[nnyeah] Centralize error handling (#15064)

- Due to microsoft/vstest#3658 it is not possible to test code that exits the process on error
- Create a base class for nnyeah exceptions that we want to explicitly report (and not crash), ConversionException
- Move Main to Main2 and wrap it in a try/catch for this exception

tools/nnyeah/nnyeah/Errors.resx

@@ -41,6 +41,10 @@
 		<value>If you want to compare assemblies, the earlier and later assembly options *must* be set.</value>
 	</data>
 
+	<data name="N0008" xml:space="preserve">
+		<value>Unexpected error - Please file a bug report at https://github.com/xamarin/xamarin-macios/issues/new</value>
+	</data>
+
 	<data name="E0001" xml:space="preserve">
 		<value>Input file '{0}' doesn't exist.</value>
 	</data>

tools/nnyeah/nnyeah/MemberNotFoundException.cs

@@ -1,6 +1,6 @@
 using System;
 namespace Microsoft.MaciOS.Nnyeah {
-	public class MemberNotFoundException : Exception {
+	public class MemberNotFoundException : ConversionException {
 		public MemberNotFoundException (string memberName)
 			: base ($"Member {memberName} not found.")
 		{

tools/nnyeah/nnyeah/Program.cs

@@ -7,8 +7,34 @@
 using System.Diagnostics.CodeAnalysis;
 
 namespace Microsoft.MaciOS.Nnyeah {
+	public class ConversionException : Exception {
+		public ConversionException (string message) : base (message)
+		{
+		}
+
+		public ConversionException (string message, params object? [] args) : base (string.Format(message, args))
+		{
+		}
+	}
+
 	public class Program {
-		static void Main (string [] args)
+		static int Main (string [] args)
+		{
+			try {
+				Main2 (args);
+				return 0;
+			}
+			catch (ConversionException e) {
+				Console.Error.WriteLine (e.Message);
+				return 1;
+			} catch (Exception e) {
+				Console.Error.WriteLine (Errors.N0008);
+				Console.Error.WriteLine (e);
+				return 1;
+			}
+		}
+
+		static void Main2 (string [] args)
 		{
 			var doHelp = false;
 			string? infile = null, outfile = null;
@@ -35,22 +61,20 @@ static void Main (string [] args)
 			}
 
 			if (infile is null || outfile is null) {
-				Console.Error.WriteLine (Errors.E0014);
-				Environment.Exit (1);
+				throw new ConversionException (Errors.E0014);
 			}
 
 			// TODO - Long term this should default to files packaged within the tool but allow overrides
 			if (xamarinAssembly is null || microsoftAssembly is null) {
-				Console.Error.WriteLine (Errors.E0015);
-				Environment.Exit (1);
+				throw new ConversionException (Errors.E0015);
 			}
 
 			if (doHelp) {
 				PrintOptions (options, Console.Out);
-				Environment.Exit (0);
 			}
-			ProcessAssembly (xamarinAssembly!, microsoftAssembly!, infile!,
-				outfile!, verbose, forceOverwrite, suppressWarnings);
+			else {
+				ProcessAssembly (xamarinAssembly!, microsoftAssembly!, infile!, outfile!, verbose, forceOverwrite, suppressWarnings);
+			}
 		}
 
 		public static void ProcessAssembly (string xamarinAssembly,
@@ -134,9 +158,7 @@ static bool TryLoadTypeAndModuleMap (string earlier, string later, bool publicOn
 
 				return Reworker.CreateReworker (stm, moduleContainer, typeMap);
 			} catch (Exception e) {
-				Console.Error.WriteLine (Errors.E0003, infile, e.Message);
-				Environment.Exit (1);
-				throw;
+				throw new ConversionException (Errors.E0003, infile, e.Message);
 			}
 		}
 
@@ -149,13 +171,11 @@ static void ReworkFile (string infile, string outfile, bool verbose, bool forceO
 			var transforms = new List<string> ();
 
 			if (!File.Exists (infile)) {
-				Console.Error.WriteLine (Errors.E0001, infile);
-				Environment.Exit (1);
+				throw new ConversionException (Errors.E0001, infile);
 			}
 
 			if (File.Exists (outfile) && !forceOverwrite) {
-				Console.Error.WriteLine (Errors.E0002, outfile);
-				Environment.Exit (1);
+				throw new ConversionException (Errors.E0002, outfile);
 			}
 
 			if (CreateReworker (infile, typeMap, xamarinModule, microsoftModule) is Reworker reworker) {
@@ -172,14 +192,11 @@ static void ReworkFile (string infile, string outfile, bool verbose, bool forceO
 						warnings.ForEach (Console.WriteLine);
 					}
 				} catch (TypeNotFoundException e) {
-					Console.Error.Write (Errors.E0012, e.TypeName);
-					Environment.Exit (1);
+					throw new ConversionException (Errors.E0012, e.TypeName);
 				} catch (MemberNotFoundException e) {
-					Console.Error.WriteLine (Errors.E0013, e.MemberName);
-					Environment.Exit (1);
+					throw new ConversionException (Errors.E0013, e.MemberName);
 				} catch (Exception e) {
-					Console.Error.WriteLine (Errors.E0004, e.Message);
-					Environment.Exit (1);
+					throw new ConversionException (Errors.E0004, e.Message);
 				}
 			} else {
 				if (verbose) {
@@ -193,15 +210,12 @@ static Stream TryOpenRead (string path)
 			try {
 				var stm = new FileStream (path, FileMode.Open, FileAccess.Read);
 				if (stm is null) {
-					Console.Error.WriteLine (Errors.E0006, path, "");
-					Environment.Exit (1);
+					throw new ConversionException (Errors.E0006, path, "");
 				}
 				return stm;
 			} catch (Exception e) {
-				Console.Error.WriteLine (Errors.E0006, path, e.Message);
-				Environment.Exit (1);
+				throw new ConversionException (Errors.E0006, path, e.Message);
 			}
-			return new MemoryStream (); // never reached, thanks code analysis
 		}
 
 		static void PrintOptions (OptionSet options, TextWriter writer)

tools/nnyeah/nnyeah/TypeNotFoundException.cs

@@ -1,6 +1,6 @@
 using System;
 namespace Microsoft.MaciOS.Nnyeah {
-	public class TypeNotFoundException : Exception {
+	public class TypeNotFoundException : ConversionException {
 		public TypeNotFoundException (string typeName)
 			: base ($"The type {typeName} was not found.")
 		{