fix help error when an option is required

Author: jonsequitur

src/System.CommandLine.Tests/UseHelpTests.cs

@@ -8,7 +8,6 @@
 using System.CommandLine.Tests.Utility;
 using System.Threading.Tasks;
 using FluentAssertions;
-using FluentAssertions.Primitives;
 using Xunit;
 
 namespace System.CommandLine.Tests
@@ -144,6 +143,25 @@ public void There_are_no_parse_errors_when_help_is_invoked_on_a_command_with_sub
             result.Errors.Should().BeEmpty();
         }
 
+        [Fact]
+        public void There_are_no_parse_errors_when_help_is_invoked_on_a_command_with_required_options()
+        {
+            var command = new RootCommand
+            {
+                new Option<string>("-x")
+                {
+                    Required = true
+                },
+            };
+
+            var result = new CommandLineBuilder(command)
+                         .UseHelp()
+                         .Build()
+                         .Parse("-h");
+
+            result.Errors.Should().BeEmpty();
+        }
+
         [Theory]
         [InlineData("-h")]
         [InlineData("inner -h")]

src/System.CommandLine/Builder/CommandLineBuilder.cs

@@ -27,7 +27,7 @@ public CommandLineBuilder(Command? rootCommand = null)
 
         internal Func<BindingContext, IHelpBuilder>? HelpBuilderFactory { get; set; }
 
-        internal Option? HelpOption { get; set; }
+        internal HelpOption? HelpOption { get; set; }
 
         internal ValidationMessages? ValidationMessages { get; set; }
 

src/System.CommandLine/Builder/CommandLineBuilderExtensions.cs

@@ -282,7 +282,7 @@ public static CommandLineBuilder UseHelp(this CommandLineBuilder builder)
 
         internal static CommandLineBuilder UseHelp(
             this CommandLineBuilder builder,
-            Option helpOption)
+            HelpOption helpOption)
         {
             if (builder.HelpOption is null)
             {

src/System.CommandLine/Parsing/ParseResultVisitor.cs

@@ -154,8 +154,18 @@ protected override void VisitUnknownNode(SyntaxNode node)
 
         protected override void Stop(SyntaxNode node)
         {
+            var helpWasRequested =
+                _innermostCommandResult
+                    ?.Children
+                    .Any(o => o.Symbol is HelpOption) == true;
+
+            if (helpWasRequested)
+            {
+                return;
+            }
+
             ValidateCommandHandler();
-          
+
             PopulateDefaultValues();
 
             ValidateCommandResult();
@@ -229,7 +239,7 @@ private void ValidateCommandResult()
 
         private void ValidateCommandHandler()
         {
-            if (!(_innermostCommandResult!.Command is Command cmd) || 
+            if (!(_innermostCommandResult!.Command is Command cmd) ||
                 cmd.Handler != null)
             {
                 return;
@@ -240,15 +250,11 @@ private void ValidateCommandHandler()
                 return;
             }
 
-            if (!_innermostCommandResult
-                 .Children
-                 .Select(o => o.Symbol is HelpOption).Any())
-            {
-                _errors.Insert(0,
-                               new ParseError(
-                                   _innermostCommandResult.ValidationMessages.RequiredCommandWasNotProvided(),
-                                   _innermostCommandResult));
-            }
+            _errors.Insert(
+                0,
+                new ParseError(
+                    _innermostCommandResult.ValidationMessages.RequiredCommandWasNotProvided(),
+                    _innermostCommandResult));
         }
 
         private void ValidateOptionResult(OptionResult optionResult)