Fixed #1164: AddIn opens reference assembly when trying to open symbol in ILSpy

ICSharpCode.Decompiler/DotNetCore/DotNetCorePathFinder.cs

@@ -5,6 +5,7 @@ using System.IO;
 using System.Linq;
 using System.Runtime.InteropServices;
 using System.Text;
+using ICSharpCode.Decompiler.Util;
 using LightJson.Serialization;
 using Mono.Cecil;
 
@@ -27,7 +28,7 @@ namespace ICSharpCode.Decompiler
 				this.Version = parts[1];
 				this.Type = type;
 				this.Path = path;
-				this.RuntimeComponents = runtimeComponents ?? new string[0];
+				this.RuntimeComponents = runtimeComponents ?? Empty<string>.Array;
 			}
 		}
 

ICSharpCode.Decompiler/DotNetCore/DotNetCorePathFinderExtensions.cs

@@ -1,6 +1,7 @@
 using System;
 using System.Collections.Generic;
 using System.Linq;
+using System.Text.RegularExpressions;
 using ICSharpCode.Decompiler.TypeSystem.Implementation;
 using Mono.Cecil;
 
@@ -8,7 +9,11 @@ namespace ICSharpCode.Decompiler
 {
 	public static class DotNetCorePathFinderExtensions
 	{
-		public static string DetectTargetFrameworkId(this AssemblyDefinition assembly)
+		static readonly string RefPathPattern =
+			@"(Reference Assemblies[/\\]Microsoft[/\\]Framework[/\\](?<1>.NETFramework)[/\\]v(?<2>[^/\\]+)[/\\])" +
+			@"|(NuGetFallbackFolder[/\\](?<1>[^/\\]+)\\(?<2>[^/\\]+)([/\\].*)?[/\\]ref[/\\])";
+
+		public static string DetectTargetFrameworkId(this AssemblyDefinition assembly, string assemblyPath = null)
 		{
 			if (assembly == null)
 				throw new ArgumentNullException(nameof(assembly));
@@ -24,6 +29,31 @@ namespace ICSharpCode.Decompiler
 				}
 			}
 
+			// Optionally try to detect target version through assembly path as a fallback (use case: reference assemblies)
+			if (assemblyPath != null) {
+				/*
+				 * Detected path patterns (examples):
+				 * 
+				 * - .NETFramework -> C:\Program Files (x86)\Reference Assemblies\Microsoft\Framework\.NETFramework\v4.6.1\mscorlib.dll
+				 * - .NETCore      -> C:\Program Files\dotnet\sdk\NuGetFallbackFolder\microsoft.netcore.app\2.1.0\ref\netcoreapp2.1\System.Console.dll
+				 * - .NETStandard  -> C:\Program Files\dotnet\sdk\NuGetFallbackFolder\netstandard.library\2.0.3\build\netstandard2.0\ref\netstandard.dll
+				 */
+				var pathMatch = Regex.Match(assemblyPath, RefPathPattern, 
+					RegexOptions.IgnoreCase | RegexOptions.Compiled | RegexOptions.ExplicitCapture);
+				if (pathMatch.Success) {
+					var type = pathMatch.Groups[1].Value;
+					var version = pathMatch.Groups[2].Value;
+
+					if (type == ".NETFramework") {
+						return $".NETFramework,Version=v{version}";
+					} else if (type.Contains("netcore")) {
+						return $".NETCoreApp,Version=v{version}";
+					} else if (type.Contains("netstandard")) {
+						return $".NETStandard,Version=v{version}";
+					}
+				}
+			}
+
 			return string.Empty;
 		}
 	}

ILSpy.AddIn/AssemblyFileFinder.cs

@@ -0,0 +1,61 @@
+using System;
+using System.Collections.Generic;
+using System.IO;
+using System.Linq;
+using System.Text;
+using System.Text.RegularExpressions;
+using ICSharpCode.Decompiler;
+using ICSharpCode.Decompiler.Util;
+using Mono.Cecil;
+
+namespace ICSharpCode.ILSpy.AddIn
+{
+	public class AssemblyFileFinder
+	{
+		public static string FindAssemblyFile(AssemblyDefinition assemblyDefinition, string assemblyFile)
+		{
+			var assemblyName = assemblyDefinition.Name;
+
+			var detectedTargetFramework = assemblyDefinition.DetectTargetFrameworkId(assemblyFile);
+			if (string.IsNullOrEmpty(detectedTargetFramework)) {
+				// Without a target framework id it makes no sense to continue
+				return null;
+			}
+
+			var targetFramework = detectedTargetFramework.Split(new[] { ",Version=v" }, StringSplitOptions.None);
+			string file = null;
+			switch (targetFramework[0]) {
+				case ".NETCoreApp":
+				case ".NETStandard":
+					if (targetFramework.Length != 2)
+						return FindAssemblyFromGAC(assemblyDefinition);
+					var version = targetFramework[1].Length == 3 ? targetFramework[1] + ".0" : targetFramework[1];
+					var dotNetCorePathFinder = new DotNetCorePathFinder(assemblyFile, detectedTargetFramework, version);
+					file = dotNetCorePathFinder.TryResolveDotNetCore(assemblyName);
+					if (file != null)
+						return file;
+					return FindAssemblyFromGAC(assemblyDefinition);
+				default:
+					return FindAssemblyFromGAC(assemblyDefinition);
+			}
+		}
+
+		static string FindAssemblyFromGAC(AssemblyDefinition assemblyDefinition)
+		{
+			return GacInterop.FindAssemblyInNetGac(assemblyDefinition.Name);
+		}
+
+		static readonly string RefPathPattern = @"NuGetFallbackFolder[/\\][^/\\]+[/\\][^/\\]+[/\\]ref[/\\]";
+
+		public static bool IsReferenceAssembly(AssemblyDefinition assemblyDef, string assemblyFile)
+		{
+			if (assemblyDef.CustomAttributes.Any(ca => ca.AttributeType.FullName == "System.Runtime.CompilerServices.ReferenceAssemblyAttribute"))
+				return true;
+
+			// Try to detect reference assembly through specific path pattern
+			var refPathMatch = Regex.Match(assemblyFile, RefPathPattern, RegexOptions.IgnoreCase | RegexOptions.Compiled);
+			return refPathMatch.Success;
+		}
+
+	}
+}

ILSpy.AddIn/Commands/OpenILSpyCommand.cs

@@ -89,8 +89,8 @@ namespace ICSharpCode.ILSpy.AddIn.Commands
 			foreach (var reference in parentProject.MetadataReferences) {
 				using (var assemblyDef = AssemblyDefinition.ReadAssembly(reference.Display)) {
 					string assemblyName = assemblyDef.Name.Name;
-					if (IsReferenceAssembly(assemblyDef)) {
+					if (AssemblyFileFinder.IsReferenceAssembly(assemblyDef, reference.Display)) {
-						string resolvedAssemblyFile = GacInterop.FindAssemblyInNetGac(assemblyDef.Name);
+						string resolvedAssemblyFile = AssemblyFileFinder.FindAssemblyFile(assemblyDef, reference.Display);
 						dict.Add(assemblyName, 
 							new DetectedReference(assemblyName, resolvedAssemblyFile, false));
 					} else {
@@ -127,11 +127,6 @@ namespace ICSharpCode.ILSpy.AddIn.Commands
 
 			return null;
 		}
-
-		protected bool IsReferenceAssembly(AssemblyDefinition assemblyDef)
-		{
-			return assemblyDef.CustomAttributes.Any(ca => ca.AttributeType.FullName == "System.Runtime.CompilerServices.ReferenceAssemblyAttribute");
-		}
 	}
 
 	class OpenILSpyCommand : ILSpyCommand

ILSpy.AddIn/ILSpy.AddIn.csproj

@@ -85,6 +85,7 @@
     <Compile Include="Properties\AssemblyInfo.cs" />
     <Compile Include="PkgCmdID.cs" />
     <Compile Include="SyntaxNodeExtensions.cs" />
+    <Compile Include="AssemblyFileFinder.cs" />
     <Compile Include="Utils.cs" />
   </ItemGroup>