Update CommandOption/Argument.value to return DefaultValue

Directory.Build.props

@@ -30,7 +30,7 @@
   <PropertyGroup>
     <SuppressNETCoreSdkPreviewMessage>true</SuppressNETCoreSdkPreviewMessage>
     <WarningsNotAsErrors>$(WarningsNotAsErrors);1591</WarningsNotAsErrors>
-    <LangVersion>8.0</LangVersion>
+    <LangVersion>9.0</LangVersion>
     <Nullable>annotations</Nullable>
     <AssemblyOriginatorKeyFile>$(MSBuildThisFileDirectory)src\StrongName.snk</AssemblyOriginatorKeyFile>
     <SignAssembly>true</SignAssembly>

README.md

@@ -81,21 +81,19 @@ using McMaster.Extensions.CommandLineUtils;
 var app = new CommandLineApplication();
 
 app.HelpOption();
-var optionSubject = app.Option("-s|--subject <SUBJECT>", "The subject", CommandOptionType.SingleValue);
-var optionRepeat = app.Option<int>("-n|--count <N>", "Repeat", CommandOptionType.SingleValue);
+
+var subject = app.Option("-s|--subject <SUBJECT>", "The subject", CommandOptionType.SingleValue);
+subject.DefaultValue = "world";
+
+var repeat = app.Option<int>("-n|--count <N>", "Repeat", CommandOptionType.SingleValue);
+repeat.DefaultValue = 1;
 
 app.OnExecute(() =>
 {
-    var subject = optionSubject.HasValue()
-        ? optionSubject.Value()
-        : "world";
-
-    var count = optionRepeat.HasValue() ? optionRepeat.ParsedValue : 1;
-    for (var i = 0; i < count; i++)
+    for (var i = 0; i < repeat.ParsedValue; i++)
     {
-        Console.WriteLine($"Hello {subject}!");
+        Console.WriteLine($"Hello {subject.Value()}!");
     }
-    return 0;
 });
 
 return app.Execute(args);

docs/docs/intro.md

@@ -64,15 +64,12 @@ public class Program
         var app = new CommandLineApplication();
 
         app.HelpOption();
-        var optionSubject = app.Option("-s|--subject <SUBJECT>", "The subject", CommandOptionType.SingleValue);
+        var subject = app.Option("-s|--subject <SUBJECT>", "The subject", CommandOptionType.SingleValue);
+        subject.DefaultValue = "world";
 
         app.OnExecute(() =>
         {
-            var subject = optionSubject.HasValue()
-                ? optionSubject.Value()
-                : "world";
-
-            Console.WriteLine($"Hello {subject}!");
+            Console.WriteLine($"Hello {subject.Value()}!");
             return 0;
         });
 

docs/samples/custom-attribute/Program.cs

@@ -44,12 +44,10 @@ public void Apply(ConventionContext context, MemberInfo member)
         if (member is FieldInfo field)
         {
             var opt = context.Application.Option("--working-dir", "The working directory", CommandOptionType.SingleOrNoValue);
+            opt.DefaultValue = context.Application.WorkingDirectory;
             context.Application.OnParsingComplete(_ =>
             {
-                var cwd = opt.HasValue()
-                    ? opt.Value()
-                    : context.Application.WorkingDirectory;
-                field.SetValue(context.ModelAccessor.GetModel(), cwd);
+                field.SetValue(context.ModelAccessor.GetModel(), opt.Value());
             });
         }
     }

docs/samples/helloworld-async/Program.cs

@@ -5,24 +5,22 @@
 var app = new CommandLineApplication();
 
 app.HelpOption();
-var optionSubject = app.Option("-s|--subject <SUBJECT>", "The subject", CommandOptionType.SingleValue);
-var optionRepeat = app.Option<int>("-n|--count <N>", "Repeat", CommandOptionType.SingleValue);
+var subject = app.Option("-s|--subject <SUBJECT>", "The subject", CommandOptionType.SingleValue);
+subject.DefaultValue = "world";
+
+var repeat = app.Option<int>("-n|--count <N>", "Repeat", CommandOptionType.SingleValue);
+repeat.DefaultValue = 1;
 
 app.OnExecuteAsync(async cancellationToken =>
 {
-    var subject = optionSubject.HasValue()
-        ? optionSubject.Value()
-        : "world";
-
-    var count = optionRepeat.HasValue() ? optionRepeat.ParsedValue : 1;
-    for (var i = 0; i < count; i++)
+    for (var i = 0; i < repeat.ParsedValue; i++)
     {
         Console.Write($"Hello");
 
         // Pause for dramatic effect
         await Task.Delay(2000, cancellationToken);
 
-        Console.WriteLine($" {subject}!");
+        Console.WriteLine($" {subject.Value()}!");
     }
 });
 

docs/samples/helloworld/HelloWorld.csproj

@@ -3,6 +3,7 @@
   <PropertyGroup>
     <OutputType>Exe</OutputType>
     <TargetFramework>net5.0</TargetFramework>
+    <Nullable>enable</Nullable>
   </PropertyGroup>
 
   <ItemGroup>

docs/samples/helloworld/Program.cs

@@ -4,21 +4,17 @@
 var app = new CommandLineApplication();
 
 app.HelpOption();
-var optionSubject = app.Option("-s|--subject <SUBJECT>", "The subject", CommandOptionType.SingleValue);
-var optionRepeat = app.Option<int>("-n|--count <N>", "Repeat", CommandOptionType.SingleValue);
+var subject = app.Option("-s|--subject <SUBJECT>", "The subject", CommandOptionType.SingleValue);
+subject.DefaultValue = "world";
+var repeat = app.Option<int?>("-n|--count <N>", "Repeat", CommandOptionType.SingleValue);
+repeat.DefaultValue = 1;
 
 app.OnExecute(() =>
 {
-    var subject = optionSubject.HasValue()
-        ? optionSubject.Value()
-        : "world";
-
-    var count = optionRepeat.HasValue() ? optionRepeat.ParsedValue : 1;
-    for (var i = 0; i < count; i++)
+    for (var i = 0; i < repeat.ParsedValue; i++)
     {
-        Console.WriteLine($"Hello {subject}!");
+        Console.WriteLine($"Hello {subject.Value()}!");
     }
-    return 0;
 });
 
 return app.Execute(args);

src/CommandLineUtils/CommandArgument.cs

@@ -36,15 +36,25 @@ public class CommandArgument
         /// <summary>
         /// All values specified, if any.
         /// </summary>
-        public IReadOnlyList<string?> Values => _values;
+        public IReadOnlyList<string?> Values
+        {
+            get
+            {
+                if (_values.Count == 0 && DefaultValue != null)
+                {
+                    return new List<string?> { DefaultValue };
+                }
+                return _values;
+            }
+        }
 
         /// <summary>
         /// Allow multiple values.
         /// </summary>
         public bool MultipleValues { get; set; }
 
         /// <summary>
-        /// The first value from <see cref="Values"/>, if any.
+        /// The first value from <see cref="Values"/>, if any, or <see cref="DefaultValue" />.
         /// </summary>
         public string? Value => Values.FirstOrDefault();
 
@@ -54,7 +64,7 @@ public class CommandArgument
         public string? DefaultValue { get; set; }
 
         /// <summary>
-        /// True if this argument has been assigned values.
+        /// True when <see cref="Values"/> is not empty or when a <see cref="DefaultValue" /> is given.
         /// </summary>
         public bool HasValue => Values.Any();
 

src/CommandLineUtils/CommandArgument{T}.cs

@@ -20,7 +20,9 @@ public class CommandArgument<T> : CommandArgument, IInternalCommandParamOfT
     {
         private readonly List<T> _parsedValues = new List<T>();
         private readonly IValueParser<T> _valueParser;
-        private T _defaultValue;
+        private bool _hasBeenParsed;
+        private bool _hasDefaultValue;
+        private T? _defaultValue;
 
         /// <summary>
         /// Initializes a new instance of <see cref="CommandArgument{T}" />
@@ -30,36 +32,53 @@ public CommandArgument(IValueParser<T> valueParser)
         {
             _valueParser = valueParser ?? throw new ArgumentNullException(nameof(valueParser));
             UnderlyingType = typeof(T);
-            SetBaseDefaultValue(default);
         }
 
         /// <summary>
         /// The parsed value.
         /// </summary>
-        public T ParsedValue => _parsedValues.FirstOrDefault();
+        public T ParsedValue => ParsedValues.FirstOrDefault();
 
         /// <summary>
         /// All parsed values;
         /// </summary>
-        public IReadOnlyList<T> ParsedValues => _parsedValues;
+        public IReadOnlyList<T> ParsedValues
+        {
+            get
+            {
+                if (!_hasBeenParsed)
+                {
+                    ((IInternalCommandParamOfT)this).Parse(CultureInfo.CurrentCulture);
+                }
+
+                if (_parsedValues.Count == 0 && _hasDefaultValue)
+                {
+                    return new[] { DefaultValue };
+                }
+
+                return _parsedValues;
+            }
+        }
 
         /// <summary>
         /// The default value of the argument.
         /// </summary>
-        public new T DefaultValue
+        public new T? DefaultValue
         {
             get => _defaultValue;
             set
             {
+                _hasDefaultValue = value != null;
                 _defaultValue = value;
                 SetBaseDefaultValue(value);
             }
         }
 
         void IInternalCommandParamOfT.Parse(CultureInfo culture)
         {
+            _hasBeenParsed = true;
             _parsedValues.Clear();
-            foreach (var t in Values)
+            foreach (var t in base._values)
             {
                 _parsedValues.Add(_valueParser.Parse(Name, t, culture));
             }
@@ -79,5 +98,13 @@ void SetBaseDefaultValue(T value)
                 }
             }
         }
+
+        /// <inheritdoc />
+        public override void Reset()
+        {
+            _hasBeenParsed = false;
+            _parsedValues.Clear();
+            base.Reset();
+        }
     }
 }

src/CommandLineUtils/CommandOption.cs

@@ -100,7 +100,17 @@ internal CommandOption(CommandOptionType type)
         /// <summary>
         /// Any values found during parsing, if any.
         /// </summary>
-        public IReadOnlyList<string?> Values => _values;
+        public IReadOnlyList<string?> Values
+        {
+            get
+            {
+                if (_values.Count == 0 && DefaultValue != null)
+                {
+                    return new List<string?> { DefaultValue };
+                }
+                return _values;
+            }
+        }
 
         /// <summary>
         /// The default value of the option.
@@ -171,7 +181,7 @@ public bool TryParse(string? value)
         }
 
         /// <summary>
-        /// True when <see cref="Values"/> is not empty.
+        /// True when <see cref="Values"/> is not empty or when a <see cref="DefaultValue" /> is given.
         /// </summary>
         /// <returns></returns>
         public bool HasValue()
@@ -180,13 +190,10 @@ public bool HasValue()
         }
 
         /// <summary>
-        /// Returns the first element of <see cref="Values"/>, if any.
+        /// Returns the first element of <see cref="Values"/>, if any, or <see cref="DefaultValue" />.
         /// </summary>
         /// <returns></returns>
-        public string? Value()
-        {
-            return HasValue() ? Values[0] : null;
-        }
+        public string? Value() => Values.FirstOrDefault();
 
         /// <summary>
         /// Generates the template string in the format "-{Symbol}|-{Short}|--{Long} &lt;{Value}&gt;" for display in help text.