Types cleanup (#2076)

* remove ServiceProviderExtensions (an empty class)

* remove CompletionItemKind, merge it's two fields into CompletionItem TYPE

* remove unused types

* merge Platform class into ConsoleExtensions, as it's the only user of that API

Author: adamsitnik

src/System.CommandLine/Binding/ServiceProviderExtensions.cs

@@ -234,7 +234,7 @@ void AddCompletionsFor(Symbol identifier, AliasSet? aliases)
                 {
                     if (identifier.Name.ContainsCaseInsensitive(textToMatch))
                     {
-                        completions.Add(new CompletionItem(identifier.Name, CompletionItemKind.Keyword, detail: identifier.Description));
+                        completions.Add(new CompletionItem(identifier.Name, CompletionItem.KindKeyword, detail: identifier.Description));
                     }
 
                     if (aliases is not null)
@@ -243,7 +243,7 @@ void AddCompletionsFor(Symbol identifier, AliasSet? aliases)
                         {
                             if (alias.ContainsCaseInsensitive(textToMatch))
                             {
-                                completions.Add(new CompletionItem(alias, CompletionItemKind.Keyword, detail: identifier.Description));
+                                completions.Add(new CompletionItem(alias, CompletionItem.KindKeyword, detail: identifier.Description));
                             }
                         }
                     }

src/System.CommandLine/Command.cs

@@ -8,6 +8,10 @@ namespace System.CommandLine.Completions
     /// </summary>
     public class CompletionItem : IEquatable<CompletionItem>
     {
+        // reference: https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_completion
+        internal const string KindKeyword = "Keyword";
+        internal const string KindValue = "Value";
+
         /// <param name="label">The label value, which is the text displayed to users and, unless <paramref name="insertText"/> is set, is also used to populate the <see cref="InsertText"/> property.</param>
         /// <param name="kind">The kind of completion item.</param>
         /// <param name="sortText">The value used to sort the completion item in a list. If this is not provided, then <paramref name="label"/>  is used.</param>
@@ -16,7 +20,7 @@ public class CompletionItem : IEquatable<CompletionItem>
         /// <param name="detail">Additional details regarding the completion item.</param>
         public CompletionItem(
             string label,
-            string kind = CompletionItemKind.Value,
+            string kind = CompletionItem.KindValue,
             string? sortText = null,
             string? insertText = null,
             string? documentation = null,

src/System.CommandLine/Completions/CompletionItem.cs

@@ -5,27 +5,51 @@ namespace System.CommandLine.IO
 {
     internal static class ConsoleExtensions
     {
+        private static bool? _isConsoleRedirectionCheckSupported;
+
+        private static bool IsConsoleRedirectionCheckSupported
+        {
+            get
+            {
+                if (_isConsoleRedirectionCheckSupported is null)
+                {
+                    try
+                    {
+                        var check = Console.IsOutputRedirected;
+                        _isConsoleRedirectionCheckSupported = true;
+                    }
+
+                    catch (PlatformNotSupportedException)
+                    {
+                        _isConsoleRedirectionCheckSupported = false;
+                    }
+                }
+
+                return _isConsoleRedirectionCheckSupported.Value;
+            }
+        }
+        
         internal static void SetTerminalForegroundRed(this IConsole console)
         {
-            if (Platform.IsConsoleRedirectionCheckSupported &&
+            if (IsConsoleRedirectionCheckSupported &&
                 !Console.IsOutputRedirected)
             {
                 Console.ForegroundColor = ConsoleColor.Red;
             }
-            else if (Platform.IsConsoleRedirectionCheckSupported)
+            else if (IsConsoleRedirectionCheckSupported)
             {
                 Console.ForegroundColor = ConsoleColor.Red;
             }
         }
 
         internal static void ResetTerminalForegroundColor(this IConsole console)
         {
-            if (Platform.IsConsoleRedirectionCheckSupported &&
+            if (IsConsoleRedirectionCheckSupported &&
                 !Console.IsOutputRedirected)
             {
                 Console.ResetColor();
             }
-            else if (Platform.IsConsoleRedirectionCheckSupported)
+            else if (IsConsoleRedirectionCheckSupported)
             {
                 Console.ResetColor();
             }