R: code cleanup and a few micro-optimizations

Author: jonsequitur

src/System.CommandLine/Argument.cs

@@ -53,7 +53,7 @@ public IArgumentArity Arity
                     return ArgumentArity.Default(
                         ArgumentType, 
                         this, 
-                        Parents.FirstOrDefault());
+                        Parents);
                 }
 
                 return _arity;

src/System.CommandLine/ArgumentArity.cs

@@ -3,7 +3,9 @@
 
 using System.Collections;
 using System.CommandLine.Binding;
+using System.CommandLine.Collections;
 using System.CommandLine.Parsing;
+using System.Linq;
 
 namespace System.CommandLine
 {
@@ -107,8 +109,20 @@ public ArgumentArity(int minimumNumberOfValues, int maximumNumberOfValues)
         /// </summary>
         public static IArgumentArity OneOrMore => new ArgumentArity(1, MaximumArity);
 
-        internal static IArgumentArity Default(Type type, Argument argument, ISymbol parent)
+        internal static IArgumentArity Default(Type type, Argument argument, ISymbolSet parents)
         {
+            if (type == typeof(bool))
+            {
+                return ZeroOrOne;
+            }
+
+            if (type == typeof(void))
+            {
+                return Zero;
+            }
+
+            var parent = parents.FirstOrDefault();
+
             if (typeof(IEnumerable).IsAssignableFrom(type) &&
                 type != typeof(string))
             {
@@ -117,23 +131,13 @@ internal static IArgumentArity Default(Type type, Argument argument, ISymbol par
                            : OneOrMore;
             }
 
-            if (type == typeof(bool))
-            {
-                return ZeroOrOne;
-            }
-
             if (parent is ICommand &&
                 (argument.HasDefaultValue ||
                  type.IsNullable()))
             {
                 return ZeroOrOne;
             }
 
-            if (type == typeof(void))
-            {
-                return Zero;
-            }
-
             return ExactlyOne;
         }
     }

src/System.CommandLine/Binding/ArgumentConverter.cs

@@ -154,12 +154,7 @@ public static ArgumentConversionResult ConvertStrings(
                       .GetInterfaces()
                       .FirstOrDefault(IsEnumerable);
 
-            if (enumerableInterface is {})
-            {
-                return enumerableInterface.GenericTypeArguments[0];
-            }
-
-            return null;
+            return enumerableInterface?.GenericTypeArguments[0];
         }
 
         internal static bool IsEnumerable(this Type type)
@@ -227,7 +222,7 @@ private static bool TryFindConstructorWithSingleParameterOfType(
             Type parameterType,
             [NotNullWhen(true)] out ConstructorInfo? ctor)
         {
-            var (x, y) = type.GetConstructors()
+            var (x, _) = type.GetConstructors()
                              .Select(c => (ctor: c, parameters: c.GetParameters()))
                              .SingleOrDefault(tuple => tuple.ctor.IsPublic &&
                                                        tuple.parameters.Length == 1 &&

src/System.CommandLine/CommandLineConfiguration.cs

@@ -16,8 +16,6 @@ namespace System.CommandLine
     /// </summary>
     public class CommandLineConfiguration
     {
-        private readonly IReadOnlyCollection<InvocationMiddleware> _middlewarePipeline;
-        private readonly Func<BindingContext, IHelpBuilder> _helpBuilderFactory;
         private readonly SymbolSet _symbols = new SymbolSet();
 
         /// <summary>
@@ -56,15 +54,15 @@ public CommandLineConfiguration(
 
             if (argumentDelimiters is null)
             {
-                ArgumentDelimitersInternal = new []
+                ArgumentDelimiters = new []
                 {
                     ':',
                     '='
                 };
             }
             else
             {
-                ArgumentDelimitersInternal = argumentDelimiters.Distinct().ToArray();
+                ArgumentDelimiters = argumentDelimiters.Distinct().ToArray();
             }
 
             foreach (var symbol in symbols)
@@ -119,8 +117,8 @@ public CommandLineConfiguration(
             EnableDirectives = enableDirectives;
             ValidationMessages = validationMessages ?? ValidationMessages.Instance;
             ResponseFileHandling = responseFileHandling;
-            _middlewarePipeline = middlewarePipeline ?? new List<InvocationMiddleware>();
-            _helpBuilderFactory = helpBuilderFactory ?? (context => new HelpBuilder(context.Console));
+            Middleware = middlewarePipeline ?? new List<InvocationMiddleware>();
+            HelpBuilderFactory = helpBuilderFactory ?? (context => new HelpBuilder(context.Console));
         }
 
         private void AddGlobalOptionsToChildren(Command parentCommand)
@@ -150,10 +148,8 @@ private void AddGlobalOptionsToChildren(Command parentCommand)
         /// <summary>
         /// Represents all of the argument delimiters.
         /// </summary>
-        public IReadOnlyList<char> ArgumentDelimiters => ArgumentDelimitersInternal;
+        public IReadOnlyList<char> ArgumentDelimiters { get; }
 
-        internal IReadOnlyList<char> ArgumentDelimitersInternal { get; }
-     
         /// <summary>
         /// Gets whether directives are enabled.
         /// </summary>
@@ -172,9 +168,9 @@ private void AddGlobalOptionsToChildren(Command parentCommand)
         /// </summary>
         public ValidationMessages ValidationMessages { get; }
 
-        internal Func<BindingContext, IHelpBuilder> HelpBuilderFactory => _helpBuilderFactory;
+        internal Func<BindingContext, IHelpBuilder> HelpBuilderFactory { get; }
 
-        internal IReadOnlyCollection<InvocationMiddleware> Middleware => _middlewarePipeline;
+        internal IReadOnlyCollection<InvocationMiddleware> Middleware { get; }
 
         /// <summary>
         /// Gets the root command.

src/System.CommandLine/EnumerableExtensions.cs

@@ -2,7 +2,6 @@
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
 using System.Collections.Generic;
-using System.Linq;
 
 namespace System.CommandLine
 {

src/System.CommandLine/Parsing/ParseResultExtensions.cs

@@ -190,7 +190,7 @@ public static bool HasOption(
                 throw new ArgumentNullException(nameof(parseResult));
             }
 
-            return parseResult.CommandResult.Children.Any(s => Equals(s.Symbol, option));
+            return parseResult.FindResultFor(option) is { };
         }
 
         public static bool HasOption(

src/System.CommandLine/Parsing/StringExtensions.cs

@@ -68,7 +68,7 @@ internal static TokenizeResult Tokenize(
             var foundEndOfDirectives = !configuration.EnableDirectives;
             var argList = NormalizeRootCommand(configuration, args);
 
-            var argumentDelimiters = configuration.ArgumentDelimitersInternal.ToArray();
+            var argumentDelimiters = configuration.ArgumentDelimiters.ToArray();
 
             var knownTokens = configuration.RootCommand.ValidTokens();
 
@@ -417,11 +417,9 @@ internal static bool TrySplitIntoSubtokens(
             out string? first,
             out string? rest)
         {
-            var delimitersArray = delimiters;
-
             for (var j = 0; j < delimiters.Length; j++)
             {
-                var i = arg.IndexOfAny(delimitersArray);
+                var i = arg.IndexOfAny(delimiters);
 
                 if (i >= 0)
                 {
@@ -513,8 +511,12 @@ private static IEnumerable<string> ExpandResponseFile(
             string filePath,
             ResponseFileHandling responseFileHandling)
         {
-            foreach (var line in File.ReadAllLines(filePath))
+            var lines = File.ReadAllLines(filePath);
+
+            for (var i = 0; i < lines.Length; i++)
             {
+                var line = lines[i];
+
                 foreach (var p in SplitLine(line))
                 {
                     if (p.GetResponseFileReference() is { } path)