#include <Arduino.h>
#include <ESP8266WiFi.h>
#include <WiFiClient.h>
#include <ESP8266WebServer.h>
#include <ESP8266mDNS.h>
#include <ESP8266HTTPUpdateServer.h>

#ifndef STASSID
#define STASSID "test"
#define STAPSK  "test"
#endif

const char* host = "test";
const char* ssid = STASSID;
const char* password = STAPSK;

ESP8266WebServer httpServer(80);
ESP8266HTTPUpdateServer httpUpdater;

void setup(void) {
  WiFi.mode(WIFI_AP_STA);
  WiFi.begin(ssid, password);
  while (WiFi.waitForConnectResult() != WL_CONNECTED) {
    WiFi.begin(ssid, password);
  }
  MDNS.begin(host);
  httpUpdater.setup(&httpServer);
  httpServer.begin();
  MDNS.addService("http", "tcp", 80);
}

void loop(void) {
  httpServer.handleClient();
  MDNS.update();
}

Debug Messages

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