Better errors for incorrect usage

src/CLI.cs

@@ -30,19 +30,42 @@ private class Options
 
 	public int Run(string[] args)
 	{
-		Console.Out.WriteLine("https://github.com/timabell/sln-items-sync");
-		Console.Out.WriteLine("https://www.nuget.org/packages/sln-items-sync");
-		Console.Out.WriteLine("A-GPL v3 Licensed");
+		Console.Error.WriteLine("https://github.com/timabell/sln-items-sync");
+		Console.Error.WriteLine("https://www.nuget.org/packages/sln-items-sync");
+		Console.Error.WriteLine("A-GPL v3 Licensed");
+		Console.Error.WriteLine();
 		var parserResult = Parser.Default.ParseArguments<Options>(args);
 		if (parserResult.Errors.Any())
 		{
+			WriteUsage();
 			return 1;
 		}
 
-		parserResult
-			.WithParsed(opts =>
-				_slnSync.SyncSlnFile(slnPath: opts.SlnPath, slnFolder: opts.SlnFolder, opts.Paths));
+		try
+		{
+			parserResult
+				.WithParsed(opts =>
+					_slnSync.SyncSlnFile(slnPath: opts.SlnPath, slnFolder: opts.SlnFolder, opts.Paths));
+		} catch(InvalidSlnPathException ex) {
+			Console.Error.WriteLine(ex.Message);
+			return 2;
+		} catch(PathNotFoundException ex) {
+			Console.Error.WriteLine(ex.Message);
+			return 3;
+		} catch(EmptyPathListException) {
+			Console.Error.WriteLine("No paths supplied to sync with.");
+			Console.Error.WriteLine("Supply a list of folder/file arguments that you want to be sync'd into the target solution folder.");
+			Console.Error.WriteLine();
+			WriteUsage();
+			return 4;
+		}
 
+		Console.Out.WriteLine("Sync completed.");
 		return 0;
 	}
+
+	private static void WriteUsage()
+	{
+		Console.Error.WriteLine("Usage: sln-items-sync --solution <SolutionFile.sln> paths-to-sync ...");
+	}
 }

src/SlnSync.cs

@@ -1,3 +1,4 @@
+using System.Runtime.Serialization;
 using System.Text;
 using SlnEditor.Models;
 
@@ -19,6 +20,14 @@ public SlnSync() : this(new DefaultGuidGenerator())
 	/// <param name="paths">list of paths to recursively add/update SolutionItems virtual folders with</param>
 	public void SyncSlnFile(string slnPath, string slnFolder, IEnumerable<string> paths)
 	{
+		if (!File.Exists(slnPath) || !slnPath.EndsWith(".sln"))
+		{
+			throw new InvalidSlnPathException($"'{slnPath}' is not a sln file");
+		}
+		if (!paths.Any())
+		{
+			throw new EmptyPathListException();
+		}
 		var contents = File.ReadAllText(slnPath);
 		var updatedSln = SyncSlnText(contents, slnFolder, paths);
 		File.WriteAllText(slnPath, updatedSln, Encoding.UTF8); // explicit UTF-8 to get byte-order marker (which sln files seem to have)
@@ -42,7 +51,7 @@ public string SyncSlnText(string contents, string slnFolder, IEnumerable<string>
 			}
 			else
 			{
-				throw new Exception($"path not found: '{path}'");
+				throw new PathNotFoundException(path);
 			}
 		}
 
@@ -111,3 +120,7 @@ private SolutionFolder FindOrCreateSolutionFolder(ICollection<IProject> solution
 	private static SolutionFolder? FindSolutionFolder(IEnumerable<IProject> solutionProjects, string folderName)
 		=> solutionProjects.OfType<SolutionFolder>().FirstOrDefault(project => project.Name == folderName);
 }
+
+public class PathNotFoundException(string path) : Exception($"Path '{path}' not found");
+public class InvalidSlnPathException(string s) : Exception(s);
+public class EmptyPathListException() : Exception();

tests/IntegrationTests.cs

@@ -425,8 +425,13 @@ public void AddsBOM()
 EndGlobal
 ");
 
+		SetupFilesystem(new[]
+		{
+			"some-file.txt",
+		});
+
 		// Act
-		_cli.Run(["-s", TargetSlnFile]);
+		_cli.Run(["-s", TargetSlnFile, "some-file.txt"]);
 
 		File.ReadAllText(Path.Combine(_testFolder, TargetSlnFile));