From cd55898011d9a91978a49b725d2294181d5ce06f Mon Sep 17 00:00:00 2001
From: Alexey Golub <Tyrrrrrr@gmail.com>
Date: Tue, 20 Aug 2019 17:24:06 +0300
Subject: [PATCH] Refactor CliApplication

---
 CliFx/CliApplication.cs      | 19 ++++++++++++-------
 CliFx/Internal/Extensions.cs |  8 ++++++++
 2 files changed, 20 insertions(+), 7 deletions(-)

diff --git a/CliFx/CliApplication.cs b/CliFx/CliApplication.cs
index 2a524cc..75c2158 100644
--- a/CliFx/CliApplication.cs
+++ b/CliFx/CliApplication.cs
@@ -75,16 +75,21 @@ namespace CliFx
                     // Get parent command schema
                     var parentCommandSchema = availableCommandSchemas.FindParent(commandInput.CommandName);
 
-                    // Use a stub if parent command schema is not found
-                    if (parentCommandSchema == null)
+                    // Show help for parent command if it's defined
+                    if (parentCommandSchema != null)
                     {
-                        parentCommandSchema = CommandSchema.StubDefaultCommand;
-                        availableCommandSchemas = availableCommandSchemas.Concat(new[] { parentCommandSchema }).ToArray();
+                        var helpTextSource = new HelpTextSource(_metadata, availableCommandSchemas, parentCommandSchema);
+                        _helpTextRenderer.RenderHelpText(_console, helpTextSource);
                     }
+                    // Otherwise show help for a stub default command
+                    else
+                    {
+                        var helpTextSource = new HelpTextSource(_metadata,
+                            availableCommandSchemas.Concat(CommandSchema.StubDefaultCommand).ToArray(),
+                            CommandSchema.StubDefaultCommand);
 
-                    // Show help
-                    var helpTextSource = new HelpTextSource(_metadata, availableCommandSchemas, parentCommandSchema);
-                    _helpTextRenderer.RenderHelpText(_console, helpTextSource);
+                        _helpTextRenderer.RenderHelpText(_console, helpTextSource);
+                    }
 
                     return isError ? -1 : 0;
                 }
diff --git a/CliFx/Internal/Extensions.cs b/CliFx/Internal/Extensions.cs
index 0e4c65a..7233642 100644
--- a/CliFx/Internal/Extensions.cs
+++ b/CliFx/Internal/Extensions.cs
@@ -31,6 +31,14 @@ namespace CliFx.Internal
 
         public static IEnumerable<T> ExceptNull<T>(this IEnumerable<T> source) where T : class => source.Where(i => i != null);
 
+        public static IEnumerable<T> Concat<T>(this IEnumerable<T> source, T value)
+        {
+            foreach (var i in source)
+                yield return i;
+
+            yield return value;
+        }
+
         public static bool Implements(this Type type, Type interfaceType) => type.GetInterfaces().Contains(interfaceType);
 
         public static Type GetEnumerableUnderlyingType(this Type type)