#2362: Provide more information on assembly resolve errors

ICSharpCode.Decompiler/CSharp/ProjectDecompiler/TargetServices.cs

@@ -250,7 +250,7 @@ namespace ICSharpCode.Decompiler.CSharp.ProjectDecompiler
 				{
 					resolvedReference = assemblyResolver.Resolve(reference);
 				}
-				catch (AssemblyResolutionException)
+				catch (ResolutionException)
 				{
 					resolvedReference = null;
 				}

ICSharpCode.Decompiler/Metadata/AssemblyReferences.cs

@@ -19,7 +19,6 @@
 #nullable enable
 
 using System;
-using System.IO;
 using System.Linq;
 using System.Reflection;
 using System.Reflection.Metadata;
@@ -29,19 +28,31 @@ using System.Threading.Tasks;
 
 namespace ICSharpCode.Decompiler.Metadata
 {
-	public sealed class AssemblyResolutionException : FileNotFoundException
+	public sealed class ResolutionException : Exception
 	{
-		public IAssemblyReference Reference { get; }
+		public IAssemblyReference? Reference { get; }
 
-		public AssemblyResolutionException(IAssemblyReference reference)
+		public string? ModuleName { get; }
-			: this(reference, null)
+
+		public string? MainModuleFullPath { get; }
+
+		public string? ResolvedFullPath { get; }
+
+		public ResolutionException(IAssemblyReference reference, string? resolvedPath, Exception? innerException)
+			: base($"Failed to resolve assembly: '{reference}'{Environment.NewLine}" +
+				  $"Resolve result: {resolvedPath ?? "<not found>"}", innerException)
 		{
+			this.Reference = reference ?? throw new ArgumentNullException(nameof(reference));
+			this.ResolvedFullPath = resolvedPath;
 		}
 
-		public AssemblyResolutionException(IAssemblyReference reference, Exception? innerException)
+		public ResolutionException(string mainModule, string moduleName, string? resolvedPath, Exception? innerException)
-			: base($"Failed to resolve assembly: '{reference}'", innerException)
+			: base($"Failed to resolve module: '{moduleName} of {mainModule}'{Environment.NewLine}" +
+				  $"Resolve result: {resolvedPath ?? "<not found>"}", innerException)
 		{
-			this.Reference = reference;
+			this.MainModuleFullPath = mainModule ?? throw new ArgumentNullException(nameof(mainModule));
+			this.ModuleName = moduleName ?? throw new ArgumentNullException(nameof(moduleName));
+			this.ResolvedFullPath = resolvedPath;
 		}
 	}
 

ICSharpCode.Decompiler/Metadata/UniversalAssemblyResolver.cs

@@ -194,26 +194,41 @@ namespace ICSharpCode.Decompiler.Metadata
 		public PEFile Resolve(IAssemblyReference name)
 		{
 			var file = FindAssemblyFile(name);
-			if (file == null)
+			return CreatePEFileFromFileName(file, ex => new ResolutionException(name, file, ex));
-			{
-				if (throwOnError)
-					throw new AssemblyResolutionException(name);
-				return null;
-			}
-			return new PEFile(file, new FileStream(file, FileMode.Open, FileAccess.Read), streamOptions, metadataOptions);
 		}
 
 		public PEFile ResolveModule(PEFile mainModule, string moduleName)
 		{
 			string baseDirectory = Path.GetDirectoryName(mainModule.FileName);
 			string moduleFileName = Path.Combine(baseDirectory, moduleName);
-			if (!File.Exists(moduleFileName))
+			return CreatePEFileFromFileName(moduleFileName, ex => new ResolutionException(mainModule.FileName, moduleName, moduleFileName, ex));
+		}
+
+		private PEFile CreatePEFileFromFileName(string fileName, Func<Exception?, Exception> makeException)
+		{
+			if (fileName == null)
 			{
 				if (throwOnError)
-					throw new Exception($"Module {moduleName} could not be found!");
+					throw makeException(null);
 				return null;
 			}
-			return new PEFile(moduleFileName, new FileStream(moduleFileName, FileMode.Open, FileAccess.Read), streamOptions, metadataOptions);
+
+			try
+			{
+				FileStream stream = new FileStream(fileName, FileMode.Open, FileAccess.Read);
+				return new PEFile(fileName, stream, streamOptions, metadataOptions);
+			}
+			catch (BadImageFormatException ex)
+			{
+				if (throwOnError)
+					throw makeException(ex);
+			}
+			catch (IOException ex)
+			{
+				if (throwOnError)
+					throw makeException(ex);
+			}
+			return null;
 		}
 
 		public Task<PEFile> ResolveAsync(IAssemblyReference name)
@@ -401,7 +416,7 @@ namespace ICSharpCode.Decompiler.Metadata
 			}
 
 			if (throwOnError)
-				throw new AssemblyResolutionException(name);
+				throw new ResolutionException(name, null, null);
 			return null;
 		}