GH-1874 Do not allow launching instances during an update

application/MainWindow.cpp

@@ -989,8 +989,14 @@ void MainWindow::downloadUpdates(GoUpdate::Status status)
 	// If the task succeeds, install the updates.
 	if (updateDlg.execWithTask(&updateTask))
 	{
+		/**
+		 * NOTE: This disables launching instances until the update either succeeds (and this process exits)
+		 * or the update fails (and the control leaves this scope).
+		 */
+		MMC->updateIsRunning(true);
 		UpdateController update(this, MMC->root(), updateTask.updateFilesDir(), updateTask.operations());
 		update.installUpdates();
+		MMC->updateIsRunning(false);
 	}
 	else
 	{

application/MultiMC.cpp

@@ -939,7 +939,11 @@ bool MultiMC::openJsonEditor(const QString &filename)
 
 bool MultiMC::launch(InstancePtr instance, bool online, BaseProfilerFactory *profiler)
 {
-	if(instance->canLaunch())
+	if(m_updateRunning)
+	{
+		qDebug() << "Cannot launch instances while an update is running.";
+	}
+	else if(instance->canLaunch())
 	{
 		auto & extras = m_instanceExtras[instance->id()];
 		auto & window = extras.window;
@@ -1027,6 +1031,12 @@ bool MultiMC::updatesAreAllowed()
 	return m_runningInstances == 0;
 }
 
+void MultiMC::updateIsRunning(bool running)
+{
+	m_updateRunning = running;
+}
+
+
 void MultiMC::controllerSucceeded()
 {
 	auto controller = qobject_cast<LaunchController *>(QObject::sender());

application/MultiMC.h

@@ -151,6 +151,7 @@ public:
 		return m_runningInstances;
 	}
 
+	void updateIsRunning(bool running);
 	bool updatesAreAllowed();
 
 signals:
@@ -227,8 +228,11 @@ private:
 		shared_qobject_ptr<LaunchController> controller;
 	};
 	std::map<QString, InstanceXtras> m_instanceExtras;
+
+	// main state variables
 	size_t m_openWindows = 0;
 	size_t m_runningInstances = 0;
+	bool m_updateRunning = false;
 
 	// main window, if any
 	MainWindow * m_mainWindow = nullptr;