Bind to the target type to find OnValidationError

Author: natemcmaster

src/CommandLineUtils/CommandLineApplication.Execute.cs

@@ -123,10 +123,16 @@ public static async Task<int> ExecuteAsync<TApp>(IConsole console, params string
 
         private static int HandleValidationError<TApp>(IConsole console, BindContext bindResult)
         {
-            var method = typeof(TApp).GetTypeInfo().GetMethod("OnValidationError", BindingFlags.Instance | BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic);
+            const BindingFlags MethodFlags = BindingFlags.Instance | BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic;
+
+            var method = bindResult.Target
+                .GetType()
+                .GetTypeInfo()
+                .GetMethod("OnValidationError", MethodFlags);
+
             if (method == null)
             {
-                return bindResult.App.DefaultValidationErrorHandler(bindResult.ValidationResult);
+                return bindResult.RootApp.DefaultValidationErrorHandler(bindResult.ValidationResult);
             }
 
             var arguments = ReflectionHelper.BindParameters(method, console, bindResult);
@@ -147,20 +153,19 @@ private static int HandleValidationError<TApp>(IConsole console, BindContext bin
             }
 
             var applicationBuilder = new ReflectionAppBuilder<TApp>();
-            var bindResult = applicationBuilder.Bind(console, args).GetBottomContext();
-            return bindResult;
+            return applicationBuilder.Bind(console, args).GetBottomContext();
         }
 
         private static bool IsShowingInfo(BindContext bindResult)
         {
-            if (bindResult.App.IsShowingInformation)
+            if (bindResult.RootApp.IsShowingInformation)
             {
-                if (bindResult.App.OptionHelp?.HasValue() == true && bindResult.App.StopParsingAfterHelpOption)
+                if (bindResult.RootApp.OptionHelp?.HasValue() == true && bindResult.RootApp.StopParsingAfterHelpOption)
                 {
                     return true;
                 }
 
-                if (bindResult.App.OptionVersion?.HasValue() == true && bindResult.App.StopParsingAfterVersionOption)
+                if (bindResult.RootApp.OptionVersion?.HasValue() == true && bindResult.RootApp.StopParsingAfterVersionOption)
                 {
                     return true;
                 }

src/CommandLineUtils/Internal/BindContext.cs

@@ -7,11 +7,36 @@ namespace McMaster.Extensions.CommandLineUtils
 {
     internal class BindContext
     {
-        public CommandLineApplication App { get; set; }
+        /// <summary>
+        /// The top-level application generated by the app builder
+        /// </summary>
+        public CommandLineApplication RootApp { get; set; }
+
+        /// <summary>
+        /// The command selected based on input args.
+        /// </summary>
+        public CommandLineApplication SelectedCommand { get; set; }
+
+        /// <summary>
+        /// An instance of the object that matches <see cref="SelectedCommand" />.
+        /// </summary>
         public object Target { get; set; }
+
+        /// <summary>
+        /// The binding context for the object for the next subcommand, if SelectedCommand != App.
+        /// </summary>
+        /// <returns></returns>
         public BindContext Child { get; set; }
+
+        /// <summary>
+        /// Validation result, if any.
+        /// </summary>
         public ValidationResult ValidationResult { get; set; }
 
+        /// <summary>
+        /// Get the binding context that matches <see cref="Target" />.
+        /// </summary>
+        /// <returns>The context.</returns>
         public BindContext GetBottomContext()
         {
             var retVal = this;

src/CommandLineUtils/Internal/ReflectionAppBuilder.cs

@@ -381,7 +381,7 @@ private int OnExecute()
 
             var ctx = new BindContext
             {
-                App = App,
+                RootApp = App,
                 Target = new TTarget(),
             };
 

src/CommandLineUtils/Internal/ReflectionHelper.cs

@@ -43,7 +43,7 @@ public static object[] BindParameters(MethodInfo method, IConsole console, BindC
 
                 if (typeof(CommandLineApplication).GetTypeInfo().IsAssignableFrom(methodParam.ParameterType))
                 {
-                    arguments[i] = bindResult.App;
+                    arguments[i] = bindResult.RootApp;
                 }
                 else if (typeof(IConsole).GetTypeInfo().IsAssignableFrom(methodParam.ParameterType))
                 {

test/CommandLineUtils.Tests/ValidationTests.cs

@@ -32,7 +32,7 @@ public void ValidationHandlerInvoked()
         public void ValidationHandlerOfSubcommandIsInvoked()
         {
             var app = new CommandLineApplication();
-            var sub = app.Command("sub", c => {});
+            var sub = app.Command("sub", c => { });
             var called = false;
             sub.OnValidationError(_ => called = true);
             sub.Argument("t", "test").IsRequired();
@@ -182,6 +182,7 @@ public void ValidatesEmailOption(string[] args, int exitCode)
             Assert.Equal(exitCode, CommandLineApplication.Execute<EmailOptionApp>(args));
         }
 
+        [Subcommand("sub", typeof(ValidationErrorSubcommand))]
         private class ValidationErrorApp
         {
             [Required, Option]
@@ -192,12 +193,29 @@ private int OnValidationError()
             }
         }
 
+        private class ValidationErrorSubcommand
+        {
+            [Argument(0), Required]
+            public string[] Args { get; }
+
+            private int OnValidationError()
+            {
+                return 49;
+            }
+        }
+
         [Fact]
         public void OnValidationErrorIsInvokedOnError()
         {
             Assert.Equal(7, CommandLineApplication.Execute<ValidationErrorApp>(new TestConsole(_output)));
         }
 
+        [Fact]
+        public void OnValidationErrorIsInvokedOnSubcommandError()
+        {
+            Assert.Equal(49, CommandLineApplication.Execute<ValidationErrorApp>(new TestConsole(_output), "sub"));
+        }
+
         private class ThrowOnExecuteApp
         {
             [Option, Required]