Merge pull request #701 from Noggog/wabbajack-lib-nullability

Wabbajack.Lib Nullability Enabled

.editorconfig

@@ -184,4 +184,10 @@ dotnet_diagnostic.CS8609.severity = error
 dotnet_diagnostic.CS8714.severity = error
 
 # CS8605: Unboxing a possibly null value.
-dotnet_diagnostic.CS8605.severity = error 
+dotnet_diagnostic.CS8605.severity = error
+
+# CS8613: Nullability of reference types in return type doesn't match implicitly implemented member.
+dotnet_diagnostic.CS8613.severity = error
+
+# CS8632: The annotation for nullable reference types should only be used in code within a '#nullable' annotations context.
+dotnet_diagnostic.CS8632.severity = error

Wabbajack.BuildServer.Test/IndexedFilesTests.cs

@@ -53,14 +53,14 @@ namespace Wabbajack.BuildServer.Test
         public async Task CanNotifyOfInis()
         {
             var archive =
-                new Archive
+                new Archive(
-                {
+                    new NexusDownloader.State
-                    State = new NexusDownloader.State
                     {
                         Game = Game.SkyrimSpecialEdition,
                         ModID = long.MaxValue >> 3,
                         FileID = long.MaxValue >> 3,
-                    },
+                    })
+                {
                     Name = Guid.NewGuid().ToString()
                 };
             Assert.True(await AuthorAPI.UploadPackagedInis(new[] {archive}));

Wabbajack.BuildServer.Test/ModListValidationTests.cs

@@ -122,19 +122,14 @@ namespace Wabbajack.BuildServer.Test
 
 
 
-            var modListData = new ModList
+            var modListData = new ModList();
-            {
+            modListData.Archives.Add(
-                Archives = new List<Archive>
+                new Archive(new HTTPDownloader.State(MakeURL("test_archive.txt")))
                 {
-                    new Archive
+                    Hash = await test_archive_path.FileHashAsync(),
-                    {
+                    Name = "test_archive",
-                        Hash = await test_archive_path.FileHashAsync(),
+                    Size = test_archive_path.Size,
-                        Name = "test_archive",
+                });
-                        Size = test_archive_path.Size,
-                        State = new HTTPDownloader.State {Url = MakeURL("test_archive.txt")}
-                    }
-                }
-            };
             
             var modListPath = "test_modlist.wabbajack".RelativeTo(Fixture.ServerPublicFolder);
 

Wabbajack.BuildServer.Test/ModlistUpdater.cs

@@ -42,13 +42,9 @@ namespace Wabbajack.BuildServer.Test
             {
                 Payload = new IndexJob
                 {
-                    Archive = new Archive
+                    Archive = new Archive(new HTTPDownloader.State(MakeURL("old_file_data.random")))
                     {
                         Name = "Oldfile",
-                        State = new HTTPDownloader.State
-                        {
-                            Url = MakeURL("old_file_data.random"),
-                        }
                     }
                 }
             });
@@ -57,13 +53,9 @@ namespace Wabbajack.BuildServer.Test
             {
                 Payload = new IndexJob
                 {
-                    Archive = new Archive
+                    Archive = new Archive(new HTTPDownloader.State(MakeURL("new_file_data.random")))
                     {
                         Name = "Newfile",
-                        State = new HTTPDownloader.State
-                        {
-                            Url = MakeURL("new_file_data.random"),
-                        }
                     }
                 }
             });
@@ -126,6 +118,5 @@ namespace Wabbajack.BuildServer.Test
             Assert.True($"{oldDataHash.ToHex()}_{newDataHash.ToHex()}".RelativeTo(Fixture.ServerUpdatesFolder).IsFile);
 
         }
-        
     }
 }

Wabbajack.BuildServer/Controllers/IndexedFiles.cs

@@ -102,10 +102,9 @@ namespace Wabbajack.BuildServer.Controllers
                     Priority = Job.JobPriority.Low,
                     Payload = new IndexJob
                     {
-                        Archive = new Archive
+                        Archive = new Archive(data)
                         {
                             Name = entry.Name,
-                            State = data
                         }
                     }
                 });

Wabbajack.BuildServer/Controllers/Jobs.cs

@@ -22,7 +22,7 @@ namespace Wabbajack.BuildServer.Controllers
         public async Task<long> EnqueueJob(string JobName)
         {
             var jobtype = AJobPayload.NameToType[JobName];
-            var job = new Job{Priority = Job.JobPriority.High, Payload = (AJobPayload)jobtype.GetConstructor(new Type[0]).Invoke(new object?[0])};
+            var job = new Job{Priority = Job.JobPriority.High, Payload = (AJobPayload)jobtype.GetConstructor(new Type[0]).Invoke(new object[0])};
             await SQL.EnqueueJob(job);
             return job.Id;
         }

Wabbajack.BuildServer/Controllers/ModlistUpdater.cs

@@ -175,15 +175,19 @@ namespace Wabbajack.BuildServer.Controllers
             var allMods = await api.GetModFiles(state.Game, state.ModID);
             var archive = allMods.files.Where(m => !string.IsNullOrEmpty(m.category_name))
                 .OrderBy(s => Math.Abs((long)s.size - origSize))
-                .Select(s => new Archive {
+                .Select(s =>
-                    Name = s.file_name,
+                    new Archive(
-                    Size = (long)s.size,
+                        new NexusDownloader.State
-                    State = new NexusDownloader.State 
+                        {
+                            Game = state.Game,
+                            ModID = state.ModID,
+                            FileID = s.file_id
+                        })
                     {
-                    Game = state.Game, 
+                        Name = s.file_name,
-                    ModID = state.ModID, 
+                        Size = (long)s.size,
-                    FileID = s.file_id
+                    })
-                }}).FirstOrDefault();
+                .FirstOrDefault();
 
             if (archive == null)
             {

Wabbajack.BuildServer/Models/Jobs/EnqueueAllGameFiles.cs

@@ -21,13 +21,12 @@ namespace Wabbajack.BuildServer.Models.Jobs
             {
                 Utils.Log($"Indexing game files");
                 var states = GameRegistry.Games.Values
-                    .Where(game => game.GameLocation() != null && game.MainExecutable != null)
+                    .Where(game => game.TryGetGameLocation() != null && game.MainExecutable != null)
-                    .SelectMany(game => game.GameLocation().Value.EnumerateFiles()
+                    .SelectMany(game => game.GameLocation().EnumerateFiles()
-                        .Select(file => new GameFileSourceDownloader.State
+                        .Select(file => new GameFileSourceDownloader.State(game.InstalledVersion)
                         {
                             Game = game.Game,
-                            GameVersion = game.InstalledVersion,
+                            GameFile = file.RelativeTo(game.GameLocation()),
-                            GameFile = file.RelativeTo(game.GameLocation().Value),
                         }))
                     .ToList();
                 
@@ -41,7 +40,7 @@ namespace Wabbajack.BuildServer.Models.Jobs
 
                 await states.PMap(queue, async state =>
                 {
-                    var path = state.Game.MetaData().GameLocation().Value.Combine(state.GameFile);
+                    var path = state.Game.MetaData().GameLocation().Combine(state.GameFile);
                     Utils.Log($"Hashing Game file {path}");
                     try
                     {
@@ -55,16 +54,15 @@ namespace Wabbajack.BuildServer.Models.Jobs
 
                 var with_hash = states.Where(state => state.Hash != default).ToList();
                 Utils.Log($"Inserting {with_hash.Count} jobs.");
-                var jobs = states.Select(state => new IndexJob {Archive = new Archive {Name = state.GameFile.FileName.ToString(), State = state}})
+                var jobs = states.Select(state => new IndexJob {Archive = new Archive(state) { Name = state.GameFile.FileName.ToString()}})
                     .Select(j => new Job {Payload = j, RequiresNexus = j.UsesNexus})
                     .ToList();
 
                 foreach (var job in jobs)
-                    await sql.EnqueueJob(job);                
+                    await sql.EnqueueJob(job);
                 
                 return JobResult.Success();
             }
-            
         }
 
         protected override IEnumerable<object> PrimaryKey => new object[0];

Wabbajack.BuildServer/Models/Jobs/IndexDynDOLOD.cs

@@ -39,13 +39,9 @@ namespace Wabbajack.BuildServer.Models.Jobs
                 {
                     Payload = new IndexJob
                     {
-                        Archive = new Archive
+                        Archive = new Archive(new MegaDownloader.State(url.ToString()))
                         {
                             Name = Guid.NewGuid() + ".7z",
-                            State = new MegaDownloader.State
-                            {
-                                Url = url.ToString()
-                            }
                         }
                     }
                 })

Wabbajack.BuildServer/Models/Jobs/UploadToCDN.cs

@@ -57,15 +57,11 @@ namespace Wabbajack.BuildServer.Models.Jobs
                     Priority = Job.JobPriority.High,
                     Payload = new IndexJob
                     {
-                        Archive = new Archive
+                        Archive = new Archive(new HTTPDownloader.State(file.Uri))
                         {
                             Name = file.MungedName,
                             Size = file.Size,
                             Hash = file.Hash,
-                            State = new HTTPDownloader.State
-                            {
-                                Url = file.Uri
-                            }
                         }
                     }
                 });

Wabbajack.BuildServer/Models/Sql/SqlService.cs

@@ -524,9 +524,8 @@ namespace Wabbajack.BuildServer.Model.Models
             var result = await conn.QueryFirstOrDefaultAsync<string>(@"SELECT JsonState FROM dbo.DownloadStates  
                                                                WHERE Hash = @hash AND PrimaryKey like 'NexusDownloader+State|%'",
                 new {Hash = (long)startingHash});
-            return result == null ? null : new Archive
+            return result == null ? null : new Archive(result.FromJsonString<AbstractDownloadState>())
             {
-                State = result.FromJsonString<AbstractDownloadState>(),
                 Hash = startingHash
             };
         }
@@ -536,9 +535,8 @@ namespace Wabbajack.BuildServer.Model.Models
             await using var conn = await Open();
             var result = await conn.QueryFirstOrDefaultAsync<(long Hash, string State)>(@"SELECT Hash, JsonState FROM dbo.DownloadStates WHERE PrimaryKey = @PrimaryKey",
                 new {PrimaryKey = primaryKey});
-            return result == default ? null : new Archive
+            return result == default ? null : new Archive(result.State.FromJsonString<AbstractDownloadState>())
             {
-                State = result.State.FromJsonString<AbstractDownloadState>(),
                 Hash = Hash.FromLong(result.Hash)
             };
         }

Wabbajack.CLI/Verbs/Changelog.cs

@@ -318,7 +318,7 @@ namespace Wabbajack.CLI.Verbs
 
         private static async Task<string> GetTextFileFromModlist(AbsolutePath archive, ModList modlist, RelativePath sourceID)
         {
-            var installer = new MO2Installer(archive, modlist, default, default, null);
+            var installer = new MO2Installer(archive, modlist, default, default, parameters: null!);
             byte[] bytes = await installer.LoadBytesFromPath(sourceID);
             return Encoding.Default.GetString(bytes);
         }
@@ -328,9 +328,9 @@ namespace Wabbajack.CLI.Verbs
             return header.Trim().Replace(" ", "").Replace(".", "");
         }
 
-        private static string GetModName(Archive a)
+        private static string? GetModName(Archive a)
         {
-            var result = a.Name;
+            string? result = a.Name;
 
             if (a.State is IMetaState metaState)
             {

Wabbajack.CLI/Verbs/DeleteFile.cs

@@ -9,7 +9,7 @@ namespace Wabbajack.CLI.Verbs
     public class DeleteFile : AVerb
     {
         [Option('n', "name", Required = true, HelpText = @"Full name (as returned by my-files) of the file")]
-        public string? Name { get; set; }
+        public string Name { get; set; } = null!;
 
         protected override async Task<ExitCode> Run()
         {

Wabbajack.CLI/Verbs/DownloadUrl.cs

@@ -35,7 +35,7 @@ namespace Wabbajack.CLI.Verbs
                 new[] {state}
                 .PMap(queue, async s =>
                 {
-                    await s.Download(new Archive {Name = Path.GetFileName(Output)}, (AbsolutePath)Output);
+                    await s.Download(new Archive(state: null!) {Name = Path.GetFileName(Output)}, (AbsolutePath)Output);
                 }).Wait();
 
             File.WriteAllLines(Output + ".meta", state.GetMetaIni());

Wabbajack.Common/Extensions/DictionaryExt.cs

@@ -21,6 +21,9 @@ namespace Wabbajack
             return ret;
         }
 
+        /// <summary>
+        /// Adds the given values to the dictionary.  If a key already exists, it will throw an exception
+        /// </summary>
         public static void Add<K, V>(this IDictionary<K, V> dict, IEnumerable<KeyValuePair<K, V>> vals)
             where K : notnull
         {
@@ -30,6 +33,9 @@ namespace Wabbajack
             }
         }
 
+        /// <summary>
+        /// Adds the given values to the dictionary.  If a key already exists, it will be replaced
+        /// </summary>
         public static void Set<K, V>(this IDictionary<K, V> dict, IEnumerable<KeyValuePair<K, V>> vals)
             where K : notnull
         {
@@ -38,5 +44,15 @@ namespace Wabbajack
                 dict[val.Key] = val.Value;
             }
         }
+
+        /// <summary>
+        /// Clears the dictionary and adds the given values
+        /// </summary>
+        public static void SetTo<K, V>(this IDictionary<K, V> dict, IEnumerable<KeyValuePair<K, V>> vals)
+            where K : notnull
+        {
+            dict.Clear();
+            dict.Set(vals);
+        }
     }
 }

Wabbajack.Common/Extensions/EnumerableExt.cs

@@ -33,5 +33,32 @@ namespace Wabbajack
             yield return next;
             foreach (var itm in coll) yield return itm;
         }
+
+        /// <summary>
+        /// Converts and filters a nullable enumerable to a non-nullable enumerable
+        /// </summary>
+        public static IEnumerable<T> NotNull<T>(this IEnumerable<T?> e)
+            where T : class
+        {
+            // Filter out nulls
+            return e.Where(e => e != null)
+                // Cast to non nullable type
+                .Select(e => e!);
+        }
+
+        /// <summary>
+        /// Selects items that are castable to the desired type
+        /// </summary>
+        /// <typeparam name="T">Type of the original enumerable to cast from</typeparam>
+        /// <typeparam name="R">Type to attempt casting to</typeparam>
+        /// <param name="e">Enumerable to process</param>
+        /// <returns>Enumerable with only objects that were castable</returns>
+        public static IEnumerable<R> WhereCastable<T, R>(this IEnumerable<T> e)
+            where T : class
+            where R : T
+        {
+            return e.Where(e => e is R)
+                .Select(e => (R)e);
+        }
     }
 }

Wabbajack.Common/Extensions/ListExt.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Wabbajack.Common
+{
+    public static class ListExt
+    {
+        public static void SetTo<T>(this List<T> list, IEnumerable<T> rhs)
+        {
+            list.Clear();
+            list.AddRange(rhs);
+        }
+    }
+}

Wabbajack.Common/GameMetaData.cs

@@ -2,6 +2,7 @@
 using System.Collections.Generic;
 using System.ComponentModel;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using Alphaleonis.Win32.Filesystem;
 using Microsoft.Win32;
@@ -85,23 +86,44 @@ namespace Wabbajack.Common
         {
             get
             {
-                AbsolutePath? gameLoc = GameLocation();
+                if (!TryGetGameLocation(out var gameLoc))
-                if (gameLoc == null)
                     throw new GameNotInstalledException(this);
                 if (MainExecutable == null)
                     throw new NotImplementedException();
 
-                return FileVersionInfo.GetVersionInfo((string)gameLoc.Value.Combine(MainExecutable)).ProductVersion;
+                return FileVersionInfo.GetVersionInfo((string)gameLoc.Combine(MainExecutable)).ProductVersion;
             }
         }
 
-        public bool IsInstalled => GameLocation() != null;
+        public bool IsInstalled => TryGetGameLocation() != null;
 
         public string? MainExecutable { get; internal set; }
 
-        public AbsolutePath? GameLocation()
+        public AbsolutePath? TryGetGameLocation()
         {
-            return Consts.TestMode ? AbsolutePath.GetCurrentDirectory() : StoreHandler.Instance.GetGamePath(Game);
+            return Consts.TestMode ? AbsolutePath.GetCurrentDirectory() : StoreHandler.Instance.TryGetGamePath(Game);
+        }
+
+        public bool TryGetGameLocation(out AbsolutePath path)
+        {
+            var ret = TryGetGameLocation();
+            if (ret != null)
+            {
+                path = ret.Value;
+                return true;
+            }
+            else
+            {
+                path = default;
+                return false;
+            }
+        }
+
+        public AbsolutePath GameLocation()
+        {
+            var ret = TryGetGameLocation();
+            if (ret == null) throw new ArgumentNullException();
+            return ret.Value;
         }
     }
 
@@ -156,16 +178,24 @@ namespace Wabbajack.Common
         }
 
         /// <summary>
-        /// Tries to parse game data from an arbitrary string. Tries first via parsing as a game Enum, then by Nexus name,
+        /// Parse game data from an arbitrary string. Tries first via parsing as a game Enum, then by Nexus name.
-        /// <param nambe="someName"></param>
+        /// <param nambe="someName">Name to query</param>
-        /// <returns></returns>
+        /// <returns>GameMetaData found</returns>
-        public static GameMetaData? GetByFuzzyName(string someName)
+        /// <exception cref="ArgumentNullException">If string could not be translated to a game</exception>
+        public static GameMetaData GetByFuzzyName(string someName)
+        {
+            return TryGetByFuzzyName(someName) ?? throw new ArgumentNullException($"{someName} could not be translated to a game");
+        }
+
+        /// <summary>
+        /// Tries to parse game data from an arbitrary string. Tries first via parsing as a game Enum, then by Nexus name.
+        /// <param nambe="someName">Name to query</param>
+        /// <returns>GameMetaData if found, otherwise null</returns>
+        public static GameMetaData? TryGetByFuzzyName(string someName)
         {
             if (Enum.TryParse(typeof(Game), someName, true, out var metadata)) return ((Game)metadata!).MetaData();
 
-            GameMetaData? result = null;
+            GameMetaData? result = GetByNexusName(someName);
-
-            result = GetByNexusName(someName);
             if (result != null) return result;
 
             result = GetByMO2ArchiveName(someName);
@@ -174,6 +204,12 @@ namespace Wabbajack.Common
             return int.TryParse(someName, out int id) ? GetBySteamID(id) : null;
         }
 
+        public static bool TryGetByFuzzyName(string someName, [MaybeNullWhen(false)] out GameMetaData gameMetaData)
+        {
+            gameMetaData = TryGetByFuzzyName(someName);
+            return gameMetaData != null;
+        }
+
         public static IReadOnlyDictionary<Game, GameMetaData> Games = new Dictionary<Game, GameMetaData>
         {
             {

Wabbajack.Common/Http/Client.cs

@@ -11,7 +11,7 @@ namespace Wabbajack.Common.Http
 {
     public class Client
     {
-        public List<(string, string)> Headers = new List<(string, string)>();
+        public List<(string, string?)> Headers = new List<(string, string?)>();
         public List<Cookie> Cookies = new List<Cookie>();
         public async Task<HttpResponseMessage> GetAsync(string url, HttpCompletionOption responseHeadersRead = HttpCompletionOption.ResponseHeadersRead)
         {

Wabbajack.Common/Json.cs

@@ -62,16 +62,12 @@ namespace Wabbajack.Common
             return JsonConvert.SerializeObject(obj, JsonSettings);
         }
 
-        public static T FromJson<T>(this AbsolutePath filename,
+        public static T FromJson<T>(this AbsolutePath filename)
-            TypeNameHandling handling = TypeNameHandling.All,
-            TypeNameAssemblyFormatHandling format = TypeNameAssemblyFormatHandling.Full)
         {
             return JsonConvert.DeserializeObject<T>(filename.ReadAllText(), JsonSettings)!;
         }
 
-        public static T FromJsonString<T>(this string data,
+        public static T FromJsonString<T>(this string data)
-            TypeNameHandling handling = TypeNameHandling.Objects,
-            TypeNameAssemblyFormatHandling format = TypeNameAssemblyFormatHandling.Full)
         {
             return JsonConvert.DeserializeObject<T>(data, JsonSettings)!;
         }
@@ -230,8 +226,7 @@ namespace Wabbajack.Common
                     return (Game)i;
                 }
 
-                GameMetaData? game = GameRegistry.GetByFuzzyName(str);
+                if (!GameRegistry.TryGetByFuzzyName(str, out var game))
-                if (game == null)
                 {
                     throw new ArgumentException($"Could not convert {str} to a Game type.");
                 }

Wabbajack.Common/StoreHandlers/SteamHandler.cs

@@ -5,6 +5,7 @@ using System.Linq;
 using System.Security;
 using DynamicData;
 using Microsoft.Win32;
+#nullable enable
 
 namespace Wabbajack.Common.StoreHandlers
 {
@@ -21,9 +22,14 @@ namespace Wabbajack.Common.StoreHandlers
 
     public class SteamWorkshopItem
     {
-        public SteamGame? Game;
+        public readonly SteamGame Game;
         public int ItemID;
         public int Size;
+
+        public SteamWorkshopItem(SteamGame game)
+        {
+            Game = game;
+        }
     }
 
     public class SteamHandler : AStoreHandler
@@ -202,14 +208,14 @@ namespace Wabbajack.Common.StoreHandlers
                 var bracketStart = 0;
                 var bracketEnd = 0;
 
-                SteamWorkshopItem? currentItem = new SteamWorkshopItem();
+                SteamWorkshopItem? currentItem = new SteamWorkshopItem(game);
 
                 lines.Do(l =>
                 {
                     if (end)
                         return;
                     if (currentItem == null)
-                        currentItem = new SteamWorkshopItem();
+                        currentItem = new SteamWorkshopItem(game);
 
                     var currentLine = lines.IndexOf(l);
                     if (l.ContainsCaseInsensitive("\"appid\"") && !foundAppID)
@@ -271,7 +277,6 @@ namespace Wabbajack.Common.StoreHandlers
 
                     bracketStart = 0;
                     bracketEnd = 0;
-                    currentItem.Game = game;
                     game.WorkshopItems.Add(currentItem);
 
                     Utils.Log($"Found Steam Workshop item {currentItem.ItemID}");

Wabbajack.Common/StoreHandlers/StoreHandler.cs

@@ -52,7 +52,7 @@ namespace Wabbajack.Common.StoreHandlers
             }
         }
 
-        public AbsolutePath? GetGamePath(Game game)
+        public AbsolutePath? TryGetGamePath(Game game)
         {
             return StoreGames.FirstOrDefault(g => g.Game == game)?.Path;
         }

Wabbajack.Common/WorkQueue.cs

@@ -49,7 +49,7 @@ namespace Wabbajack.Common
         private readonly BehaviorSubject<(int DesiredCPUs, int CurrentCPUs)> _cpuCountSubj = new BehaviorSubject<(int DesiredCPUs, int CurrentCPUs)>((0, 0));
         public IObservable<(int CurrentCPUs, int DesiredCPUs)> CurrentCpuCount => _cpuCountSubj;
 
-        private readonly Subject<IObservable<int>> _activeNumThreadsObservable = new Subject<IObservable<int>>();
+        private readonly Subject<IObservable<int>?> _activeNumThreadsObservable = new Subject<IObservable<int>?>();
 
         public static TimeSpan PollMS = TimeSpan.FromMilliseconds(200);
 
@@ -66,7 +66,7 @@ namespace Wabbajack.Common
         /// Creates a WorkQueue whos number of threads is determined by the given observable
         /// </summary>
         /// <param name="numThreads">Driving observable that determines how many threads should be actively pulling jobs from the queue</param>
-        public WorkQueue(IObservable<int> numThreads)
+        public WorkQueue(IObservable<int>? numThreads)
         {
             // Hook onto the number of active threads subject, and subscribe to it for changes
             _activeNumThreadsObservable
@@ -86,7 +86,7 @@ namespace Wabbajack.Common
         /// Sets the driving observable that determines how many threads should be actively pulling jobs from the queue
         /// </summary>
         /// <param name="numThreads">Driving observable that determines how many threads should be actively pulling jobs from the queue</param>
-        public void SetActiveThreadsObservable(IObservable<int> numThreads)
+        public void SetActiveThreadsObservable(IObservable<int>? numThreads)
         {
             _activeNumThreadsObservable.OnNext(numThreads);
         }

Wabbajack.Lib/ABatchProcessor.cs

@@ -15,9 +15,9 @@ namespace Wabbajack.Lib
     {
         public WorkQueue Queue { get; } = new WorkQueue();
 
-        public Context VFS { get; private set; }
+        public Context VFS { get; }
 
-        protected StatusUpdateTracker UpdateTracker { get; private set; }
+        protected StatusUpdateTracker UpdateTracker { get; }
 
         private Subject<Percent> _percentCompleted { get; } = new Subject<Percent>();
 
@@ -42,7 +42,6 @@ namespace Wabbajack.Lib
         private Subject<bool> _isRunning { get; } = new Subject<bool>();
         public IObservable<bool> IsRunning => _isRunning;
 
-        private int _configured;
         private int _started;
         private readonly CancellationTokenSource _cancel = new CancellationTokenSource();
 
@@ -53,21 +52,16 @@ namespace Wabbajack.Lib
         public BehaviorSubject<byte> MaxCores = new BehaviorSubject<byte>(byte.MaxValue);
         public BehaviorSubject<Percent> TargetUsagePercent = new BehaviorSubject<Percent>(Percent.One);
 
-        protected void ConfigureProcessor(int steps, IObservable<int> numThreads = null)
+        public ABatchProcessor(int steps)
         {
-            if (1 == Interlocked.CompareExchange(ref _configured, 1, 1))
-            {
-                throw new InvalidDataException("Can't configure a processor twice");
-            }
-            Queue.SetActiveThreadsObservable(numThreads);
             UpdateTracker = new StatusUpdateTracker(steps);
+            VFS = new Context(Queue) { UpdateTracker = UpdateTracker };
             Queue.Status.Subscribe(_queueStatus)
                 .DisposeWith(_subs);
             Queue.LogMessages.Subscribe(_logMessages)
                 .DisposeWith(_subs);
             UpdateTracker.Progress.Subscribe(_percentCompleted);
             UpdateTracker.StepName.Subscribe(_textStatus);
-            VFS = new Context(Queue) { UpdateTracker = UpdateTracker };
         }
 
         /// <summary>

Wabbajack.Lib/ACompiler.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.IO;
 using System.IO.Compression;
@@ -19,10 +19,10 @@ namespace Wabbajack.Lib
 {
     public abstract class ACompiler : ABatchProcessor
     {
-        public string ModListName, ModListAuthor, ModListDescription, ModListWebsite;
+        public string? ModListName, ModListAuthor, ModListDescription, ModListWebsite;
         public AbsolutePath ModListImage, ModListReadme;
         public bool ReadmeIsWebsite;
-        protected Version WabbajackVersion;
+        protected Version? WabbajackVersion;
 
         public abstract AbsolutePath VFSCacheName { get; }
         //protected string VFSCacheName => Path.Combine(Consts.LocalAppDataPath, $"vfs_compile_cache.bin");
@@ -42,14 +42,19 @@ namespace Wabbajack.Lib
 
         public bool IgnoreMissingFiles { get; set; }
 
-        public ICollection<Archive> SelectedArchives = new List<Archive>();
+        public List<Archive> SelectedArchives { get; protected set; } = new List<Archive>();
-        public List<Directive> InstallDirectives = new List<Directive>();
+        public List<Directive> InstallDirectives { get; protected set; } = new List<Directive>();
-        public List<RawSourceFile> AllFiles = new List<RawSourceFile>();
+        public List<RawSourceFile> AllFiles { get; protected set; } = new List<RawSourceFile>();
         public ModList ModList = new ModList();
 
         public List<IndexedArchive> IndexedArchives = new List<IndexedArchive>();
         public Dictionary<Hash, IEnumerable<VirtualFile>> IndexedFiles = new Dictionary<Hash, IEnumerable<VirtualFile>>();
 
+        public ACompiler(int steps)
+            : base(steps)
+        {
+        }
+
         public static void Info(string msg)
         {
             Utils.Log(msg);
@@ -216,7 +221,7 @@ namespace Wabbajack.Lib
                 .GroupBy(f => f.File.Hash)
                 .ToDictionary(f => f.Key, f => f.First());
 
-            SelectedArchives = await hashes.PMap(Queue, hash => ResolveArchive(hash, archives));
+            SelectedArchives.SetTo(await hashes.PMap(Queue, hash => ResolveArchive(hash, archives)));
         }
 
         public async Task<Archive> ResolveArchive(Hash hash, IDictionary<Hash, IndexedArchive> archives)
@@ -226,8 +231,7 @@ namespace Wabbajack.Lib
                 return await ResolveArchive(found);
             }
 
-            Error($"No match found for Archive sha: {hash.ToBase64()} this shouldn't happen");
+            throw new ArgumentException($"No match found for Archive sha: {hash.ToBase64()} this shouldn't happen");
-            return null;
         }
 
         public async Task<Archive> ResolveArchive(IndexedArchive archive)
@@ -238,10 +242,7 @@ namespace Wabbajack.Lib
                 Error(
                     $"No download metadata found for {archive.Name}, please use MO2 to query info or add a .meta file and try again.");
 
-            var result = new Archive
+            var result = new Archive(await DownloadDispatcher.ResolveArchive(archive.IniData));
-            {
-                State = await DownloadDispatcher.ResolveArchive(archive.IniData)
-            };
 
             if (result.State == null)
                 Error($"{archive.Name} could not be handled by any of the downloaders");

Wabbajack.Lib/AInstaller.cs

@@ -27,11 +27,12 @@ namespace Wabbajack.Lib
 
         public AbsolutePath ModListArchive { get; private set; }
         public ModList ModList { get; private set; }
-        public Dictionary<Hash, AbsolutePath> HashedArchives { get; set; }
+        public Dictionary<Hash, AbsolutePath> HashedArchives { get; } = new Dictionary<Hash, AbsolutePath>();
         
-        public SystemParameters SystemParameters { get; set; }
+        public SystemParameters? SystemParameters { get; set; }
 
-        public AInstaller(AbsolutePath archive, ModList modList, AbsolutePath outputFolder, AbsolutePath downloadFolder, SystemParameters parameters)
+        public AInstaller(AbsolutePath archive, ModList modList, AbsolutePath outputFolder, AbsolutePath downloadFolder, SystemParameters? parameters, int steps)
+            : base(steps)
         {
             ModList = modList;
             ModListArchive = archive;
@@ -166,6 +167,10 @@ namespace Wabbajack.Lib
                   .PDoIndexed(queue, async (idx, group) =>
             {
                 Utils.Status("Installing files", Percent.FactoryPutInRange(idx, vFiles.Count));
+                if (group.Key == null)
+                {
+                    throw new ArgumentNullException("FromFile was null");
+                }
                 var firstDest = OutputFolder.Combine(group.First().To);
                 await CopyFile(group.Key.StagedPath, firstDest, true);
                 
@@ -173,7 +178,6 @@ namespace Wabbajack.Lib
                 {
                     await CopyFile(firstDest, OutputFolder.Combine(copy.To), false);
                 }
-
             });
 
             Status("Unstaging files");
@@ -278,11 +282,11 @@ namespace Wabbajack.Lib
             var hashResults = await DownloadFolder.EnumerateFiles()
                 .Where(e => e.Extension != Consts.HashFileExtension)
                 .PMap(Queue, async e => (await e.FileHashCachedAsync(), e));
-            HashedArchives = hashResults
+            HashedArchives.SetTo(hashResults
                 .OrderByDescending(e => e.Item2.LastModified)
                 .GroupBy(e => e.Item1)
                 .Select(e => e.First())
-                .ToDictionary(e => e.Item1, e => e.Item2);
+                .Select(e => new KeyValuePair<Hash, AbsolutePath>(e.Item1, e.Item2)));
         }
 
         /// <summary>
@@ -391,8 +395,13 @@ namespace Wabbajack.Lib
                 
                 return await path.FileHashAsync() == d.Hash ? d : null;
             }))
-              .Where(d => d != null)
+              .Do(d =>
-              .Do(d => indexed.Remove(d.To));
+              {
+                  if (d != null)
+                  {
+                      indexed.Remove(d.To);
+                  }
+              });
 
             UpdateTracker.NextStep("Updating ModList");
             Utils.Log($"Optimized {ModList.Directives.Count} directives to {indexed.Count} required");

Wabbajack.Lib/ClientAPI.cs

@@ -14,7 +14,7 @@ namespace Wabbajack.Lib
             return client;
         }
 
-        public static async Task<Archive> GetModUpgrade(Hash hash)
+        public static async Task<Archive?> GetModUpgrade(Hash hash)
         {
             using var response = await GetClient()
                 .GetAsync($"{Consts.WabbajackBuildServerUri}alternative/{hash.ToHex()}");
@@ -33,7 +33,7 @@ namespace Wabbajack.Lib
         /// </summary>
         /// <param name="hash"></param>
         /// <returns></returns>
-        public static async Task<string> GetModIni(Hash hash)
+        public static async Task<string?> GetModIni(Hash hash)
         {
             var client = new Common.Http.Client();
             try

Wabbajack.Lib/CompilationSteps/ACompilationStep.cs

@@ -11,7 +11,7 @@ namespace Wabbajack.Lib.CompilationSteps
             _compiler = compiler;
         }
 
-        public abstract ValueTask<Directive> Run(RawSourceFile source);
+        public abstract ValueTask<Directive?> Run(RawSourceFile source);
         public abstract IState GetState();
     }
 }

Wabbajack.Lib/CompilationSteps/DeconstructBSAs.cs

@@ -51,7 +51,7 @@ namespace Wabbajack.Lib.CompilationSteps
             return new State();
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             if (!Consts.SupportedBSAs.Contains(source.Path.Extension)) return null;
 
@@ -79,12 +79,12 @@ namespace Wabbajack.Lib.CompilationSteps
             CreateBSA directive;
             using (var bsa = BSADispatch.OpenRead(source.AbsolutePath))
             {
-                directive = new CreateBSA
+                directive = new CreateBSA(
+                    state: bsa.State, 
+                    items: bsa.Files.Select(f => f.State).ToList())
                 {
                     To = source.Path,
                     TempID = (RelativePath)id,
-                    State = bsa.State,
-                    FileStates = bsa.Files.Select(f => f.State).ToList()
                 };
             }
 

Wabbajack.Lib/CompilationSteps/DirectMatch.cs

@@ -11,7 +11,7 @@ namespace Wabbajack.Lib.CompilationSteps
         {
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             if (!_compiler.IndexedFiles.TryGetValue(source.Hash, out var found)) return null;
             var result = source.EvolveTo<FromArchive>();

Wabbajack.Lib/CompilationSteps/DropAll.cs

@@ -10,7 +10,7 @@ namespace Wabbajack.Lib.CompilationSteps
         {
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             var result = source.EvolveTo<NoMatch>();
             result.Reason = "No Match in Stack";

Wabbajack.Lib/CompilationSteps/ICompilationStep.cs

@@ -4,7 +4,7 @@ namespace Wabbajack.Lib.CompilationSteps
 {
     public interface ICompilationStep
     {
-        ValueTask<Directive> Run(RawSourceFile source);
+        ValueTask<Directive?> Run(RawSourceFile source);
         IState GetState();
     }
 

Wabbajack.Lib/CompilationSteps/IgnoreDisabledMods.cs

@@ -25,7 +25,7 @@ namespace Wabbajack.Lib.CompilationSteps
                 .ToList();
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             if (!source.AbsolutePath.InFolder(_mo2Compiler.MO2ModsFolder)) return null;
             if (_allEnabledMods.Any(mod => source.AbsolutePath.InFolder(mod)))

Wabbajack.Lib/CompilationSteps/IgnoreEndsWith.cs

@@ -14,7 +14,7 @@ namespace Wabbajack.Lib.CompilationSteps
             _reason = $"Ignored because path ends with {postfix}";
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             if (!((string)source.Path).EndsWith(_postfix)) return null;
             var result = source.EvolveTo<IgnoredDirectly>();
@@ -30,17 +30,13 @@ namespace Wabbajack.Lib.CompilationSteps
         [JsonObject("IgnoreEndsWith")]
         public class State : IState
         {
+            public string Postfix { get; set; }
+
             public State(string postfix)
             {
                 Postfix = postfix;
             }
 
-            public State()
-            {
-            }
-
-            public string Postfix { get; set; }
-
             public ICompilationStep CreateStep(ACompiler compiler)
             {
                 return new IgnoreEndsWith(compiler, Postfix);

Wabbajack.Lib/CompilationSteps/IgnoreGameFiles.cs

@@ -13,7 +13,7 @@ namespace Wabbajack.Lib.CompilationSteps
             _startDir = Consts.GameFolderFilesDir + "\\";
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             if (!((string)source.Path).StartsWith(_startDir)) return null;
             var i = source.EvolveTo<IgnoredDirectly>();

Wabbajack.Lib/CompilationSteps/IgnoreGameFilesIfGameFolderFilesExist.cs

@@ -15,7 +15,7 @@ namespace Wabbajack.Lib.CompilationSteps
             _gameFolder = compiler.GamePath;
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             if (_gameFolderFilesExists)
             {

Wabbajack.Lib/CompilationSteps/IgnorePathContains.cs

@@ -14,7 +14,7 @@ namespace Wabbajack.Lib.CompilationSteps
             _reason = $"Ignored because path contains {_pattern}";
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             if (!((string)source.Path).Contains(_pattern)) return null;
             var result = source.EvolveTo<IgnoredDirectly>();
@@ -30,17 +30,13 @@ namespace Wabbajack.Lib.CompilationSteps
         [JsonObject("IgnorePathContains")]
         public class State : IState
         {
-            public State()
+            public string Pattern { get; set; }
-            {
-            }
 
             public State(string pattern)
             {
                 Pattern = pattern;
             }
 
-            public string Pattern { get; set; }
-
             public ICompilationStep CreateStep(ACompiler compiler)
             {
                 return new IgnorePathContains(compiler, Pattern);

Wabbajack.Lib/CompilationSteps/IgnoreRegex.cs

@@ -17,7 +17,7 @@ namespace Wabbajack.Lib.CompilationSteps
             _regex = new Regex(pattern);
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             if (!_regex.IsMatch((string)source.Path)) return null;
             var result = source.EvolveTo<IgnoredDirectly>();
@@ -33,17 +33,13 @@ namespace Wabbajack.Lib.CompilationSteps
         [JsonObject("IgnorePattern")]
         public class State : IState
         {
-            public State()
+            public string Pattern { get; set; }
-            {
-            }
 
             public State(string pattern)
             {
                 Pattern = pattern;
             }
 
-            public string Pattern { get; set; }
-
             public ICompilationStep CreateStep(ACompiler compiler)
             {
                 return new IgnoreRegex(compiler, Pattern);

Wabbajack.Lib/CompilationSteps/IgnoreStartsWith.cs

@@ -14,7 +14,7 @@ namespace Wabbajack.Lib.CompilationSteps
             _reason = string.Format("Ignored because path starts with {0}", _prefix);
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             if (!((string)source.Path).StartsWith(_prefix))
             {
@@ -35,17 +35,13 @@ namespace Wabbajack.Lib.CompilationSteps
         [JsonObject("IgnoreStartsWith")]
         public class State : IState
         {
-            public State()
+            public string Prefix { get; set; }
-            {
-            }
 
             public State(string prefix)
             {
                 Prefix = prefix;
             }
 
-            public string Prefix { get; set; }
-
             public ICompilationStep CreateStep(ACompiler compiler)
             {
                 return new IgnoreStartsWith(compiler, Prefix);

Wabbajack.Lib/CompilationSteps/IgnoreWabbajackInstallCruft.cs

@@ -19,7 +19,7 @@ namespace Wabbajack.Lib.CompilationSteps
             };
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             if (!_cruftFiles.Any(f => source.Path.StartsWith(f))) return null;
             var result = source.EvolveTo<IgnoredDirectly>();

Wabbajack.Lib/CompilationSteps/IncludeAll.cs

@@ -10,7 +10,7 @@ namespace Wabbajack.Lib.CompilationSteps
         {
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             var inline = source.EvolveTo<InlineFile>();
             inline.SourceDataID = await _compiler.IncludeFile(await source.AbsolutePath.ReadAllBytesAsync());

Wabbajack.Lib/CompilationSteps/IncludeAllConfigs.cs

@@ -11,7 +11,7 @@ namespace Wabbajack.Lib.CompilationSteps
         {
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             if (!Consts.ConfigFileExtensions.Contains(source.Path.Extension)) return null;
             var result = source.EvolveTo<InlineFile>();

Wabbajack.Lib/CompilationSteps/IncludeDummyESPs.cs

@@ -11,7 +11,7 @@ namespace Wabbajack.Lib.CompilationSteps
         {
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             if (source.AbsolutePath.Extension != Consts.ESP &&
                 source.AbsolutePath.Extension != Consts.ESM) return null;

Wabbajack.Lib/CompilationSteps/IncludeLOOTFiles.cs

@@ -14,7 +14,7 @@ namespace Wabbajack.Lib.CompilationSteps
             _prefix = Consts.LOOTFolderFilesDir + "\\";
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             if (!source.Path.StartsWith(_prefix)) return null;
             var result = source.EvolveTo<InlineFile>();

Wabbajack.Lib/CompilationSteps/IncludeModIniData.cs

@@ -11,7 +11,7 @@ namespace Wabbajack.Lib.CompilationSteps
         {
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             if (!source.Path.StartsWith("mods\\") || source.Path.FileName != Consts.MetaIni) return null;
             var e = source.EvolveTo<InlineFile>();

Wabbajack.Lib/CompilationSteps/IncludeOtherProfiles.cs

@@ -23,7 +23,7 @@ namespace Wabbajack.Lib.CompilationSteps
                 .ToList();
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             if (!source.AbsolutePath.InFolder(_modProfilesFolder)) return null;
             if (_profiles.Any(profile => source.AbsolutePath.InFolder(profile))) return null;

Wabbajack.Lib/CompilationSteps/IncludePatches.cs

@@ -12,11 +12,11 @@ namespace Wabbajack.Lib.CompilationSteps
     public class IncludePatches : ACompilationStep
     {
         private readonly Dictionary<RelativePath, IGrouping<RelativePath, VirtualFile>> _indexed;
-        private VirtualFile _bsa;
+        private VirtualFile? _bsa;
         private Dictionary<RelativePath, VirtualFile> _indexedByName;
         private MO2Compiler _mo2Compiler;
 
-        public IncludePatches(ACompiler compiler, VirtualFile constructingFromBSA = null) : base(compiler)
+        public IncludePatches(ACompiler compiler, VirtualFile? constructingFromBSA = null) : base(compiler)
         {
             _bsa = constructingFromBSA;
             _mo2Compiler = (MO2Compiler)compiler;
@@ -30,9 +30,8 @@ namespace Wabbajack.Lib.CompilationSteps
                                      .ToDictionary(f => f.FullPath.FileName);
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
-            
             var name = source.File.Name.FileName;
             RelativePath nameWithoutExt = name;
             if (name.Extension == Consts.MOHIDDEN)
@@ -41,7 +40,7 @@ namespace Wabbajack.Lib.CompilationSteps
             if (!_indexed.TryGetValue(name, out var choices))
                 _indexed.TryGetValue(nameWithoutExt, out choices);
 
-            dynamic modIni = null;
+            dynamic? modIni = null;
             if (source.AbsolutePath.InFolder(_mo2Compiler.MO2ModsFolder))
             {
                 if (_bsa == null)
@@ -55,7 +54,7 @@ namespace Wabbajack.Lib.CompilationSteps
 
             var installationFile = (RelativePath)modIni?.General?.installationFile;
 
-            VirtualFile found = null;
+            VirtualFile? found = null;
             
             // Find based on exact file name + ext
             if (choices != null)

Wabbajack.Lib/CompilationSteps/IncludePropertyFiles.cs

@@ -14,7 +14,7 @@ namespace Wabbajack.Lib.CompilationSteps
         {
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             var files = new HashSet<AbsolutePath>
             {

Wabbajack.Lib/CompilationSteps/IncludeRegex.cs

@@ -16,7 +16,7 @@ namespace Wabbajack.Lib.CompilationSteps
             _regex = new Regex(pattern);
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             if (!_regex.IsMatch((string)source.Path)) return null;
 
@@ -33,17 +33,13 @@ namespace Wabbajack.Lib.CompilationSteps
         [JsonObject("IncludeRegex")]
         public class State : IState
         {
-            public State()
+            public string Pattern { get; set; }
-            {
-            }
 
             public State(string pattern)
             {
                 Pattern = pattern;
             }
 
-            public string Pattern { get; set; }
-
             public ICompilationStep CreateStep(ACompiler compiler)
             {
                 return new IncludeRegex(compiler, Pattern);

Wabbajack.Lib/CompilationSteps/IncludeSteamWorkshopItems.cs

@@ -18,7 +18,7 @@ namespace Wabbajack.Lib.CompilationSteps
             _game = steamGame;
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             if (!_regex.IsMatch((string)source.Path)) 
                 return null;
@@ -31,7 +31,7 @@ namespace Wabbajack.Lib.CompilationSteps
                 if (id == 0)
                     return null;
 
-                SteamWorkshopItem item = null;
+                SteamWorkshopItem? item = null;
                 _game.WorkshopItems.Where(i => i.ItemID == id).Do(i => item = i);
                 if (item == null)
                     return null;

Wabbajack.Lib/CompilationSteps/IncludeStubbedConfigfiles.cs

@@ -15,7 +15,7 @@ namespace Wabbajack.Lib.CompilationSteps
             _mo2Compiler = (MO2Compiler) compiler;
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             return Consts.ConfigFileExtensions.Contains(source.Path.Extension) ? await RemapFile(source) : null;
         }
@@ -25,7 +25,7 @@ namespace Wabbajack.Lib.CompilationSteps
             return new State();
         }
 
-        private async Task<Directive> RemapFile(RawSourceFile source)
+        private async Task<Directive?> RemapFile(RawSourceFile source)
         {
             var data = await source.AbsolutePath.ReadAllTextAsync();
             var originalData = data;

Wabbajack.Lib/CompilationSteps/IncludeTaggedMods.cs

@@ -26,7 +26,7 @@ namespace Wabbajack.Lib.CompilationSteps
             }).Select(kv => $"mods\\{kv.Key}\\");
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             if (!source.Path.StartsWith(Consts.MO2ModFolderName)) return null;
             foreach (var modpath in _includeDirectly)
@@ -48,17 +48,13 @@ namespace Wabbajack.Lib.CompilationSteps
         [JsonObject("IncludeTaggedMods")]
         public class State : IState
         {
-            public State()
+            public string Tag { get; set; }
-            {
-            }
 
             public State(string tag)
             {
                 Tag = tag;
             }
 
-            public string Tag { get; set; }
-
             public ICompilationStep CreateStep(ACompiler compiler)
             {
                 return new IncludeTaggedMods(compiler, Tag);

Wabbajack.Lib/CompilationSteps/IncludeThisProfile.cs

@@ -19,7 +19,7 @@ namespace Wabbajack.Lib.CompilationSteps
             _correctProfiles = _mo2Compiler.SelectedProfiles.Select(p => _mo2Compiler.MO2ProfileDir.Parent.Combine(p)).ToList();
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             if (!_correctProfiles.Any(p => source.AbsolutePath.InFolder(p)))
                 return null;

Wabbajack.Lib/CompilationSteps/IncludeVortexDeployment.cs

@@ -12,7 +12,7 @@ namespace Wabbajack.Lib.CompilationSteps
         {
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             // * TODO I don't know what this does
             /*

Wabbajack.Lib/CompilationSteps/PatchStockESMs.cs

@@ -16,7 +16,7 @@ namespace Wabbajack.Lib.CompilationSteps
             _mo2Compiler = (MO2Compiler) compiler;
         }
 
-        public override async ValueTask<Directive> Run(RawSourceFile source)
+        public override async ValueTask<Directive?> Run(RawSourceFile source)
         {
             var filename = source.Path.FileName;
             var gameFile = _mo2Compiler.GamePath.Combine((RelativePath)"Data", filename);

Wabbajack.Lib/Data.cs

@@ -43,22 +43,22 @@ namespace Wabbajack.Lib
         /// <summary>
         ///     Archives required by this modlist
         /// </summary>
-        public List<Archive> Archives;
+        public List<Archive> Archives = new List<Archive>();
 
         /// <summary>
         ///     Author of the ModList
         /// </summary>
-        public string Author;
+        public string Author = string.Empty;
 
         /// <summary>
         ///     Description of the ModList
         /// </summary>
-        public string Description;
+        public string Description = string.Empty;
 
         /// <summary>
         ///     Install directives
         /// </summary>
-        public List<Directive> Directives;
+        public List<Directive> Directives = new List<Directive>();
 
         /// <summary>
         ///     The game variant to which this game applies
@@ -78,12 +78,12 @@ namespace Wabbajack.Lib
         /// <summary>
         ///     Name of the ModList
         /// </summary>
-        public string Name;
+        public string Name = string.Empty;
 
         /// <summary>
         ///     readme path or website
         /// </summary>
-        public string Readme;
+        public string Readme = string.Empty;
 
         /// <summary>
         ///     Whether readme is a website
@@ -93,12 +93,12 @@ namespace Wabbajack.Lib
         /// <summary>
         ///     The build version of Wabbajack used when compiling the Modlist
         /// </summary>
-        public Version WabbajackVersion;
+        public Version? WabbajackVersion;
 
         /// <summary>
         ///     Website of the ModList
         /// </summary>
-        public Uri Website;
+        public Uri? Website;
 
         /// <summary>
         ///     The size of all the archives once they're downloaded
@@ -134,7 +134,7 @@ namespace Wabbajack.Lib
 
     public class IgnoredDirectly : Directive
     {
-        public string Reason;
+        public string Reason = string.Empty;
     }
 
     public class NoMatch : IgnoredDirectly
@@ -190,12 +190,12 @@ namespace Wabbajack.Lib
     [JsonName("FromArchive")]
     public class FromArchive : Directive
     {
-        private string _fullPath;
+        private string? _fullPath;
 
         public HashRelativePath ArchiveHashPath { get; set; }
 
         [JsonIgnore]
-        public VirtualFile FromFile { get; set; }
+        public VirtualFile? FromFile { get; set; }
 
         [JsonIgnore]
         public string FullPath => _fullPath ??= string.Join("|", ArchiveHashPath);
@@ -205,8 +205,17 @@ namespace Wabbajack.Lib
     public class CreateBSA : Directive
     {
         public RelativePath TempID { get; set; }
-        public ArchiveStateObject State { get; set; }
+        public ArchiveStateObject State { get; }
-        public List<FileStateObject> FileStates { get; set; }
+        public List<FileStateObject> FileStates { get; set; } = new List<FileStateObject>();
+
+        public CreateBSA(ArchiveStateObject state, IEnumerable<FileStateObject>? items = null)
+        {
+            State = state;
+            if (items != null)
+            {
+                FileStates.AddRange(items);
+            }
+        }
     }
 
     [JsonName("PatchedFromArchive")]
@@ -231,7 +240,7 @@ namespace Wabbajack.Lib
     public class MergedPatch : Directive
     {
         public RelativePath PatchID { get; set; }
-        public List<SourcePatch> Sources { get; set; }
+        public List<SourcePatch> Sources { get; set; } = new List<SourcePatch>();
     }
 
     [JsonName("Archive")]
@@ -245,49 +254,33 @@ namespace Wabbajack.Lib
         /// <summary>
         ///     Meta INI for the downloaded archive
         /// </summary>
-        public string Meta { get; set; }
+        public string? Meta { get; set; }
 
         /// <summary>
         ///     Human friendly name of this archive
         /// </summary>
-        public string Name { get; set; }
+        public string Name { get; set; } = string.Empty;
 
         public long Size { get; set; }
         
-        public AbstractDownloadState State { get; set; }
+        public AbstractDownloadState State { get; }
+
+        public Archive(AbstractDownloadState state)
+        {
+            State = state;
+        }
     }
 
     public class IndexedArchive
     {
-        public dynamic IniData;
+        public dynamic? IniData;
-        public string Meta;
+        public string Meta = string.Empty;
-        public string Name;
+        public string Name = string.Empty;
-        public VirtualFile File { get; internal set; }
+        public VirtualFile File { get; }
-    }
 
-    /// <summary>
+        public IndexedArchive(VirtualFile file)
-    ///     A archive entry
+        {
-    /// </summary>
+            File = file;
-    public class IndexedEntry
+        }
-    {
-        /// <summary>
-        ///     MurMur3 hash of this file
-        /// </summary>
-        public string Hash;
-
-        /// <summary>
-        ///     Path in the archive to this file
-        /// </summary>
-        public string Path;
-
-        /// <summary>
-        ///     Size of the file (uncompressed)
-        /// </summary>
-        public long Size;
-    }
-
-    public class IndexedArchiveEntry : IndexedEntry
-    {
-        public string[] HashPath;
     }
 }

Wabbajack.Lib/Downloaders/AbstractDownloadState.cs

@@ -11,19 +11,18 @@ namespace Wabbajack.Lib.Downloaders
     public interface IMetaState
     {
         Uri URL { get; }
-        string Name { get; set; }
+        string? Name { get; set; }
-        string Author { get; set; }
+        string? Author { get; set; }
-        string Version { get; set; }
+        string? Version { get; set; }
-        string ImageURL { get; set; }
+        string? ImageURL { get; set; }
         bool IsNSFW { get; set; }
-        string Description { get; set; }
+        string? Description { get; set; }
 
         Task<bool> LoadMetaData();
     }
 
     public abstract class AbstractDownloadState
     {
-
         public static List<Type> KnownSubTypes = new List<Type>
         {
             typeof(HTTPDownloader.State),
@@ -48,7 +47,7 @@ namespace Wabbajack.Lib.Downloaders
 
         static AbstractDownloadState()
         {
-            NameToType = KnownSubTypes.ToDictionary(t => t.FullName.Substring(t.Namespace.Length + 1), t => t);
+            NameToType = KnownSubTypes.ToDictionary(t => t.FullName!.Substring(t.Namespace!.Length + 1), t => t);
             TypeToName = NameToType.ToDictionary(k => k.Value, k => k.Key);
         }
 
@@ -68,7 +67,6 @@ namespace Wabbajack.Lib.Downloaders
             }
         }
 
-
         /// <summary>
         /// Returns true if this file is allowed to be downloaded via whitelist
         /// </summary>
@@ -85,7 +83,9 @@ namespace Wabbajack.Lib.Downloaders
         public async Task<bool> Download(AbsolutePath destination)
         {
             destination.Parent.CreateDirectory();
-            return await Download(new Archive {Name = (string)destination.FileName}, destination);
+            // ToDo
+            // Is this null override needed?  Why is state allowed to be null here?
+            return await Download(new Archive(state: null!) {Name = (string)destination.FileName}, destination);
         }
 
         /// <summary>
@@ -96,7 +96,7 @@ namespace Wabbajack.Lib.Downloaders
 
         public abstract IDownloader GetDownloader();
 
-        public abstract string GetManifestURL(Archive a);
+        public abstract string? GetManifestURL(Archive a);
         public abstract string[] GetMetaIni();
     }
 }

Wabbajack.Lib/Downloaders/AbstractIPS4Downloader.cs

@@ -18,10 +18,12 @@ namespace Wabbajack.Lib.Downloaders
         where TState : AbstractIPS4Downloader<TDownloader, TState>.State<TDownloader>, new()
         where TDownloader : IDownloader
     {
-        public override string SiteName { get; }
+        protected AbstractIPS4Downloader(Uri loginUri, string encryptedKeyName, string cookieDomain)
-        public override Uri SiteURL { get; }
+            : base(loginUri, encryptedKeyName, cookieDomain, "ips4_member_id")
+        {
+        }
 
-        public async Task<AbstractDownloadState> GetDownloaderState(dynamic archiveINI, bool quickMode)
+        public async Task<AbstractDownloadState?> GetDownloaderState(dynamic archiveINI, bool quickMode)
         {
             Uri url = DownloaderUtils.GetDirectURL(archiveINI);
 
@@ -70,23 +72,23 @@ namespace Wabbajack.Lib.Downloaders
             };
         }
 
-        
+        public class State<TStateDownloader> : AbstractDownloadState, IMetaState 
-        public class State<TStateDownloader> : AbstractDownloadState, IMetaState where TStateDownloader : IDownloader
+            where TStateDownloader : IDownloader
         {
-            public string FullURL { get; set; }
+            public string FullURL { get; set; } = string.Empty;
             public bool IsAttachment { get; set; }
-            public string FileID { get; set; }
+            public string FileID { get; set; } = string.Empty;
-            
+
-            public string FileName { get; set; }
+            public string FileName { get; set; } = string.Empty;
             
             // from IMetaState
             public Uri URL => new Uri($"{Site}/files/file/{FileName}");
-            public string Name { get; set; }
+            public string? Name { get; set; }
-            public string Author { get; set; }
+            public string? Author { get; set; }
-            public string Version { get; set; }
+            public string? Version { get; set; }
-            public string ImageURL { get; set; }
+            public string? ImageURL { get; set; }
             public virtual bool IsNSFW { get; set; }
-            public string Description { get; set; }
+            public string? Description { get; set; }
 
             private static bool IsHTTPS => Downloader.SiteURL.AbsolutePath.StartsWith("https://");
             private static string URLPrefix => IsHTTPS ? "https://" : "http://";
@@ -119,6 +121,7 @@ namespace Wabbajack.Lib.Downloaders
             public override async Task<bool> Download(Archive a, AbsolutePath destination)
             {
                 await using var stream = await ResolveDownloadStream();
+                if (stream == null) return false;
                 await using (var file = destination.Create())
                 {
                     await stream.CopyToAsync(file);
@@ -126,7 +129,7 @@ namespace Wabbajack.Lib.Downloaders
                 return true;
             }
 
-            private async Task<Stream> ResolveDownloadStream()
+            private async Task<Stream?> ResolveDownloadStream()
             {
                 TOP:
                 string url;
@@ -236,12 +239,5 @@ namespace Wabbajack.Lib.Downloaders
                 return false;
             }
         }
-
-        protected AbstractIPS4Downloader(Uri loginUri, string encryptedKeyName, string cookieDomain) : 
-            base(loginUri, encryptedKeyName, cookieDomain, "ips4_member_id")
-        {
-        }
-
-
     }
 }

Wabbajack.Lib/Downloaders/AbstractNeedsLoginDownloader.cs

@@ -21,7 +21,17 @@ namespace Wabbajack.Lib.Downloaders
         private readonly string _encryptedKeyName;
         private readonly string _cookieDomain;
         private readonly string _cookieName;
-        internal Common.Http.Client AuthedClient;
+        // ToDo
+        // Remove null assignment.  Either add nullability to type, or figure way to prepare it safely
+        public Common.Http.Client AuthedClient { get; private set; } = null!;
+
+        public ReactiveCommand<Unit, Unit> TriggerLogin { get; }
+        public ReactiveCommand<Unit, Unit> ClearLogin { get; }
+        public IObservable<bool> IsLoggedIn => Utils.HaveEncryptedJsonObservable(_encryptedKeyName);
+        public abstract string SiteName { get; }
+        public virtual IObservable<string>? MetaInfo { get; }
+        public abstract Uri SiteURL { get; }
+        public virtual Uri? IconUri { get; }
 
         /// <summary>
         /// Sets up all the login facilites needed for a INeedsLogin downloader based on having the user log
@@ -48,14 +58,6 @@ namespace Wabbajack.Lib.Downloaders
                 execute: () => Utils.CatchAndLog(() => Utils.DeleteEncryptedJson(_encryptedKeyName)),
                 canExecute: IsLoggedIn.ObserveOnGuiThread());
         }
-        
-        public ReactiveCommand<Unit, Unit> TriggerLogin { get; }
-        public ReactiveCommand<Unit, Unit> ClearLogin { get; }
-        public IObservable<bool> IsLoggedIn => Utils.HaveEncryptedJsonObservable(_encryptedKeyName);
-        public abstract string SiteName { get; }
-        public virtual IObservable<string> MetaInfo { get; }
-        public abstract Uri SiteURL { get; }
-        public virtual Uri IconUri { get; }
 
         protected virtual async Task WhileWaiting(IWebDriver browser)
         {
@@ -120,7 +122,7 @@ namespace Wabbajack.Lib.Downloaders
                 Downloader = downloader;
             }
             public override string ShortDescription => $"Getting {Downloader.SiteName} Login";
-            public override string ExtendedDescription { get; }
+            public override string ExtendedDescription { get; } = string.Empty;
 
             private readonly TaskCompletionSource<Helpers.Cookie[]> _source = new TaskCompletionSource<Helpers.Cookie[]>();
             public Task<Helpers.Cookie[]> Task => _source.Task;
@@ -138,6 +140,4 @@ namespace Wabbajack.Lib.Downloaders
             }
         }
     }
-
-
 }

Wabbajack.Lib/Downloaders/BethesdaNetDownloader.cs

@@ -30,6 +30,15 @@ namespace Wabbajack.Lib.Downloaders
     public class BethesdaNetDownloader : IUrlDownloader, INeedsLogin
     {
         public const string DataName = "bethesda-net-data";
+
+        public ReactiveCommand<Unit, Unit> TriggerLogin { get; }
+        public ReactiveCommand<Unit, Unit> ClearLogin { get; }
+        public IObservable<bool> IsLoggedIn => Utils.HaveEncryptedJsonObservable(DataName);
+        public string SiteName => "Bethesda.NET";
+        public IObservable<string> MetaInfo => Observable.Return(""); //"Wabbajack will start the game, then exit once you enter the Mods page";
+        public Uri SiteURL => new Uri("https://bethesda.net");
+        public Uri? IconUri { get; }
+
         public BethesdaNetDownloader()
         {
             TriggerLogin = ReactiveCommand.CreateFromTask(() => Utils.CatchAndLog(RequestLoginAndCache), IsLoggedIn.Select(b => !b).ObserveOn(RxApp.MainThreadScheduler));
@@ -38,23 +47,23 @@ namespace Wabbajack.Lib.Downloaders
 
         private static async Task RequestLoginAndCache()
         {
-            var result = await Utils.Log(new RequestBethesdaNetLogin()).Task;
+            await Utils.Log(new RequestBethesdaNetLogin()).Task;
         }
 
-        public async Task<AbstractDownloadState> GetDownloaderState(dynamic archiveINI, bool quickMode)
+        public async Task<AbstractDownloadState?> GetDownloaderState(dynamic archiveINI, bool quickMode)
         {
             var url = (Uri)DownloaderUtils.GetDirectURL(archiveINI);
             return StateFromUrl(url);
         }
 
-        internal static AbstractDownloadState StateFromUrl(Uri url)
+        internal static AbstractDownloadState? StateFromUrl(Uri url)
         {
             if (url != null && url.Host == "bethesda.net" && url.AbsolutePath.StartsWith("/en/mods/"))
             {
                 var split = url.AbsolutePath.Split('/');
                 var game = split[3];
                 var modId = split[5];
-                return new State {GameName = game, ContentId = modId};
+                return new State(gameName: game, contentId: modId);
             }
             return null;
         }
@@ -65,10 +74,11 @@ namespace Wabbajack.Lib.Downloaders
             await Utils.Log(new RequestBethesdaNetLogin()).Task;
         }
 
-        public static async Task<BethesdaNetData> Login(Game game)
+        public static async Task<BethesdaNetData?> Login(Game game)
         {
             var metadata = game.MetaData();
-            var gamePath = metadata.GameLocation()?.Combine(metadata.MainExecutable);
+            if (metadata.MainExecutable == null) throw new NotImplementedException();
+            var gamePath = metadata.GameLocation().Combine(metadata.MainExecutable);
             var info = new ProcessStartInfo
             {
                 FileName = @"Downloaders\BethesdaNet\bethnetlogin.exe",
@@ -103,28 +113,25 @@ namespace Wabbajack.Lib.Downloaders
             }
         }
 
-        public AbstractDownloadState GetDownloaderState(string url)
+        public AbstractDownloadState? GetDownloaderState(string url)
         {
             return StateFromUrl(new Uri(url));
         }
 
-        public ReactiveCommand<Unit, Unit> TriggerLogin { get; }
-        public ReactiveCommand<Unit, Unit> ClearLogin { get; }
-        public IObservable<bool> IsLoggedIn => Utils.HaveEncryptedJsonObservable(DataName);
-        public string SiteName => "Bethesda.NET";
-        public IObservable<string> MetaInfo => Observable.Return(""); //"Wabbajack will start the game, then exit once you enter the Mods page";
-        public Uri SiteURL => new Uri("https://bethesda.net");
-        public Uri IconUri { get; }
-
-        
         [JsonName("BethesdaNetDownloader")]
         public class State : AbstractDownloadState
         {
-            public string GameName { get; set; }
+            public string GameName { get; }
-            public string ContentId { get; set; }
+            public string ContentId { get; }
-            
+
             [JsonIgnore]
-            public override object[] PrimaryKey => new object[] {GameName, ContentId};
+            public override object[] PrimaryKey => new object[] { GameName, ContentId };
+
+            public State(string gameName, string contentId)
+            {
+                GameName = gameName;
+                ContentId = contentId;
+            }
 
             public override bool IsWhitelisted(ServerWhitelist whitelist)
             {
@@ -143,8 +150,8 @@ namespace Wabbajack.Lib.Downloaders
                     using var got = await client.GetAsync(
                         $"https://content.cdp.bethesda.net/{collected.CDPProductId}/{collected.CDPPropertiesId}/{chunk.sha}");
                     var data = await got.Content.ReadAsByteArrayAsync();
-                    if (collected.AESKey != null) 
+                    if (collected.AESKey != null)
-                        AESCTRDecrypt(collected.AESKey, collected.AESIV, data);
+                        AESCTRDecrypt(collected.AESKey, collected.AESIV!, data);
 
                     if (chunk.uncompressed_size == chunk.chunk_size)
                         await file.WriteAsync(data, 0, data.Length);
@@ -198,7 +205,7 @@ namespace Wabbajack.Lib.Downloaders
 
             public override async Task<bool> Verify(Archive archive)
             {
-                var info = await ResolveDownloadInfo();
+                await ResolveDownloadInfo();
                 return true;
             }
 
@@ -222,7 +229,7 @@ namespace Wabbajack.Lib.Downloaders
                 client.Headers.Add(("x-cdp-app", "UGC SDK"));
                 client.Headers.Add(("x-cdp-app-ver", "0.9.11314/debug"));
                 client.Headers.Add(("x-cdp-lib-ver", "0.9.11314/debug"));
-                client.Headers.Add(("x-cdp-platform","Win/32"));
+                client.Headers.Add(("x-cdp-platform", "Win/32"));
 
                 posted = await client.PostAsync("https://api.bethesda.net/cdp-user/auth",
                     new StringContent("{\"access_token\": \"" + info.AccessToken + "\"}", Encoding.UTF8,
@@ -233,10 +240,10 @@ namespace Wabbajack.Lib.Downloaders
                 var got = await client.GetAsync($"https://api.bethesda.net/mods/ugc-workshop/content/get?content_id={ContentId}");
                 JObject data = JObject.Parse(await got.Content.ReadAsStringAsync());
 
-                var content = data["platform"]["response"]["content"];
+                var content = data["platform"]!["response"]!["content"]!;
 
-                info.CDPBranchId = (int)content["cdp_branch_id"];
+                info.CDPBranchId = (int)content["cdp_branch_id"]!;
-                info.CDPProductId = (int)content["cdp_product_id"];
+                info.CDPProductId = (int)content["cdp_product_id"]!;
 
                 client.Headers.Add(("Authorization", $"Token {info.CDPToken}"));
                 client.Headers.Add(("Accept", "application/json"));
@@ -246,7 +253,7 @@ namespace Wabbajack.Lib.Downloaders
                     $"https://api.bethesda.net/cdp-user/projects/{info.CDPProductId}/branches/{info.CDPBranchId}/tree/.json");
 
                 var tree = (await got.Content.ReadAsStringAsync()).FromJsonString<CDPTree>();
-                
+
                 got.Dispose();
                 got = await client.PostAsync($"https://api.bethesda.net/mods/ugc-content/add-subscription", new StringContent($"{{\"content_id\": \"{ContentId}\"}}", Encoding.UTF8, "application/json"));
 
@@ -255,14 +262,14 @@ namespace Wabbajack.Lib.Downloaders
                     $"https://api.bethesda.net/cdp-user/projects/{info.CDPProductId}/branches/{info.CDPBranchId}/depots/.json");
 
                 var props_obj = JObject.Parse(await got.Content.ReadAsStringAsync()).Properties().First();
-                info.CDPPropertiesId = (int)props_obj.Value["properties_id"];
+                info.CDPPropertiesId = (int)props_obj.Value["properties_id"]!;
-                
+
                 info.AESKey = props_obj.Value["ex_info_A"].Select(e => (byte)e).ToArray();
                 info.AESIV = props_obj.Value["ex_info_B"].Select(e => (byte)e).Take(16).ToArray();
 
                 return (client, tree, info);
             }
-            
+
             static int AESCTRDecrypt(byte[] Key, byte[] IV, byte[] Data)
             {
                 IBufferedCipher cipher = CipherUtilities.GetCipher("AES/CTR/NoPadding");
@@ -283,27 +290,26 @@ namespace Wabbajack.Lib.Downloaders
 
             public override string[] GetMetaIni()
             {
-                return new[] {"[General]", $"directURL=https://bethesda.net/en/mods/{GameName}/mod-detail/{ContentId}"};
+                return new[] { "[General]", $"directURL=https://bethesda.net/en/mods/{GameName}/mod-detail/{ContentId}" };
             }
 
 
             private class BeamLoginResponse
             {
-                public string access_token { get; set; }
+                public string access_token { get; set; } = string.Empty;
-
             }
 
             private class CDPLoginResponse
             {
-                public string token { get; set; }
+                public string token { get; set; } = string.Empty;
             }
 
             private class CollectedBNetInfo
             {
-                public byte[] AESKey { get; set; }
+                public byte[] AESKey { get; set; } = null!;
-                public byte[] AESIV { get; set; }
+                public byte[] AESIV { get; set; } = null!;
-                public string AccessToken { get; set; }
+                public string AccessToken { get; set; } = string.Empty;
-                public string CDPToken { get; set; }
+                public string CDPToken { get; set; } = string.Empty;
                 public int CDPBranchId { get; set; }
                 public int CDPProductId { get; set; }
                 public int CDPPropertiesId { get; set; }
@@ -311,24 +317,24 @@ namespace Wabbajack.Lib.Downloaders
 
             public class CDPTree
             {
-                public List<Depot> depot_list { get; set; }
+                public List<Depot> depot_list { get; set; } = null!;
 
                 public class Depot
                 {
-                    public List<CDPFile> file_list { get; set; }
+                    public List<CDPFile> file_list { get; set; } = null!;
 
                     public class CDPFile
                     {
                         public int chunk_count { get; set; }
-                        public List<Chunk> chunk_list { get; set; }
+                        public List<Chunk> chunk_list { get; set; } = null!;
 
-                        public string name { get; set; }
+                        public string? name { get; set; }
 
                         public class Chunk
                         {
                             public int chunk_size { get; set; }
                             public int index { get; set; }
-                            public string sha { get; set; }
+                            public string sha { get; set; } = string.Empty;
                             public int uncompressed_size { get; set; }
                         }
                     }
@@ -345,7 +351,7 @@ namespace Wabbajack.Lib.Downloaders
     public class RequestBethesdaNetLogin : AUserIntervention
     {
         public override string ShortDescription => "Logging into Bethesda.NET";
-        public override string ExtendedDescription { get; }
+        public override string ExtendedDescription { get; } = string.Empty;
 
         private readonly TaskCompletionSource<BethesdaNetData> _source = new TaskCompletionSource<BethesdaNetData>();
         public Task<BethesdaNetData> Task => _source.Task;
@@ -367,8 +373,7 @@ namespace Wabbajack.Lib.Downloaders
     [JsonName("BethesdaNetData")]
     public class BethesdaNetData
     {
-        public string body { get; set; }
+        public string body { get; set; } = string.Empty;
         public Dictionary<string, string> headers = new Dictionary<string, string>();
     }
-
 }

Wabbajack.Lib/Downloaders/DownloadDispatcher.cs

@@ -43,7 +43,7 @@ namespace Wabbajack.Lib.Downloaders
             IndexedDownloaders = Downloaders.ToDictionary(d => d.GetType());
         }
 
-        public static async Task<AbstractDownloadState> Infer(Uri uri)
+        public static async Task<AbstractDownloadState?> Infer(Uri uri)
         {
             foreach (var inf in Inferencers)
             {
@@ -73,7 +73,7 @@ namespace Wabbajack.Lib.Downloaders
         /// </summary>
         /// <param name="ini"></param>
         /// <returns></returns>
-        public static AbstractDownloadState ResolveArchive(string url)
+        public static AbstractDownloadState? ResolveArchive(string url)
         {
             return Downloaders.OfType<IUrlDownloader>().Select(d => d.GetDownloaderState(url)).FirstOrDefault(result => result != null);
         }
@@ -111,13 +111,9 @@ namespace Wabbajack.Lib.Downloaders
             var patchName = $"{archive.Hash.ToHex()}_{upgrade.Hash.ToHex()}";
             var patchPath = destination.Parent.Combine("_Patch_" + patchName);
 
-            var patchState = new Archive
+            var patchState = new Archive(new HTTPDownloader.State($"https://wabbajackcdn.b-cdn.net/updates/{patchName}"))
             {
                 Name = patchName,
-                State = new HTTPDownloader.State
-                {
-                    Url = $"https://wabbajackcdn.b-cdn.net/updates/{patchName}"
-                }
             };
 
             var patchResult = await Download(patchState, patchPath);

Wabbajack.Lib/Downloaders/DownloaderUtils.cs

@@ -4,7 +4,7 @@ namespace Wabbajack.Lib.Downloaders
 {
     public static class DownloaderUtils
     {
-        public static Uri GetDirectURL(dynamic meta)
+        public static Uri? GetDirectURL(dynamic? meta)
         {
             var url = meta?.General?.directURL;
             if (url == null) return null;

Wabbajack.Lib/Downloaders/DropboxDownloader.cs

@@ -7,13 +7,13 @@ namespace Wabbajack.Lib.Downloaders
 {
     public class DropboxDownloader : IDownloader, IUrlDownloader
     {
-        public async Task<AbstractDownloadState> GetDownloaderState(dynamic archiveINI, bool quickMode)
+        public async Task<AbstractDownloadState?> GetDownloaderState(dynamic archiveINI, bool quickMode)
         {
             var urlstring = archiveINI?.General?.directURL;
             return GetDownloaderState(urlstring);
         }
 
-        public AbstractDownloadState GetDownloaderState(string url)
+        public AbstractDownloadState? GetDownloaderState(string url)
         {
             try
             {
@@ -29,10 +29,7 @@ namespace Wabbajack.Lib.Downloaders
 
                 uri.Query = query.ToString();
 
-                return new HTTPDownloader.State()
+                return new HTTPDownloader.State(uri.ToString().Replace("dropbox.com:443/", "dropbox.com/"));
-                {
-                    Url = uri.ToString().Replace("dropbox.com:443/", "dropbox.com/")
-                };
             }
             catch (Exception)
             {

Wabbajack.Lib/Downloaders/GameFileSourceDownloader.cs

@@ -9,33 +9,30 @@ namespace Wabbajack.Lib.Downloaders
 {
     public class GameFileSourceDownloader : IDownloader
     {
-        public async Task<AbstractDownloadState> GetDownloaderState(dynamic archiveINI, bool quickMode)
+        public async Task<AbstractDownloadState?> GetDownloaderState(dynamic archiveINI, bool quickMode)
         {
-            var gameName = (string)archiveINI?.General?.gameName;
+            var gameName = (string?)archiveINI?.General?.gameName;
-            var gameFile = (string)archiveINI?.General?.gameFile;
+            var gameFile = (string?)archiveINI?.General?.gameFile;
 
-            if (gameFile == null || gameFile == null)
+            if (gameName == null || gameFile == null)
                 return null;
 
-            var game = GameRegistry.GetByFuzzyName(gameName);
+            if (!GameRegistry.TryGetByFuzzyName(gameName, out var game)) return null;
-            if (game == null) return null;
 
-            var path = game.GameLocation();
+            var path = game.TryGetGameLocation();
             var filePath = path?.Combine(gameFile);
             
-            
+            if (!(filePath?.Exists ?? false))
-            if (!filePath?.Exists ?? false)
                 return null;
 
             var fp = filePath.Value;
             var hash = await fp.FileHashCachedAsync();
 
-            return new State
+            return new State(game.InstalledVersion)
             {
                 Game = game.Game, 
                 GameFile = (RelativePath)gameFile,
-                Hash = hash,
+                Hash = hash
-                GameVersion = game.InstalledVersion
             };
         }
 
@@ -49,10 +46,15 @@ namespace Wabbajack.Lib.Downloaders
             public Game Game { get; set; }
             public RelativePath GameFile { get; set; }
             public Hash Hash { get; set; }
-            public string GameVersion { get; set; }
+            public string GameVersion { get; }
+
+            public State(string gameVersion)
+            {
+                GameVersion = gameVersion;
+            }
 
             [JsonIgnore]
-            internal AbsolutePath SourcePath => Game.MetaData().GameLocation().Value.Combine(GameFile);
+            internal AbsolutePath SourcePath => Game.MetaData().GameLocation().Combine(GameFile);
 
             [JsonIgnore]
             public override object[] PrimaryKey { get => new object[] {Game, GameVersion, GameFile}; }
@@ -82,7 +84,7 @@ namespace Wabbajack.Lib.Downloaders
                 return DownloadDispatcher.GetInstance<GameFileSourceDownloader>();
             }
 
-            public override string GetManifestURL(Archive a)
+            public override string? GetManifestURL(Archive a)
             {
                 return null;
             }

Wabbajack.Lib/Downloaders/GoogleDriveDownloader.cs

@@ -10,22 +10,19 @@ namespace Wabbajack.Lib.Downloaders
 {
     public class GoogleDriveDownloader : IDownloader, IUrlDownloader
     {
-        public async Task<AbstractDownloadState> GetDownloaderState(dynamic archiveINI, bool quickMode)
+        public async Task<AbstractDownloadState?> GetDownloaderState(dynamic archiveINI, bool quickMode)
         {
             var url = archiveINI?.General?.directURL;
             return GetDownloaderState(url);
         }
 
-        public AbstractDownloadState GetDownloaderState(string url)
+        public AbstractDownloadState? GetDownloaderState(string url)
         {
             if (url != null && url.StartsWith("https://drive.google.com"))
             {
                 var regex = new Regex("((?<=id=)[a-zA-Z0-9_-]*)|(?<=\\/file\\/d\\/)[a-zA-Z0-9_-]*");
                 var match = regex.Match(url);
-                return new State
+                return new State(match.ToString());
-                {
-                    Id = match.ToString()
-                };
             }
 
             return null;
@@ -38,10 +35,15 @@ namespace Wabbajack.Lib.Downloaders
         [JsonName("GoogleDriveDownloader")]
         public class State : AbstractDownloadState
         {
-            public string Id { get; set; }
+            public string Id { get; }
             
             [JsonIgnore]
-            public override object[] PrimaryKey { get => new object[] {Id}; }
+            public override object[] PrimaryKey => new object[] { Id };
+
+            public State(string id)
+            {
+                Id = id;
+            }
 
             public override bool IsWhitelisted(ServerWhitelist whitelist)
             {
@@ -64,7 +66,7 @@ namespace Wabbajack.Lib.Downloaders
                 var regex = new Regex("(?<=/uc\\?export=download&amp;confirm=).*(?=;id=)");
                 var confirm = regex.Match(await response.Content.ReadAsStringAsync());
                 var url = $"https://drive.google.com/uc?export=download&confirm={confirm}&id={Id}";
-                var httpState = new HTTPDownloader.State {Url = url, Client = client};
+                var httpState = new HTTPDownloader.State(url) { Client = client };
                 return httpState;
             }
 

Wabbajack.Lib/Downloaders/HTTPDownloader.cs

@@ -15,29 +15,24 @@ namespace Wabbajack.Lib.Downloaders
 {
     public class HTTPDownloader : IDownloader, IUrlDownloader
     {
-
+        public async Task<AbstractDownloadState?> GetDownloaderState(dynamic archiveINI, bool quickMode)
-        public async Task<AbstractDownloadState> GetDownloaderState(dynamic archiveINI, bool quickMode)
         {
             var url = archiveINI?.General?.directURL;
             return GetDownloaderState(url, archiveINI);
         }
 
-        public AbstractDownloadState GetDownloaderState(string uri)
+        public AbstractDownloadState? GetDownloaderState(string uri)
         {
             return GetDownloaderState(uri, null);
         }
 
-        public AbstractDownloadState GetDownloaderState(string url, dynamic archiveINI)
+        public AbstractDownloadState? GetDownloaderState(string url, dynamic? archiveINI)
         {
             if (url != null)
             {
-                var tmp = new State
+                var tmp = new State(url);
-                {
-                    Url = url
-                };
                 if (archiveINI?.General?.directURLHeaders != null)
                 {
-                    tmp.Headers = new List<string>();
                     tmp.Headers.AddRange(archiveINI?.General.directURLHeaders.Split('|'));
                 }
                 return tmp;
@@ -53,15 +48,20 @@ namespace Wabbajack.Lib.Downloaders
         [JsonName("HttpDownloader")]
         public class State : AbstractDownloadState
         {
-            public string Url { get; set; }
+            public string Url { get; }
 
-            public List<string> Headers { get; set; }
+            public List<string> Headers { get; } = new List<string>();
 
             [JsonIgnore]
-            public Common.Http.Client Client { get; set; }
+            public Common.Http.Client? Client { get; set; }
 
             [JsonIgnore]
-            public override object[] PrimaryKey { get => new object[] {Url};}
+            public override object[] PrimaryKey => new object[] { Url };
+
+            public State(string url)
+            {
+                Url = url;
+            }
 
             public override bool IsWhitelisted(ServerWhitelist whitelist)
             {
@@ -85,19 +85,18 @@ namespace Wabbajack.Lib.Downloaders
                     var client = Client ?? new Common.Http.Client();
                     client.Headers.Add(("User-Agent", Consts.UserAgent));
 
-                    if (Headers != null)
+                    foreach (var header in Headers)
-                        foreach (var header in Headers)
+                    {
-                        {
+                        var idx = header.IndexOf(':');
-                            var idx = header.IndexOf(':');
+                        var k = header.Substring(0, idx);
-                            var k = header.Substring(0, idx);
+                        var v = header.Substring(idx + 1);
-                            var v = header.Substring(idx + 1);
+                        client.Headers.Add((k, v));
-                            client.Headers.Add((k, v));
+                    }
-                        }
 
                     long totalRead = 0;
                     var bufferSize = 1024 * 32;
 
-                    Utils.Status($"Starting Download {a?.Name ?? Url}", Percent.Zero);
+                    Utils.Status($"Starting Download {a.Name ?? Url}", Percent.Zero);
                     var response = await client.GetAsync(Url);
 TOP:
 
@@ -177,7 +176,7 @@ TOP:
                             if (read == 0) break;
                             Utils.Status($"Downloading {a.Name}", Percent.FactoryPutInRange(totalRead, contentSize));
 
-                            fs.Write(buffer, 0, read);
+                            fs!.Write(buffer, 0, read);
                             totalRead += read;
                         }
                     }
@@ -203,7 +202,7 @@ TOP:
 
             public override string[] GetMetaIni()
             {
-                if (Headers != null)
+                if (Headers.Count > 0)
                     return new [] {"[General]",
                           $"directURL={Url}",
                           $"directURLHeaders={string.Join("|", Headers)}"};

Wabbajack.Lib/Downloaders/IDownloader.cs

@@ -4,12 +4,11 @@ namespace Wabbajack.Lib.Downloaders
 {
     public interface IDownloader
     {
-        Task<AbstractDownloadState> GetDownloaderState(dynamic archiveINI, bool quickMode = false);
+        Task<AbstractDownloadState?> GetDownloaderState(dynamic archiveINI, bool quickMode = false);
         
         /// <summary>
         /// Called before any downloads are inacted by the installer;
         /// </summary>
         Task Prepare();
     }
-
 }

Wabbajack.Lib/Downloaders/INeedsLogin.cs

@@ -11,9 +11,9 @@ namespace Wabbajack.Lib.Downloaders
         ReactiveCommand<Unit, Unit> ClearLogin { get; }
         IObservable<bool> IsLoggedIn { get; }
         string SiteName { get; }
-        IObservable<string> MetaInfo { get; }
+        IObservable<string>? MetaInfo { get; }
         Uri SiteURL { get; }
-        Uri IconUri { get; }
+        Uri? IconUri { get; }
     }
 
     public struct LoginReturnMessage

Wabbajack.Lib/Downloaders/IUrlDownloader.cs

@@ -2,6 +2,6 @@
 {
     public interface IUrlDownloader : IDownloader
     {
-        AbstractDownloadState GetDownloaderState(string url);
+        AbstractDownloadState? GetDownloaderState(string url);
     }
 }

Wabbajack.Lib/Downloaders/MEGADownloader.cs

@@ -23,8 +23,6 @@ namespace Wabbajack.Lib.Downloaders
             try
             {
                 authInfos = MegaApiClient.GenerateAuthInfos(username, password.ToNormalString());
-                username = null;
-                password = null;
             }
             catch (ApiException e)
             {
@@ -72,16 +70,16 @@ namespace Wabbajack.Lib.Downloaders
                 IsLoggedIn.ObserveOnGuiThread());
         }
 
-        public async Task<AbstractDownloadState> GetDownloaderState(dynamic archiveINI, bool quickMode)
+        public async Task<AbstractDownloadState?> GetDownloaderState(dynamic archiveINI, bool quickMode)
         {
             var url = archiveINI?.General?.directURL;
             return GetDownloaderState(url);
         }
 
-        public AbstractDownloadState GetDownloaderState(string url)
+        public AbstractDownloadState? GetDownloaderState(string url)
         {
             if (url != null && url.StartsWith(Consts.MegaPrefix))
-                return new State { Url = url};
+                return new State(url);
             return null;
         }
 
@@ -92,6 +90,11 @@ namespace Wabbajack.Lib.Downloaders
         [JsonName("MegaDownloader")]
         public class State : HTTPDownloader.State
         {
+            public State(string url) 
+                : base(url)
+            {
+            }
+
             private static MegaApiClient MegaApiClient => DownloadDispatcher.GetInstance<MegaDownloader>().MegaApiClient;
 
             private void MegaLogin()

Wabbajack.Lib/Downloaders/ManualDownloader.cs

@@ -18,8 +18,8 @@ namespace Wabbajack.Lib.Downloaders
 
         class FileEvent
         {
-            public string FullPath { get; set; }
+            public string FullPath { get; set; } = string.Empty;
-            public string Name { get; set; }
+            public string Name { get; set; } = string.Empty;
             public long Size { get; set; }
         }
 
@@ -57,10 +57,10 @@ namespace Wabbajack.Lib.Downloaders
             }
         }
 
-        public async Task<AbstractDownloadState> GetDownloaderState(dynamic archiveINI, bool quickMode)
+        public async Task<AbstractDownloadState?> GetDownloaderState(dynamic archiveINI, bool quickMode)
         {
             var url = archiveINI?.General?.manualURL;
-            return url != null ? new State { Url = url} : null;
+            return url != null ? new State(url) : null;
         }
 
         public async Task Prepare()
@@ -70,10 +70,15 @@ namespace Wabbajack.Lib.Downloaders
         [JsonName("ManualDownloader")]
         public class State : AbstractDownloadState
         {
-            public string Url { get; set; }
+            public string Url { get; }
             
             [JsonIgnore]
-            public override object[] PrimaryKey { get => new object[] {Url}; }
+            public override object[] PrimaryKey => new object[] { Url };
+
+            public State(string url)
+            {
+                Url = url;
+            }
 
             public override bool IsWhitelisted(ServerWhitelist whitelist)
             {
@@ -83,7 +88,7 @@ namespace Wabbajack.Lib.Downloaders
             public override async Task<bool> Download(Archive a, AbsolutePath destination)
             {
                 var (uri, client) = await Utils.Log(await ManuallyDownloadFile.Create(this)).Task;
-                var state = new HTTPDownloader.State {Url = uri.ToString(), Client = client};
+                var state = new HTTPDownloader.State(uri.ToString()) { Client = client };
                 return await state.Download(a, destination);
             }
 
@@ -104,10 +109,10 @@ namespace Wabbajack.Lib.Downloaders
 
             public override string[] GetMetaIni()
             {
-                return new [] {
+                return new [] 
+                {
                     "[General]",
-                    $"manualURL={Url}"
+                    $"manualURL={Url}",
-                    
                 };
             }
         }

Wabbajack.Lib/Downloaders/MediaFireDownloader.cs

@@ -10,22 +10,24 @@ namespace Wabbajack.Lib.Downloaders
 {
     public class MediaFireDownloader : IUrlDownloader
     {
-        public async Task<AbstractDownloadState> GetDownloaderState(dynamic archiveINI, bool quickMode)
+        public async Task<AbstractDownloadState?> GetDownloaderState(dynamic archiveINI, bool quickMode)
         {
             Uri url = DownloaderUtils.GetDirectURL(archiveINI);
             if (url == null || url.Host != "www.mediafire.com") return null;
 
-            return new State
+            return new State(url.ToString());
-            {
-                Url = url.ToString()
-            };
         }
 
         public class State : AbstractDownloadState
         {
-            public string Url { get; set; }
+            public string Url { get; }
 
-            public override object[] PrimaryKey { get => new object[] {Url};}
+            public override object[] PrimaryKey => new object[] { Url };
+
+            public State(string url)
+            {
+                Url = url;
+            }
 
             public override bool IsWhitelisted(ServerWhitelist whitelist)
             {
@@ -35,6 +37,7 @@ namespace Wabbajack.Lib.Downloaders
             public override async Task<bool> Download(Archive a, AbsolutePath destination)
             {
                 var result = await Resolve();
+                if (result == null) return false;
                 return await result.Download(a, destination);
             }
 
@@ -43,7 +46,7 @@ namespace Wabbajack.Lib.Downloaders
                 return await Resolve() != null;
             }
 
-            private async Task<HTTPDownloader.State> Resolve()
+            private async Task<HTTPDownloader.State?> Resolve()
             {
                 using (var d = await Driver.Create())
                 {
@@ -52,10 +55,9 @@ namespace Wabbajack.Lib.Downloaders
                     await Task.Delay(1000);
                     var newURL = await d.GetAttr("a.input", "href");
                     if (newURL == null || !newURL.StartsWith("http")) return null;
-                    return new HTTPDownloader.State()
+                    return new HTTPDownloader.State(newURL)
                     {
                         Client = new Common.Http.Client(),
-                        Url = newURL
                     };
                 }
             }
@@ -84,15 +86,12 @@ namespace Wabbajack.Lib.Downloaders
         {
         }
 
-        public AbstractDownloadState GetDownloaderState(string u)
+        public AbstractDownloadState? GetDownloaderState(string u)
         {
             var url = new Uri(u);
             if (url.Host != "www.mediafire.com") return null;
 
-            return new State
+            return new State(url.ToString());
-            {
-                Url = url.ToString()
-            };
         }
     }
 }

Wabbajack.Lib/Downloaders/ModDBDownloader.cs

@@ -11,20 +11,17 @@ namespace Wabbajack.Lib.Downloaders
 {
     public class ModDBDownloader : IDownloader, IUrlDownloader
     {
-        public async Task<AbstractDownloadState> GetDownloaderState(dynamic archiveINI, bool quickMode)
+        public async Task<AbstractDownloadState?> GetDownloaderState(dynamic archiveINI, bool quickMode)
         {
             var url = archiveINI?.General?.directURL;
             return GetDownloaderState(url);
         }
 
-        public AbstractDownloadState GetDownloaderState(string url)
+        public AbstractDownloadState? GetDownloaderState(string url)
         {
             if (url != null && url.StartsWith("https://www.moddb.com/downloads/start"))
             {
-                return new State
+                return new State(url);
-                {
-                    Url = url
-                };
             }
 
             return null;
@@ -37,10 +34,15 @@ namespace Wabbajack.Lib.Downloaders
         [JsonName("ModDBDownloader")]
         public class State : AbstractDownloadState
         {
-            public string Url { get; set; }
+            public string Url { get; }
             
             [JsonIgnore]
-            public override object[] PrimaryKey { get => new object[]{Url}; }
+            public override object[] PrimaryKey => new object[] { Url };
+
+            public State(string url)
+            {
+                Url = url;
+            }
 
             public override bool IsWhitelisted(ServerWhitelist whitelist)
             {
@@ -56,7 +58,7 @@ namespace Wabbajack.Lib.Downloaders
                 {
                     try
                     {
-                        await new HTTPDownloader.State {Url = url}.Download(a, destination);
+                        await new HTTPDownloader.State(url).Download(a, destination);
                         return true;
                     }
                     catch (Exception)

Wabbajack.Lib/Downloaders/NexusDownloader.cs

@@ -19,8 +19,8 @@ namespace Wabbajack.Lib.Downloaders
     {
         private bool _prepared;
         private AsyncLock _lock = new AsyncLock();
-        private UserStatus _status;
+        private UserStatus? _status;
-        private NexusApiClient _client;
+        private NexusApiClient? _client;
 
         public IObservable<bool> IsLoggedIn => Utils.HaveEncryptedJsonObservable("nexusapikey");
 
@@ -50,9 +50,9 @@ namespace Wabbajack.Lib.Downloaders
                 canExecute: IsLoggedIn.ObserveOnGuiThread());
         }
 
-        public async Task<AbstractDownloadState> GetDownloaderState(dynamic archiveINI, bool quickMode)
+        public async Task<AbstractDownloadState?> GetDownloaderState(dynamic archiveINI, bool quickMode)
         {
-            var general = archiveINI?.General;
+            var general = archiveINI.General;
 
             if (general.modID != null && general.fileID != null && general.gameName != null)
             {
@@ -135,17 +135,17 @@ namespace Wabbajack.Lib.Downloaders
             [JsonIgnore]
             public Uri URL => new Uri($"http://nexusmods.com/{Game.MetaData().NexusName}/mods/{ModID}");
 
-            public string Name { get; set; }
+            public string? Name { get; set; }
 
-            public string Author { get; set; }
+            public string? Author { get; set; }
 
-            public string Version { get; set; }
+            public string? Version { get; set; }
             
-            public string ImageURL { get; set; }
+            public string? ImageURL { get; set; }
             
             public bool IsNSFW { get; set; }
 
-            public string Description { get; set; }
+            public string? Description { get; set; }
 
             [JsonProperty("GameName")]
             [JsonConverter(typeof(Utils.GameConverter))]
@@ -184,10 +184,7 @@ namespace Wabbajack.Lib.Downloaders
 
                 Utils.Log($"Downloading Nexus Archive - {a.Name} - {Game} - {ModID} - {FileID}");
 
-                return await new HTTPDownloader.State
+                return await new HTTPDownloader.State(url).Download(a, destination);
-                {
-                    Url = url
-                }.Download(a, destination);
             }
 
             public override async Task<bool> Verify(Archive a)

Wabbajack.Lib/Downloaders/SteamWorkshopDownloader.cs

@@ -14,20 +14,21 @@ namespace Wabbajack.Lib.Downloaders
 {
     public class SteamWorkshopDownloader : IUrlDownloader
     {
-        private SteamWorkshopItem _item;
+        public async Task<AbstractDownloadState?> GetDownloaderState(dynamic archiveINI, bool quickMode)
-
-        public async Task<AbstractDownloadState> GetDownloaderState(dynamic archiveINI, bool quickMode)
         {
             var id = archiveINI?.General?.itemID;
             var steamID = archiveINI?.General?.steamID;
             var size = archiveINI?.General?.itemSize;
-            _item = new SteamWorkshopItem
+            if (steamID == null)
+            {
+                throw new ArgumentException("Steam workshop item had no steam ID.");
+            }
+            var item = new SteamWorkshopItem(GameRegistry.GetBySteamID(int.Parse(steamID)))
             {
                 ItemID = id != null ? int.Parse(id) : 0,
                 Size = size != null ? int.Parse(size) : 0,
-                Game = steamID != null ? GameRegistry.GetBySteamID(int.Parse(steamID)) : null
             };
-            return new State {Item = _item};
+            return new State(item);
         }
 
         public async Task Prepare()
@@ -41,8 +42,14 @@ namespace Wabbajack.Lib.Downloaders
 
         public class State : AbstractDownloadState
         {
-            public SteamWorkshopItem Item { get; set; }
+            public SteamWorkshopItem Item { get; }
-            public override object[] PrimaryKey { get => new object[] {Item.Game, Item.ItemID}; }
+
+            public override object[] PrimaryKey => new object[] { Item.Game, Item.ItemID };
+
+            public State(SteamWorkshopItem item)
+            {
+                Item = item;
+            }
 
             public override bool IsWhitelisted(ServerWhitelist whitelist)
             {

Wabbajack.Lib/Downloaders/UrlDownloaders/BethesdaNetInferencer.cs

@@ -5,7 +5,7 @@ namespace Wabbajack.Lib.Downloaders.UrlDownloaders
 {
     public class BethesdaNetInferencer : IUrlInferencer
     {
-        public async Task<AbstractDownloadState> Infer(Uri uri)
+        public async Task<AbstractDownloadState?> Infer(Uri uri)
         {
             return BethesdaNetDownloader.StateFromUrl(uri);
         }

Wabbajack.Lib/Downloaders/UrlDownloaders/IUrlInferencer.cs

@@ -5,6 +5,6 @@ namespace Wabbajack.Lib.Downloaders.UrlDownloaders
 {
     public interface IUrlInferencer
     {
-        Task<AbstractDownloadState> Infer(Uri uri);
+        Task<AbstractDownloadState?> Infer(Uri uri);
     }
 }

Wabbajack.Lib/Downloaders/UrlDownloaders/YoutubeInferencer.cs

@@ -8,10 +8,9 @@ namespace Wabbajack.Lib.Downloaders.UrlDownloaders
 {
     public class YoutubeInferencer : IUrlInferencer
     {
-        
+        public async Task<AbstractDownloadState?> Infer(Uri uri)
-        public async Task<AbstractDownloadState> Infer(Uri uri)
         {
-            var state = (YouTubeDownloader.State)YouTubeDownloader.UriToState(uri);
+            var state = YouTubeDownloader.UriToState(uri) as YouTubeDownloader.State;
             if (state == null) return null;
             
             var client = new YoutubeClient(Common.Http.ClientFactory.Client);
@@ -24,13 +23,13 @@ namespace Wabbajack.Lib.Downloaders.UrlDownloaders
                 .Select(line =>
                 {
                     var segments = line.Split(' ', StringSplitOptions.RemoveEmptyEntries);
-                    if (segments.Length == 0) return (TimeSpan.Zero, null);
+                    if (segments.Length == 0) return (TimeSpan.Zero, string.Empty);
                     
                     if (TryParseEx(segments.First(), out var s1))
                         return (s1, string.Join(" ", segments.Skip(1)));
                     if (TryParseEx(Enumerable.Last(segments), out var s2))
                         return (s2, string.Join(" ", Utils.ButLast(segments)));
-                    return (TimeSpan.Zero, null);
+                    return (TimeSpan.Zero, string.Empty);
                 })
                 .Where(t => t.Item2 != null)
                 .ToList();

Wabbajack.Lib/Downloaders/YouTubeDownloader.cs

@@ -21,10 +21,10 @@ namespace Wabbajack.Lib.Downloaders
 {
     public class YouTubeDownloader : IDownloader
     {
-        public async Task<AbstractDownloadState> GetDownloaderState(dynamic archiveINI, bool quickMode)
+        public async Task<AbstractDownloadState?> GetDownloaderState(dynamic archiveINI, bool quickMode)
         {
             var directURL = (Uri)DownloaderUtils.GetDirectURL(archiveINI);
-            var state = (State)UriToState(directURL);
+            var state = UriToState(directURL) as State;
             if (state == null) return state;
 
             var idx = 0;
@@ -45,7 +45,7 @@ namespace Wabbajack.Lib.Downloaders
             return state;
         }
 
-        internal static AbstractDownloadState UriToState(Uri directURL)
+        internal static AbstractDownloadState? UriToState(Uri directURL)
         {
             if (directURL == null || !directURL.Host.EndsWith("youtube.com"))
             {
@@ -53,7 +53,7 @@ namespace Wabbajack.Lib.Downloaders
             }
 
             var key = HttpUtility.ParseQueryString(directURL.Query)["v"];
-            return key != null ? new State {Key = key} : null;
+            return key != null ? new State(key) : null;
         }
 
         public async Task Prepare()
@@ -63,13 +63,18 @@ namespace Wabbajack.Lib.Downloaders
         [JsonName("YouTubeDownloader")]
         public class State : AbstractDownloadState
         {
-            public string Key { get; set; }
+            public string Key { get; }
             
             public List<Track> Tracks { get; set; } = new List<Track>();
             
             [JsonIgnore]
             public override object[] PrimaryKey => new object[] {Key};
 
+            public State(string key)
+            {
+                Key = key;
+            }
+
             [JsonName("YouTubeTrack")]
             public class Track
             {
@@ -79,8 +84,8 @@ namespace Wabbajack.Lib.Downloaders
                     WAV
                 }
                 public FormatEnum Format { get; set; }
-                
+
-                public string Name { get; set; }
+                public string Name { get; set; } = string.Empty;
                 
                 public TimeSpan Start { get; set; }
                 

Wabbajack.Lib/Exceptions/HttpException.cs

@@ -12,6 +12,5 @@ namespace Wabbajack.Lib.Exceptions
             Code = code;
             Reason = reason;
         }
-
     }
 }

Wabbajack.Lib/FileUploader/AuthorAPI.cs

@@ -21,9 +21,9 @@ namespace Wabbajack.Lib.FileUploader
     {
         public static IObservable<bool> HaveAuthorAPIKey => Utils.HaveEncryptedJsonObservable(Consts.AuthorAPIKeyFile);
 
-        public static string ApiKeyOverride = null;
+        public static string? ApiKeyOverride = null;
 
-        public static async Task<string> GetAPIKey(string apiKey = null)
+        public static async Task<string> GetAPIKey(string? apiKey = null)
         {
             if (ApiKeyOverride != null) return ApiKeyOverride;
             return apiKey ?? (await Consts.LocalAppDataPath.Combine(Consts.AuthorAPIKeyFile).ReadAllTextAsync()).Trim();
@@ -32,7 +32,7 @@ namespace Wabbajack.Lib.FileUploader
         public static Uri UploadURL => new Uri($"{Consts.WabbajackBuildServerUri}upload_file");
         public static long BLOCK_SIZE = (long)1024 * 1024 * 2;
         public static int MAX_CONNECTIONS = 8;
-        public static Task<string> UploadFile(AbsolutePath filename, Action<double> progressFn, string apikey=null)
+        public static Task<string> UploadFile(AbsolutePath filename, Action<double> progressFn, string? apikey = null)
         {
             var tcs = new TaskCompletionSource<string>();
             Task.Run(async () =>
@@ -123,7 +123,7 @@ namespace Wabbajack.Lib.FileUploader
             return tcs.Task;
         }
 
-        public static async Task<Common.Http.Client> GetAuthorizedClient(string apiKey=null)
+        public static async Task<Common.Http.Client> GetAuthorizedClient(string? apiKey = null)
         {
             var client = new Common.Http.Client();
             client.Headers.Add(("X-API-KEY", await GetAPIKey(apiKey)));

Wabbajack.Lib/LibCefHelpers/Init.cs

@@ -78,10 +78,10 @@ namespace Wabbajack.Lib.LibCefHelpers
         [JsonName("HttpCookie")]
         public class Cookie
         {
-            public string Name { get; set; }
+            public string Name { get; set; } = string.Empty;
-            public string Value { get; set; }
+            public string Value { get; set; } = string.Empty;
-            public string Domain { get; set; }
+            public string Domain { get; set; } = string.Empty;
-            public string Path { get; set; }
+            public string Path { get; set; } = string.Empty;
         }
 
         public static void Init()

Wabbajack.Lib/MO2Compiler.cs

@@ -25,7 +25,6 @@ namespace Wabbajack.Lib
 {
     public class MO2Compiler : ACompiler
     {
-
         private AbsolutePath _mo2DownloadsFolder;
         
         public AbsolutePath MO2Folder;
@@ -38,7 +37,7 @@ namespace Wabbajack.Lib
 
         public override AbsolutePath GamePath { get; }
 
-        public GameMetaData CompilingGame { get; set; }
+        public GameMetaData CompilingGame { get; }
 
         public override AbsolutePath ModListOutputFolder => ((RelativePath)"output_folder").RelativeToEntryPoint();
 
@@ -48,7 +47,19 @@ namespace Wabbajack.Lib
             Consts.LocalAppDataPath.Combine( 
             $"vfs_compile_cache-{Path.Combine((string)MO2Folder ?? "Unknown", "ModOrganizer.exe").StringSha256Hex()}.bin");
 
+        public dynamic MO2Ini { get; }
+
+        public static AbsolutePath GetTypicalDownloadsFolder(AbsolutePath mo2Folder) => mo2Folder.Combine("downloads");
+
+        public AbsolutePath MO2ProfileDir => MO2Folder.Combine("profiles", MO2Profile);
+
+        public ConcurrentBag<Directive> ExtraFiles { get; private set; } = new ConcurrentBag<Directive>();
+        public Dictionary<AbsolutePath, dynamic> ModInis { get; } = new Dictionary<AbsolutePath, dynamic>();
+
+        public HashSet<string> SelectedProfiles { get; set; } = new HashSet<string>();
+
         public MO2Compiler(AbsolutePath mo2Folder, string mo2Profile, AbsolutePath outputFile)
+            : base(steps: 20)
         {
             MO2Folder = mo2Folder;
             MO2Profile = mo2Profile;
@@ -59,8 +70,6 @@ namespace Wabbajack.Lib
             ModListOutputFile = outputFile;
         }
 
-        public dynamic MO2Ini { get; }
-
         public AbsolutePath MO2DownloadsFolder
         {
             get
@@ -75,20 +84,10 @@ namespace Wabbajack.Lib
             set => _mo2DownloadsFolder = value;
         }
 
-        public static AbsolutePath GetTypicalDownloadsFolder(AbsolutePath mo2Folder) => mo2Folder.Combine("downloads");
-
-        public AbsolutePath MO2ProfileDir => MO2Folder.Combine("profiles", MO2Profile);
-
-        internal UserStatus User { get; private set; }
-        public ConcurrentBag<Directive> ExtraFiles { get; private set; }
-        public Dictionary<AbsolutePath, dynamic> ModInis { get; private set; }
-
-        public HashSet<string> SelectedProfiles { get; set; } = new HashSet<string>();
-
         protected override async Task<bool> _Begin(CancellationToken cancel)
         {
             if (cancel.IsCancellationRequested) return false;
-            ConfigureProcessor(20, ConstructDynamicNumThreads(await RecommendQueueSize()));
+            Queue.SetActiveThreadsObservable(ConstructDynamicNumThreads(await RecommendQueueSize()));
             UpdateTracker.Reset();
             UpdateTracker.NextStep("Gathering information");
             Info("Looking for other profiles");
@@ -126,6 +125,11 @@ namespace Wabbajack.Lib
             
             if (lootPath.Exists)
             {
+                if (CompilingGame.MO2Name == null)
+                {
+                    throw new ArgumentException("Compiling game had no MO2 name specified.");
+                }
+
                 var lootGameDirs = new []
                 {
                     CompilingGame.MO2Name, // most of the games use the MO2 name
@@ -170,9 +174,8 @@ namespace Wabbajack.Lib
 
             IndexedArchives = (await MO2DownloadsFolder.EnumerateFiles()
                 .Where(f => f.WithExtension(Consts.MetaFileExtension).Exists)
-                .PMap(Queue, async f => new IndexedArchive
+                .PMap(Queue, async f => new IndexedArchive(VFS.Index.ByRootPath[f])
                 {
-                    File = VFS.Index.ByRootPath[f],
                     Name = (string)f.FileName,
                     IniData = f.WithExtension(Consts.MetaFileExtension).LoadIniFile(),
                     Meta = await f.WithExtension(Consts.MetaFileExtension).ReadAllTextAsync()
@@ -216,10 +219,9 @@ namespace Wabbajack.Lib
                 .GroupBy(f => f.Hash)
                 .ToDictionary(f => f.Key, f => f.AsEnumerable());
 
-            AllFiles = mo2Files.Concat(gameFiles)
+            AllFiles.SetTo(mo2Files.Concat(gameFiles)
                 .Concat(lootFiles)
-                .DistinctBy(f => f.Path)
+                .DistinctBy(f => f.Path));
-                .ToList();
 
             Info($"Found {AllFiles.Count} files to build into mod list");
 
@@ -239,13 +241,10 @@ namespace Wabbajack.Lib
                 Error($"Found {dups.Count} duplicates, exiting");
             }
 
-            ExtraFiles = new ConcurrentBag<Directive>();
-
-
             if (cancel.IsCancellationRequested) return false;
             UpdateTracker.NextStep("Loading INIs");
 
-            ModInis = MO2Folder.Combine(Consts.MO2ModFolderName)
+            ModInis.SetTo(MO2Folder.Combine(Consts.MO2ModFolderName)
                 .EnumerateDirectories()
                 .Select(f =>
                 {
@@ -254,7 +253,7 @@ namespace Wabbajack.Lib
                     return metaPath.Exists ? (mod_name: f, metaPath.LoadIniFile()) : default;
                 })
                 .Where(f => f.Item1 != default)
-                .ToDictionary(f => f.Item1, f => f.Item2);
+                .Select(f => new KeyValuePair<AbsolutePath, dynamic>(f.Item1, f.Item2)));
 
             if (cancel.IsCancellationRequested) return false;
             var stack = MakeStack();
@@ -270,7 +269,7 @@ namespace Wabbajack.Lib
             PrintNoMatches(noMatch);
             if (CheckForNoMatchExit(noMatch)) return false;
 
-            InstallDirectives = results.Where(i => !(i is IgnoredDirectly)).ToList();
+            InstallDirectives.SetTo(results.Where(i => !(i is IgnoredDirectly)));
 
             Info("Getting Nexus api_key, please click authorize if a browser window appears");
 
@@ -337,7 +336,7 @@ namespace Wabbajack.Lib
                 {
                     return a;
                 }
-            })).Where(a => a != null).ToHashSet();
+            })).NotNull().ToHashSet();
 
             if (remove.Count == 0)
                 return;
@@ -389,7 +388,6 @@ namespace Wabbajack.Lib
             });
         }
 
-
         private async Task IncludeArchiveMetadata()
         {
             Utils.Log($"Including {SelectedArchives.Count} .meta files for downloads");
@@ -411,13 +409,12 @@ namespace Wabbajack.Lib
         /// </summary>
         private void ResetMembers()
         {
-            AllFiles = null;
+            AllFiles = new List<RawSourceFile>();
-            InstallDirectives = null;
+            InstallDirectives = new List<Directive>();
-            SelectedArchives = null;
+            SelectedArchives = new List<Archive>();
-            ExtraFiles = null;
+            ExtraFiles = new ConcurrentBag<Directive>();
         }
 
-
         /// <summary>
         ///     Fills in the Patch fields in files that require them
         /// </summary>
@@ -487,8 +484,7 @@ namespace Wabbajack.Lib
                 return returnStream;
             }
 
-            Error($"Couldn't load data for {to}");
+            throw new ArgumentException($"Couldn't load data for {to}");
-            return null;
         }
 
         public override IEnumerable<ICompilationStep> GetStack()
@@ -567,12 +563,5 @@ namespace Wabbajack.Lib
                 new DropAll(this)
             };
         }
-
-        public class IndexedFileMatch
-        {
-            public IndexedArchive Archive;
-            public IndexedArchiveEntry Entry;
-            public DateTime LastModified;
-        }
     }
 }

Wabbajack.Lib/MO2Installer.cs

@@ -32,14 +32,18 @@ namespace Wabbajack.Lib
 
         public AbsolutePath? GameFolder { get; set; }
 
+        public GameMetaData Game { get; }
+
         public MO2Installer(AbsolutePath archive, ModList modList, AbsolutePath outputFolder, AbsolutePath downloadFolder, SystemParameters parameters)
             : base(
                   archive: archive,
                   modList: modList,
                   outputFolder: outputFolder, 
                   downloadFolder: downloadFolder,
-                  parameters: parameters)
+                  parameters: parameters,
+                  steps: 20)
         {
+            Game = ModList.GameType.MetaData();
         }
 
         protected override async Task<bool> _Begin(CancellationToken cancel)
@@ -48,28 +52,27 @@ namespace Wabbajack.Lib
             var metric = Metrics.Send(Metrics.BeginInstall, ModList.Name);
             Utils.Log("Configuring Processor");
 
-            ConfigureProcessor(20, ConstructDynamicNumThreads(await RecommendQueueSize()));
+            Queue.SetActiveThreadsObservable(ConstructDynamicNumThreads(await RecommendQueueSize()));
-            var game = ModList.GameType.MetaData();
 
             if (GameFolder == null)
-                GameFolder = game.GameLocation();
+                GameFolder = Game.TryGetGameLocation();
 
             if (GameFolder == null)
             {
-                var otherGame = game.CommonlyConfusedWith.Where(g => g.MetaData().IsInstalled).Select(g => g.MetaData()).FirstOrDefault();
+                var otherGame = Game.CommonlyConfusedWith.Where(g => g.MetaData().IsInstalled).Select(g => g.MetaData()).FirstOrDefault();
                 if (otherGame != null)
                 {
                     await Utils.Log(new CriticalFailureIntervention(
-                            $"In order to do a proper install Wabbajack needs to know where your {game.HumanFriendlyGameName} folder resides. However this game doesn't seem to be installed, we did however find a installed " +
+                            $"In order to do a proper install Wabbajack needs to know where your {Game.HumanFriendlyGameName} folder resides. However this game doesn't seem to be installed, we did however find a installed " +
                             $"copy of {otherGame.HumanFriendlyGameName}, did you install the wrong game?",
-                            $"Could not locate {game.HumanFriendlyGameName}"))
+                            $"Could not locate {Game.HumanFriendlyGameName}"))
                         .Task;
                 }
                 else
                 {
                     await Utils.Log(new CriticalFailureIntervention(
-                            $"In order to do a proper install Wabbajack needs to know where your {game.HumanFriendlyGameName} folder resides. However this game doesn't seem to be installed",
+                            $"In order to do a proper install Wabbajack needs to know where your {Game.HumanFriendlyGameName} folder resides. However this game doesn't seem to be installed",
-                            $"Could not locate {game.HumanFriendlyGameName}"))
+                            $"Could not locate {Game.HumanFriendlyGameName}"))
                         .Task;
                 }
 
@@ -169,7 +172,6 @@ namespace Wabbajack.Lib
 
         private void CreateOutputMods()
         {
-            
             OutputFolder.Combine("profiles")
                 .EnumerateFiles(true)
                 .Where(f => f.FileName == Consts.SettingsIni)
@@ -235,7 +237,7 @@ namespace Wabbajack.Lib
             foreach (var esm in ModList.Directives.OfType<CleanedESM>().ToList())
             {
                 var filename = esm.To.FileName;
-                var gameFile = GameFolder.Value.Combine((RelativePath)"Data", filename);
+                var gameFile = GameFolder!.Value.Combine((RelativePath)"Data", filename);
                 Utils.Log($"Validating {filename}");
                 var hash = gameFile.FileHash();
                 if (hash != esm.SourceESMHash)
@@ -310,7 +312,7 @@ namespace Wabbajack.Lib
         private async Task GenerateCleanedESM(CleanedESM directive)
         {
             var filename = directive.To.FileName;
-            var gameFile = GameFolder.Value.Combine((RelativePath)"Data", filename);
+            var gameFile = GameFolder!.Value.Combine((RelativePath)"Data", filename);
             Info($"Generating cleaned ESM for {filename}");
             if (!gameFile.Exists) throw new InvalidDataException($"Missing {filename} at {gameFile}");
             Status($"Hashing game version of {filename}");
@@ -329,6 +331,10 @@ namespace Wabbajack.Lib
 
         private void SetScreenSizeInPrefs()
         {
+            if (SystemParameters == null)
+            {
+                throw new ArgumentNullException("System Parameters was null.  Cannot set screen size prefs");
+            }
             var config = new IniParserConfiguration {AllowDuplicateKeys = true, AllowDuplicateSections = true};
             foreach (var file in OutputFolder.Combine("profiles").EnumerateFiles()
                 .Where(f => ((string)f.FileName).EndsWith("refs.ini")))
@@ -375,8 +381,8 @@ namespace Wabbajack.Lib
         {
             var data = Encoding.UTF8.GetString(await LoadBytesFromPath(directive.SourceDataID));
 
-            data = data.Replace(Consts.GAME_PATH_MAGIC_BACK, (string)GameFolder);
+            data = data.Replace(Consts.GAME_PATH_MAGIC_BACK, (string)GameFolder!);
-            data = data.Replace(Consts.GAME_PATH_MAGIC_DOUBLE_BACK, ((string)GameFolder).Replace("\\", "\\\\"));
+            data = data.Replace(Consts.GAME_PATH_MAGIC_DOUBLE_BACK, ((string)GameFolder!).Replace("\\", "\\\\"));
             data = data.Replace(Consts.GAME_PATH_MAGIC_FORWARD, ((string)GameFolder).Replace("\\", "/"));
 
             data = data.Replace(Consts.MO2_PATH_MAGIC_BACK, (string)OutputFolder);

Wabbajack.Lib/Manifest.cs

@@ -41,12 +41,11 @@ namespace Wabbajack.Lib
             InstallSize = modlist.InstallSize;
 
             // meta is being omitted due to it being useless and not very space friendly
-            Archives = modlist.Archives.Select(a => new Archive
+            Archives = modlist.Archives.Select(a => new Archive(a.State)
             {
                 Hash = a.Hash,
                 Name = a.Name,
                 Size = a.Size,
-                State = a.State
             }).ToList();
         }
     }

Wabbajack.Lib/ModListRegistry/ModListMetadata.cs

@@ -13,13 +13,13 @@ namespace Wabbajack.Lib.ModListRegistry
     public class ModlistMetadata
     {
         [JsonProperty("title")]
-        public string Title { get; set; }
+        public string Title { get; set; } = string.Empty;
 
         [JsonProperty("description")]
-        public string Description { get; set; }
+        public string Description { get; set; } = string.Empty;
 
         [JsonProperty("author")]
-        public string Author { get; set; }
+        public string Author { get; set; } = string.Empty;
 
         [JsonProperty("game")]
         public Game Game { get; set; }
@@ -33,7 +33,7 @@ namespace Wabbajack.Lib.ModListRegistry
         public LinksObject Links { get; set; } = new LinksObject();
 
         [JsonProperty("download_metadata")]
-        public DownloadMetadata DownloadMetadata { get; set; }
+        public DownloadMetadata? DownloadMetadata { get; set; }
 
         [JsonIgnore] 
         public ModListSummary ValidationSummary { get; set; } = new ModListSummary();
@@ -42,22 +42,18 @@ namespace Wabbajack.Lib.ModListRegistry
         public class LinksObject
         {
             [JsonProperty("image")]
-            public string ImageUri { get; set; }
+            public string ImageUri { get; set; } = string.Empty;
 
             [JsonProperty("readme")]
-            public string Readme { get; set; }
+            public string Readme { get; set; } = string.Empty;
 
             [JsonProperty("download")]
-            public string Download { get; set; }
+            public string Download { get; set; } = string.Empty;
-            
+
             [JsonProperty("machineURL")]
-            public string MachineURL { get; set; }
+            public string MachineURL { get; set; } = string.Empty;
         }
 
-
-
-
-
         public static async Task<List<ModlistMetadata>> LoadFromGithub()
         {
             var client = new Common.Http.Client();
@@ -103,18 +99,17 @@ namespace Wabbajack.Lib.ModListRegistry
         public long SizeOfArchives { get; set; }
         public long NumberOfInstalledFiles { get; set; }
         public long SizeOfInstalledFiles { get; set; }
-
     }
 
     [JsonName("ModListSummary")]
     public class ModListSummary
     {
         [JsonProperty("name")]
-        public string Name { get; set; }
+        public string Name { get; set; } = string.Empty;
-        
+
         [JsonProperty("machineURL")]
-        public string MachineURL { get; set; }
+        public string MachineURL { get; set; } = string.Empty;
-        
+
         [JsonProperty("checked")]
         public DateTime Checked { get; set; }
         [JsonProperty("failed")]

Wabbajack.Lib/NexusApi/Dtos.cs

@@ -4,57 +4,57 @@ namespace Wabbajack.Lib.NexusApi
 {
     public class UserStatus
     {
-        public string email;
+        public string email = string.Empty;
         public bool is_premium;
         public bool is_supporter;
-        public string key;
+        public string key = string.Empty;
-        public string name;
+        public string name = string.Empty;
-        public string profile_url;
+        public string profile_url = string.Empty;
-        public string user_id;
+        public string user_id = string.Empty;
     }
 
     public class NexusFileInfo
     {
         public long category_id { get; set; }
-        public string category_name { get; set; }
+        public string category_name { get; set; } = string.Empty;
-        public string changelog_html { get; set; }
+        public string changelog_html { get; set; } = string.Empty;
-        public string description { get; set; }
+        public string description { get; set; } = string.Empty;
-        public string external_virus_scan_url { get; set; }
+        public string external_virus_scan_url { get; set; } = string.Empty;
         public long file_id { get; set; }
-        public string file_name { get; set; }
+        public string file_name { get; set; } = string.Empty;
         public bool is_primary { get; set; }
-        public string mod_version { get; set; }
+        public string mod_version { get; set; } = string.Empty;
-        public string name { get; set; }
+        public string name { get; set; } = string.Empty;
         public long size { get; set; }
         public long size_kb { get; set; }
         public DateTime uploaded_time { get; set; }
         public long uploaded_timestamp { get; set; }
-        public string version { get; set; }
+        public string version { get; set; } = string.Empty;
     }
 
     public class ModInfo
     {
         public uint _internal_version { get; set; }
-        public string game_name { get; set; }
+        public string game_name { get; set; } = string.Empty;
-        public string mod_id { get; set; }
+        public string mod_id { get; set; } = string.Empty;
-        public string name { get; set; }
+        public string name { get; set; } = string.Empty;
-        public string summary { get; set; }
+        public string summary { get; set; } = string.Empty;
-        public string author { get; set; }
+        public string author { get; set; } = string.Empty;
-        public string uploaded_by { get; set; }
+        public string uploaded_by { get; set; } = string.Empty;
-        public string uploaded_users_profile_url { get; set; }
+        public string uploaded_users_profile_url { get; set; } = string.Empty;
-        public string picture_url { get; set; }
+        public string picture_url { get; set; } = string.Empty;
         public bool contains_adult_content { get; set; }
     }
 
     public class MD5Response
     {
-        public ModInfo mod;
+        public ModInfo? mod;
-        public NexusFileInfo file_details;
+        public NexusFileInfo? file_details;
     }
 
     public class EndorsementResponse
     {
-        public string message;
+        public string message = string.Empty;
-        public string status;
+        public string status = string.Empty;
     }
 }

Wabbajack.Lib/NexusApi/NexusApi.cs

@@ -27,12 +27,11 @@ namespace Wabbajack.Lib.NexusApi
 
         #region Authentication
 
-        public string ApiKey { get; }
+        public string? ApiKey { get; }
 
         public bool IsAuthenticated => ApiKey != null;
 
-        private Task<UserStatus> _userStatus;
+        private Task<UserStatus>? _userStatus;
-
         public Task<UserStatus> UserStatus
         {
             get
@@ -214,7 +213,7 @@ namespace Wabbajack.Lib.NexusApi
 
         #endregion
 
-        private NexusApiClient(string apiKey = null)
+        private NexusApiClient(string? apiKey = null)
         {
             ApiKey = apiKey;
 
@@ -230,9 +229,9 @@ namespace Wabbajack.Lib.NexusApi
                 Directory.CreateDirectory(Consts.NexusCacheDirectory);
         }
 
-        public static async Task<NexusApiClient> Get(string apiKey = null)
+        public static async Task<NexusApiClient> Get(string? apiKey = null)
         {
-            apiKey = apiKey ?? await GetApiKey();
+            apiKey ??= await GetApiKey();
             return new NexusApiClient(apiKey);
         }
 
@@ -316,9 +315,10 @@ namespace Wabbajack.Lib.NexusApi
                 throw;
             }
         }
+
         public class GetModFilesResponse
         {
-            public List<NexusFileInfo> files { get; set; }
+            public List<NexusFileInfo> files { get; set; } = new List<NexusFileInfo>();
         }
 
         public async Task<GetModFilesResponse> GetModFiles(Game game, long modid, bool useCache = true)
@@ -350,18 +350,18 @@ namespace Wabbajack.Lib.NexusApi
 
         private class DownloadLink
         {
-            public string URI { get; set; }
+            public string URI { get; set; } = string.Empty;
         }
 
-        public static MethodInfo CacheMethod { get; set; }
+        private static string? _localCacheDir;
-
-        private static string _localCacheDir;
         public static string LocalCacheDir
         {
             get
             {
                 if (_localCacheDir == null)
                     _localCacheDir = Environment.GetEnvironmentVariable("NEXUSCACHEDIR");
+                if (_localCacheDir == null)
+                    throw new ArgumentNullException($"Enviornment variable could not be located: NEXUSCACHEDIR");
                 return _localCacheDir;
             }
             set => _localCacheDir = value;

Wabbajack.Lib/NexusApi/NexusApiUtils.cs

@@ -19,15 +19,10 @@ namespace Wabbajack.Lib.NexusApi
 
         public static string FixupSummary(string argSummary)
         {
-            if (argSummary != null)
+            return argSummary.Replace("'", "'")
-            {
+                             .Replace("<br/>", "\n\n")
-                return argSummary.Replace("&#39;", "'")
+                             .Replace("<br />", "\n\n")
-                                 .Replace("<br/>", "\n\n")
+                             .Replace("&#33;", "!");
-                                 .Replace("<br />", "\n\n")
-                                 .Replace("&#33;", "!");
-            }
-
-            return argSummary;
         }
     }
 }

Wabbajack.Lib/NexusApi/NexusUpdatesFeeds.cs

@@ -26,8 +26,7 @@ namespace Wabbajack.Lib.NexusApi
         {
             var parts = link.Uri.AbsolutePath.Split('/', StringSplitOptions.RemoveEmptyEntries);
 
-            var foundGame = GameRegistry.GetByFuzzyName(parts[0]);
+            if (!GameRegistry.TryGetByFuzzyName(parts[0], out var foundGame))
-            if (foundGame == null)
             {
                 game = Game.Oblivion;
                 modId = 0;
@@ -65,7 +64,8 @@ namespace Wabbajack.Lib.NexusApi
                     }
 
                     return null;
-                }).Where(v => v != null);
+                })
+                .NotNull();
         }
 
 

Wabbajack.Lib/NexusApi/RequestNexusAuthorization.cs

@@ -10,7 +10,7 @@ namespace Wabbajack.Lib.NexusApi
     public class RequestNexusAuthorization : AUserIntervention
     {
         public override string ShortDescription  => "Getting User's Nexus API Key";
-        public override string ExtendedDescription { get; }
+        public override string ExtendedDescription { get; } = string.Empty;
 
         private readonly TaskCompletionSource<string> _source = new TaskCompletionSource<string>();
         public Task<string> Task => _source.Task;

Wabbajack.Lib/StatusMessages/ConfirmUpdateOfExistingInstall.cs

@@ -10,7 +10,7 @@ namespace Wabbajack.Lib
     public class ConfirmUpdateOfExistingInstall : ConfirmationIntervention
     {
         public AbsolutePath OutputFolder { get; set; }
-        public string ModListName { get; set; }
+        public string ModListName { get; set; } = string.Empty;
 
         public override string ShortDescription { get; } = "Do you want to overwrite existing files?";
 

Wabbajack.Lib/StatusMessages/ManuallyDownloadFile.cs

@@ -9,9 +9,9 @@ namespace Wabbajack.Lib
     public class ManuallyDownloadFile : AUserIntervention
     {
         public ManualDownloader.State State { get; }
-        public override string ShortDescription { get; }
+        public override string ShortDescription { get; } = string.Empty;
-        public override string ExtendedDescription { get; }
+        public override string ExtendedDescription { get; } = string.Empty;
-        
+
         private TaskCompletionSource<(Uri, Common.Http.Client)> _tcs = new TaskCompletionSource<(Uri, Common.Http.Client)>();
         public Task<(Uri, Common.Http.Client)> Task => _tcs.Task;
 

Wabbajack.Lib/StatusMessages/ManuallyDownloadNexusFile.cs

@@ -9,9 +9,9 @@ namespace Wabbajack.Lib
     public class ManuallyDownloadNexusFile : AUserIntervention
     {
         public  NexusDownloader.State State { get; }
-        public override string ShortDescription { get; }
+        public override string ShortDescription { get; } = string.Empty;
-        public override string ExtendedDescription { get; }
+        public override string ExtendedDescription { get; } = string.Empty;
-        
+
         private TaskCompletionSource<Uri> _tcs = new TaskCompletionSource<Uri>();
         public Task<Uri> Task => _tcs.Task;
 

Wabbajack.Lib/SystemParameters.cs

@@ -14,9 +14,9 @@ namespace Wabbajack.Lib
         public int ScreenWidth { get; set; }
         public long VideoMemorySize { get; set; }
         public long SystemMemorySize { get; set; }
-        
+
-        public Version WindowsVersion { get; set; }
+        public Version WindowsVersion { get; set; } = Environment.OSVersion.Version;
-        
+
         /// <summary>
         /// Value used in LE ENBs for VideoMemorySizeMb
         /// </summary>

Wabbajack.Lib/Validation/DTOs.cs

@@ -10,33 +10,32 @@ namespace Wabbajack.Lib.Validation
         public bool? CanUseInOtherGames { get; set; }
     }
 
-    public class Author
+    //public class Author
-    {
+    //{
-        public Permissions Permissions { get; set; }
+    //    public Permissions Permissions { get; set; }
-        public Dictionary<string, Game> Games;
+    //    public Dictionary<string, Game> Games;
-    }
+    //}
 
-    public class Game
+    //public class Game
-    {
+    //{
-        public Permissions Permissions;
+    //    public Permissions Permissions;
-        public Dictionary<string, Mod> Mods;
+    //    public Dictionary<string, Mod> Mods;
-    }
+    //}
 
-    public class Mod
+    //public class Mod
-    {
+    //{
-        public Permissions Permissions;
+    //    public Permissions Permissions;
-        public Dictionary<string, File> Files;
+    //    public Dictionary<string, File> Files;
-    }
+    //}
-
-    public class File
-    {
-        public Permissions Permissions;
-    }
 
+    //public class File
+    //{
+    //    public Permissions Permissions;
+    //}
 
     public class ServerWhitelist
     {
-        public List<string> GoogleIDs;
+        public List<string> GoogleIDs = new List<string>();
-        public List<string> AllowedPrefixes;
+        public List<string> AllowedPrefixes = new List<string>();
     }
 }

Wabbajack.Lib/ViewModel.cs

@@ -24,7 +24,7 @@ namespace Wabbajack.Lib
         protected void RaiseAndSetIfChanged<T>(
             ref T item,
             T newItem,
-            [CallerMemberName] string propertyName = null)
+            [CallerMemberName] string? propertyName = null)
         {
             if (EqualityComparer<T>.Default.Equals(item, newItem)) return;
             item = newItem;

Wabbajack.Lib/VortexInstaller.cs

@@ -11,6 +11,7 @@ using Directory = Alphaleonis.Win32.Filesystem.Directory;
 using DirectoryInfo = Alphaleonis.Win32.Filesystem.DirectoryInfo;
 using File = Alphaleonis.Win32.Filesystem.File;
 using Path = Alphaleonis.Win32.Filesystem.Path;
+#nullable disable
 
 namespace Wabbajack.Lib
 {
@@ -26,7 +27,8 @@ namespace Wabbajack.Lib
                   modList: modList,
                   outputFolder: outputFolder,
                   downloadFolder: downloadFolder,
-                  parameters: parameters)
+                  parameters: parameters,
+                  steps: 10)
         {
             #if DEBUG
             // TODO: only for testing
@@ -51,7 +53,7 @@ namespace Wabbajack.Lib
             }
 
             if (cancel.IsCancellationRequested) return false;
-            ConfigureProcessor(10, ConstructDynamicNumThreads(await RecommendQueueSize()));
+            Queue.SetActiveThreadsObservable(ConstructDynamicNumThreads(await RecommendQueueSize()));
             DownloadFolder.CreateDirectory();
 
             if (cancel.IsCancellationRequested) return false;
@@ -122,7 +124,7 @@ namespace Wabbajack.Lib
 
             var manualFilesDir = OutputFolder.Combine(Consts.ManualGameFilesDir);
 
-            var gameFolder = GameInfo.GameLocation();
+            var gameFolder = GameInfo.TryGetGameLocation();
 
             Info($"Copying files from {manualFilesDir} " +
                  $"to the game folder at {gameFolder}");

Wabbajack.Lib/Wabbajack.Lib.csproj

@@ -1,9 +1,10 @@
 <?xml version="1.0" encoding="utf-8"?>
 <Project Sdk="Microsoft.NET.Sdk">
     <PropertyGroup>
-        <TargetFramework>netcoreapp3.1</TargetFramework>
+      <TargetFramework>netcoreapp3.1</TargetFramework>
-        <Platforms>x64</Platforms>
+      <Platforms>x64</Platforms>
-        <RuntimeIdentifier>win10-x64</RuntimeIdentifier>
+      <RuntimeIdentifier>win10-x64</RuntimeIdentifier>
+      <Nullable>enable</Nullable>
     </PropertyGroup>
     <ItemGroup>
       <PackageReference Include="CefSharp.Common">

Wabbajack.Lib/WebAutomation/CefSharpWrapper.cs

@@ -13,8 +13,8 @@ namespace Wabbajack.Lib.WebAutomation
 {
     public class CefSharpWrapper : IWebDriver
     {
-        private IWebBrowser _browser;
+        private readonly IWebBrowser _browser;
-        public Action<Uri> DownloadHandler { get; set; }
+        public Action<Uri>? DownloadHandler { get; set; }
         public CefSharpWrapper(IWebBrowser browser)
         {
             _browser = browser;
@@ -24,7 +24,7 @@ namespace Wabbajack.Lib.WebAutomation
         {
             var tcs = new TaskCompletionSource<bool>();
 
-            EventHandler<LoadingStateChangedEventArgs> handler = null;
+            EventHandler<LoadingStateChangedEventArgs>? handler = null;
             handler = (sender, e) =>
             {
                 if (!e.IsLoading)
@@ -68,7 +68,7 @@ namespace Wabbajack.Lib.WebAutomation
 
     public class PopupBlocker : ILifeSpanHandler
     {
-        private CefSharpWrapper _wrapper;
+        private readonly CefSharpWrapper _wrapper;
 
         public PopupBlocker(CefSharpWrapper cefSharpWrapper)
         {
@@ -77,7 +77,7 @@ namespace Wabbajack.Lib.WebAutomation
 
         public bool OnBeforePopup(IWebBrowser chromiumWebBrowser, IBrowser browser, IFrame frame, string targetUrl,
             string targetFrameName, WindowOpenDisposition targetDisposition, bool userGesture, IPopupFeatures popupFeatures,
-            IWindowInfo windowInfo, IBrowserSettings browserSettings, ref bool noJavascriptAccess, out IWebBrowser newBrowser)
+            IWindowInfo windowInfo, IBrowserSettings browserSettings, ref bool noJavascriptAccess, out IWebBrowser? newBrowser)
         {
             // Block popups
             newBrowser = null;
@@ -86,7 +86,6 @@ namespace Wabbajack.Lib.WebAutomation
 
         public void OnAfterCreated(IWebBrowser chromiumWebBrowser, IBrowser browser)
         {
-            
         }
 
         public bool DoClose(IWebBrowser chromiumWebBrowser, IBrowser browser)
@@ -96,7 +95,6 @@ namespace Wabbajack.Lib.WebAutomation
 
         public void OnBeforeClose(IWebBrowser chromiumWebBrowser, IBrowser browser)
         {
-            
         }
     }
 
@@ -112,7 +110,7 @@ namespace Wabbajack.Lib.WebAutomation
         public void OnBeforeDownload(IWebBrowser chromiumWebBrowser, IBrowser browser, DownloadItem downloadItem,
             IBeforeDownloadCallback callback)
         {
-            _wrapper.DownloadHandler(new Uri(downloadItem.Url));
+            _wrapper.DownloadHandler?.Invoke(new Uri(downloadItem.Url));
         }
 
         public void OnDownloadUpdated(IWebBrowser chromiumWebBrowser, IBrowser browser, DownloadItem downloadItem,