Nullable reference types

Examples/Examples.csproj

@@ -5,6 +5,7 @@
     <OutputType>Exe</OutputType>
     <IsPackable>false</IsPackable>
     <LangVersion>latest</LangVersion>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>

README.md

@@ -2,6 +2,14 @@
 
 .NET module/assembly reader/writer library
 
+v4 breaking changes compared to v3
+----------------------------------
+
+- Nullable reference types was enabled. Some things that used to return `null` may now return some default value, eg. when it has some invalid metadata.
+- `UTF8String(string)` constructor doesn't allow a `null` argument.
+- Some constructors that could be called without initializing all non-nullable reference type fields have been removed or updated to take more parameters.
+- TODO:
+
 Opening a .NET assembly/module
 ------------------------------
 

src/DotNet/AssemblyDef.cs

@@ -11,6 +11,7 @@
 using dnlib.DotNet.Pdb;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 
 namespace dnlib.DotNet {
 	/// <summary>
@@ -155,8 +156,9 @@ public CustomAttributeCollection CustomAttributes {
 			}
 		}
 		/// <summary/>
-		protected CustomAttributeCollection customAttributes;
+		protected CustomAttributeCollection? customAttributes;
 		/// <summary>Initializes <see cref="customAttributes"/></summary>
+		[MemberNotNull(nameof(customAttributes))]
 		protected virtual void InitializeCustomAttributes() =>
 			Interlocked.CompareExchange(ref customAttributes, new CustomAttributeCollection(), null);
 
@@ -181,8 +183,9 @@ public IList<PdbCustomDebugInfo> CustomDebugInfos {
 			}
 		}
 		/// <summary/>
-		protected IList<PdbCustomDebugInfo> customDebugInfos;
+		protected IList<PdbCustomDebugInfo>? customDebugInfos;
 		/// <summary>Initializes <see cref="customDebugInfos"/></summary>
+		[MemberNotNull(nameof(customDebugInfos))]
 		protected virtual void InitializeCustomDebugInfos() =>
 			Interlocked.CompareExchange(ref customDebugInfos, new List<PdbCustomDebugInfo>(), null);
 		/// <inheritdoc/>
@@ -197,7 +200,7 @@ protected virtual void InitializeCustomDebugInfos() =>
 		/// Gets the manifest (main) module. This is always the first module in <see cref="Modules"/>.
 		/// <c>null</c> is returned if <see cref="Modules"/> is empty.
 		/// </summary>
-		public ModuleDef ManifestModule => Modules.Count == 0 ? null : Modules[0];
+		public ModuleDef? ManifestModule => Modules.Count == 0 ? null : Modules[0];
 
 		/// <summary>
 		/// Modify <see cref="attributes"/> property: <see cref="attributes"/> =

src/DotNet/AssemblyHash.cs

@@ -39,11 +39,8 @@ public void Dispose() {
 		/// <see cref="AssemblyHashAlgorithm.SHA1"/> will be used as the hash algorithm.</remarks>
 		/// <param name="data">The data</param>
 		/// <param name="hashAlgo">The algorithm to use</param>
-		/// <returns>Hashed data or null if <paramref name="data"/> was <c>null</c></returns>
+		/// <returns>Hashed data</returns>
 		public static byte[] Hash(byte[] data, AssemblyHashAlgorithm hashAlgo) {
-			if (data is null)
-				return null;
-
 			using (var asmHash = new AssemblyHash(hashAlgo)) {
 				asmHash.Hash(data);
 				return asmHash.ComputeHash();
@@ -88,7 +85,7 @@ public void Hash(Stream stream, uint length, byte[] buffer) {
 		/// </summary>
 		public byte[] ComputeHash() {
 			hasher.TransformFinalBlock(Array2.Empty<byte>(), 0, 0);
-			return hasher.Hash;
+			return hasher.Hash ?? throw new InvalidOperationException();
 		}
 
 		/// <summary>
@@ -98,7 +95,7 @@ public byte[] ComputeHash() {
 		/// order, is used as the public key token</remarks>
 		/// <param name="publicKeyData">The data</param>
 		/// <returns>A new <see cref="PublicKeyToken"/> instance</returns>
-		public static PublicKeyToken CreatePublicKeyToken(byte[] publicKeyData) {
+		public static PublicKeyToken CreatePublicKeyToken(byte[]? publicKeyData) {
 			if (publicKeyData is null)
 				return new PublicKeyToken();
 			var hash = Hash(publicKeyData, AssemblyHashAlgorithm.SHA1);

src/DotNet/AssemblyHashAlgorithm.cs

@@ -34,7 +34,7 @@ public enum AssemblyHashAlgorithm : uint {
 	}
 
 	public static partial class Extensions {
-		internal static string GetName(this AssemblyHashAlgorithm hashAlg) =>
+		internal static string? GetName(this AssemblyHashAlgorithm hashAlg) =>
 			hashAlg switch {
 				AssemblyHashAlgorithm.MD2 => null,
 				AssemblyHashAlgorithm.MD4 => null,

src/DotNet/AssemblyNameComparer.cs

@@ -98,7 +98,7 @@ public enum AssemblyNameComparerFlags {
 		/// <param name="a">First</param>
 		/// <param name="b">Second</param>
 		/// <returns>&lt; 0 if a &lt; b, 0 if a == b, &gt; 0 if a &gt; b</returns>
-		public int CompareTo(IAssembly a, IAssembly b) {
+		public int CompareTo(IAssembly? a, IAssembly? b) {
 			if (a == b)
 				return 0;
 			if (a is null)
@@ -128,7 +128,7 @@ public int CompareTo(IAssembly a, IAssembly b) {
 		/// <param name="a">First</param>
 		/// <param name="b">Second</param>
 		/// <returns><c>true</c> if equal, <c>false</c> otherwise</returns>
-		public bool Equals(IAssembly a, IAssembly b) => CompareTo(a, b) == 0;
+		public bool Equals(IAssembly? a, IAssembly? b) => CompareTo(a, b) == 0;
 
 		/// <summary>
 		/// Figures out which of two assembly names is closer to another assembly name
@@ -138,11 +138,11 @@ public int CompareTo(IAssembly a, IAssembly b) {
 		/// <param name="b">Second</param>
 		/// <returns>-1 if both are equally close, 0 if <paramref name="a"/> is closest, 1 if
 		/// <paramref name="b"/> is closest</returns>
-		public int CompareClosest(IAssembly requested, IAssembly a, IAssembly b) {
+		public int CompareClosest(IAssembly requested, IAssembly? a, IAssembly? b) {
 			if (a == b)
 				return 0;
 			if (a is null)
-				return !CompareName ? 1 : UTF8String.CaseInsensitiveEquals(requested.Name, b.Name) ? 1 : 0;
+				return !CompareName ? 1 : UTF8String.CaseInsensitiveEquals(requested.Name, b?.Name) ? 1 : 0;
 			if (b is null)
 				return !CompareName ? 0 : UTF8String.CaseInsensitiveEquals(requested.Name, a.Name) ? 0 : 1;
 
@@ -236,7 +236,7 @@ public int CompareClosest(IAssembly requested, IAssembly a, IAssembly b) {
 		/// </summary>
 		/// <param name="a">Assembly name</param>
 		/// <returns>The hash code</returns>
-		public int GetHashCode(IAssembly a) {
+		public int GetHashCode(IAssembly? a) {
 			if (a is null)
 				return 0;
 

src/DotNet/AssemblyNameInfo.cs

@@ -9,11 +9,11 @@ namespace dnlib.DotNet {
 	/// </summary>
 	public sealed class AssemblyNameInfo : IAssembly {
 		AssemblyHashAlgorithm hashAlgId;
-		Version version;
+		Version? version;
 		AssemblyAttributes flags;
 		PublicKeyBase publicKeyOrToken;
 		UTF8String name;
-		UTF8String culture;
+		UTF8String? culture;
 
 		/// <summary>
 		/// Gets/sets the <see cref="AssemblyHashAlgorithm"/>
@@ -26,7 +26,7 @@ public AssemblyHashAlgorithm HashAlgId {
 		/// <summary>
 		/// Gets/sets the <see cref="Version"/> or <c>null</c> if none specified
 		/// </summary>
-		public Version Version {
+		public Version? Version {
 			get => version;
 			set => version = value;
 		}
@@ -58,7 +58,7 @@ public UTF8String Name {
 		/// <summary>
 		/// Gets/sets the culture or <c>null</c> if none specified
 		/// </summary>
-		public UTF8String Culture {
+		public UTF8String? Culture {
 			get => culture;
 			set => culture = value;
 		}

src/DotNet/AssemblyRef.cs

@@ -3,6 +3,7 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
+using System.Diagnostics.CodeAnalysis;
 using System.Reflection;
 using System.Threading;
 using dnlib.DotNet.MD;
@@ -123,8 +124,9 @@ public CustomAttributeCollection CustomAttributes {
 			}
 		}
 		/// <summary/>
-		protected CustomAttributeCollection customAttributes;
+		protected CustomAttributeCollection? customAttributes;
 		/// <summary>Initializes <see cref="customAttributes"/></summary>
+		[MemberNotNull(nameof(customAttributes))]
 		protected virtual void InitializeCustomAttributes() =>
 			Interlocked.CompareExchange(ref customAttributes, new CustomAttributeCollection(), null);
 
@@ -148,8 +150,9 @@ public IList<PdbCustomDebugInfo> CustomDebugInfos {
 			}
 		}
 		/// <summary/>
-		protected IList<PdbCustomDebugInfo> customDebugInfos;
+		protected IList<PdbCustomDebugInfo>? customDebugInfos;
 		/// <summary>Initializes <see cref="customDebugInfos"/></summary>
+		[MemberNotNull(nameof(customDebugInfos))]
 		protected virtual void InitializeCustomDebugInfos() =>
 			Interlocked.CompareExchange(ref customDebugInfos, new List<PdbCustomDebugInfo>(), null);
 

src/DotNet/AssemblyResolver.cs

@@ -210,7 +210,7 @@ public AssemblyResolver(ModuleContext defaultModuleContext) {
 		}
 
 		/// <inheritdoc/>
-		public AssemblyDef Resolve(IAssembly assembly, ModuleDef sourceModule) {
+		public AssemblyDef? Resolve(IAssembly? assembly, ModuleDef? sourceModule) {
 			if (assembly is null)
 				return null;
 
@@ -387,7 +387,7 @@ static string GetAssemblyNameKey(IAssembly asmName) {
 			return asmName.FullNameToken;
 		}
 
-		AssemblyDef Resolve2(IAssembly assembly, ModuleDef sourceModule) {
+		AssemblyDef Resolve2(IAssembly assembly, ModuleDef? sourceModule) {
 			if (cachedAssemblies.TryGetValue(GetAssemblyNameKey(assembly), out var resolvedAssembly))
 				return resolvedAssembly;
 
@@ -530,7 +530,7 @@ IEnumerable<string> FindAssemblies2(IAssembly assembly, IEnumerable<string> path
 		/// <param name="sourceModule">The module that needs to resolve an assembly or <c>null</c></param>
 		/// <param name="matchExactly">We're trying to find an exact match</param>
 		/// <returns><c>null</c> or an enumerable of full paths to try</returns>
-		protected virtual IEnumerable<string> PreFindAssemblies(IAssembly assembly, ModuleDef sourceModule, bool matchExactly) {
+		protected virtual IEnumerable<string> PreFindAssemblies(IAssembly assembly, ModuleDef? sourceModule, bool matchExactly) {
 			foreach (var path in FindAssemblies2(assembly, preSearchPaths))
 				yield return path;
 		}
@@ -542,7 +542,7 @@ protected virtual IEnumerable<string> PreFindAssemblies(IAssembly assembly, Modu
 		/// <param name="sourceModule">The module that needs to resolve an assembly or <c>null</c></param>
 		/// <param name="matchExactly">We're trying to find an exact match</param>
 		/// <returns><c>null</c> or an enumerable of full paths to try</returns>
-		protected virtual IEnumerable<string> PostFindAssemblies(IAssembly assembly, ModuleDef sourceModule, bool matchExactly) {
+		protected virtual IEnumerable<string> PostFindAssemblies(IAssembly assembly, ModuleDef? sourceModule, bool matchExactly) {
 			foreach (var path in FindAssemblies2(assembly, postSearchPaths))
 				yield return path;
 		}
@@ -554,7 +554,7 @@ protected virtual IEnumerable<string> PostFindAssemblies(IAssembly assembly, Mod
 		/// <param name="sourceModule">The module that needs to resolve an assembly or <c>null</c></param>
 		/// <param name="matchExactly">We're trying to find an exact match</param>
 		/// <returns><c>null</c> or an enumerable of full paths to try</returns>
-		protected virtual IEnumerable<string> FindAssemblies(IAssembly assembly, ModuleDef sourceModule, bool matchExactly) {
+		protected virtual IEnumerable<string> FindAssemblies(IAssembly assembly, ModuleDef? sourceModule, bool matchExactly) {
 			if (assembly.IsContentTypeWindowsRuntime) {
 				string path;
 				try {
@@ -577,13 +577,13 @@ protected virtual IEnumerable<string> FindAssemblies(IAssembly assembly, ModuleD
 				yield return path;
 		}
 
-		IEnumerable<string> FindAssembliesGac(IAssembly assembly, ModuleDef sourceModule, bool matchExactly) {
+		IEnumerable<string> FindAssembliesGac(IAssembly assembly, ModuleDef? sourceModule, bool matchExactly) {
 			if (matchExactly)
 				return FindAssembliesGacExactly(assembly, sourceModule);
 			return FindAssembliesGacAny(assembly, sourceModule);
 		}
 
-		IEnumerable<GacInfo> GetGacInfos(ModuleDef sourceModule) {
+		IEnumerable<GacInfo> GetGacInfos(ModuleDef? sourceModule) {
 			int version = sourceModule is null ? int.MinValue : sourceModule.IsClr40 ? 4 : 2;
 			// Try the correct GAC first (eg. GAC4 if it's a .NET Framework 4 assembly)
 			foreach (var gacInfo in gacInfos) {
@@ -596,7 +596,7 @@ IEnumerable<GacInfo> GetGacInfos(ModuleDef sourceModule) {
 			}
 		}
 
-		IEnumerable<string> FindAssembliesGacExactly(IAssembly assembly, ModuleDef sourceModule) {
+		IEnumerable<string> FindAssembliesGacExactly(IAssembly assembly, ModuleDef? sourceModule) {
 			foreach (var gacInfo in GetGacInfos(sourceModule)) {
 				foreach (var path in FindAssembliesGacExactly(gacInfo, assembly, sourceModule))
 					yield return path;
@@ -607,7 +607,7 @@ IEnumerable<string> FindAssembliesGacExactly(IAssembly assembly, ModuleDef sourc
 			}
 		}
 
-		static IEnumerable<string> GetExtraMonoPaths(IAssembly assembly, ModuleDef sourceModule) {
+		static IEnumerable<string> GetExtraMonoPaths(IAssembly assembly, ModuleDef? sourceModule) {
 			if (extraMonoPaths is not null) {
 				foreach (var dir in extraMonoPaths) {
 					string file;
@@ -624,7 +624,7 @@ static IEnumerable<string> GetExtraMonoPaths(IAssembly assembly, ModuleDef sourc
 			}
 		}
 
-		IEnumerable<string> FindAssembliesGacExactly(GacInfo gacInfo, IAssembly assembly, ModuleDef sourceModule) {
+		IEnumerable<string> FindAssembliesGacExactly(GacInfo gacInfo, IAssembly assembly, ModuleDef? sourceModule) {
 			var pkt = PublicKeyBase.ToPublicKeyToken(assembly.PublicKeyOrToken);
 			if (gacInfo is not null && pkt is not null) {
 				string pktString = pkt.ToString();
@@ -650,7 +650,7 @@ IEnumerable<string> FindAssembliesGacExactly(GacInfo gacInfo, IAssembly assembly
 			}
 		}
 
-		IEnumerable<string> FindAssembliesGacAny(IAssembly assembly, ModuleDef sourceModule) {
+		IEnumerable<string> FindAssembliesGacAny(IAssembly assembly, ModuleDef? sourceModule) {
 			foreach (var gacInfo in GetGacInfos(sourceModule)) {
 				foreach (var path in FindAssembliesGacAny(gacInfo, assembly, sourceModule))
 					yield return path;
@@ -661,7 +661,7 @@ IEnumerable<string> FindAssembliesGacAny(IAssembly assembly, ModuleDef sourceMod
 			}
 		}
 
-		IEnumerable<string> FindAssembliesGacAny(GacInfo gacInfo, IAssembly assembly, ModuleDef sourceModule) {
+		IEnumerable<string> FindAssembliesGacAny(GacInfo gacInfo, IAssembly assembly, ModuleDef? sourceModule) {
 			if (gacInfo is not null) {
 				var asmSimpleName = UTF8String.ToSystemStringOrEmpty(assembly.Name);
 				foreach (var subDir in gacInfo.SubDirs) {
@@ -695,7 +695,7 @@ IEnumerable<string> GetDirs(string baseDir) {
 			return dirs;
 		}
 
-		IEnumerable<string> FindAssembliesModuleSearchPaths(IAssembly assembly, ModuleDef sourceModule, bool matchExactly) {
+		IEnumerable<string> FindAssembliesModuleSearchPaths(IAssembly assembly, ModuleDef? sourceModule, bool matchExactly) {
 			string asmSimpleName = UTF8String.ToSystemStringOrEmpty(assembly.Name);
 			var searchPaths = GetSearchPaths(sourceModule);
 			var exts = assembly.IsContentTypeWindowsRuntime ? winMDAssemblyExtensions : assemblyExtensions;
@@ -725,7 +725,7 @@ IEnumerable<string> FindAssembliesModuleSearchPaths(IAssembly assembly, ModuleDe
 		/// </summary>
 		/// <param name="module">The module or <c>null</c> if unknown</param>
 		/// <returns>A list of all search paths to use for this module</returns>
-		IEnumerable<string> GetSearchPaths(ModuleDef module) {
+		IEnumerable<string> GetSearchPaths(ModuleDef? module) {
 			var keyModule = module;
 			if (keyModule is null)
 				keyModule = nullModule;
@@ -742,14 +742,14 @@ IEnumerable<string> GetSearchPaths(ModuleDef module) {
 		/// </summary>
 		/// <param name="module">The module or <c>null</c> if unknown</param>
 		/// <returns>A list of search paths</returns>
-		protected virtual IEnumerable<string> GetModuleSearchPaths(ModuleDef module) => GetModulePrivateSearchPaths(module);
+		protected virtual IEnumerable<string> GetModuleSearchPaths(ModuleDef? module) => GetModulePrivateSearchPaths(module);
 
 		/// <summary>
 		/// Gets all private assembly search paths as found in the module's <c>.config</c> file.
 		/// </summary>
 		/// <param name="module">The module or <c>null</c> if unknown</param>
 		/// <returns>A list of search paths</returns>
-		protected IEnumerable<string> GetModulePrivateSearchPaths(ModuleDef module) {
+		protected IEnumerable<string> GetModulePrivateSearchPaths(ModuleDef? module) {
 			if (module is null)
 				return Array2.Empty<string>();
 			var asm = module.Assembly;

src/DotNet/Constant.cs

@@ -37,12 +37,12 @@ public ElementType Type {
 		/// <summary>
 		/// From column Constant.Value
 		/// </summary>
-		public object Value {
+		public object? Value {
 			get => value;
 			set => this.value = value;
 		}
 		/// <summary/>
-		protected object value;
+		protected object? value;
 	}
 
 	/// <summary>
@@ -128,7 +128,7 @@ public ConstantMD(ModuleDefMD readerModule, uint rid) {
 			value = GetValue(type, ref reader);
 		}
 
-		static object GetValue(ElementType etype, ref DataReader reader) {
+		static object? GetValue(ElementType etype, ref DataReader reader) {
 			switch (etype) {
 			case ElementType.Boolean:
 				if (reader.Length < 1)

src/DotNet/CorLibTypes.cs

@@ -97,15 +97,9 @@ public CorLibTypes(ModuleDef module)
 		/// <param name="module">The owner module</param>
 		/// <param name="corLibAssemblyRef">Corlib assembly reference or <c>null</c> if a default
 		/// assembly reference should be created</param>
-		public CorLibTypes(ModuleDef module, AssemblyRef corLibAssemblyRef) {
+		public CorLibTypes(ModuleDef module, AssemblyRef? corLibAssemblyRef) {
 			this.module = module;
 			this.corLibAssemblyRef = corLibAssemblyRef ?? CreateCorLibAssemblyRef();
-			Initialize();
-		}
-
-		AssemblyRef CreateCorLibAssemblyRef() => module.UpdateRowId(AssemblyRefUser.CreateMscorlibReferenceCLR20());
-
-		void Initialize() {
 			bool isCorLib = module.Assembly.IsCorLib();
 			typeVoid	= new CorLibTypeSig(CreateCorLibTypeRef(isCorLib, "Void"),		ElementType.Void);
 			typeBoolean	= new CorLibTypeSig(CreateCorLibTypeRef(isCorLib, "Boolean"),	ElementType.Boolean);
@@ -127,6 +121,8 @@ void Initialize() {
 			typeObject	= new CorLibTypeSig(CreateCorLibTypeRef(isCorLib, "Object"),	ElementType.Object);
 		}
 
+		AssemblyRef CreateCorLibAssemblyRef() => module.UpdateRowId(AssemblyRefUser.CreateMscorlibReferenceCLR20());
+
 		ITypeDefOrRef CreateCorLibTypeRef(bool isCorLib, string name) {
 			var tr = new TypeRefUser(module, "System", name, corLibAssemblyRef);
 			if (isCorLib) {