style: C# cleanup to use more C# 8 features, and fix a few analyzer warnings

Author: natemcmaster

src/CommandLineUtils/CommandLineApplication.Execute.cs

@@ -51,12 +51,10 @@ public static int Execute<TApp>(CommandLineContext context)
 
             try
             {
-                using (var app = new CommandLineApplication<TApp>())
-                {
-                    app.SetContext(context);
-                    app.Conventions.UseDefaultConventions();
-                    return app.Execute(context.Arguments);
-                }
+                using var app = new CommandLineApplication<TApp>();
+                app.SetContext(context);
+                app.Conventions.UseDefaultConventions();
+                return app.Execute(context.Arguments);
             }
             catch (CommandParsingException ex)
             {
@@ -101,7 +99,7 @@ public static int Execute<TApp>(params string[] args)
         public static int Execute<TApp>(IConsole console, params string[] args)
             where TApp : class
         {
-            args = args ?? new string[0];
+            args ??= Util.EmptyArray<string>();
             var context = new DefaultCommandLineContext(console, Directory.GetCurrentDirectory(), args);
             return Execute<TApp>(context);
         }
@@ -134,7 +132,7 @@ public static Task<int> ExecuteAsync<TApp>(params string[] args)
         public static Task<int> ExecuteAsync<TApp>(IConsole console, params string[] args)
             where TApp : class
         {
-            args = args ?? new string[0];
+            args ??= Util.EmptyArray<string>();
             var context = new DefaultCommandLineContext(console, Directory.GetCurrentDirectory(), args);
             return ExecuteAsync<TApp>(context);
         }

src/CommandLineUtils/CommandLineApplication.cs

@@ -917,7 +917,8 @@ public void ShowHelp(string? commandName = null)
         public virtual string GetHelpText()
         {
             var sb = new StringBuilder();
-            _helpTextGenerator.Generate(this, new StringWriter(sb));
+            using var writer = new StringWriter(sb);
+            _helpTextGenerator.Generate(this, writer);
             return sb.ToString();
         }
 

src/CommandLineUtils/Conventions/ExecuteMethodConvention.cs

@@ -49,7 +49,7 @@ private async Task<int> OnExecute(ConventionContext context)
                 throw new InvalidOperationException(Strings.AmbiguousOnExecuteMethod);
             }
 
-            method = method ?? asyncMethod;
+            method ??= asyncMethod;
 
             if (method == null)
             {

src/CommandLineUtils/Conventions/RemainingArgsPropertyConvention.cs

@@ -28,7 +28,7 @@ public virtual void Apply(ConventionContext context)
 
             var typeInfo = context.ModelType.GetTypeInfo();
             var prop = typeInfo.GetProperty("RemainingArguments", PropertyBindingFlags);
-            prop = prop ?? typeInfo.GetProperty("RemainingArgs", PropertyBindingFlags);
+            prop ??= typeInfo.GetProperty("RemainingArgs", PropertyBindingFlags);
             if (prop == null)
             {
                 return;

src/CommandLineUtils/IO/ConsoleReporter.cs

@@ -12,7 +12,7 @@ namespace McMaster.Extensions.CommandLineUtils
     /// </summary>
     public class ConsoleReporter : IReporter
     {
-        private object _writeLock = new object();
+        private readonly object _writeLock = new object();
 
         /// <summary>
         /// Initializes an instance of <see cref="ConsoleReporter"/>.
@@ -57,7 +57,7 @@ public ConsoleReporter(IConsole console, bool verbose, bool quiet)
         /// <param name="message"></param>
         /// <param name="foregroundColor"></param>
         /// <param name="backgroundColor"></param>
-        protected virtual void WriteLine(TextWriter writer, string message, ConsoleColor? foregroundColor, ConsoleColor? backgroundColor = default(ConsoleColor?))
+        protected virtual void WriteLine(TextWriter writer, string message, ConsoleColor? foregroundColor, ConsoleColor? backgroundColor = default)
         {
             lock (_writeLock)
             {

src/CommandLineUtils/Internal/AnsiConsole.cs

@@ -21,7 +21,7 @@ private AnsiConsole(TextWriter writer, bool useConsoleColor)
         }
 
         private int _boldRecursion;
-        private bool _useConsoleColor;
+        private readonly bool _useConsoleColor;
 
         public static AnsiConsole GetOutput(bool useConsoleColor)
         {

src/CommandLineUtils/Internal/CommandLineProcessor.cs

@@ -8,13 +8,11 @@
 using System.IO;
 using System.Linq;
 using McMaster.Extensions.CommandLineUtils.Abstractions;
-using McMaster.Extensions.CommandLineUtils.Internal;
 
 namespace McMaster.Extensions.CommandLineUtils
 {
     internal sealed class CommandLineProcessor
     {
-        private readonly CommandLineApplication _app;
         private readonly CommandLineApplication _initialCommand;
         private readonly ArgumentEnumerator _enumerator;
 
@@ -33,10 +31,13 @@ private CommandLineApplication _currentCommand
         public CommandLineProcessor(CommandLineApplication command,
             IReadOnlyList<string> arguments)
         {
-            _app = command;
             _initialCommand = command;
             _enumerator = new ArgumentEnumerator(command, arguments ?? new string[0]);
+            CheckForShortOptionClustering(command);
+        }
 
+        private static void CheckForShortOptionClustering(CommandLineApplication command)
+        {
             if (!command.ClusterOptionsWasSetExplicitly)
             {
                 foreach (var option in AllOptions(command))

src/CommandLineUtils/Internal/ReflectionHelper.cs

@@ -83,11 +83,7 @@ public static object[] BindParameters(MethodInfo method, CommandLineApplication
                 else
                 {
                     object? service = command.AdditionalServices?.GetService(methodParam.ParameterType);
-                    if (service == null)
-                    {
-                        throw new InvalidOperationException(Strings.UnsupportedParameterTypeOnMethod(method.Name, methodParam));
-                    }
-                    arguments[i] = service;
+                    arguments[i] = service ?? throw new InvalidOperationException(Strings.UnsupportedParameterTypeOnMethod(method.Name, methodParam));
                 }
             }
 

src/Hosting.CommandLine/HostBuilderExtensions.cs

@@ -54,17 +54,15 @@ public static async Task<int> RunCommandLineApplicationAsync<TApp>(
                         .AddSingleton<ICommandLineService, CommandLineService<TApp>>();
                 });
 
-            using (var host = hostBuilder.Build())
-            {
-                await host.RunAsync(cancellationToken);
-
-                if (exceptionHandler.StoredException != null)
-                {
-                    ExceptionDispatchInfo.Capture(exceptionHandler.StoredException).Throw();
-                }
+            using var host = hostBuilder.Build();
+            await host.RunAsync(cancellationToken);
 
-                return state.ExitCode;
+            if (exceptionHandler.StoredException != null)
+            {
+                ExceptionDispatchInfo.Capture(exceptionHandler.StoredException).Throw();
             }
+
+            return state.ExitCode;
         }
     }
 }

src/Hosting.CommandLine/Internal/CommandLineLifetime.cs

@@ -101,6 +101,7 @@ public Task WaitForStartAsync(CancellationToken cancellationToken)
         public void Dispose()
         {
             _disposeComplete.Set();
+            _disposeComplete.Dispose();
         }
     }
 }