Added CliDataSymbol to simplify code

This will remove a ton of places where Option and Argument had to be separately handled

Author: KathleenDollard

src/System.CommandLine/CliArgument.cs

@@ -10,16 +10,17 @@ namespace System.CommandLine
     /// <summary>
     /// A symbol defining a value that can be passed on the command line to a <see cref="CliCommand">command</see> or <see cref="CliOption">option</see>.
     /// </summary>
-    public abstract class CliArgument : CliSymbol
+    public abstract class CliArgument : CliDataSymbol
     {
         private ArgumentArity _arity;
-// TODO: custom parser, completion, validators
-/*
+        // TODO: custom parser, completion, validators
+        /*
         private TryConvertArgument? _convertArguments;
         private List<Func<CompletionContext, IEnumerable<CompletionItem>>>? _completionSources = null;
         private List<Action<ArgumentResult>>? _validators = null;
-*/
-        private protected CliArgument(string name) : base(name, allowWhitespace: true)
+        */
+        private protected CliArgument(string name)
+            : base(name, allowWhitespace: true)
         {
         }
 
@@ -39,24 +40,24 @@ public ArgumentArity Arity
             }
             set => _arity = value;
         }
-// TODO: help, completion
-/*
+        // TODO: help, completion
+        /*
         /// <summary>
         /// The name used in help output to describe the argument. 
         /// </summary>
         public string? HelpName { get; set; }
-*/
+        */
         internal TryConvertArgument? ConvertArguments => ArgumentConverter.GetConverter(this);
-// TODO: custom parsers
-/*
+        // TODO: custom parsers
+        /*
         {
             get => _convertArguments ??= ArgumentConverter.GetConverter(this);
             set => _convertArguments = value;
         }
-*/
+        */
 
-// TODO: completion;
-/*
+        // TODO: completion;
+        /*
         /// <summary>
         /// Gets the list of completion sources for the argument.
         /// </summary>
@@ -94,21 +95,16 @@ public List<Func<CompletionContext, IEnumerable<CompletionItem>>> CompletionSour
                 return _completionSources;
             }
         }
-*/
-        /// <summary>
-        /// Gets or sets the <see cref="Type" /> that the argument's parsed tokens will be converted to.
-        /// </summary>
-        public abstract Type ValueType { get; }
 
-/* TODO: validators
+        /* TODO: validators
         /// <summary>
         /// Provides a list of argument validators. Validators can be used
         /// to provide custom errors based on user input.
         /// </summary>
         public List<Action<ArgumentResult>> Validators => _validators ??= new ();
 
         internal bool HasValidators => (_validators?.Count ?? 0) > 0;
-*/
+        */
         /// <summary>
         /// Gets the default value for the argument.
         /// </summary>
@@ -124,8 +120,8 @@ public List<Func<CompletionContext, IEnumerable<CompletionItem>>> CompletionSour
         /// Specifies if a default value is defined for the argument.
         /// </summary>
         public abstract bool HasDefaultValue { get; }
-// TODO: completion
-/*
+        // TODO: completion
+        /*
         /// <inheritdoc />
         public override IEnumerable<CompletionItem> GetCompletions(CompletionContext context)
         {
@@ -134,10 +130,8 @@ public override IEnumerable<CompletionItem> GetCompletions(CompletionContext con
                    .Distinct()
                    .OrderBy(c => c.SortText, StringComparer.OrdinalIgnoreCase);
         }
-*/
+        */
         /// <inheritdoc />
         public override string ToString() => $"{nameof(CliArgument)}: {Name}";
-
-        internal bool IsBoolean() => ValueType == typeof(bool) || ValueType == typeof(bool?);
     }
 }

src/System.CommandLine/CliDataSymbol.cs

@@ -0,0 +1,19 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+namespace System.CommandLine;
+
+public abstract class CliDataSymbol : CliSymbol
+{
+    protected CliDataSymbol(string name, bool allowWhitespace = false)
+        : base(name, allowWhitespace)
+    { }
+
+    /// <summary>
+    /// Gets or sets the <see cref="Type" /> that the argument's parsed tokens will be converted to.
+    /// </summary>
+    public abstract Type ValueType { get; }
+
+    internal bool IsBoolean() => ValueType == typeof(bool) || ValueType == typeof(bool?);
+
+}

src/System.CommandLine/CliOption.cs

@@ -10,23 +10,25 @@ namespace System.CommandLine
     /// <summary>
     /// A symbol defining a named parameter and a value for that parameter. 
     /// </summary>
-    public abstract class CliOption : CliSymbol
+    public abstract class CliOption : CliDataSymbol
     {
-        // TODO: don't expose field
         internal AliasSet? _aliases;
-/*
+        /*
         private List<Action<OptionResult>>? _validators;
 
         */
 
-        private protected CliOption(string name, string[] aliases) : base(name)
+        private protected CliOption(string name, string[] aliases)
+            : base(name)
         {
-            if (aliases is { Length: > 0 }) 
+            if (aliases is { Length: > 0 })
             {
                 _aliases = new(aliases);
             }
         }
 
+        public override Type ValueType => Argument.ValueType;
+
         /// <summary>
         /// Gets the <see cref="Argument">argument</see> for the option.
         /// </summary>
@@ -37,8 +39,8 @@ private protected CliOption(string name, string[] aliases) : base(name)
         /// </summary>
         public bool HasDefaultValue => Argument.HasDefaultValue;
 
-// TODO: help
-/*
+        // TODO: help
+        /*
         /// <summary>
         /// Gets or sets the name of the Option when displayed in help.
         /// </summary>
@@ -51,7 +53,7 @@ public string? HelpName
             get => Argument.HelpName;
             set => Argument.HelpName = value;
         }
-*/
+        */
 
         /// <summary>
         /// Gets or sets the arity of the option.
@@ -62,8 +64,8 @@ public ArgumentArity Arity
             set => Argument.Arity = value;
         }
 
-// TODO: recursive options, validators, completion
-/*
+        // TODO: recursive options, validators, completion
+        /*
         /// <summary>
         /// When set to true, this option will be applied to its immediate parent command or commands and recursively to their subcommands.
         /// </summary>
@@ -80,9 +82,9 @@ public ArgumentArity Arity
         /// Gets the list of completion sources for the option.
         /// </summary>
         public List<Func<CompletionContext, IEnumerable<CompletionItem>>> CompletionSources => Argument.CompletionSources;
-*/
+        */
 
-// TODO: what does this even mean?
+        // TODO: what does this even mean?
         /// <summary>
         /// Gets a value that indicates whether multiple argument tokens are allowed for each option identifier token.
         /// </summary>
@@ -98,10 +100,10 @@ public ArgumentArity Arity
         /// </example>
         public bool AllowMultipleArgumentsPerToken { get; set; }
 
-// TODO: rename to IsGreedy
+        // TODO: rename to IsGreedy
         internal virtual bool Greedy => Argument.Arity.MinimumNumberOfValues > 0 && Argument.ValueType != typeof(bool);
-        
-// TODO: rename to IsRequired
+
+        // TODO: rename to IsRequired and move to Validation
         /// <summary>
         /// Indicates whether the option is required when its parent command is invoked.
         /// </summary>
@@ -114,8 +116,8 @@ public ArgumentArity Arity
         /// <remarks>The collection does not contain the <see cref="CliSymbol.Name"/> of the Option.</remarks>
         public ICollection<string> Aliases => _aliases ??= new();
 
-// TODO: invocation, completion
-/*
+        // TODO: invocation, completion
+        /*
         /// <summary>
         /// Gets or sets the <see cref="CliAction"/> for the Option. The handler represents the action
         /// that will be performed when the Option is invoked.

src/System.CommandLine/System.CommandLine.csproj

@@ -27,6 +27,7 @@
     <Compile Include="AliasSet.cs" />
     <Compile Include="ArgumentArity.cs" />
     <Compile Include="Binding\ArgumentConversionResult.cs" />
+    <Compile Include="CliDataSymbol.cs" />
     <Compile Include="Parsing\CommandValueResult.cs" />
     <Compile Include="Parsing\SymbolLookupByName.cs" />
     <Compile Include="Parsing\ValueResultOutcome.cs" />