#nullable enable for UniversalAssemblyResolver

ICSharpCode.Decompiler/Metadata/AssemblyReferences.cs

@@ -19,6 +19,7 @@
 #nullable enable
 
 using System;
+using System.Diagnostics.CodeAnalysis;
 using System.Linq;
 using System.Reflection;
 using System.Reflection.Metadata;
@@ -81,7 +82,7 @@ namespace ICSharpCode.Decompiler.Metadata
 		/// For .NET Core framework references, the WholeProjectDecompiler will omit the
 		/// assembly reference if the runtimePack is already included as an SDK.
 		/// </summary>
-		public virtual bool IsSharedAssembly(IAssemblyReference reference, out string? runtimePack)
+		public virtual bool IsSharedAssembly(IAssemblyReference reference, [NotNullWhen(true)] out string? runtimePack)
 		{
 			runtimePack = null;
 			return false;

ICSharpCode.Decompiler/Metadata/UniversalAssemblyResolver.cs

@@ -16,8 +16,11 @@
 // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
 // DEALINGS IN THE SOFTWARE.
 
+#nullable enable
+
 using System;
 using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
 using System.IO;
 using System.Linq;
 using System.Reflection.Metadata;
@@ -64,13 +67,13 @@ namespace ICSharpCode.Decompiler.Metadata
 		readonly bool throwOnError;
 		readonly PEStreamOptions streamOptions;
 		readonly MetadataReaderOptions metadataOptions;
-		readonly string mainAssemblyFileName;
-		readonly string baseDirectory;
-		readonly List<string> directories = new List<string>();
+		readonly string? mainAssemblyFileName;
+		readonly string? baseDirectory;
+		readonly List<string?> directories = new List<string?>();
 		static readonly List<string> gac_paths = GetGacPaths();
 		static readonly DecompilerRuntime decompilerRuntime;
 
-		public void AddSearchDirectory(string directory)
+		public void AddSearchDirectory(string? directory)
 		{
 			directories.Add(directory);
 			if (dotNetCorePathFinder.IsValueCreated)
@@ -79,7 +82,7 @@ namespace ICSharpCode.Decompiler.Metadata
 			}
 		}
 
-		public void RemoveSearchDirectory(string directory)
+		public void RemoveSearchDirectory(string? directory)
 		{
 			directories.Remove(directory);
 			if (dotNetCorePathFinder.IsValueCreated)
@@ -88,7 +91,7 @@ namespace ICSharpCode.Decompiler.Metadata
 			}
 		}
 
-		public string[] GetSearchDirectories()
+		public string?[] GetSearchDirectories()
 		{
 			return directories.ToArray();
 		}
@@ -121,8 +124,8 @@ namespace ICSharpCode.Decompiler.Metadata
 		/// If omitted, falling back to "Microsoft.NETCore.App" and this is ignored in case of classic .NET</param>
 		/// <param name="streamOptions">Options used for the <see cref="PEReader"/>.</param>
 		/// <param name="metadataOptions">Options used for the <see cref="MetadataReader"/>.</param>
-		public UniversalAssemblyResolver(string mainAssemblyFileName, bool throwOnError, string targetFramework,
-			string runtimePack = null, PEStreamOptions streamOptions = PEStreamOptions.Default, MetadataReaderOptions metadataOptions = MetadataReaderOptions.Default)
+		public UniversalAssemblyResolver(string? mainAssemblyFileName, bool throwOnError, string? targetFramework,
+			string? runtimePack = null, PEStreamOptions streamOptions = PEStreamOptions.Default, MetadataReaderOptions metadataOptions = MetadataReaderOptions.Default)
 		{
 			this.mainAssemblyFileName = mainAssemblyFileName;
 			this.throwOnError = throwOnError;
@@ -162,7 +165,7 @@ namespace ICSharpCode.Decompiler.Metadata
 					break;
 			}
 
-			Version version = null;
+			Version? version = null;
 
 			for (int i = 1; i < tokens.Length; i++)
 			{
@@ -191,20 +194,20 @@ namespace ICSharpCode.Decompiler.Metadata
 		}
 
 #if !VSADDIN
-		public PEFile Resolve(IAssemblyReference name)
+		public PEFile? Resolve(IAssemblyReference name)
 		{
 			var file = FindAssemblyFile(name);
 			return CreatePEFileFromFileName(file, ex => new ResolutionException(name, file, ex));
 		}
 
-		public PEFile ResolveModule(PEFile mainModule, string moduleName)
+		public PEFile? ResolveModule(PEFile mainModule, string moduleName)
 		{
 			string baseDirectory = Path.GetDirectoryName(mainModule.FileName);
 			string moduleFileName = Path.Combine(baseDirectory, moduleName);
 			return CreatePEFileFromFileName(moduleFileName, ex => new ResolutionException(mainModule.FileName, moduleName, moduleFileName, ex));
 		}
 
-		private PEFile CreatePEFileFromFileName(string fileName, Func<Exception?, Exception> makeException)
+		private PEFile? CreatePEFileFromFileName(string? fileName, Func<Exception?, Exception> makeException)
 		{
 			if (fileName == null)
 			{
@@ -231,30 +234,30 @@ namespace ICSharpCode.Decompiler.Metadata
 			return null;
 		}
 
-		public Task<PEFile> ResolveAsync(IAssemblyReference name)
+		public Task<PEFile?> ResolveAsync(IAssemblyReference name)
 		{
 			return Task.Run(() => Resolve(name));
 		}
 
-		public Task<PEFile> ResolveModuleAsync(PEFile mainModule, string moduleName)
+		public Task<PEFile?> ResolveModuleAsync(PEFile mainModule, string moduleName)
 		{
 			return Task.Run(() => ResolveModule(mainModule, moduleName));
 		}
 #endif
 
-		public override bool IsSharedAssembly(IAssemblyReference reference, out string runtimePack)
+		public override bool IsSharedAssembly(IAssemblyReference reference, [NotNullWhen(true)] out string? runtimePack)
 		{
 			return dotNetCorePathFinder.Value.TryResolveDotNetCoreShared(reference, out runtimePack) != null;
 		}
 
-		public string FindAssemblyFile(IAssemblyReference name)
+		public string? FindAssemblyFile(IAssemblyReference name)
 		{
 			if (name.IsWindowsRuntime)
 			{
 				return FindWindowsMetadataFile(name);
 			}
 
-			string file;
+			string? file;
 			switch (targetFrameworkIdentifier)
 			{
 				case TargetFrameworkIdentifier.NETCoreApp:
@@ -291,14 +294,14 @@ namespace ICSharpCode.Decompiler.Metadata
 			return dotNetCorePathFinder;
 		}
 
-		string FindWindowsMetadataFile(IAssemblyReference name)
+		string? FindWindowsMetadataFile(IAssemblyReference name)
 		{
 			// Finding Windows Metadata (winmd) is currently only supported on Windows.
 			if (Environment.OSVersion.Platform != PlatformID.Win32NT)
 				return null;
 
 			// TODO : Find a way to detect the base directory for the required Windows SDK.
-			string basePath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ProgramFilesX86), "Windows Kits", "10", "References");
+			string? basePath = Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ProgramFilesX86), "Windows Kits", "10", "References");
 
 			if (!Directory.Exists(basePath))
 				return FindWindowsMetadataInSystemDirectory(name);
@@ -332,7 +335,7 @@ namespace ICSharpCode.Decompiler.Metadata
 			return file;
 		}
 
-		string FindWindowsMetadataInSystemDirectory(IAssemblyReference name)
+		string? FindWindowsMetadataInSystemDirectory(IAssemblyReference name)
 		{
 			string file = Path.Combine(Environment.SystemDirectory, "WinMetadata", name.Name + ".winmd");
 			if (File.Exists(file))
@@ -343,7 +346,7 @@ namespace ICSharpCode.Decompiler.Metadata
 		/// <summary>
 		/// This only works on Windows
 		/// </summary>
-		string ResolveSilverlight(IAssemblyReference name, Version version)
+		string? ResolveSilverlight(IAssemblyReference name, Version? version)
 		{
 			string[] targetFrameworkSearchPaths = {
 				Path.Combine(Environment.GetFolderPath(Environment.SpecialFolder.ProgramFiles), "Microsoft Silverlight"),
@@ -362,19 +365,19 @@ namespace ICSharpCode.Decompiler.Metadata
 			return null;
 		}
 
-		string FindClosestVersionDirectory(string basePath, Version version)
+		string FindClosestVersionDirectory(string? basePath, Version? version)
 		{
-			string path = null;
+			string? path = null;
 			foreach (var folder in new DirectoryInfo(basePath).GetDirectories().Select(d => DotNetCorePathFinder.ConvertToVersion(d.Name))
 				.Where(v => v.Item1 != null).OrderByDescending(v => v.Item1))
 			{
-				if (path == null || folder.Item1 >= version)
+				if (path == null || version == null || folder.Item1 >= version)
 					path = folder.Item2;
 			}
-			return path ?? version.ToString();
+			return path ?? version?.ToString() ?? ".";
 		}
 
-		string ResolveInternal(IAssemblyReference name)
+		string? ResolveInternal(IAssemblyReference name)
 		{
 			if (name == null)
 				throw new ArgumentNullException(nameof(name));
@@ -421,11 +424,11 @@ namespace ICSharpCode.Decompiler.Metadata
 		}
 
 		#region .NET / mono GAC handling
-		string SearchDirectory(IAssemblyReference name, IEnumerable<string> directories)
+		string? SearchDirectory(IAssemblyReference name, IEnumerable<string?> directories)
 		{
 			foreach (var directory in directories)
 			{
-				string file = SearchDirectory(name, directory);
+				string? file = SearchDirectory(name, directory);
 				if (file != null)
 					return file;
 			}
@@ -438,7 +441,7 @@ namespace ICSharpCode.Decompiler.Metadata
 			return IsZeroOrAllOnes(reference.Version) || reference.IsRetargetable;
 		}
 
-		string SearchDirectory(IAssemblyReference name, string directory)
+		string? SearchDirectory(IAssemblyReference name, string? directory)
 		{
 			var extensions = name.IsWindowsRuntime ? new[] { ".winmd", ".dll" } : new[] { ".dll", ".exe" };
 			foreach (var extension in extensions)
@@ -458,7 +461,7 @@ namespace ICSharpCode.Decompiler.Metadata
 			return null;
 		}
 
-		static bool IsZeroOrAllOnes(Version version)
+		static bool IsZeroOrAllOnes(Version? version)
 		{
 			return version == null
 				|| (version.Major == 0 && version.Minor == 0 && version.Build == 0 && version.Revision == 0)
@@ -467,7 +470,7 @@ namespace ICSharpCode.Decompiler.Metadata
 
 		internal static Version ZeroVersion = new Version(0, 0, 0, 0);
 
-		string GetCorlib(IAssemblyReference reference)
+		string? GetCorlib(IAssemblyReference reference)
 		{
 			var version = reference.Version;
 			var corlib = typeof(object).Assembly.GetName();
@@ -481,15 +484,19 @@ namespace ICSharpCode.Decompiler.Metadata
 			if (reference.PublicKeyToken == null)
 				return null;
 
-			string path;
+			string? path;
 			if (decompilerRuntime == DecompilerRuntime.Mono)
 			{
 				path = GetMonoMscorlibBasePath(version);
 			}
-			else
+			else if (version != null)
 			{
 				path = GetMscorlibBasePath(version, reference.PublicKeyToken.ToHexString(8));
 			}
+			else
+			{
+				path = null;
+			}
 
 			if (path == null)
 				return null;
@@ -501,9 +508,9 @@ namespace ICSharpCode.Decompiler.Metadata
 			return null;
 		}
 
-		string GetMscorlibBasePath(Version version, string publicKeyToken)
+		string? GetMscorlibBasePath(Version version, string? publicKeyToken)
 		{
-			string GetSubFolderForVersion()
+			string? GetSubFolderForVersion()
 			{
 				switch (version.Major)
 				{
@@ -540,7 +547,7 @@ namespace ICSharpCode.Decompiler.Metadata
 					Path.Combine(rootPath, "Framework64")
 				};
 
-				string folder = GetSubFolderForVersion();
+				string? folder = GetSubFolderForVersion();
 
 				if (folder != null)
 				{
@@ -558,7 +565,7 @@ namespace ICSharpCode.Decompiler.Metadata
 			return null;
 		}
 
-		string GetMonoMscorlibBasePath(Version version)
+		string? GetMonoMscorlibBasePath(Version? version)
 		{
 			var path = Directory.GetParent(typeof(object).Module.FullyQualifiedName).Parent.FullName;
 			if (version.Major == 1)
@@ -614,7 +621,7 @@ namespace ICSharpCode.Decompiler.Metadata
 					continue;
 
 				var gac_path = Path.Combine(Path.Combine(Path.Combine(prefix, "lib"), "mono"), "gac");
-				if (Directory.Exists(gac_path) && !paths.Contains(gac))
+				if (Directory.Exists(gac_path) && !paths.Contains(gac_path))
 					paths.Add(gac_path);
 			}
 
@@ -629,7 +636,7 @@ namespace ICSharpCode.Decompiler.Metadata
 				"gac");
 		}
 
-		public static string GetAssemblyInGac(IAssemblyReference reference)
+		public static string? GetAssemblyInGac(IAssemblyReference reference)
 		{
 			if (reference.PublicKeyToken == null || reference.PublicKeyToken.Length == 0)
 				return null;
@@ -640,7 +647,7 @@ namespace ICSharpCode.Decompiler.Metadata
 			return GetAssemblyInNetGac(reference);
 		}
 
-		static string GetAssemblyInMonoGac(IAssemblyReference reference)
+		static string? GetAssemblyInMonoGac(IAssemblyReference reference)
 		{
 			for (int i = 0; i < gac_paths.Count; i++)
 			{
@@ -653,7 +660,7 @@ namespace ICSharpCode.Decompiler.Metadata
 			return null;
 		}
 
-		static string GetAssemblyInNetGac(IAssemblyReference reference)
+		static string? GetAssemblyInNetGac(IAssemblyReference reference)
 		{
 			var gacs = new[] { "GAC_MSIL", "GAC_32", "GAC_64", "GAC" };
 			var prefixes = new[] { string.Empty, "v4.0_" };
@@ -672,7 +679,7 @@ namespace ICSharpCode.Decompiler.Metadata
 			return null;
 		}
 
-		static string GetAssemblyFile(IAssemblyReference reference, string prefix, string gac)
+		static string GetAssemblyFile(IAssemblyReference reference, string? prefix, string? gac)
 		{
 			var gac_folder = new StringBuilder()
 				.Append(prefix)

ICSharpCode.Decompiler/Util/NullAttributes.cs

@@ -14,5 +14,16 @@ namespace System.Diagnostics.CodeAnalysis
 			ParameterName = parameterName;
 		}
 	}
+
+	[AttributeUsage(AttributeTargets.Parameter, Inherited = false)]
+	internal sealed class NotNullWhenAttribute : Attribute
+	{
+		public NotNullWhenAttribute(bool returnValue)
+		{
+			ReturnValue = returnValue;
+		}
+
+		public bool ReturnValue { get; }
+	}
 }
 #endif

ILSpy.AddIn/ILSpy.AddIn.csproj

@@ -72,6 +72,7 @@
     <Compile Include="..\ICSharpCode.Decompiler\Metadata\LightJson\Serialization\TextScanner.cs" Link="Decompiler\LightJson\Serialization\TextScanner.cs" />
     <Compile Include="..\ICSharpCode.Decompiler\Metadata\UniversalAssemblyResolver.cs" Link="UniversalAssemblyResolver.cs" />
     <Compile Include="..\ICSharpCode.Decompiler\Util\EmptyList.cs" Link="Decompiler\EmptyList.cs" />
+    <Compile Include="..\ICSharpCode.Decompiler\Util\NullAttributes.cs" Link="NullAttributes.cs" />
     <Compile Include="..\ILSpy\NativeMethods.cs" Link="NativeMethods.cs" />
     <Compile Include="Commands\AssemblyReferenceForILSpy.cs" />
     <Compile Include="Commands\NuGetReferenceForILSpy.cs" />