Make WebUI error non-fatal

* Do not exit the app when WebUI is failed for start.
* Print the error to stdout.

PR #19697.
Closes #19695.
Closes #19469.

src/app/application.cpp

@@ -890,13 +890,17 @@ int Application::exec()
 #ifndef DISABLE_WEBUI
         m_webui = new WebUI(this);
 #ifdef DISABLE_GUI
-        if (m_webui->isErrored())
-            QCoreApplication::exit(EXIT_FAILURE);
-        connect(m_webui, &WebUI::fatalError, this, []() { QCoreApplication::exit(EXIT_FAILURE); });
+        connect(m_webui, &WebUI::error, this, [](const QString &message) { fprintf(stderr, "%s\n", qUtf8Printable(message)); });
 
         printf("%s", qUtf8Printable(u"\n******** %1 ********\n"_s.arg(tr("Information"))));
 
-        if (m_webui->isEnabled())
+        if (m_webui->isErrored())
+        {
+            const QString error = m_webui->errorMessage() + u'\n'
+                    + tr("To fix the error, you may need to edit the config file manually.");
+            fprintf(stderr, "%s\n", qUtf8Printable(error));
+        }
+        else if (m_webui->isEnabled())
         {
             const QHostAddress address = m_webui->hostAddress();
             const QString url = u"%1://%2:%3"_s.arg((m_webui->isHttps() ? u"https"_s : u"http"_s)

src/webui/webui.cpp

@@ -48,6 +48,7 @@ WebUI::WebUI(IApplication *app)
 void WebUI::configure()
 {
     m_isErrored = false; // clear previous error state
+    m_errorMsg.clear();
 
     const QString portForwardingProfile = u"webui"_s;
     const Preferences *pref = Preferences::instance();
@@ -113,13 +114,13 @@ void WebUI::configure()
             }
             else
             {
-                const QString errorMsg = tr("Web UI: Unable to bind to IP: %1, port: %2. Reason: %3")
+                m_errorMsg = tr("Web UI: Unable to bind to IP: %1, port: %2. Reason: %3")
                     .arg(serverAddressString).arg(port).arg(m_httpServer->errorString());
-                LogMsg(errorMsg, Log::CRITICAL);
-                qCritical() << errorMsg;
+                LogMsg(m_errorMsg, Log::CRITICAL);
+                qCritical() << m_errorMsg;
 
                 m_isErrored = true;
-                emit fatalError();
+                emit error(m_errorMsg);
             }
         }
 
@@ -156,6 +157,11 @@ bool WebUI::isErrored() const
     return m_isErrored;
 }
 
+QString WebUI::errorMessage() const
+{
+    return m_errorMsg;
+}
+
 bool WebUI::isHttps() const
 {
     if (!m_httpServer) return false;

src/webui/webui.h

@@ -56,12 +56,13 @@ public:
 
     bool isEnabled() const;
     bool isErrored() const;
+    QString errorMessage() const;
     bool isHttps() const;
     QHostAddress hostAddress() const;
     quint16 port() const;
 
 signals:
-    void fatalError();
+    void error(const QString &message);
 
 private slots:
     void configure();
@@ -69,6 +70,7 @@ private slots:
 private:
     bool m_isEnabled = false;
     bool m_isErrored = false;
+    QString m_errorMsg;
     QPointer<Http::Server> m_httpServer;
     QPointer<Net::DNSUpdater> m_dnsUpdater;
     QPointer<WebApplication> m_webapp;