Replaced hardcoded SourceType with custom defined ISourceResolver.

OpenRA.Mods.Common/Installer/SourceResolvers/RegistryDirectoryFromFileSourceResolver.cs

@@ -0,0 +1,50 @@
+#region Copyright & License Information
+/*
+ * Copyright 2007-2022 The OpenRA Developers (see AUTHORS)
+ * This file is part of OpenRA, which is free software. It is made
+ * available to you under the terms of the GNU General Public License
+ * as published by the Free Software Foundation, either version 3 of
+ * the License, or (at your option) any later version. For more
+ * information, see COPYING.
+ */
+#endregion
+
+using System.IO;
+using System.Runtime.InteropServices;
+
+namespace OpenRA.Mods.Common.Installer
+{
+	public class RegistryDirectoryFromFileSourceResolver : ISourceResolver
+	{
+		public string FindSourcePath(ModContent.ModSource source)
+		{
+			if (source.RegistryKey == null)
+				return null;
+
+			if (Platform.CurrentPlatform != PlatformType.Windows)
+				return null;
+
+			// We need an extra check for the platform here to silence a warning when the registry is accessed
+			// TODO: Remove this once our platform checks use the same method
+			if (!RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
+				return null;
+
+			foreach (var prefix in source.RegistryPrefixes)
+			{
+				if (!(Microsoft.Win32.Registry.GetValue(prefix + source.RegistryKey, source.RegistryValue, null) is string path))
+					continue;
+
+				path = Path.GetDirectoryName(path);
+
+				return InstallerUtils.IsValidSourcePath(path, source) ? path : null;
+			}
+
+			return null;
+		}
+
+		public Availability GetAvailability()
+		{
+			return Platform.CurrentPlatform != PlatformType.Windows ? Availability.DigitalInstall : Availability.Unavailable;
+		}
+	}
+}