[Ironpython-users] Binding problem with default parameters in public classes

[Markus Schaber]

Hi,

Our tests recently caught a strange regression in our application. One can make 
existing scripts fail by changing an internal class to public.

The attached program reproduces the issue. The problem is that the method has 
optional parameters, but those are only declared at the interface.

Now, when the class changes from “internal” to “public”, IronPython binds 
directly to the public methods without considering the interfaces any more, and 
thus does not recognize the optional parameters.

Now, the question is whether this could be considered a bug in IronPython, or 
whether it should be considered a bug to implement an interface method without 
replicating the default parameter values…

Best regards

Markus Schaber

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using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace IronPythonInterfaceBindingTest
{
    using IronPython.Hosting;

    public interface IFooBar
    {
        void DoSomething(int param, string text = null);
    }

    internal class InternalImpl : IFooBar
    {
        public void DoSomething(int param, string text)
        {
            Console.WriteLine("Internal: Param: {0} Text: {1}", param, 
text??"<null>");
        }
    }

    public class PublicImpl : IFooBar
    {
        public void DoSomething(int param, string text)
        {
            Console.WriteLine("Public: Param: {0} Text: {1}", param, text ?? 
"<null>");
        }
    }

    public static class Program
    {
        const string TESTSCRIPT = @"
internalimpl.DoSomething(5, 'mit text')
internalimpl.DoSomething(5)
publicimpl.DoSomething(5, 'mit text')
publicimpl.DoSomething(5)
";

        static void Main(string[] args)
        {
            try
            {
                var engine = Python.CreateEngine();
                var scope = engine.CreateScope();

                scope.SetVariable("internalimpl", new InternalImpl());
                scope.SetVariable("publicimpl", new PublicImpl());

                engine.Execute(TESTSCRIPT, scope);
            }
            catch (Exception ex)
            {
                Console.WriteLine(ex);
            }
            Console.ReadKey();
        }
    }
}

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