Refactor

CliFx.Tests/ConsoleSpecs.cs

@@ -51,6 +51,8 @@ namespace CliFx.Tests
             console.ResetColor();
             console.ForegroundColor = ConsoleColor.DarkMagenta;
             console.BackgroundColor = ConsoleColor.DarkMagenta;
+            console.CursorLeft = 42;
+            console.CursorTop = 24;
 
             // Assert
             stdInData.Should().Be("input");

CliFx.Tests/HelpTextSpecs.Commands.cs

@@ -1,11 +1,7 @@
 using System;
-using System.Collections;
 using System.Collections.Generic;
-using System.Globalization;
-using System.Linq;
 using System.Threading.Tasks;
 using CliFx.Attributes;
-using CliFx.Exceptions;
 
 namespace CliFx.Tests
 {
@@ -89,16 +85,16 @@ namespace CliFx.Tests
         [Command("cmd-with-enum-args")]
         private class EnumArgumentsCommand : ICommand
         {
-            public enum TestEnum { Value1, Value2, Value3 };
+            public enum CustomEnum { Value1, Value2, Value3 };
 
             [CommandParameter(0, Name = "value", Description = "Enum parameter.")]
-            public TestEnum ParamA { get; set; }
+            public CustomEnum ParamA { get; set; }
 
             [CommandOption("value", Description = "Enum option.", IsRequired = true)]
-            public TestEnum OptionA { get; set; } = TestEnum.Value1;
+            public CustomEnum OptionA { get; set; } = CustomEnum.Value1;
 
             [CommandOption("nullable-value", Description = "Nullable enum option.")]
-            public TestEnum? OptionB { get; set; }
+            public CustomEnum? OptionB { get; set; }
 
             public ValueTask ExecuteAsync(IConsole console) => default;
         }
@@ -116,8 +112,10 @@ namespace CliFx.Tests
         }
 
         [Command("cmd-with-defaults")]
-        private class DefaultArgumentsCommand : ICommand
+        private class ArgumentsWithDefaultValuesCommand : ICommand
         {
+            public enum CustomEnum { Value1, Value2, Value3 };
+
             [CommandOption(nameof(Object))]
             public object? Object { get; set; } = 42;
 
@@ -127,98 +125,29 @@ namespace CliFx.Tests
             [CommandOption(nameof(EmptyString))]
             public string EmptyString { get; set; } = "";
 
-            [CommandOption(nameof(WhiteSpaceString))]
-            public string WhiteSpaceString { get; set; } = " ";
-
             [CommandOption(nameof(Bool))]
             public bool Bool { get; set; } = true;
 
             [CommandOption(nameof(Char))]
             public char Char { get; set; } = 't';
 
-            [CommandOption(nameof(Sbyte))]
-            public sbyte Sbyte { get; set; } = -0b11;
-
-            [CommandOption(nameof(Byte))]
-            public byte Byte { get; set; } = 0b11;
-
-            [CommandOption(nameof(Short))]
-            public short Short { get; set; } = -1234;
-
-            [CommandOption(nameof(Ushort))]
-            public short Ushort { get; set; } = 1234;
-
             [CommandOption(nameof(Int))]
             public int Int { get; set; } = 1337;
 
-            [CommandOption(nameof(Uint))]
-            public uint Uint { get; set; } = 2345;
-
-            [CommandOption(nameof(Long))]
-            public long Long { get; set; } = -1234567;
-
-            [CommandOption(nameof(Ulong))]
-            public ulong Ulong { get; set; } = 12345678;
-
-            [CommandOption(nameof(Float))]
-            public float Float { get; set; } = 123.4567F;
-
-            [CommandOption(nameof(Double))]
-            public double Double { get; set; } = 420.1337;
-
-            [CommandOption(nameof(Decimal))]
-            public decimal Decimal { get; set; } = 1337.420M;
-
-            [CommandOption(nameof(DateTime))]
-            public DateTime DateTime { get; set; } = new DateTime(2020, 4, 20);
-            
-            [CommandOption(nameof(DateTimeOffset))]
-            public DateTimeOffset DateTimeOffset { get; set; } = 
-                new DateTimeOffset(2008, 5, 1, 0, 0, 0, new TimeSpan(0, 1, 0, 0, 0));
-
             [CommandOption(nameof(TimeSpan))]
             public TimeSpan TimeSpan { get; set; } = TimeSpan.FromMinutes(123);
 
-            public enum TestEnum { Value1, Value2, Value3 };
+            [CommandOption(nameof(Enum))]
-
+            public CustomEnum Enum { get; set; } = CustomEnum.Value2;
-            [CommandOption(nameof(CustomEnum))]
-            public TestEnum CustomEnum { get; set; } = TestEnum.Value2;
 
             [CommandOption(nameof(IntNullable))]
             public int? IntNullable { get; set; } = 1337;
 
-            [CommandOption(nameof(CustomEnumNullable))]
-            public TestEnum? CustomEnumNullable { get; set; } = TestEnum.Value2;
-
-            [CommandOption(nameof(TimeSpanNullable))]
-            public TimeSpan? TimeSpanNullable { get; set; } = TimeSpan.FromMinutes(234);
-
-            [CommandOption(nameof(ObjectArray))]
-            public object[]? ObjectArray { get; set; } = new object[] { "123", 4, 3.14 };
-
             [CommandOption(nameof(StringArray))]
-            public string[]? StringArray { get; set; } = new[] { "foo", "bar", "baz" };
+            public string[]? StringArray { get; set; } = { "foo", "bar", "baz" };
 
             [CommandOption(nameof(IntArray))]
-            public int[]? IntArray { get; set; } = new[] { 1, 2, 3 };
+            public int[]? IntArray { get; set; } = { 1, 2, 3 };
-
-            [CommandOption(nameof(CustomEnumArray))]
-            public TestEnum[]? CustomEnumArray { get; set; } = new[] { TestEnum.Value1, TestEnum.Value3 };
-
-            [CommandOption(nameof(IntNullableArray))]
-            public int?[]? IntNullableArray { get; set; } = new int?[] { 2, 3, 4, null, 5 };
-
-            [CommandOption(nameof(EnumerableNullable))]
-            public IEnumerable? EnumerableNullable { get; set; } = Enumerable.Repeat("foo", 3);
-
-            [CommandOption(nameof(StringEnumerable))]
-            public IEnumerable<string>? StringEnumerable { get; set; } = Enumerable.Repeat("bar", 3);
-
-            [CommandOption(nameof(StringReadOnlyList))]
-            public IReadOnlyList<string>? StringReadOnlyList { get; set; } = new[] { "foo", "bar", "baz" };
-
-            [CommandOption(nameof(StringList))]
-            public List<string>? StringList { get; set; } = new List<string>() { "foo", "bar", "baz" };
 
             public ValueTask ExecuteAsync(IConsole console) => default;
         }

CliFx.Tests/HelpTextSpecs.cs

@@ -304,7 +304,7 @@ namespace CliFx.Tests
             var console = new VirtualConsole(output: stdOut);
 
             var application = new CliApplicationBuilder()
-                .AddCommand(typeof(DefaultArgumentsCommand))
+                .AddCommand(typeof(ArgumentsWithDefaultValuesCommand))
                 .UseConsole(console)
                 .Build();
 
@@ -317,38 +317,17 @@ namespace CliFx.Tests
                 "Usage",
                 "cmd-with-defaults", "[options]",
                 "Options",
-                "--Object",             "(Default: 42)",
+                "--Object", "Default: \"42\"",
-                "--String",             "(Default: foo)",
+                "--String", "Default: \"foo\"",
-                "--EmptyString",        "(Default: \"\"",
+                "--EmptyString", "Default: \"\"",
-                "--WhiteSpaceString",   "(Default: \" \"",
+                "--Bool", "Default: \"True\"",
-                "--Bool",               "(Default: True)",
+                "--Char", "Default: \"t\"",
-                "--Char",               "(Default: t)",
+                "--Int", "Default: \"1337\"",
-                "--Sbyte",              "(Default: -3)",
+                "--TimeSpan", "Default: \"02:03:00\"",
-                "--Byte",               "(Default: 3)",
+                "--Enum", "Default: \"Value2\"",
-                "--Short",              "(Default: -1234)",
+                "--IntNullable", "Default: \"1337\"",
-                "--Ushort",             "(Default: 1234)",
+                "--StringArray", "Default: \"foo\" \"bar\" \"baz\"",
-                "--Int",                "(Default: 1337)",
+                "--IntArray", "Default: \"1\" \"2\" \"3\""
-                "--Uint",               "(Default: 2345)",
-                "--Long",               "(Default: -1234567)",
-                "--Ulong",              "(Default: 12345678)",
-                "--Float",              "(Default: 123.4567)",
-                "--Double",             "(Default: 420.1337)",
-                "--Decimal",            "(Default: 1337.420)",
-                "--DateTime",          $"(Default: {new DateTime(2020, 4, 20)}",
-                "--DateTimeOffset",    $"(Default: {new DateTimeOffset(2008, 5, 1, 0, 0, 0, new TimeSpan(0, 1, 0, 0, 0))}",
-                "--TimeSpan",           "(Default: 02:03:00)",
-                "--IntNullable",        "(Default: 1337)",
-                "--CustomEnumNullable", "(Default: Value2)",
-                "--TimeSpanNullable",   "(Default: 03:54:00)",
-                "--ObjectArray",        "(Default: 123 4 3.14)",
-                "--StringArray",        "(Default: foo bar baz)",
-                "--IntArray",           "(Default: 1 2 3)",
-                "--CustomEnumArray",    "(Default: Value1 Value3)",
-                "--IntNullableArray",   "(Default: 2 3 4 5)",
-                "--EnumerableNullable", "(Default: foo foo foo)",
-                "--StringEnumerable",   "(Default: bar bar bar)",
-                "--StringReadOnlyList", "(Default: foo bar baz)",
-                "--StringList",         "(Default: foo bar baz)"
             );
 
             _output.WriteLine(stdOutData);

CliFx/CliApplication.cs

@@ -6,6 +6,7 @@ using System.Linq;
 using System.Threading.Tasks;
 using CliFx.Domain;
 using CliFx.Exceptions;
+using CliFx.Internal;
 
 namespace CliFx
 {
@@ -33,7 +34,7 @@ namespace CliFx
             _console = console;
             _typeActivator = typeActivator;
 
-            _helpTextWriter = new HelpTextWriter(metadata, console);
+            _helpTextWriter = new HelpTextWriter(metadata, console, typeActivator);
         }
 
         private async ValueTask<int?> HandleDebugDirectiveAsync(CommandLineInput commandLineInput)
@@ -42,8 +43,10 @@ namespace CliFx
             if (!isDebugMode)
                 return null;
 
+            var processId = ProcessEx.GetCurrentProcessId();
+
             _console.WithForegroundColor(ConsoleColor.Green, () =>
-                _console.Output.WriteLine($"Attach debugger to PID {Process.GetCurrentProcess().Id} to continue."));
+                _console.Output.WriteLine($"Attach debugger to PID {processId} to continue."));
 
             while (!Debugger.IsAttached)
                 await Task.Delay(100);
@@ -124,7 +127,7 @@ namespace CliFx
             // Get the command schema that matches the input or use a dummy default command as a fallback
             var commandSchema =
                 applicationSchema.TryFindCommand(commandLineInput) ??
-                CommandSchema.StubDefaultCommand;
+                CommandSchema.StubDefaultCommand.Schema;
 
             _helpTextWriter.Write(applicationSchema, commandSchema);
 
@@ -143,17 +146,13 @@ namespace CliFx
             return 0;
         }
 
-        /// <summary>
+        private int HandleCliFxException(IReadOnlyList<string> commandLineArguments, CliFxException ex)
-        /// Handle <see cref="CommandException"/>s differently from the rest because we want to
-        /// display it different based on whether we are showing the help text or not.
-        /// </summary>
-        private int HandleCliFxException(IReadOnlyList<string> commandLineArguments, CliFxException cfe)
         {
-            var showHelp = cfe.ShowHelp;
+            var showHelp = ex.ShowHelp;
 
-            var errorMessage = cfe.HasMessage
+            var errorMessage = ex.HasMessage
-                ? cfe.Message
+                ? ex.Message
-                : cfe.ToString();
+                : ex.ToString();
 
             _console.WithForegroundColor(ConsoleColor.Red, () => _console.Error.WriteLine(errorMessage));
 
@@ -162,11 +161,11 @@ namespace CliFx
                 var applicationSchema = ApplicationSchema.Resolve(_configuration.CommandTypes);
                 var commandLineInput = CommandLineInput.Parse(commandLineArguments);
                 var commandSchema = applicationSchema.TryFindCommand(commandLineInput) ??
-                    CommandSchema.StubDefaultCommand;
+                    CommandSchema.StubDefaultCommand.Schema;
                 _helpTextWriter.Write(applicationSchema, commandSchema);
             }
 
-            return cfe.ExitCode;
+            return ex.ExitCode;
         }
 
         /// <summary>
@@ -188,16 +187,15 @@ namespace CliFx
                     HandleHelpOption(applicationSchema, commandLineInput) ??
                     await HandleCommandExecutionAsync(applicationSchema, commandLineInput, environmentVariables);
             }
-            catch (CliFxException cfe)
+            catch (CliFxException ex)
             {
-                // We want to catch exceptions in order to print errors and return correct exit codes.
+                // Some exceptions may specify exit code or request help
-                // Doing this also gets rid of the annoying Windows troubleshooting dialog that shows up on unhandled exceptions.
+                return HandleCliFxException(commandLineArguments, ex);
-                var exitCode = HandleCliFxException(commandLineArguments, cfe);
-                return exitCode;
             }
             catch (Exception ex)
             {
-                // For all other errors, we just write the entire thing to stderr.
+                // We want to catch all exceptions in order to print errors and return correct exit codes.
+                // Doing this also gets rid of the annoying Windows troubleshooting dialog that shows up on unhandled exceptions.
                 _console.WithForegroundColor(ConsoleColor.Red, () => _console.Error.WriteLine(ex.ToString()));
                 return ex.HResult;
             }

CliFx/DelegateTypeActivator.cs

@@ -18,6 +18,6 @@ namespace CliFx
 
         /// <inheritdoc />
         public object CreateInstance(Type type) =>
-            _func(type) ?? throw CliFxException.DelegateActivatorReceivedNull(type);
+            _func(type) ?? throw CliFxException.DelegateActivatorReturnedNull(type);
     }
 }

CliFx/Domain/CommandArgumentSchema.cs

@@ -15,8 +15,6 @@ namespace CliFx.Domain
 
         public string? Description { get; }
 
-        public abstract string DisplayName { get; }
-
         public bool IsScalar => TryGetEnumerableArgumentUnderlyingType() == null;
 
         protected CommandArgumentSchema(PropertyInfo property, string? description)
@@ -51,17 +49,17 @@ namespace CliFx.Domain
                         : null;
 
                 // String-constructable
-                var stringConstructor = GetStringConstructor(targetType);
+                var stringConstructor = targetType.GetConstructor(new[] {typeof(string)});
                 if (stringConstructor != null)
                     return stringConstructor.Invoke(new object[] {value!});
 
                 // String-parseable (with format provider)
-                var parseMethodWithFormatProvider = GetStaticParseMethodWithFormatProvider(targetType);
+                var parseMethodWithFormatProvider = targetType.GetStaticParseMethod(true);
                 if (parseMethodWithFormatProvider != null)
-                    return parseMethodWithFormatProvider.Invoke(null, new object[] {value!, ConversionFormatProvider});
+                    return parseMethodWithFormatProvider.Invoke(null, new object[] {value!, FormatProvider});
 
                 // String-parseable (without format provider)
-                var parseMethod = GetStaticParseMethod(targetType);
+                var parseMethod = targetType.GetStaticParseMethod();
                 if (parseMethod != null)
                     return parseMethod.Invoke(null, new object[] {value!});
             }
@@ -117,11 +115,62 @@ namespace CliFx.Domain
 
         public void Inject(ICommand command, params string[] values) =>
             Inject(command, (IReadOnlyList<string>) values);
+
+        public IReadOnlyList<string> GetValidValues()
+        {
+            var result = new List<string>();
+
+            // Some arguments may have this as null due to a hack that enables built-in options
+            // TODO fix this
+            if (Property == null)
+                return result;
+
+            var underlyingType =
+                Property.PropertyType.GetNullableUnderlyingType() ?? Property.PropertyType;
+
+            // Enum
+            if (underlyingType.IsEnum)
+                result.AddRange(Enum.GetNames(underlyingType));
+
+            return result;
+        }
+
+        public string? TryGetDefaultValue(ICommand instance)
+        {
+            // Some arguments may have this as null due to a hack that enables built-in options
+            // TODO fix this
+            if (Property == null)
+                return null;
+
+            var rawDefaultValue = Property.GetValue(instance);
+
+            if (!(rawDefaultValue is string) && rawDefaultValue is IEnumerable rawDefaultValues)
+            {
+                var elementType = rawDefaultValues.GetType().GetEnumerableUnderlyingType() ?? typeof(object);
+
+                return elementType.IsToStringOverriden()
+                    ? rawDefaultValues
+                        .Cast<object?>()
+                        .Where(o => o != null)
+                        .Select(o => o!.ToFormattableString(FormatProvider).Quote())
+                        .JoinToString(" ")
+                    : null;
+            }
+
+            if (rawDefaultValue != null && !Equals(rawDefaultValue, rawDefaultValue.GetType().GetDefaultValue()))
+            {
+                return rawDefaultValue.GetType().IsToStringOverriden()
+                    ? rawDefaultValue.ToFormattableString(FormatProvider).Quote()
+                    : null;
+            }
+
+            return null;
+        }
     }
 
     internal partial class CommandArgumentSchema
     {
-        private static readonly IFormatProvider ConversionFormatProvider = CultureInfo.InvariantCulture;
+        private static readonly IFormatProvider FormatProvider = CultureInfo.InvariantCulture;
 
         private static readonly IReadOnlyDictionary<Type, Func<string?, object?>> PrimitiveConverters =
             new Dictionary<Type, Func<string?, object?>>
@@ -130,112 +179,20 @@ namespace CliFx.Domain
                 [typeof(string)] = v => v,
                 [typeof(bool)] = v => string.IsNullOrWhiteSpace(v) || bool.Parse(v),
                 [typeof(char)] = v => v.Single(),
-                [typeof(sbyte)] = v => sbyte.Parse(v, ConversionFormatProvider),
+                [typeof(sbyte)] = v => sbyte.Parse(v, FormatProvider),
-                [typeof(byte)] = v => byte.Parse(v, ConversionFormatProvider),
+                [typeof(byte)] = v => byte.Parse(v, FormatProvider),
-                [typeof(short)] = v => short.Parse(v, ConversionFormatProvider),
+                [typeof(short)] = v => short.Parse(v, FormatProvider),
-                [typeof(ushort)] = v => ushort.Parse(v, ConversionFormatProvider),
+                [typeof(ushort)] = v => ushort.Parse(v, FormatProvider),
-                [typeof(int)] = v => int.Parse(v, ConversionFormatProvider),
+                [typeof(int)] = v => int.Parse(v, FormatProvider),
-                [typeof(uint)] = v => uint.Parse(v, ConversionFormatProvider),
+                [typeof(uint)] = v => uint.Parse(v, FormatProvider),
-                [typeof(long)] = v => long.Parse(v, ConversionFormatProvider),
+                [typeof(long)] = v => long.Parse(v, FormatProvider),
-                [typeof(ulong)] = v => ulong.Parse(v, ConversionFormatProvider),
+                [typeof(ulong)] = v => ulong.Parse(v, FormatProvider),
-                [typeof(float)] = v => float.Parse(v, ConversionFormatProvider),
+                [typeof(float)] = v => float.Parse(v, FormatProvider),
-                [typeof(double)] = v => double.Parse(v, ConversionFormatProvider),
+                [typeof(double)] = v => double.Parse(v, FormatProvider),
-                [typeof(decimal)] = v => decimal.Parse(v, ConversionFormatProvider),
+                [typeof(decimal)] = v => decimal.Parse(v, FormatProvider),
-                [typeof(DateTime)] = v => DateTime.Parse(v, ConversionFormatProvider),
+                [typeof(DateTime)] = v => DateTime.Parse(v, FormatProvider),
-                [typeof(DateTimeOffset)] = v => DateTimeOffset.Parse(v, ConversionFormatProvider),
+                [typeof(DateTimeOffset)] = v => DateTimeOffset.Parse(v, FormatProvider),
-                [typeof(TimeSpan)] = v => TimeSpan.Parse(v, ConversionFormatProvider),
+                [typeof(TimeSpan)] = v => TimeSpan.Parse(v, FormatProvider),
             };
-
-        private static ConstructorInfo? GetStringConstructor(Type type) =>
-            type.GetConstructor(new[] {typeof(string)});
-
-        private static MethodInfo? GetStaticParseMethod(Type type) =>
-            type.GetMethod("Parse",
-                BindingFlags.Public | BindingFlags.Static,
-                null, new[] {typeof(string)}, null);
-
-        private static MethodInfo? GetStaticParseMethodWithFormatProvider(Type type) =>
-            type.GetMethod("Parse",
-                BindingFlags.Public | BindingFlags.Static,
-                null, new[] {typeof(string), typeof(IFormatProvider)}, null);
-    }
-
-    // Default and valid value handling.
-    internal partial class CommandArgumentSchema
-    {
-        /// <summary>
-        /// Retrieves the valid values of this command argument.
-        /// </summary>
-        /// <returns>A string collection of this command's valid values.</returns>
-        public IReadOnlyList<string> GetValidValues()
-        {
-            var result = new List<string>();
-
-            // Some arguments may have this as null due to a hack that enables built-in options
-            if (Property == null)
-                return result;
-
-            var underlyingPropertyType =
-                Property.PropertyType.GetNullableUnderlyingType() ?? Property.PropertyType;
-
-            // Enum
-            if (underlyingPropertyType.IsEnum)
-                result.AddRange(Enum.GetNames(underlyingPropertyType));
-
-            return result;
-        }
-
-        /// <summary>
-        /// Gets the default value of this command argument.
-        /// Returns null if there's no default value.
-        /// </summary>
-        /// <param name="instance">A dummy instance of the command 
-        /// this command argument belongs to.</param>
-        /// <returns>The string representation of the default value. 
-        /// If there's no default value, it returns null.</returns>
-        /// <remarks>
-        /// We need a dummy instance in order to implement this because
-        /// we cannot retrieve it from a PropertyInfo.
-        /// </remarks>
-        public string? GetDefaultValue(ICommand? instance)
-        {
-            if (Property is null || instance is null)
-            {
-                return null;
-            }
-
-            var propertyName = Property?.Name;
-            string? defaultValue = null;
-            // Get the current culture so that the default value string
-            // matches the user's culture for cultured information like
-            // DateTimes and TimeSpans.
-            var culture = CultureInfo.CurrentCulture;
-
-            if (!string.IsNullOrWhiteSpace(propertyName))
-            {
-                var instanceProperty = instance.GetType().GetProperty(propertyName);
-                var value = instanceProperty.GetValue(instance);
-
-                if (value.OverridesToStringMethod())
-                {
-                    // Wrap empty or whitespace strings in quotes so that they're not
-                    // just an ugly blank in the output.
-                    defaultValue = value.ToCulturedString(culture)
-                        .WrapWithQuotesIfEmptyOrWhiteSpace();
-                }
-                else if (value is IEnumerable values)
-                {
-                    // Cast 'values' to IEnumerable<object> so we can use LINQ on it.
-                    defaultValue = 
-                        string.Join(" ", 
-                            values.Cast<object>()
-                            .Where(v => v != null)
-                            .Select(v => v.ToCulturedString(culture)
-                                .WrapWithQuotesIfEmptyOrWhiteSpace()));
-                }
-            }
-
-            return defaultValue;
-        }
     }
 }

CliFx/Domain/CommandDirectiveInput.cs

@@ -10,10 +10,7 @@ namespace CliFx.Domain
 
         public bool IsPreviewDirective => string.Equals(Name, "preview", StringComparison.OrdinalIgnoreCase);
 
-        public CommandDirectiveInput(string name)
+        public CommandDirectiveInput(string name) => Name = name;
-        {
-            Name = name;
-        }
 
         public override string ToString() => $"[{Name}]";
     }

CliFx/Domain/CommandOptionInput.cs

@@ -8,10 +8,9 @@ namespace CliFx.Domain
     {
         public string Alias { get; }
 
-        public string DisplayAlias =>
+        public string RawAlias => Alias.Length > 1
-            Alias.Length > 1
+            ? $"--{Alias}"
-                ? $"--{Alias}"
+            : $"-{Alias}";
-                : $"-{Alias}";
 
         public IReadOnlyList<string> Values { get; }
 
@@ -29,7 +28,7 @@ namespace CliFx.Domain
         {
             var buffer = new StringBuilder();
 
-            buffer.Append(DisplayAlias);
+            buffer.Append(RawAlias);
 
             foreach (var value in Values)
             {

CliFx/Domain/CommandOptionSchema.cs

@@ -12,10 +12,6 @@ namespace CliFx.Domain
 
         public char? ShortName { get; }
 
-        public override string DisplayName => !string.IsNullOrWhiteSpace(Name)
-            ? $"--{Name}"
-            : $"-{ShortName}";
-
         public string? EnvironmentVariableName { get; }
 
         public bool IsRequired { get; }
@@ -51,27 +47,35 @@ namespace CliFx.Domain
             !string.IsNullOrWhiteSpace(EnvironmentVariableName) &&
             string.Equals(EnvironmentVariableName, environmentVariableName, StringComparison.OrdinalIgnoreCase);
 
-        public override string ToString()
+        public string GetUserFacingDisplayString()
         {
             var buffer = new StringBuilder();
 
             if (!string.IsNullOrWhiteSpace(Name))
             {
-                buffer.Append("--");
+                buffer
-                buffer.Append(Name);
+                    .Append("--")
+                    .Append(Name);
             }
 
             if (!string.IsNullOrWhiteSpace(Name) && ShortName != null)
+            {
                 buffer.Append('|');
+            }
 
             if (ShortName != null)
             {
-                buffer.Append('-');
+                buffer
-                buffer.Append(ShortName);
+                    .Append('-')
+                    .Append(ShortName);
             }
 
             return buffer.ToString();
         }
+
+        public string GetInternalDisplayString() => $"{Property.Name} ('{GetUserFacingDisplayString()}')";
+
+        public override string ToString() => GetInternalDisplayString();
     }
 
     internal partial class CommandOptionSchema

CliFx/Domain/CommandParameterSchema.cs

@@ -8,31 +8,30 @@ namespace CliFx.Domain
     {
         public int Order { get; }
 
-        public string? Name { get; }
+        public string Name { get; }
 
-        public override string DisplayName =>
+        public CommandParameterSchema(PropertyInfo property, int order, string name, string? description)
-            !string.IsNullOrWhiteSpace(Name)
-                ? Name
-                : Property.Name.ToLowerInvariant();
-
-        public CommandParameterSchema(PropertyInfo property, int order, string? name, string? description)
             : base(property, description)
         {
             Order = order;
             Name = name;
         }
 
-        public override string ToString()
+        public string GetUserFacingDisplayString()
         {
             var buffer = new StringBuilder();
 
             buffer
                 .Append('<')
-                .Append(DisplayName)
+                .Append(Name)
                 .Append('>');
 
             return buffer.ToString();
         }
+
+        public string GetInternalDisplayString() => $"{Property.Name} ([{Order}] {GetUserFacingDisplayString()})";
+
+        public override string ToString() => GetInternalDisplayString();
     }
 
     internal partial class CommandParameterSchema
@@ -43,10 +42,12 @@ namespace CliFx.Domain
             if (attribute == null)
                 return null;
 
+            var name = attribute.Name ?? property.Name.ToLowerInvariant();
+
             return new CommandParameterSchema(
                 property,
                 attribute.Order,
-                attribute.Name,
+                name,
                 attribute.Description
             );
         }

CliFx/Domain/CommandSchema.cs

@@ -3,7 +3,7 @@ using System.Collections.Generic;
 using System.IO;
 using System.Linq;
 using System.Reflection;
-using System.Text;
+using System.Threading.Tasks;
 using CliFx.Attributes;
 using CliFx.Exceptions;
 using CliFx.Internal;
@@ -173,27 +173,11 @@ namespace CliFx.Domain
             return command;
         }
 
-        public override string ToString()
+        public string GetUserFacingDisplayString() => Name ?? "";
-        {
-            var buffer = new StringBuilder();
 
-            if (!string.IsNullOrWhiteSpace(Name))
+        public string GetInternalDisplayString() => $"{Type.FullName} ('{GetUserFacingDisplayString()}')";
-                buffer.Append(Name);
 
-            foreach (var parameter in Parameters)
+        public override string ToString() => GetInternalDisplayString();
-            {
-                buffer.AppendIfNotEmpty(' ');
-                buffer.Append(parameter);
-            }
-
-            foreach (var option in Options)
-            {
-                buffer.AppendIfNotEmpty(' ');
-                buffer.Append(option);
-            }
-
-            return buffer.ToString();
-        }
     }
 
     internal partial class CommandSchema
@@ -233,7 +217,13 @@ namespace CliFx.Domain
 
     internal partial class CommandSchema
     {
-        public static CommandSchema StubDefaultCommand { get; } =
+        // TODO: won't work with dep injection
-            new CommandSchema(null!, null, null, new CommandParameterSchema[0], new CommandOptionSchema[0]);
+        [Command]
+        public class StubDefaultCommand : ICommand
+        {
+            public ValueTask ExecuteAsync(IConsole console) => default;
+
+            public static CommandSchema Schema { get; } = TryResolve(typeof(StubDefaultCommand))!;
+        }
     }
 }

CliFx/Domain/CommandUnboundArgumentInput.cs

@@ -4,10 +4,7 @@
     {
         public string Value { get; }
 
-        public CommandUnboundArgumentInput(string value)
+        public CommandUnboundArgumentInput(string value) => Value = value;
-        {
-            Value = value;
-        }
 
         public override string ToString() => Value;
     }

CliFx/Domain/HelpTextWriter.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Linq;
 using CliFx.Internal;
 
@@ -8,353 +9,342 @@ namespace CliFx.Domain
     {
         private readonly ApplicationMetadata _metadata;
         private readonly IConsole _console;
+        private readonly ITypeActivator _typeActivator;
 
-        public HelpTextWriter(ApplicationMetadata metadata, IConsole console)
+        private int _column;
+        private int _row;
+
+        private bool IsEmpty => _column == 0 && _row == 0;
+
+        public HelpTextWriter(ApplicationMetadata metadata, IConsole console, ITypeActivator typeActivator)
         {
             _metadata = metadata;
             _console = console;
+            _typeActivator = typeActivator;
         }
 
-        public void Write(ApplicationSchema applicationSchema, CommandSchema command)
+        private void Write(char value)
         {
-            var column = 0;
+            _console.Output.Write(value);
-            var row = 0;
+            _column++;
+        }
 
-            var childCommands = applicationSchema.GetChildCommands(command.Name);
+        private void Write(string value)
+        {
+            _console.Output.Write(value);
+            _column += value.Length;
+        }
 
-            bool IsEmpty() => column == 0 && row == 0;
+        private void Write(ConsoleColor foregroundColor, string value)
+        {
+            _console.WithForegroundColor(foregroundColor, () => Write(value));
+        }
 
-            void Render(string text)
+        private void WriteLine()
+        {
+            _console.Output.WriteLine();
+            _column = 0;
+            _row++;
+        }
+
+        private void WriteVerticalMargin(int size = 1)
+        {
+            if (IsEmpty)
+                return;
+
+            for (var i = 0; i < size; i++)
+                WriteLine();
+        }
+
+        private void WriteHorizontalMargin(int size = 2)
+        {
+            if (IsEmpty)
+                return;
+
+            for (var i = 0; i < size; i++)
+                Write(' ');
+        }
+
+        private void WriteHorizontalColumnMargin(int columnSize = 20, int offsetSize = 2)
+        {
+            if (_column + offsetSize < columnSize)
+                WriteHorizontalMargin(columnSize - _column);
+            else
+                WriteHorizontalMargin(offsetSize);
+        }
+
+        private void WriteHeader(string text)
+        {
+            Write(ConsoleColor.Magenta, text);
+            WriteLine();
+        }
+
+        private void WriteApplicationInfo(CommandSchema commandSchema)
+        {
+            if (!commandSchema.IsDefault)
+                return;
+
+            // Title and version
+            Write(ConsoleColor.Yellow, _metadata.Title);
+            Write(' ');
+            Write(ConsoleColor.Yellow, _metadata.VersionText);
+            WriteLine();
+
+            // Description
+            if (!string.IsNullOrWhiteSpace(_metadata.Description))
             {
-                _console.Output.Write(text);
+                WriteHorizontalMargin();
+                Write(_metadata.Description);
+                WriteLine();
+            }
+        }
 
-                column += text.Length;
+        private void WriteCommandDescription(CommandSchema commandSchema)
+        {
+            if (string.IsNullOrWhiteSpace(commandSchema.Description))
+                return;
+
+            WriteVerticalMargin();
+            WriteHeader("Description");
+
+            WriteHorizontalMargin();
+            Write(commandSchema.Description);
+            WriteLine();
+        }
+
+        private void WriteCommandUsage(
+            CommandSchema commandSchema,
+            IReadOnlyList<CommandSchema> childCommandSchemas)
+        {
+            WriteVerticalMargin();
+            WriteHeader("Usage");
+
+            // Exe name
+            WriteHorizontalMargin();
+            Write(_metadata.ExecutableName);
+
+            // Command name
+            if (!string.IsNullOrWhiteSpace(commandSchema.Name))
+            {
+                Write(' ');
+                Write(ConsoleColor.Cyan, commandSchema.Name);
             }
 
-            void RenderNewLine()
+            // Child command placeholder
+            if (childCommandSchemas.Any())
             {
-                _console.Output.WriteLine();
+                Write(' ');
-
+                Write(ConsoleColor.Cyan, "[command]");
-                column = 0;
-                row++;
             }
 
-            void RenderMargin(int lines = 1)
+            // Parameters
+            foreach (var parameterSchema in commandSchema.Parameters)
             {
-                if (!IsEmpty())
+                Write(' ');
+                Write(parameterSchema.IsScalar
+                    ? $"<{parameterSchema.Name}>"
+                    : $"<{parameterSchema.Name}...>"
+                );
+            }
+
+            // Required options
+            foreach (var optionSchema in commandSchema.Options.Where(o => o.IsRequired))
+            {
+                Write(' ');
+                Write(ConsoleColor.White, !string.IsNullOrWhiteSpace(optionSchema.Name)
+                    ? $"--{optionSchema.Name}"
+                    : $"-{optionSchema.ShortName}"
+                );
+
+                Write(' ');
+                Write(optionSchema.IsScalar
+                    ? "<value>"
+                    : "<values...>"
+                );
+            }
+
+            // Options placeholder
+            Write(' ');
+            Write(ConsoleColor.White, "[options]");
+
+            WriteLine();
+        }
+
+        private void WriteCommandParameters(CommandSchema commandSchema)
+        {
+            if (!commandSchema.Parameters.Any())
+                return;
+
+            WriteVerticalMargin();
+            WriteHeader("Parameters");
+
+            foreach (var parameterSchema in commandSchema.Parameters.OrderBy(p => p.Order))
+            {
+                Write(ConsoleColor.Red, "* ");
+                Write(ConsoleColor.White, $"{parameterSchema.Name}");
+
+                WriteHorizontalColumnMargin();
+
+                // Description
+                if (!string.IsNullOrWhiteSpace(parameterSchema.Description))
                 {
-                    for (var i = 0; i < lines; i++)
+                    Write(parameterSchema.Description);
-                        RenderNewLine();
+                    Write(' ');
                 }
-            }
 
-            void RenderIndent(int spaces = 2)
+                // Valid values
-            {
+                var validValues = parameterSchema.GetValidValues();
-                Render(' '.Repeat(spaces));
+                if (validValues.Any())
-            }
-
-            void RenderColumnIndent(int spaces = 20, int margin = 2)
-            {
-                if (column + margin < spaces)
                 {
-                    RenderIndent(spaces - column);
+                    Write($"Valid values: {string.Join(", ", validValues)}.");
+                }
+
+                WriteLine();
+            }
+        }
+
+        private void WriteCommandOptions(CommandSchema commandSchema, ICommand command)
+        {
+            WriteVerticalMargin();
+            WriteHeader("Options");
+
+            var actualOptionSchemas = commandSchema.Options
+                .OrderByDescending(o => o.IsRequired)
+                .Concat(commandSchema.GetBuiltInOptions());
+
+            foreach (var optionSchema in actualOptionSchemas)
+            {
+                if (optionSchema.IsRequired)
+                {
+                    Write(ConsoleColor.Red, "* ");
                 }
                 else
                 {
-                    RenderIndent(margin);
+                    WriteHorizontalMargin();
                 }
-            }
 
-            void RenderWithColor(string text, ConsoleColor foregroundColor)
+                // Short name
-            {
+                if (optionSchema.ShortName != null)
-                _console.WithForegroundColor(foregroundColor, () => Render(text));
+                {
-            }
+                    Write(ConsoleColor.White, $"-{optionSchema.ShortName}");
+                }
 
-            void RenderHeader(string text)
+                // Delimiter
-            {
+                if (!string.IsNullOrWhiteSpace(optionSchema.Name) && optionSchema.ShortName != null)
-                RenderWithColor(text, ConsoleColor.Magenta);
+                {
-                RenderNewLine();
+                    Write('|');
-            }
+                }
 
-            void RenderApplicationInfo()
+                // Name
-            {
+                if (!string.IsNullOrWhiteSpace(optionSchema.Name))
-                if (!command.IsDefault)
+                {
-                    return;
+                    Write(ConsoleColor.White, $"--{optionSchema.Name}");
+                }
 
-                // Title and version
+                WriteHorizontalColumnMargin();
-                RenderWithColor(_metadata.Title, ConsoleColor.Yellow);
-                Render(" ");
-                RenderWithColor(_metadata.VersionText, ConsoleColor.Yellow);
-                RenderNewLine();
 
                 // Description
-                if (!string.IsNullOrWhiteSpace(_metadata.Description))
+                if (!string.IsNullOrWhiteSpace(optionSchema.Description))
                 {
-                    Render(_metadata.Description);
+                    Write(optionSchema.Description);
-                    RenderNewLine();
+                    Write(' ');
                 }
-            }
 
-            void RenderDescription()
+                // Valid values
+                var validValues = optionSchema.GetValidValues();
+                if (validValues.Any())
+                {
+                    Write($"Valid values: {validValues.Select(v => v.Quote()).JoinToString(", ")}.");
+                    Write(' ');
+                }
+
+                // Environment variable
+                if (!string.IsNullOrWhiteSpace(optionSchema.EnvironmentVariableName))
+                {
+                    Write($"Environment variable: \"{optionSchema.EnvironmentVariableName}\".");
+                    Write(' ');
+                }
+
+                // Default value
+                if (!optionSchema.IsRequired)
+                {
+                    // TODO: move quoting logic here?
+                    var defaultValue = optionSchema.TryGetDefaultValue(command);
+                    if (defaultValue != null)
+                    {
+                        Write($"Default: {defaultValue}.");
+                    }
+                }
+
+                WriteLine();
+            }
+        }
+
+        private void WriteCommandChildren(
+            CommandSchema commandSchema,
+            IReadOnlyList<CommandSchema> childCommandSchemas)
+        {
+            if (!childCommandSchemas.Any())
+                return;
+
+            WriteVerticalMargin();
+            WriteHeader("Commands");
+
+            foreach (var childCommandSchema in childCommandSchemas)
             {
-                if (string.IsNullOrWhiteSpace(command.Description))
+                var relativeCommandName = !string.IsNullOrWhiteSpace(commandSchema.Name)
-                    return;
+                    ? childCommandSchema.Name!.Substring(commandSchema.Name.Length + 1)
+                    : childCommandSchema.Name!;
 
-                RenderMargin();
+                // Name
-                RenderHeader("Description");
+                WriteHorizontalMargin();
+                Write(ConsoleColor.Cyan, relativeCommandName);
 
-                RenderIndent();
+                // Description
-                Render(command.Description);
+                if (!string.IsNullOrWhiteSpace(childCommandSchema.Description))
-                RenderNewLine();
+                {
+                    WriteHorizontalColumnMargin();
+                    Write(childCommandSchema.Description);
+                }
+
+                WriteLine();
             }
 
-            void RenderUsage()
+            // Child command help tip
+            WriteVerticalMargin();
+            Write("You can run `");
+            Write(_metadata.ExecutableName);
+
+            if (!string.IsNullOrWhiteSpace(commandSchema.Name))
             {
-                RenderMargin();
+                Write(' ');
-                RenderHeader("Usage");
+                Write(ConsoleColor.Cyan, commandSchema.Name);
-
-                // Exe name
-                RenderIndent();
-                Render(_metadata.ExecutableName);
-
-                // Command name
-                if (!string.IsNullOrWhiteSpace(command.Name))
-                {
-                    Render(" ");
-                    RenderWithColor(command.Name, ConsoleColor.Cyan);
-                }
-
-                // Child command placeholder
-                if (childCommands.Any())
-                {
-                    Render(" ");
-                    RenderWithColor("[command]", ConsoleColor.Cyan);
-                }
-
-                // Parameters
-                foreach (var parameter in command.Parameters)
-                {
-                    Render(" ");
-                    Render(parameter.IsScalar
-                        ? $"<{parameter.DisplayName}>"
-                        : $"<{parameter.DisplayName}...>");
-                }
-
-                // Required options
-                var requiredOptionSchemas = command.Options
-                    .Where(o => o.IsRequired)
-                    .ToArray();
-
-                foreach (var option in requiredOptionSchemas)
-                {
-                    Render(" ");
-                    if (!string.IsNullOrWhiteSpace(option.Name))
-                    {
-                        RenderWithColor($"--{option.Name}", ConsoleColor.White);
-                        Render(" ");
-                        Render(option.IsScalar
-                            ? "<value>"
-                            : "<values...>");
-                    }
-                    else
-                    {
-                        RenderWithColor($"-{option.ShortName}", ConsoleColor.White);
-                        Render(" ");
-                        Render(option.IsScalar
-                            ? "<value>"
-                            : "<values...>");
-                    }
-                }
-
-                // Options placeholder
-                if (command.Options.Count != requiredOptionSchemas.Length)
-                {
-                    Render(" ");
-                    RenderWithColor("[options]", ConsoleColor.White);
-                }
-
-                RenderNewLine();
             }
 
-            void RenderParameters()
+            Write(' ');
-            {
+            Write(ConsoleColor.Cyan, "[command]");
-                if (!command.Parameters.Any())
-                    return;
 
-                RenderMargin();
+            Write(' ');
-                RenderHeader("Parameters");
+            Write(ConsoleColor.White, "--help");
 
-                var parameters = command.Parameters
+            Write("` to show help on a specific command.");
-                    .OrderBy(p => p.Order)
-                    .ToArray();
 
-                foreach (var parameter in parameters)
+            WriteLine();
-                {
+        }
-                    RenderWithColor("* ", ConsoleColor.Red);
-                    RenderWithColor($"{parameter.DisplayName}", ConsoleColor.White);
 
-                    RenderColumnIndent();
+        public void Write(ApplicationSchema applicationSchema, CommandSchema commandSchema)
-
+        {
-                    // Description
+            var childCommandSchemas = applicationSchema.GetChildCommands(commandSchema.Name);
-                    if (!string.IsNullOrWhiteSpace(parameter.Description))
+            var command = (ICommand) _typeActivator.CreateInstance(commandSchema.Type);
-                    {
-                        Render(parameter.Description);
-                        Render(" ");
-                    }
-
-                    // Valid values
-                    var validValues = parameter.GetValidValues();
-                    if (validValues.Any())
-                    {
-                        Render($"Valid values: {string.Join(", ", validValues)}.");
-                        Render(" ");
-                    }
-
-                    RenderNewLine();
-                }
-            }
-
-            void RenderOptions()
-            {
-                RenderMargin();
-                RenderHeader("Options");
-
-                // Instantiate a temporary instance of the command so we can get default values from it.
-                ICommand? tempInstance = command.Type is null ? null : Activator.CreateInstance(command.Type) as ICommand;
-
-                var options = command.Options
-                    .OrderByDescending(o => o.IsRequired)
-                    .Concat(command.GetBuiltInOptions())
-                    .ToArray();
-
-                foreach (var option in options)
-                {
-                    if (option.IsRequired)
-                    {
-                        RenderWithColor("* ", ConsoleColor.Red);
-                    }
-                    else
-                    {
-                        RenderIndent();
-                    }
-
-                    // Short name
-                    if (option.ShortName != null)
-                    {
-                        RenderWithColor($"-{option.ShortName}", ConsoleColor.White);
-                    }
-
-                    // Delimiter
-                    if (!string.IsNullOrWhiteSpace(option.Name) && option.ShortName != null)
-                    {
-                        Render("|");
-                    }
-
-                    // Name
-                    if (!string.IsNullOrWhiteSpace(option.Name))
-                    {
-                        RenderWithColor($"--{option.Name}", ConsoleColor.White);
-                    }
-
-                    RenderColumnIndent();
-
-                    // Description
-                    if (!string.IsNullOrWhiteSpace(option.Description))
-                    {
-                        Render(option.Description);
-                        Render(" ");
-                    }
-
-                    // Valid values
-                    var validValues = option.GetValidValues();
-                    if (validValues.Any())
-                    {
-                        Render($"Valid values: {string.Join(", ", validValues)}.");
-                        Render(" ");
-                    }
-
-                    // Environment variable
-                    if (!string.IsNullOrWhiteSpace(option.EnvironmentVariableName))
-                    {
-                        Render($"(Environment variable: {option.EnvironmentVariableName})");
-                        Render(" ");
-                    }
-
-                    // Default value
-                    if (!option.IsRequired)
-                    {
-                        var defaultValue = option.GetDefaultValue(tempInstance);
-                        // If 'defaultValue' is null, it means there's no default value.
-                        if (defaultValue is object)
-                        {
-                            Render($"(Default: {defaultValue})");
-                            Render(" ");
-                        }
-                    }
-
-                    RenderNewLine();
-                }
-            }
-
-            void RenderChildCommands()
-            {
-                if (!childCommands.Any())
-                    return;
-
-                RenderMargin();
-                RenderHeader("Commands");
-
-                foreach (var childCommand in childCommands)
-                {
-                    var relativeCommandName =
-                        !string.IsNullOrWhiteSpace(command.Name)
-                            ? childCommand.Name!.Substring(command.Name.Length + 1)
-                            : childCommand.Name!;
-
-                    // Name
-                    RenderIndent();
-                    RenderWithColor(relativeCommandName, ConsoleColor.Cyan);
-
-                    // Description
-                    if (!string.IsNullOrWhiteSpace(childCommand.Description))
-                    {
-                        RenderColumnIndent();
-                        Render(childCommand.Description);
-                    }
-
-                    RenderNewLine();
-                }
-
-                RenderMargin();
-
-                // Child command help tip
-                Render("You can run `");
-                Render(_metadata.ExecutableName);
-
-                if (!string.IsNullOrWhiteSpace(command.Name))
-                {
-                    Render(" ");
-                    RenderWithColor(command.Name, ConsoleColor.Cyan);
-                }
-
-                Render(" ");
-                RenderWithColor("[command]", ConsoleColor.Cyan);
-
-                Render(" ");
-                RenderWithColor("--help", ConsoleColor.White);
-
-                Render("` to show help on a specific command.");
-
-                RenderNewLine();
-            }
 
             _console.ResetColor();
-            RenderApplicationInfo();
+
-            RenderDescription();
+            WriteApplicationInfo(commandSchema);
-            RenderUsage();
+            WriteCommandDescription(commandSchema);
-            RenderParameters();
+            WriteCommandUsage(commandSchema, childCommandSchemas);
-            RenderOptions();
+            WriteCommandParameters(commandSchema);
-            RenderChildCommands();
+            WriteCommandOptions(commandSchema, command);
+            WriteCommandChildren(commandSchema, childCommandSchemas);
         }
     }
 }

CliFx/Exceptions/CliFxException.cs

@@ -3,6 +3,7 @@ using System.Collections.Generic;
 using System.Linq;
 using CliFx.Attributes;
 using CliFx.Domain;
+using CliFx.Internal;
 
 namespace CliFx.Exceptions
 {
@@ -35,14 +36,6 @@ namespace CliFx.Exceptions
         /// </summary>
         public int ExitCode { get; }
 
-        /// <summary>
-        /// Initializes an instance of <see cref="CliFxException"/>.
-        /// </summary>
-        public CliFxException(string? message, bool showHelp = false)
-            : this(message, null, showHelp: showHelp)
-        {
-        }
-
         /// <summary>
         /// Initializes an instance of <see cref="CliFxException"/>.
         /// </summary>
@@ -52,9 +45,18 @@ namespace CliFx.Exceptions
             ExitCode = exitCode != 0
                 ? exitCode
                 : throw new ArgumentException("Exit code must not be zero in order to signify failure.");
+
             HasMessage = !string.IsNullOrWhiteSpace(message);
             ShowHelp = showHelp;
         }
+
+        /// <summary>
+        /// Initializes an instance of <see cref="CliFxException"/>.
+        /// </summary>
+        public CliFxException(string? message, bool showHelp = false)
+            : this(message, null, showHelp: showHelp)
+        {
+        }
     }
 
     // Mid-user-facing exceptions
@@ -75,7 +77,7 @@ Refer to the readme to learn how to integrate a dependency container of your cho
             return new CliFxException(message.Trim(), innerException);
         }
 
-        internal static CliFxException DelegateActivatorReceivedNull(Type type)
+        internal static CliFxException DelegateActivatorReturnedNull(Type type)
         {
             var message = $@"
 Failed to create an instance of type '{type.FullName}', received <null> instead.
@@ -112,12 +114,11 @@ If you're experiencing problems, please refer to the readme for a quickstart exa
             return new CliFxException(message.Trim());
         }
 
-        internal static CliFxException CommandsTooManyDefaults(
+        internal static CliFxException CommandsTooManyDefaults(IReadOnlyList<CommandSchema> invalidCommandSchemas)
-            IReadOnlyList<CommandSchema> invalidCommands)
         {
             var message = $@"
-Application configuration is invalid because there are {invalidCommands.Count} default commands:
+Application configuration is invalid because there are {invalidCommandSchemas.Count} default commands:
-{string.Join(Environment.NewLine, invalidCommands.Select(p => p.Type.FullName))}
+{invalidCommandSchemas.JoinToString(Environment.NewLine)}
 
 There can only be one default command (i.e. command with no name) in an application.
 Other commands must have unique non-empty names that identify them.";
@@ -127,11 +128,11 @@ Other commands must have unique non-empty names that identify them.";
 
         internal static CliFxException CommandsDuplicateName(
             string name,
-            IReadOnlyList<CommandSchema> invalidCommands)
+            IReadOnlyList<CommandSchema> invalidCommandSchemas)
         {
             var message = $@"
-Application configuration is invalid because there are {invalidCommands.Count} commands with the same name ('{name}'):
+Application configuration is invalid because there are {invalidCommandSchemas.Count} commands with the same name ('{name}'):
-{string.Join(Environment.NewLine, invalidCommands.Select(p => p.Type.FullName))}
+{invalidCommandSchemas.JoinToString(Environment.NewLine)}
 
 Commands must have unique names.
 Names are not case-sensitive.";
@@ -140,13 +141,13 @@ Names are not case-sensitive.";
         }
 
         internal static CliFxException CommandParametersDuplicateOrder(
-            CommandSchema command,
+            CommandSchema commandSchema,
             int order,
-            IReadOnlyList<CommandParameterSchema> invalidParameters)
+            IReadOnlyList<CommandParameterSchema> invalidParameterSchemas)
         {
             var message = $@"
-Command '{command.Type.FullName}' is invalid because it contains {invalidParameters.Count} parameters with the same order ({order}):
+Command '{commandSchema.Type.FullName}' is invalid because it contains {invalidParameterSchemas.Count} parameters with the same order ({order}):
-{string.Join(Environment.NewLine, invalidParameters.Select(p => p.Property.Name))}
+{invalidParameterSchemas.JoinToString(Environment.NewLine)}
 
 Parameters must have unique order.";
 
@@ -154,13 +155,13 @@ Parameters must have unique order.";
         }
 
         internal static CliFxException CommandParametersDuplicateName(
-            CommandSchema command,
+            CommandSchema commandSchema,
             string name,
-            IReadOnlyList<CommandParameterSchema> invalidParameters)
+            IReadOnlyList<CommandParameterSchema> invalidParameterSchemas)
         {
             var message = $@"
-Command '{command.Type.FullName}' is invalid because it contains {invalidParameters.Count} parameters with the same name ('{name}'):
+Command '{commandSchema.Type.FullName}' is invalid because it contains {invalidParameterSchemas.Count} parameters with the same name ('{name}'):
-{string.Join(Environment.NewLine, invalidParameters.Select(p => p.Property.Name))}
+{invalidParameterSchemas.JoinToString(Environment.NewLine)}
 
 Parameters must have unique names to avoid potential confusion in the help text.
 Names are not case-sensitive.";
@@ -169,12 +170,12 @@ Names are not case-sensitive.";
         }
 
         internal static CliFxException CommandParametersTooManyNonScalar(
-            CommandSchema command,
+            CommandSchema commandSchema,
-            IReadOnlyList<CommandParameterSchema> invalidParameters)
+            IReadOnlyList<CommandParameterSchema> invalidParameterSchemas)
         {
             var message = $@"
-Command '{command.Type.FullName}' is invalid because it contains {invalidParameters.Count} non-scalar parameters:
+Command '{commandSchema.Type.FullName}' is invalid because it contains {invalidParameterSchemas.Count} non-scalar parameters:
-{string.Join(Environment.NewLine, invalidParameters.Select(p => p.Property.Name))}
+{invalidParameterSchemas.JoinToString(Environment.NewLine)}
 
 Non-scalar parameter is such that is bound from more than one value (e.g. array or a complex object).
 Only one parameter in a command may be non-scalar and it must be the last one in order.
@@ -185,12 +186,12 @@ If it's not feasible to fit into these constraints, consider using options inste
         }
 
         internal static CliFxException CommandParametersNonLastNonScalar(
-            CommandSchema command,
+            CommandSchema commandSchema,
-            CommandParameterSchema invalidParameter)
+            CommandParameterSchema invalidParameterSchema)
         {
             var message = $@"
-Command '{command.Type.FullName}' is invalid because it contains a non-scalar parameter which is not the last in order:
+Command '{commandSchema.Type.FullName}' is invalid because it contains a non-scalar parameter which is not the last in order:
-{invalidParameter.Property.Name}
+{invalidParameterSchema}
 
 Non-scalar parameter is such that is bound from more than one value (e.g. array or a complex object).
 Only one parameter in a command may be non-scalar and it must be the last one in order.
@@ -201,12 +202,12 @@ If it's not feasible to fit into these constraints, consider using options inste
         }
 
         internal static CliFxException CommandOptionsNoName(
-            CommandSchema command,
+            CommandSchema commandSchema,
-            IReadOnlyList<CommandOptionSchema> invalidOptions)
+            IReadOnlyList<CommandOptionSchema> invalidOptionSchemas)
         {
             var message = $@"
-Command '{command.Type.FullName}' is invalid because it contains one or more options without a name:
+Command '{commandSchema.Type.FullName}' is invalid because it contains one or more options without a name:
-{string.Join(Environment.NewLine, invalidOptions.Select(o => o.Property.Name))}
+{invalidOptionSchemas.JoinToString(Environment.NewLine)}
 
 Options must have either a name or a short name or both.";
 
@@ -214,12 +215,12 @@ Options must have either a name or a short name or both.";
         }
 
         internal static CliFxException CommandOptionsInvalidLengthName(
-            CommandSchema command,
+            CommandSchema commandSchema,
-            IReadOnlyList<CommandOptionSchema> invalidOptions)
+            IReadOnlyList<CommandOptionSchema> invalidOptionSchemas)
         {
             var message = $@"
-Command '{command.Type.FullName}' is invalid because it contains one or more options whose names are too short:
+Command '{commandSchema.Type.FullName}' is invalid because it contains one or more options whose names are too short:
-{string.Join(Environment.NewLine, invalidOptions.Select(o => $"{o.Property.Name} ('{o.DisplayName}')"))}
+{invalidOptionSchemas.JoinToString(Environment.NewLine)}
 
 Option names must be at least 2 characters long to avoid confusion with short names.
 If you intended to set the short name instead, use the attribute overload that accepts a char.";
@@ -228,30 +229,28 @@ If you intended to set the short name instead, use the attribute overload that a
         }
 
         internal static CliFxException CommandOptionsDuplicateName(
-            CommandSchema command,
+            CommandSchema commandSchema,
             string name,
-            IReadOnlyList<CommandOptionSchema> invalidOptions)
+            IReadOnlyList<CommandOptionSchema> invalidOptionSchemas)
         {
             var message = $@"
-Command '{command.Type.FullName}' is invalid because it contains {invalidOptions.Count} options with the same name ('{name}'):
+Command '{commandSchema.Type.FullName}' is invalid because it contains {invalidOptionSchemas.Count} options with the same name ('{name}'):
-{string.Join(Environment.NewLine, invalidOptions.Select(o => o.Property.Name))}
+{invalidOptionSchemas.JoinToString(Environment.NewLine)}
 
-Options must have unique names, because that's what identifies them.
+Options must have unique names.
-Names are not case-sensitive.
+Names are not case-sensitive.";
-
-To fix this, ensure that all options have different names.";
 
             return new CliFxException(message.Trim());
         }
 
         internal static CliFxException CommandOptionsDuplicateShortName(
-            CommandSchema command,
+            CommandSchema commandSchema,
             char shortName,
-            IReadOnlyList<CommandOptionSchema> invalidOptions)
+            IReadOnlyList<CommandOptionSchema> invalidOptionSchemas)
         {
             var message = $@"
-Command '{command.Type.FullName}' is invalid because it contains {invalidOptions.Count} options with the same short name ('{shortName}'):
+Command '{commandSchema.Type.FullName}' is invalid because it contains {invalidOptionSchemas.Count} options with the same short name ('{shortName}'):
-{string.Join(Environment.NewLine, invalidOptions.Select(o => o.Property.Name))}
+{invalidOptionSchemas.JoinToString(Environment.NewLine)}
 
 Options must have unique short names.
 Short names are case-sensitive (i.e. 'a' and 'A' are different short names).";
@@ -260,13 +259,13 @@ Short names are case-sensitive (i.e. 'a' and 'A' are different short names).";
         }
 
         internal static CliFxException CommandOptionsDuplicateEnvironmentVariableName(
-            CommandSchema command,
+            CommandSchema commandSchema,
             string environmentVariableName,
-            IReadOnlyList<CommandOptionSchema> invalidOptions)
+            IReadOnlyList<CommandOptionSchema> invalidOptionSchemas)
         {
             var message = $@"
-Command '{command.Type.FullName}' is invalid because it contains {invalidOptions.Count} options with the same fallback environment variable name ('{environmentVariableName}'):
+Command '{commandSchema.Type.FullName}' is invalid because it contains {invalidOptionSchemas.Count} options with the same fallback environment variable name ('{environmentVariableName}'):
-{string.Join(Environment.NewLine, invalidOptions.Select(o => o.Property.Name))}
+{invalidOptionSchemas.JoinToString(Environment.NewLine)}
 
 Options cannot share the same environment variable as a fallback.
 Environment variable names are not case-sensitive.";
@@ -283,92 +282,148 @@ Environment variable names are not case-sensitive.";
         {
             var message = $@"
 Can't find a command that matches the following arguments:
-{string.Join(" ", input.UnboundArguments.Select(a => a.Value))}";
+{input.UnboundArguments.JoinToString(" ")}";
 
             return new CliFxException(message.Trim(), showHelp: true);
         }
 
         internal static CliFxException CannotConvertMultipleValuesToNonScalar(
-            CommandArgumentSchema argument,
+            CommandParameterSchema parameterSchema,
             IReadOnlyList<string> values)
         {
-            var argumentDisplayText = argument is CommandParameterSchema
-                ? $"Parameter <{argument.DisplayName}>"
-                : $"Option '{argument.DisplayName}'";
-
             var message = $@"
-{argumentDisplayText} expects a single value, but provided with multiple:
+Parameter {parameterSchema.GetUserFacingDisplayString()} expects a single value, but provided with multiple:
-{string.Join(", ", values.Select(v => $"'{v}'"))}";
+{values.Select(v => v.Quote()).JoinToString(" ")}";
 
             return new CliFxException(message.Trim(), showHelp: true);
         }
 
+        internal static CliFxException CannotConvertMultipleValuesToNonScalar(
+            CommandOptionSchema optionSchema,
+            IReadOnlyList<string> values)
+        {
+            var message = $@"
+Option {optionSchema.GetUserFacingDisplayString()} expects a single value, but provided with multiple:
+{values.Select(v => v.Quote()).JoinToString(" ")}";
+
+            return new CliFxException(message.Trim(), showHelp: true);
+        }
+
+        internal static CliFxException CannotConvertMultipleValuesToNonScalar(
+            CommandArgumentSchema argumentSchema,
+            IReadOnlyList<string> values) => argumentSchema switch
+        {
+            CommandParameterSchema parameterSchema => CannotConvertMultipleValuesToNonScalar(parameterSchema, values),
+            CommandOptionSchema optionSchema => CannotConvertMultipleValuesToNonScalar(optionSchema, values),
+            _ => throw new ArgumentOutOfRangeException(nameof(argumentSchema))
+        };
+
         internal static CliFxException CannotConvertToType(
-            CommandArgumentSchema argument,
+            CommandParameterSchema parameterSchema,
             string? value,
             Type type,
             Exception? innerException = null)
         {
-            var argumentDisplayText = argument is CommandParameterSchema
-                ? $"parameter <{argument.DisplayName}>"
-                : $"option '{argument.DisplayName}'";
-
             var message = $@"
-Can't convert value '{value ?? "<null>"}' to type '{type.FullName}' for {argumentDisplayText}.
+Can't convert value ""{value ?? "<null>"}"" to type '{type.Name}' for parameter {parameterSchema.GetUserFacingDisplayString()}.
 {innerException?.Message ?? "This type is not supported."}";
 
             return new CliFxException(message.Trim(), innerException, showHelp: true);
         }
 
+        internal static CliFxException CannotConvertToType(
+            CommandOptionSchema optionSchema,
+            string? value,
+            Type type,
+            Exception? innerException = null)
+        {
+            var message = $@"
+Can't convert value ""{value ?? "<null>"}"" to type '{type.Name}' for option {optionSchema.GetUserFacingDisplayString()}.
+{innerException?.Message ?? "This type is not supported."}";
+
+            return new CliFxException(message.Trim(), innerException, showHelp: true);
+        }
+
+        internal static CliFxException CannotConvertToType(
+            CommandArgumentSchema argumentSchema,
+            string? value,
+            Type type,
+            Exception? innerException = null) => argumentSchema switch
+        {
+            CommandParameterSchema parameterSchema => CannotConvertToType(parameterSchema, value, type, innerException),
+            CommandOptionSchema optionSchema => CannotConvertToType(optionSchema, value, type, innerException),
+            _ => throw new ArgumentOutOfRangeException(nameof(argumentSchema))
+        };
+
         internal static CliFxException CannotConvertNonScalar(
-            CommandArgumentSchema argument,
+            CommandParameterSchema parameterSchema,
             IReadOnlyList<string> values,
             Type type)
         {
-            var argumentDisplayText = argument is CommandParameterSchema
-                ? $"parameter <{argument.DisplayName}>"
-                : $"option '{argument.DisplayName}'";
-
             var message = $@"
-Can't convert provided values to type '{type.FullName}' for {argumentDisplayText}:
+Can't convert provided values to type '{type.Name}' for parameter {parameterSchema.GetUserFacingDisplayString()}:
-{string.Join(", ", values.Select(v => $"'{v}'"))}
+{values.Select(v => v.Quote()).JoinToString(" ")}
 
 Target type is not assignable from array and doesn't have a public constructor that takes an array.";
 
             return new CliFxException(message.Trim(), showHelp: true);
         }
 
-        internal static CliFxException ParameterNotSet(CommandParameterSchema parameter)
+        internal static CliFxException CannotConvertNonScalar(
+            CommandOptionSchema optionSchema,
+            IReadOnlyList<string> values,
+            Type type)
         {
             var message = $@"
-Missing value for parameter <{parameter.DisplayName}>.";
+Can't convert provided values to type '{type.Name}' for option {optionSchema.GetUserFacingDisplayString()}:
+{values.Select(v => v.Quote()).JoinToString(" ")}
+
+Target type is not assignable from array and doesn't have a public constructor that takes an array.";
 
             return new CliFxException(message.Trim(), showHelp: true);
         }
 
-        internal static CliFxException RequiredOptionsNotSet(IReadOnlyList<CommandOptionSchema> options)
+        internal static CliFxException CannotConvertNonScalar(
+            CommandArgumentSchema argumentSchema,
+            IReadOnlyList<string> values,
+            Type type) => argumentSchema switch
+        {
+            CommandParameterSchema parameterSchema => CannotConvertNonScalar(parameterSchema, values, type),
+            CommandOptionSchema optionSchema => CannotConvertNonScalar(optionSchema, values, type),
+            _ => throw new ArgumentOutOfRangeException(nameof(argumentSchema))
+        };
+
+        internal static CliFxException ParameterNotSet(CommandParameterSchema parameterSchema)
+        {
+            var message = $@"
+Missing value for parameter {parameterSchema.GetUserFacingDisplayString()}.";
+
+            return new CliFxException(message.Trim(), showHelp: true);
+        }
+
+        internal static CliFxException RequiredOptionsNotSet(IReadOnlyList<CommandOptionSchema> optionSchemas)
         {
             var message = $@"
 Missing values for one or more required options:
-{string.Join(Environment.NewLine, options.Select(o => o.DisplayName))}";
+{optionSchemas.Select(o => o.GetUserFacingDisplayString()).JoinToString(Environment.NewLine)}";
 
             return new CliFxException(message.Trim(), showHelp: true);
         }
 
-        internal static CliFxException UnrecognizedParametersProvided(IReadOnlyList<CommandUnboundArgumentInput> inputs)
+        internal static CliFxException UnrecognizedParametersProvided(IReadOnlyList<CommandUnboundArgumentInput> argumentInputs)
         {
             var message = $@"
 Unrecognized parameters provided:
-{string.Join(Environment.NewLine, inputs.Select(i => $"<{i.Value}>"))}";
+{argumentInputs.Select(a => a.Value.Quote()).JoinToString(" ")}";
 
             return new CliFxException(message.Trim(), showHelp: true);
         }
 
-        internal static CliFxException UnrecognizedOptionsProvided(IReadOnlyList<CommandOptionInput> inputs)
+        internal static CliFxException UnrecognizedOptionsProvided(IReadOnlyList<CommandOptionInput> optionInputs)
         {
             var message = $@"
 Unrecognized options provided:
-{string.Join(Environment.NewLine, inputs.Select(i => i.DisplayAlias))}";
+{optionInputs.Select(o => o.RawAlias).JoinToString(Environment.NewLine)}";
 
             return new CliFxException(message.Trim(), showHelp: true);
         }

CliFx/Exceptions/CommandException.cs

@@ -14,16 +14,15 @@ namespace CliFx.Exceptions
         /// </summary>
         public CommandException(string? message, Exception? innerException,
             int exitCode = DefaultExitCode, bool showHelp = false)
-                : base(message, innerException, exitCode, showHelp)
+            : base(message, innerException, exitCode, showHelp)
         {
-            
         }
 
         /// <summary>
         /// Initializes an instance of <see cref="CommandException"/>.
         /// </summary>
         public CommandException(string? message, int exitCode = DefaultExitCode, bool showHelp = false)
-                : this(message, null, exitCode, showHelp)
+            : this(message, null, exitCode, showHelp)
         {
         }
 

CliFx/ICommand.cs

@@ -9,7 +9,7 @@ namespace CliFx
     {
         /// <summary>
         /// Executes the command using the specified implementation of <see cref="IConsole"/>.
-        /// This is the method that's called when the command is invoked by a user through command line interface.
+        /// This is the method that's called when the command is invoked by a user through command line.
         /// </summary>
         /// <remarks>If the execution of the command is not asynchronous, simply end the method with <code>return default;</code></remarks>
         ValueTask ExecuteAsync(IConsole console);

CliFx/ITypeActivator.cs

@@ -3,12 +3,12 @@
 namespace CliFx
 {
     /// <summary>
-    /// Abstraction for a service can initialize objects at runtime.
+    /// Abstraction for a service that can initialize objects at runtime.
     /// </summary>
     public interface ITypeActivator
     {
         /// <summary>
-        /// Creates an instance of specified type.
+        /// Creates an instance of the specified type.
         /// </summary>
         object CreateInstance(Type type);
     }

CliFx/Internal/ProcessEx.cs

@@ -0,0 +1,13 @@
+using System.Diagnostics;
+
+namespace CliFx.Internal
+{
+    internal static class ProcessEx
+    {
+        public static int GetCurrentProcessId()
+        {
+            using var process = Process.GetCurrentProcess();
+            return process.Id;
+        }
+    }
+}

CliFx/Internal/StringExtensions.cs

@@ -1,5 +1,5 @@
 using System;
-using System.Globalization;
+using System.Collections.Generic;
 using System.Text;
 
 namespace CliFx.Internal
@@ -10,14 +10,17 @@ namespace CliFx.Internal
 
         public static string AsString(this char c) => c.Repeat(1);
 
+        public static string Quote(this string str) => $"\"{str}\"";
+
+        public static string JoinToString<T>(this IEnumerable<T> source, string separator) => string.Join(separator, source);
+
         public static StringBuilder AppendIfNotEmpty(this StringBuilder builder, char value) =>
             builder.Length > 0 ? builder.Append(value) : builder;
 
-        public static bool IsEmptyOrWhiteSpace(this string s) => s is object && string.IsNullOrWhiteSpace(s);
+        public static string ToFormattableString(this object obj,
-
+            IFormatProvider? formatProvider = null, string? format = null) =>
-        public static string WrapWithQuotesIfEmptyOrWhiteSpace(this string s) =>
+            obj is IFormattable formattable
-            s.IsEmptyOrWhiteSpace() ? $"\"{s}\"" : s;
+                ? formattable.ToString(format, formatProvider)
-
+                : obj.ToString();
-        public static string ToCulturedString(this object obj, CultureInfo culture) => Convert.ToString(obj, culture);
     }
 }

CliFx/Internal/TypeExtensions.cs

@@ -2,11 +2,17 @@
 using System.Collections;
 using System.Collections.Generic;
 using System.Linq;
+using System.Reflection;
 
 namespace CliFx.Internal
 {
     internal static class TypeExtensions
     {
+        public static object? GetDefaultValue(this Type type) =>
+            type.IsValueType
+                ? Activator.CreateInstance(type)
+                : null;
+
         public static bool Implements(this Type type, Type interfaceType) => type.GetInterfaces().Contains(interfaceType);
 
         public static Type? GetNullableUnderlyingType(this Type type) => Nullable.GetUnderlyingType(type);
@@ -22,13 +28,30 @@ namespace CliFx.Internal
             if (type.IsGenericType && type.GetGenericTypeDefinition() == typeof(IEnumerable<>))
                 return type.GetGenericArguments().FirstOrDefault();
 
-            return type.GetInterfaces()
+            return type
+                .GetInterfaces()
                 .Select(GetEnumerableUnderlyingType)
                 .Where(t => t != null)
                 .OrderByDescending(t => t != typeof(object)) // prioritize more specific types
                 .FirstOrDefault();
         }
 
+        public static MethodInfo GetToStringMethod(this Type type) => type.GetMethod(nameof(ToString), Type.EmptyTypes);
+
+        public static bool IsToStringOverriden(this Type type) => type.GetToStringMethod() != typeof(object).GetToStringMethod();
+
+        public static MethodInfo GetStaticParseMethod(this Type type, bool withFormatProvider = false)
+        {
+            var argumentTypes = withFormatProvider
+                ? new[] {typeof(string), typeof(IFormatProvider)}
+                : new[] {typeof(string)};
+
+            return type.GetMethod("Parse",
+                BindingFlags.Public | BindingFlags.Static,
+                null, argumentTypes, null
+            );
+        }
+
         public static Array ToNonGenericArray<T>(this IEnumerable<T> source, Type elementType)
         {
             var sourceAsCollection = source as ICollection ?? source.ToArray();
@@ -38,7 +61,5 @@ namespace CliFx.Internal
 
             return array;
         }
-
-        public static bool OverridesToStringMethod(this object obj) => obj?.ToString() != obj?.GetType().ToString();
     }
 }