Add basic logic to ErrorReportingSubsystem

Author: JeanJoeris

src/System.CommandLine.Subsystems/ConsoleHack.cs

@@ -10,7 +10,7 @@ public class ConsoleHack
     private readonly StringBuilder buffer = new();
     private bool redirecting = false;
 
-    public void WriteLine(string text)
+    public void WriteLine(string text = "")
     {
         if (redirecting)
         {

src/System.CommandLine.Subsystems/ErrorReportingSubsystem.cs

@@ -1,24 +1,48 @@
 // Copyright (c) .NET Foundation and contributors. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
+using System.CommandLine.Parsing;
 using System.CommandLine.Subsystems;
 using System.CommandLine.Subsystems.Annotations;
 
 namespace System.CommandLine;
 
+/// <summary>
+/// 
+/// </summary>
+/// <remarks>
+/// </remarks>
 public class ErrorReportingSubsystem : CliSubsystem
 {
     public ErrorReportingSubsystem(IAnnotationProvider? annotationProvider = null)
         : base(ErrorReportingAnnotations.Prefix, SubsystemKind.ErrorReporting, annotationProvider)
     { }
 
-    // TODO: Stash option rather than using string
     protected internal override bool GetIsActivated(ParseResult? parseResult)
         => parseResult is not null && parseResult.Errors.Any();
 
     protected internal override CliExit Execute(PipelineContext pipelineContext)
     {
-        pipelineContext.ConsoleHack.WriteLine("You have errors!");
+        var _ = pipelineContext.ParseResult
+            ?? throw new ArgumentNullException($"{nameof(pipelineContext)}.ParseResult");
+
+        Report(pipelineContext.ConsoleHack, pipelineContext.ParseResult.Errors);
+
         return CliExit.SuccessfullyHandled(pipelineContext.ParseResult);
     }
+
+    // TODO: internal, protected virtual?
+    public void Report(ConsoleHack consoleHack, IReadOnlyList<ParseError> errors)
+    {
+        ConsoleHelpers.ResetTerminalForegroundColor();
+        ConsoleHelpers.SetTerminalForegroundRed();
+
+        foreach (var error in errors)
+        {
+            consoleHack.WriteLine(error.Message);
+        }
+        consoleHack.WriteLine();
+
+        ConsoleHelpers.ResetTerminalForegroundColor();
+    }
 }

src/System.CommandLine/ConsoleHelpers.cs

@@ -5,7 +5,8 @@
 
 namespace System.CommandLine
 {
-    internal static class ConsoleHelpers
+    // TODO: Added to project and made public for use in ErrorReportingSubsystem
+    public static class ConsoleHelpers
     {
         private static readonly bool ColorsAreSupported = GetColorsAreSupported();
 
@@ -20,15 +21,15 @@ private static bool GetColorsAreSupported()
 #endif
             && !Console.IsOutputRedirected;
 
-        internal static void SetTerminalForegroundRed()
+        public static void SetTerminalForegroundRed()
         {
             if (ColorsAreSupported)
             {
                 Console.ForegroundColor = ConsoleColor.Red;
             }
         }
 
-        internal static void ResetTerminalForegroundColor()
+        public static void ResetTerminalForegroundColor()
         {
             if (ColorsAreSupported)
             {

src/System.CommandLine/System.CommandLine.csproj

@@ -46,6 +46,7 @@
     <Compile Include="CliOption{T}.cs" />
     <Compile Include="CliRootCommand.cs" />
     <Compile Include="CliSymbol.cs" />
+    <Compile Include="ConsoleHelpers.cs" />
     <Compile Include="LocalizationResources.cs" />
     <Compile Include="ParseResult.cs" />
     <Compile Include="Parsing\ArgumentResult.cs" />