Fix and improve valid install path checks

+ Fail if child of game folder
+ Fail if child of Program Files
+ Add test for null path
* Fix success if path null
* Check if install path exists before updating download path

Wabbajack.Lib/MO2Installer.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.ComponentModel.DataAnnotations;
 using System.Globalization;
 using System.IO;
@@ -22,6 +22,7 @@ using File = Alphaleonis.Win32.Filesystem.File;
 using Path = Alphaleonis.Win32.Filesystem.Path;
 using SectionData = Wabbajack.Common.SectionData;
 using System.Collections.Generic;
+using Wabbajack.Common.IO;
 using Wabbajack.Lib.ModListRegistry;
 using Wabbajack.VirtualFileSystem;
 
@@ -503,14 +504,24 @@ namespace Wabbajack.Lib
             await OutputFolder.Combine(directive.To).WriteAllTextAsync(data);
         }
 
-        public static IErrorResponse CheckValidInstallPath(AbsolutePath path, AbsolutePath? downloadFolder)
+        public static IErrorResponse CheckValidInstallPath(AbsolutePath path, AbsolutePath? downloadFolder, GameMetaData? game)
         {
+            // Check if null path
+            if (string.IsNullOrEmpty(path.ToString())) return ErrorResponse.Fail("Please select an install directory.");
+
+            // Check if child of game folder
+            if (game?.TryGetGameLocation() != null && path.IsChildOf(game.TryGetGameLocation())) return ErrorResponse.Fail("Cannot install to game directory.");
+
+            // Check if child of Program Files
+            if (path.IsChildOf(new AbsolutePath(KnownFolders.ProgramFiles.Path))) return ErrorResponse.Fail("Cannot install to Program Files directory.");
+
+            // If the folder doesn't exist, it's empty so we don't need to check further
             if (!path.Exists) return ErrorResponse.Success;
 
             // Check folder does not have a Wabbajack ModList
             if (path.EnumerateFiles(false).Where(file => file.Exists).Any(file => file.Extension == Consts.ModListExtension))
             {
-                return ErrorResponse.Fail($"Cannot install into a folder with a Wabbajack ModList inside of it");
+                return ErrorResponse.Fail($"Cannot install into a folder with a Wabbajack ModList inside of it.");
             }
 
             // Check if folder is empty

Wabbajack.Test/MO2Tests.cs

@@ -13,14 +13,14 @@ namespace Wabbajack.Test
         public async Task CheckValidInstallPath_Empty()
         {
             await using var tempDir = await TempFolder.Create();
-            Assert.True(MO2Installer.CheckValidInstallPath(tempDir.Dir, downloadFolder: null).Succeeded);
+            Assert.True(MO2Installer.CheckValidInstallPath(tempDir.Dir, null, null).Succeeded);
         }
 
         [Fact]
         public async Task CheckValidInstallPath_DoesNotExist()
         {
             await using var tempDir = await TempFolder.Create();
-            Assert.True(MO2Installer.CheckValidInstallPath(tempDir.Dir.Combine("Subfolder"), downloadFolder: null).Succeeded);
+            Assert.True(MO2Installer.CheckValidInstallPath(tempDir.Dir.Combine("Subfolder"), null, null).Succeeded);
         }
 
         [Fact]
@@ -29,7 +29,7 @@ namespace Wabbajack.Test
             await using var tempDir = await TempFolder.Create();
             await using var mo2 = await tempDir.Dir.Combine("ModOrganizer.exe").Create();
             await using var molist = await tempDir.Dir.Combine(((RelativePath)"modlist")).WithExtension(Consts.ModListExtension).Create();
-            Assert.False(MO2Installer.CheckValidInstallPath(tempDir.Dir, downloadFolder: null).Succeeded);
+            Assert.False(MO2Installer.CheckValidInstallPath(tempDir.Dir, null, null).Succeeded);
         }
 
         [Fact]
@@ -37,7 +37,7 @@ namespace Wabbajack.Test
         {
             await using var tempDir = await TempFolder.Create();
             await using var tmp = await tempDir.Dir.Combine(Consts.ModOrganizer2Exe).Create();
-            Assert.True(MO2Installer.CheckValidInstallPath(tempDir.Dir, downloadFolder: null).Succeeded);
+            Assert.True(MO2Installer.CheckValidInstallPath(tempDir.Dir, null, null).Succeeded);
         }
 
         [Fact]
@@ -47,7 +47,7 @@ namespace Wabbajack.Test
             await tempDir.Dir.DeleteDirectory();
             tempDir.Dir.CreateDirectory();
             await using var tmp = await tempDir.Dir.Combine($"someFile.txt").Create();
-            Assert.False(MO2Installer.CheckValidInstallPath(tempDir.Dir, downloadFolder: null).Succeeded);
+            Assert.False(MO2Installer.CheckValidInstallPath(tempDir.Dir, null, null).Succeeded);
         }
 
         [Fact]
@@ -57,7 +57,14 @@ namespace Wabbajack.Test
             var downloadsFolder = tempDir.Dir.Combine("downloads");
             downloadsFolder.CreateDirectory();
             await using var tmp = await tempDir.Dir.Combine($"downloads/someFile.txt").Create();
-            Assert.True(MO2Installer.CheckValidInstallPath(tempDir.Dir, downloadFolder: downloadsFolder).Succeeded);
+            Assert.True(MO2Installer.CheckValidInstallPath(tempDir.Dir, downloadsFolder, null).Succeeded);
+        }
+
+        [Fact]
+        public async Task CheckValidInstallPath_NullPath()
+        {
+            var tempDir = new AbsolutePath("", true);
+            Assert.True(MO2Installer.CheckValidInstallPath(tempDir, null, null).Succeeded == false);
         }
         #endregion
     }

Wabbajack/View Models/Installers/MO2InstallerVM.cs

@@ -63,7 +63,7 @@ namespace Wabbajack
                     this.WhenAny(x => x.DownloadLocation.TargetPath),
                     resultSelector: (target, download) => (target, download))
                 .ObserveOn(RxApp.TaskpoolScheduler)
-                .Select(i => MO2Installer.CheckValidInstallPath(i.target, i.download))
+                .Select(i => MO2Installer.CheckValidInstallPath(i.target, i.download, Parent.ModList.SourceModList.GameType.MetaData()))
                 .ObserveOnGuiThread();
 
             _CanInstall = Observable.CombineLatest(
@@ -83,7 +83,7 @@ namespace Wabbajack
                 {
                     if (DownloadLocation.TargetPath == default || DownloadLocation.TargetPath == installPath)
                     {
-                        DownloadLocation.TargetPath = installPath.Combine("downloads");
+                        if (installPath.Exists) DownloadLocation.TargetPath = installPath.Combine("downloads");
                     }
                 })
                 .DisposeWith(CompositeDisposable);