Improve option converter and add support for dynamic types constructable or parseable from string

CliFx.Tests/CommandOptionConverterTests.cs

@@ -44,6 +44,10 @@ namespace CliFx.Tests
             yield return new TestCaseData("01:00:00", typeof(TimeSpan?), new TimeSpan(01, 00, 00));
 
             yield return new TestCaseData(null, typeof(TimeSpan?), null);
+
+            yield return new TestCaseData("value", typeof(TestStringConstructable), new TestStringConstructable("value"));
+
+            yield return new TestCaseData("value", typeof(TestStringParseable), TestStringParseable.Parse("value"));
         }
 
         [Test]

CliFx.Tests/TestObjects/TestStringConstructable.cs

@@ -0,0 +1,12 @@
+namespace CliFx.Tests.TestObjects
+{
+    public struct TestStringConstructable
+    {
+        public string Value { get; }
+
+        public TestStringConstructable(string value)
+        {
+            Value = value;
+        }
+    }
+}

CliFx.Tests/TestObjects/TestStringParseable.cs

@@ -0,0 +1,17 @@
+namespace CliFx.Tests.TestObjects
+{
+    public partial struct TestStringParseable
+    {
+        public string Value { get; }
+
+        private TestStringParseable(string value)
+        {
+            Value = value;
+        }
+    }
+
+    public partial struct TestStringParseable
+    {
+        public static TestStringParseable Parse(string value) => new TestStringParseable(value);
+    }
+}

CliFx/Exceptions/CommandOptionConvertException.cs

@@ -0,0 +1,21 @@
+using System;
+
+namespace CliFx.Exceptions
+{
+    public class CommandOptionConvertException : Exception
+    {
+        public CommandOptionConvertException()
+        {
+        }
+
+        public CommandOptionConvertException(string message)
+            : base(message)
+        {
+        }
+
+        public CommandOptionConvertException(string message, Exception innerException)
+            : base(message, innerException)
+        {
+        }
+    }
+}

CliFx/Services/CommandOptionConverter.cs

@@ -1,5 +1,8 @@
 using System;
 using System.Globalization;
+using System.Linq;
+using System.Reflection;
+using CliFx.Exceptions;
 using CliFx.Internal;
 
 namespace CliFx.Services
@@ -22,35 +25,194 @@ namespace CliFx.Services
         {
             // String or object
             if (targetType == typeof(string) || targetType == typeof(object))
+            {
                 return value;
-            
+            }
+
             // Bool
             if (targetType == typeof(bool))
-                return value.IsNullOrWhiteSpace() || bool.Parse(value);
+            {
+                if (value.IsNullOrWhiteSpace())
+                    return true;
+
+                if (bool.TryParse(value, out var result))
+                    return result;
+
+                throw new CommandOptionConvertException($"Can't convert value [{value}] to boolean.");
+            }
+
+            // Char
+            if (targetType == typeof(char))
+            {
+                if (value.Length == 1)
+                    return value[0];
+
+                throw new CommandOptionConvertException(
+                    $"Can't convert value [{value}] to char. The value is either empty or longer than one character.");
+            }
+
+            // Sbyte
+            if (targetType == typeof(sbyte))
+            {
+                if (sbyte.TryParse(value, NumberStyles.Integer, _formatProvider, out var result))
+                    return result;
+
+                throw new CommandOptionConvertException($"Can't convert value [{value}] to sbyte.");
+            }
+
+            // Byte
+            if (targetType == typeof(byte))
+            {
+                if (byte.TryParse(value, NumberStyles.Integer, _formatProvider, out var result))
+                    return result;
+
+                throw new CommandOptionConvertException($"Can't convert value [{value}] to byte.");
+            }
+
+            // Short
+            if (targetType == typeof(short))
+            {
+                if (short.TryParse(value, NumberStyles.Integer, _formatProvider, out var result))
+                    return result;
+
+                throw new CommandOptionConvertException($"Can't convert value [{value}] to short.");
+            }
+
+            // Ushort
+            if (targetType == typeof(ushort))
+            {
+                if (ushort.TryParse(value, NumberStyles.Integer, _formatProvider, out var result))
+                    return result;
+
+                throw new CommandOptionConvertException($"Can't convert value [{value}] to ushort.");
+            }
+
+            // Int
+            if (targetType == typeof(int))
+            {
+                if (int.TryParse(value, NumberStyles.Integer, _formatProvider, out var result))
+                    return result;
+
+                throw new CommandOptionConvertException($"Can't convert value [{value}] to int.");
+            }
+
+            // Uint
+            if (targetType == typeof(uint))
+            {
+                if (uint.TryParse(value, NumberStyles.Integer, _formatProvider, out var result))
+                    return result;
+
+                throw new CommandOptionConvertException($"Can't convert value [{value}] to uint.");
+            }
+
+            // Long
+            if (targetType == typeof(long))
+            {
+                if (long.TryParse(value, NumberStyles.Integer, _formatProvider, out var result))
+                    return result;
+
+                throw new CommandOptionConvertException($"Can't convert value [{value}] to long.");
+            }
+
+            // Ulong
+            if (targetType == typeof(ulong))
+            {
+                if (ulong.TryParse(value, NumberStyles.Integer, _formatProvider, out var result))
+                    return result;
+
+                throw new CommandOptionConvertException($"Can't convert value [{value}] to ulong.");
+            }
+
+            // Float
+            if (targetType == typeof(float))
+            {
+                if (float.TryParse(value, NumberStyles.Float | NumberStyles.AllowThousands, _formatProvider, out var result))
+                    return result;
+
+                throw new CommandOptionConvertException($"Can't convert value [{value}] to float.");
+            }
+
+            // Double
+            if (targetType == typeof(double))
+            {
+                if (double.TryParse(value, NumberStyles.Float | NumberStyles.AllowThousands, _formatProvider, out var result))
+                    return result;
+
+                throw new CommandOptionConvertException($"Can't convert value [{value}] to double.");
+            }
+
+            // Decimal
+            if (targetType == typeof(decimal))
+            {
+                if (decimal.TryParse(value, NumberStyles.Number, _formatProvider, out var result))
+                    return result;
+
+                throw new CommandOptionConvertException($"Can't convert value [{value}] to decimal.");
+            }
 
             // DateTime
             if (targetType == typeof(DateTime))
-                return DateTime.Parse(value, _formatProvider);
+            {
+                if (DateTime.TryParse(value, _formatProvider, DateTimeStyles.None, out var result))
+                    return result;
+
+                throw new CommandOptionConvertException($"Can't convert value [{value}] to DateTime.");
+            }
 
             // DateTimeOffset
             if (targetType == typeof(DateTimeOffset))
-                return DateTimeOffset.Parse(value, _formatProvider);
+            {
+                if (DateTimeOffset.TryParse(value, _formatProvider, DateTimeStyles.None, out var result))
+                    return result;
+
+                throw new CommandOptionConvertException($"Can't convert value [{value}] to DateTimeOffset.");
+            }
 
             // TimeSpan
             if (targetType == typeof(TimeSpan))
-                return TimeSpan.Parse(value, _formatProvider);
+            {
+                if (TimeSpan.TryParse(value, _formatProvider, out var result))
+                    return result;
+
+                throw new CommandOptionConvertException($"Can't convert value [{value}] to TimeSpan.");
+            }
 
             // Enum
             if (targetType.IsEnum)
-                return Enum.Parse(targetType, value, true);
+            {
+                if (Enum.GetNames(targetType).Contains(value, StringComparer.OrdinalIgnoreCase))
+                    return Enum.Parse(targetType, value, true);
+
+                throw new CommandOptionConvertException(
+                    $"Can't convert value [{value}] to [{targetType}]. The value is not defined on the enum.");
+            }
 
             // Nullable
             var nullableUnderlyingType = Nullable.GetUnderlyingType(targetType);
             if (nullableUnderlyingType != null)
-                return !value.IsNullOrWhiteSpace() ? ConvertOption(value, nullableUnderlyingType) : null;
+            {
+                if (value.IsNullOrWhiteSpace())
+                    return null;
 
-            // All other types
-            return Convert.ChangeType(value, targetType, _formatProvider);
+                return ConvertOption(value, nullableUnderlyingType);
+            }
+
+            // Has a constructor that accepts a single string
+            var stringConstructor = targetType.GetConstructor(new[] {typeof(string)});
+            if (stringConstructor != null)
+            {
+                return stringConstructor.Invoke(new object[] {value});
+            }
+
+            // Has a static parse method that accepts a single string
+            var parseMethod = targetType.GetMethod("Parse", BindingFlags.Public | BindingFlags.Static, null, new[] {typeof(string)}, null);
+            if (parseMethod != null)
+            {
+                return parseMethod.Invoke(null, new object[] {value});
+            }
+
+            // Unknown type
+            throw new CommandOptionConvertException($"Can't convert value [{value}] to unrecognized type [{targetType}].");
         }
     }
 }