Nullable references for Core

.editorconfig

@@ -42,9 +42,18 @@ dotnet_diagnostic.IDE0055.severity = none
 # OK to call functions that return values and not use them
 dotnet_diagnostic.IDE0058.severity = none
 
+# I like seeing when a using block ends
+dotnet_diagnostic.IDE0063.severity = none
+
 # A `using` inside a namespace is useful as a typedef
 dotnet_diagnostic.IDE0065.severity = none
 
+# 'switch' expressions are nice, but I don't need to be alerted about them
+dotnet_diagnostic.IDE0066.severity = none
+
+# Why do 'new' expressions need to be simple?
+dotnet_diagnostic.IDE0090.severity = none
+
 # Allow namespaces to be independent of folder names
 dotnet_diagnostic.IDE0130.severity = none
 

ConsoleUI/RepoScreen.cs

@@ -51,9 +51,9 @@ protected RepoScreen(IGame game, SortedDictionary<string, Repository> reps, stri
             });
 
             // mainMenu = list of default options
-            if (defaultRepos.repositories != null && defaultRepos.repositories.Length > 0) {
+            if (defaultRepos?.repositories != null && defaultRepos?.repositories.Length > 0) {
                 List<ConsoleMenuOption> opts = new List<ConsoleMenuOption>();
-                foreach (Repository r in defaultRepos.repositories) {
+                foreach (Repository r in defaultRepos?.repositories) {
                     // This variable will be remembered correctly in our lambdas later
                     Repository repo = r;
                     opts.Add(new ConsoleMenuOption(
@@ -153,7 +153,7 @@ protected bool urlValid()
         /// </summary>
         protected SortedDictionary<string, Repository> editList;
 
-        private RepositoryList defaultRepos;
+        private RepositoryList? defaultRepos;
 
         private int labelWidth => Math.Max(8, Math.Max(
             Properties.Resources.RepoNameLabel.Length,

Core/AutoUpdate/AutoUpdate.cs

@@ -17,7 +17,7 @@ public AutoUpdate()
 
         public CkanUpdate GetUpdate(bool devBuild)
         {
-            if (updates.TryGetValue(devBuild, out CkanUpdate update))
+            if (updates.TryGetValue(devBuild, out CkanUpdate? update))
             {
                 return update;
             }
@@ -30,6 +30,9 @@ public CkanUpdate GetUpdate(bool devBuild)
 
         private readonly Dictionary<bool, CkanUpdate> updates = new Dictionary<bool, CkanUpdate>();
 
+        // This is null when running tests, seemingly.
+        private static readonly string exePath = Assembly.GetEntryAssembly()?.Location ?? "";
+
         /// <summary>
         /// Report whether it's possible to run the auto-updater.
         /// Checks whether we can overwrite the running ckan.exe.
@@ -43,7 +46,7 @@ public CkanUpdate GetUpdate(bool devBuild)
         /// and then launches the helper allowing us to upgrade.
         /// </summary>
         /// <param name="launchCKANAfterUpdate">If set to <c>true</c> launch CKAN after update.</param>
-        public void StartUpdateProcess(bool launchCKANAfterUpdate, bool devBuild, IUser user = null)
+        public void StartUpdateProcess(bool launchCKANAfterUpdate, bool devBuild, IUser? user = null)
         {
             var pid = Process.GetCurrentProcess().Id;
 
@@ -84,8 +87,8 @@ public static void SetExecutable(string fileName)
                 {
                     UseShellExecute = false
                 };
-                Process permsprocess = Process.Start(permsinfo);
-                permsprocess.WaitForExit();
+                var permsprocess = Process.Start(permsinfo);
+                permsprocess?.WaitForExit();
             }
         }
 
@@ -103,8 +106,5 @@ private static bool CanWrite(string path)
                 return false;
             }
         }
-
-        // This is null when running tests, seemingly.
-        private static readonly string exePath = Assembly.GetEntryAssembly()?.Location ?? "";
     }
 }

Core/AutoUpdate/CkanUpdate.cs

@@ -11,12 +11,8 @@ namespace CKAN
     /// </summary>
     public abstract class CkanUpdate
     {
-        public CkanModuleVersion Version         { get; protected set; }
-        public Uri               ReleaseDownload { get; protected set; }
-        public long              ReleaseSize     { get; protected set; }
-        public Uri               UpdaterDownload { get; protected set; }
-        public long              UpdaterSize     { get; protected set; }
-        public string            ReleaseNotes    { get; protected set; }
+        public CkanModuleVersion? Version         { get; protected set; }
+        public string?            ReleaseNotes    { get; protected set; }
 
         public string updaterFilename = $"{Path.GetTempPath()}{Guid.NewGuid()}.exe";
         public string ckanFilename    = $"{Path.GetTempPath()}{Guid.NewGuid()}.exe";

Core/AutoUpdate/GithubReleaseCkanUpdate.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Linq;
 using System.Collections.Generic;
 
 using Autofac;
@@ -18,38 +19,47 @@ public class GitHubReleaseCkanUpdate : CkanUpdate
         /// Initialize the Object
         /// </summary>
         /// <param name="json">JSON representation of release</param>
-        public GitHubReleaseCkanUpdate(GitHubReleaseInfo releaseJson = null)
+        public GitHubReleaseCkanUpdate(GitHubReleaseInfo? releaseJson = null)
         {
             if (releaseJson == null)
             {
                 var coreConfig = ServiceLocator.Container.Resolve<IConfiguration>();
-                var token = coreConfig.TryGetAuthToken(latestCKANReleaseApiUrl.Host, out string t)
+                var token = coreConfig.TryGetAuthToken(latestCKANReleaseApiUrl.Host, out string? t)
                     ? t : null;
-                releaseJson = JsonConvert.DeserializeObject<GitHubReleaseInfo>(
-                    Net.DownloadText(latestCKANReleaseApiUrl, token));
-                if (releaseJson == null)
-                {
-                    throw new Kraken(Properties.Resources.AutoUpdateNotFetched);
-                }
+                releaseJson = Net.DownloadText(latestCKANReleaseApiUrl, token) is string content
+                              ? JsonConvert.DeserializeObject<GitHubReleaseInfo>(content)
+                              : null;
+            }
+            if (releaseJson is null
+                || releaseJson.tag_name is null
+                || releaseJson.name is null
+                || releaseJson.body is null
+                || releaseJson.assets is null)
+            {
+                throw new Kraken(Properties.Resources.AutoUpdateNotFetched);
             }
 
             Version = new CkanModuleVersion(releaseJson.tag_name.ToString(),
                                             releaseJson.name.ToString());
             ReleaseNotes = ExtractReleaseNotes(releaseJson.body.ToString());
-            foreach (var asset in releaseJson.assets)
+
+            var releaseAsset = releaseJson.assets.First(asset => asset.browser_download_url
+                                                                      ?.ToString()
+                                                                       .EndsWith("ckan.exe")
+                                                                      ?? false);
+            var updaterAsset = releaseJson.assets.First(asset => asset.browser_download_url
+                                                                      ?.ToString()
+                                                                       .EndsWith("AutoUpdater.exe")
+                                                                      ?? false);
+            if (releaseAsset.browser_download_url is null
+                || updaterAsset.browser_download_url is null)
             {
-                string url = asset.browser_download_url.ToString();
-                if (url.EndsWith("ckan.exe"))
-                {
-                    ReleaseDownload = asset.browser_download_url;
-                    ReleaseSize     = asset.size;
-                }
-                else if (url.EndsWith("AutoUpdater.exe"))
-                {
-                    UpdaterDownload = asset.browser_download_url;
-                    UpdaterSize     = asset.size;
-                }
+                throw new Kraken(Properties.Resources.AutoUpdateNotFetched);
             }
+            ReleaseDownload = releaseAsset.browser_download_url;
+            ReleaseSize     = releaseAsset.size;
+            UpdaterDownload = updaterAsset.browser_download_url;
+            UpdaterSize     = updaterAsset.size;
         }
 
         public override IList<NetAsyncDownloader.DownloadTarget> Targets => new[]
@@ -60,6 +70,11 @@ public GitHubReleaseCkanUpdate(GitHubReleaseInfo releaseJson = null)
                 ReleaseDownload, ckanFilename, ReleaseSize),
         };
 
+        private Uri  ReleaseDownload { get; set; }
+        private long ReleaseSize     { get; set; }
+        private Uri  UpdaterDownload { get; set; }
+        private long UpdaterSize     { get; set; }
+
         /// <summary>
         /// Extracts release notes from the body of text provided by the github API.
         /// By default this is everything after the first three dashes on a line by

Core/AutoUpdate/GithubReleaseInfo.cs

@@ -5,15 +5,15 @@ namespace CKAN
 {
     public class GitHubReleaseInfo
     {
-        public string      tag_name;
-        public string      name;
-        public string      body;
-        public List<Asset> assets;
+        public string?      tag_name;
+        public string?      name;
+        public string?      body;
+        public List<Asset>? assets;
 
         public sealed class Asset
         {
-            public Uri  browser_download_url;
-            public long size;
+            public Uri?  browser_download_url;
+            public long  size;
         }
     }
 }

Core/AutoUpdate/S3BuildCkanUpdate.cs

@@ -9,18 +9,15 @@ namespace CKAN
 {
     public class S3BuildCkanUpdate : CkanUpdate
     {
-        public S3BuildCkanUpdate(S3BuildVersionInfo versionJson = null)
+        public S3BuildCkanUpdate(S3BuildVersionInfo? versionJson = null)
         {
-            if (versionJson == null)
+            versionJson ??= Net.DownloadText(new Uri(S3BaseUrl, VersionJsonUrlPiece)) is string content
+                                ? JsonConvert.DeserializeObject<S3BuildVersionInfo>(content)
+                                : null;
+            if (versionJson is null || versionJson.version is null)
             {
-                versionJson = JsonConvert.DeserializeObject<S3BuildVersionInfo>(
-                    Net.DownloadText(new Uri(S3BaseUrl, VersionJsonUrlPiece)));
-                if (versionJson == null)
-                {
-                    throw new Kraken(Properties.Resources.AutoUpdateNotFetched);
-                }
+                throw new Kraken(Properties.Resources.AutoUpdateNotFetched);
             }
-
             Version         = new CkanModuleVersion(versionJson.version.ToString(), "dev");
             ReleaseNotes    = versionJson.changelog;
             UpdaterDownload = new Uri(S3BaseUrl, AutoUpdaterUrlPiece);
@@ -29,12 +26,13 @@ public S3BuildCkanUpdate(S3BuildVersionInfo versionJson = null)
 
         public override IList<NetAsyncDownloader.DownloadTarget> Targets => new[]
         {
-            new NetAsyncDownloader.DownloadTargetFile(
-                UpdaterDownload, updaterFilename),
-            new NetAsyncDownloader.DownloadTargetFile(
-                ReleaseDownload, ckanFilename),
+            new NetAsyncDownloader.DownloadTargetFile(UpdaterDownload, updaterFilename),
+            new NetAsyncDownloader.DownloadTargetFile(ReleaseDownload, ckanFilename),
         };
 
+        private Uri ReleaseDownload { get; set; }
+        private Uri UpdaterDownload { get; set; }
+
         private static readonly Uri S3BaseUrl =
             new Uri("https://ksp-ckan.s3-us-west-2.amazonaws.com/");
         private const           string VersionJsonUrlPiece = "version.json";

Core/AutoUpdate/S3BuildVersionInfo.cs

@@ -4,7 +4,7 @@ namespace CKAN
 {
     public class S3BuildVersionInfo
     {
-        public ModuleVersion version;
-        public string        changelog;
+        public ModuleVersion? version;
+        public string?        changelog;
     }
 }

Core/CKAN-core.csproj

@@ -16,7 +16,10 @@
     <Deterministic>true</Deterministic>
     <Configurations>Debug;Release;NoGUI</Configurations>
     <Prefer32Bit>false</Prefer32Bit>
-    <LangVersion>7.3</LangVersion>
+    <LangVersion>9</LangVersion>
+    <Nullable>enable</Nullable>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+    <WarningsNotAsErrors>SYSLIB0050,IDE0090</WarningsNotAsErrors>
     <NoWarn>IDE1006</NoWarn>
     <TargetFrameworks>netstandard2.0;net48;net7.0</TargetFrameworks>
     <CoreCompileDependsOn>PrepareResources;$(CompileDependsOn)</CoreCompileDependsOn>
@@ -54,6 +57,8 @@
     <PackageReference Include="NJsonSchema" Version="10.9.0" />
     <PackageReference Include="ValveKeyValue" Version="0.3.1.152" />
     <PackageReference Include="Mono.Cecil" Version="0.11.5" />
+    <PackageReference Include="Nullable" Version="1.3.1" PrivateAssets="all" />
+    <PackageReference Include="IndexRange" Version="1.0.3" />
   </ItemGroup>
   <ItemGroup>
     <Compile Include="..\_build\meta\GlobalAssemblyVersionInfo.cs">

Core/CKANPathUtils.cs

@@ -25,9 +25,8 @@ public static class CKANPathUtils
         /// <param name="path">The path to normalize</param>
         /// <returns>The normalized path</returns>
         public static string NormalizePath(string path)
-            => path == null    ? null
-             : path.Length < 2 ? path.Replace('\\', '/')
-             : path.Replace('\\', '/').TrimEnd('/');
+            => path.Length < 2 ? path.Replace('\\', '/')
+                               : path.Replace('\\', '/').TrimEnd('/');
 
         /// <summary>
         /// Gets the last path element. Ex: /a/b/c returns c
@@ -61,11 +60,6 @@ public static string GetLeadingPathElements(string path)
         /// </summary>
         public static string ToRelative(string path, string root)
         {
-            if (path == null || root == null)
-            {
-                throw new PathErrorKraken(null, "Null path provided");
-            }
-
             // We have to normalise before we check for rootedness,
             // otherwise backslash separators fail on Linux.
 
@@ -96,11 +90,6 @@ public static string ToRelative(string path, string root)
         /// </summary>
         public static string ToAbsolute(string path, string root)
         {
-            if (path == null || root == null)
-            {
-                throw new PathErrorKraken(null, "Null path provided");
-            }
-
             path = NormalizePath(path);
             root = NormalizePath(root);
 

Core/CkanTransaction.cs

@@ -86,12 +86,12 @@ private static void SetMaxTimeout(TimeSpan timeout)
             }
         }
 
-        private static void SetField(Type T, string fieldName, object value)
+        private static void SetField(Type T, string fieldName, object? value)
         {
             try
             {
                 T.GetField(fieldName, BindingFlags.NonPublic | BindingFlags.Static)
-                    .SetValue(null, value);
+                    ?.SetValue(null, value);
             }
             catch
             {

Core/CompatibleGameVersions.cs

@@ -7,7 +7,7 @@ namespace CKAN
     [JsonConverter(typeof(CompatibleGameVersionsConverter))]
     public class CompatibleGameVersions
     {
-        public string GameVersionWhenWritten { get; set; }
+        public string? GameVersionWhenWritten { get; set; }
 
         public List<string> Versions { get; set; } = new List<string>();
     }