Change ICommandLineValidatable so that Validate no longer returns a ConsoleColoredString; instead, parse failures are expected to throw CommandLineValidationException.

Author: Timwi

Src/CommandLineParser.cs

@@ -498,12 +498,15 @@ private static object parseCommandLine(string[] args, Type type, int i, Func<Con
         if (missingMandatories.Count > 0)
             throw new MissingParameterException(missingMandatories[0], swallowingField, !missingMandatories[0].IsDefined<IsPositionalAttribute>(), getHelpGenerator(type, helpProcessor));
 
-        ConsoleColoredString error = null;
-        if (typeof(ICommandLineValidatable).IsAssignableFrom(type))
-            error = ((ICommandLineValidatable) ret).Validate();
-
-        if (error != null)
-            throw new CommandLineValidationException(error, getHelpGenerator(type, helpProcessor));
+        try
+        {
+            if (ret is ICommandLineValidatable v)
+                v.Validate();
+        }
+        catch (CommandLineValidationException exc) when (exc.GenerateHelpFunc == null)
+        {
+            throw new CommandLineValidationException(exc.Message, getHelpGenerator(type, helpProcessor));
+        }
 
         return ret;
     }

Src/Exceptions.cs

@@ -181,9 +181,14 @@ public sealed class InvalidNumericParameterException(string fieldName, Func<int,
     public InvalidNumericParameterException(string fieldName, Func<int, ConsoleColoredString> helpGenerator) : this(fieldName, helpGenerator, null) { }
 }
 
-/// <summary>Specifies that the arguments specified by the user on the command-line do not pass the custom validation checks.</summary>
+/// <summary>
+///     Indicates that the arguments specified by the user on the command-line do not pass the custom validation check.</summary>
+/// <param name="message">
+///     Provide a helpful, descriptive message for the user to determine how to provide a valid command-line parameter.</param>
+/// <param name="helpGenerator">
+///     Used internally to generate the help screen; omit if throwing from a validation check.</param>
 [Serializable]
-public sealed class CommandLineValidationException(ConsoleColoredString message, Func<int, ConsoleColoredString> helpGenerator)
+public sealed class CommandLineValidationException(ConsoleColoredString message, Func<int, ConsoleColoredString> helpGenerator = null)
     : CommandLineParseException(message, helpGenerator)
 {
 }

Src/ICommandLineValidatable.cs

@@ -1,14 +1,17 @@
-using RT.Util.Consoles;
+using RT.Util.Consoles;
 
 namespace RT.CommandLine;
 
 /// <summary>
 ///     Contains methods to validate a set of parameters passed by the user on the command-line and parsed by <see
 ///     cref="CommandLineParser"/>.</summary>
+/// <remarks>
+///     If an input doesn’t parse correctly, throw <see cref="CommandLineValidationException"/> with a helpful, descriptive
+///     message that is displayed to the user.</remarks>
 public interface ICommandLineValidatable
 {
     /// <summary>
     ///     When overridden in a derived class, returns an error message if the contents of the class are invalid, otherwise
     ///     returns null.</summary>
-    ConsoleColoredString Validate();
+    void Validate();
 }

Tests/Test1.cs

@@ -14,18 +14,17 @@ class Test1Cmd : ICommandLineValidatable
 
     public static int ValidateCalled = 0;
 
-    public ConsoleColoredString Validate()
+    public void Validate()
     {
         ValidateCalled++;
-        return null;
     }
 }
 
 [CommandGroup]
 abstract class Test1SubcommandBase : ICommandLineValidatable
 {
     public static int ValidateCalled = 0;
-    public abstract ConsoleColoredString Validate();
+    public abstract void Validate();
 }
 
 [CommandName("sub1")]
@@ -34,15 +33,14 @@ sealed class Test1Subcommand1 : Test1SubcommandBase
     [IsPositional, IsMandatory]
     public string ItemName;
 
-    public override ConsoleColoredString Validate()
+    public override void Validate()
     {
         ValidateCalled++;
-        return null;
     }
 }
 
 [CommandName("sub2")]
 sealed class Test1Subcommand2 : Test1SubcommandBase
 {
-    public override ConsoleColoredString Validate() { return null; }
+    public override void Validate() { }
 }