Refactor ArgumentValueConverter into a class

CliFx.Analyzers.Tests/CommandSchemaAnalyzerTests.cs

@@ -153,9 +153,9 @@ public class MyCommand : ICommand
 
                     // language=cs
                     @"
-public class MyConverter : IArgumentValueConverter
+public class MyConverter : ArgumentValueConverter<string>
 {
-    public object ConvertFrom(string value) => value;
+    public string ConvertFrom(string value) => value;
 }
 
 [Command]
@@ -305,9 +305,9 @@ public class MyCommand : ICommand
 
                     // language=cs
                     @"
-public class MyConverter : IArgumentValueConverter
+public class MyConverter : ArgumentValueConverter<string>
 {
-    public object ConvertFrom(string value) => value;
+    public string ConvertFrom(string value) => value;
 }
 
 [Command]

CliFx.Tests/Commands/SupportedArgumentTypesCommand.cs

@@ -165,9 +165,9 @@ namespace CliFx.Tests.Commands
             public CustomConvertible(int value) => Value = value;
         }
 
-        public class CustomConvertibleConverter : IArgumentValueConverter
+        public class CustomConvertibleConverter : ArgumentValueConverter<CustomConvertible>
         {
-            public object ConvertFrom(string value) =>
+            public override CustomConvertible ConvertFrom(string value) =>
                 new CustomConvertible(int.Parse(value, CultureInfo.InvariantCulture));
         }
     }

CliFx/ArgumentValueConverter.cs

@@ -0,0 +1,30 @@
+namespace CliFx
+{
+    /// <summary>
+    /// Implements custom conversion logic that maps an argument value to a domain type.
+    /// </summary>
+    /// <remarks>
+    /// This type is public for legacy reasons.
+    /// Please derive from <see cref="ArgumentValueConverter{T}"/> instead.
+    /// </remarks>
+    public interface IArgumentValueConverter
+    {
+        /// <summary>
+        /// Converts an input value to object of required type.
+        /// </summary>
+        public object ConvertFrom(string value);
+    }
+
+    /// <summary>
+    /// A base type for custom argument converters.
+    /// </summary>
+    public abstract class ArgumentValueConverter<T> : IArgumentValueConverter
+    {
+        /// <summary>
+        /// Converts an input value to object of required type.
+        /// </summary>
+        public abstract T ConvertFrom(string value);
+
+        object IArgumentValueConverter.ConvertFrom(string value) => ConvertFrom(value)!;
+    }
+}

CliFx/Attributes/CommandArgumentAttribute.cs

@@ -15,7 +15,7 @@ namespace CliFx.Attributes
 
         /// <summary>
         /// Type of converter to use when mapping the argument value.
-        /// Converter must implement <see cref="IArgumentValueConverter"/>.
+        /// Converter must derive from <see cref="ArgumentValueConverter{T}"/>.
         /// </summary>
         public Type? Converter { get; set; }
 

CliFx/Exceptions/CliFxException.cs

@@ -181,7 +181,7 @@ If it's not feasible to fit into these constraints, consider using options inste
 Command '{command.Type.FullName}' is invalid because it contains {invalidParameters.Count} parameter(s) with invalid converters:
 {invalidParameters.JoinToString(Environment.NewLine)}
 
-Specified converter must implement {typeof(IArgumentValueConverter).FullName}.";
+Specified converter must implement {typeof(ArgumentValueConverter<>).FullName}.";
 
             return new CliFxException(message.Trim());
         }
@@ -279,7 +279,7 @@ Environment variable names are not case-sensitive.";
 Command '{command.Type.FullName}' is invalid because it contains {invalidOptions.Count} option(s) with invalid converters:
 {invalidOptions.JoinToString(Environment.NewLine)}
 
-Specified converter must implement {typeof(IArgumentValueConverter).FullName}.";
+Specified converter must implement {typeof(ArgumentValueConverter<>).FullName}.";
 
             return new CliFxException(message.Trim());
         }
@@ -292,7 +292,7 @@ Specified converter must implement {typeof(IArgumentValueConverter).FullName}.";
 Command '{command.Type.FullName}' is invalid because it contains {invalidOptions.Count} option(s) with invalid validators:
 {invalidOptions.JoinToString(Environment.NewLine)}
 
-Specified validators must inherit from {typeof(IArgumentValueValidator).FullName}.";
+Specified validators must inherit from {typeof(ArgumentValueValidator<>).FullName}.";
 
             return new CliFxException(message.Trim());
         }

CliFx/IArgumentValueConverter.cs

@@ -1,13 +0,0 @@
-namespace CliFx
-{
-    /// <summary>
-    /// Implements custom conversion logic that maps an argument value to a domain type.
-    /// </summary>
-    public interface IArgumentValueConverter
-    {
-        /// <summary>
-        /// Converts an input value to object of required type.
-        /// </summary>
-        public object ConvertFrom(string value);
-    }
-}