Fix handling of relative paths

Confuser.Core/ConfuserEngine.cs

@@ -379,10 +379,17 @@ static void OptimizeMethods(ConfuserContext context) {
 
 		static void EndModule(ConfuserContext context) {
 			string output = context.Modules[context.CurrentModuleIndex].Location;
-			if (output != null) {
+			if (!(output is null)) {
 				if (!Path.IsPathRooted(output))
-					output = Path.Combine(Environment.CurrentDirectory, output);
-				output = Utils.GetRelativePath(output, context.BaseDirectory);
+					output = Path.Combine(context.BaseDirectory, output);
+				string relativeOutput = Utils.GetRelativePath(output, context.BaseDirectory);
+				if (relativeOutput is null) {
+					context.Logger.WarnFormat("Input file is not inside the base directory. Relative path can't be created. Placing file into output root." +
+						Environment.NewLine + "Responsible file is: {0}", output);
+					output = Path.GetFileName(output);
+				} else {
+					output = relativeOutput;
+				}
 			}
 			else {
 				output = context.CurrentModule.Name;

Confuser.Core/Utils.cs

@@ -71,19 +71,33 @@ public static void AddListEntry<TKey, TValue>(this IDictionary<TKey, List<TValue
 		/// <summary>
 		///     Obtains the relative path from the specified base path.
 		/// </summary>
-		/// <param name="filespec">The file path.</param>
-		/// <param name="folder">The base path.</param>
+		/// <param name="fileSpec">The file path.</param>
+		/// <param name="baseDirectory">The base path.</param>
 		/// <returns>The path of <paramref name="filespec" /> relative to <paramref name="folder" />.</returns>
-		public static string GetRelativePath(string filespec, string folder) {
-			//http://stackoverflow.com/a/703292/462805
+		public static string GetRelativePath(string fileSpec, string baseDirectory) {
+			if (fileSpec is null) throw new ArgumentNullException(nameof(fileSpec));
+			if (baseDirectory is null) throw new ArgumentNullException(nameof(fileSpec));
 
-			var pathUri = new Uri(filespec);
-			// Folders must end in a slash
-			if (!folder.EndsWith(Path.DirectorySeparatorChar.ToString())) {
-				folder += Path.DirectorySeparatorChar;
+			return GetRelativePath(new FileInfo(fileSpec), new DirectoryInfo(baseDirectory));
+		}
+
+		public static string GetRelativePath(FileInfo fileSpec, DirectoryInfo baseDirectory) {
+			if (fileSpec is null) throw new ArgumentNullException(nameof(fileSpec));
+			if (baseDirectory is null) throw new ArgumentNullException(nameof(fileSpec));
+
+			if (baseDirectory.FullName.EndsWith(Path.DirectorySeparatorChar.ToString())) {
+				baseDirectory = new DirectoryInfo(baseDirectory.FullName.TrimEnd(Path.DirectorySeparatorChar));
 			}
-			var folderUri = new Uri(folder);
-			return Uri.UnescapeDataString(folderUri.MakeRelativeUri(pathUri).ToString().Replace('/', Path.DirectorySeparatorChar));
+
+			var relativePath = fileSpec.Name;
+			var currentDirectory = fileSpec.Directory;
+			while (!(currentDirectory is null) && !string.Equals(currentDirectory.FullName, baseDirectory.FullName, StringComparison.OrdinalIgnoreCase)) {
+				relativePath = currentDirectory.Name + Path.DirectorySeparatorChar + relativePath;
+				currentDirectory = currentDirectory.Parent;
+			}
+
+			if (currentDirectory is null) return null; //file is not inside the base directory
+			return relativePath;
 		}
 
 		/// <summary>

ConfuserEx/ViewModel/UI/ProjectTabVM.cs

@@ -117,7 +117,7 @@ void AddModule(string file) {
 			}
 			var module = new ProjectModuleVM(App.Project, new ProjectModule());
 			try {
-				module.Path = Confuser.Core.Utils.GetRelativePath(file, App.Project.BaseDirectory);
+				module.Path = Confuser.Core.Utils.GetRelativePath(file, App.Project.BaseDirectory) ?? file;
 			}
 			catch {
 				module.Path = file;

Tests/Confuser.Core.Test/UtilsTest.cs

@@ -0,0 +1,27 @@
+using System.Collections.Generic;
+using Xunit;
+
+namespace Confuser.Core.Test {
+	public class UtilsTest {
+		[Theory]
+		[MemberData(nameof(BuildRelativePathTestData))]
+		[Trait("Issue", "https://github.com/mkaring/ConfuserEx/issues/413")]
+		public void BuildRelativePath(string baseDirectory, string fileReference, string expectedRelativePath) => 
+			Assert.Equal(expectedRelativePath, Utils.GetRelativePath(fileReference, baseDirectory), ignoreCase: true);
+
+		public static IEnumerable<object[]> BuildRelativePathTestData() {
+			yield return new object[] { "C:\\Test", "C:\\Test\\Asm.dll", "Asm.dll" };
+			yield return new object[] { "C:\\Test\\", "C:\\Test\\Asm.dll", "Asm.dll" };
+			yield return new object[] { "C:\\Test", "C:\\Test\\Test2\\Asm.dll", "Test2\\Asm.dll" };
+			yield return new object[] { "C:\\Test\\", "C:\\Test\\Test2\\Asm.dll", "Test2\\Asm.dll" };
+			yield return new object[] { "C:\\Test", "C:\\Test\\Test2\\Test3\\Asm.dll", "Test2\\Test3\\Asm.dll" };
+			yield return new object[] { "C:\\Test\\", "C:\\Test\\Test2\\Test3\\Asm.dll", "Test2\\Test3\\Asm.dll" };
+			yield return new object[] { "C:\\Test", "C:\\Test2\\Asm.dll", null };
+			yield return new object[] { "C:\\Test\\", "C:\\Test2\\Asm.dll", null };
+
+			// Only for case insensitive file systems (windows)
+			yield return new object[] { "C:\\Test", "c:\\test\\test2\\test3\\asm.dll", "Test2\\Test3\\Asm.dll" };
+			yield return new object[] { "C:\\Test", "C:\\TEST\\TEST2\\TEST3\\ASM.DLL", "Test2\\Test3\\Asm.dll" };
+		}
+	}
+}