Unable to capture Console.Error messages written in C# using redirect_stderr in Python

[noxee]

Environment

• Pythonnet version: 3.0.3
• Python version: 3.11.4
• Operating System: Windows 10 x64
• .NET Runtime: Microsoft.NETCore.App 7.0.15

Details

Hi all,

I'm currently trying to capture the output of C#'s Console.Error using redirect_stderr(io.StringIO()) in Python so that I can format the text within python.

If I have the following C# class:

using static System.Console;

namespace PythonConsoleRedirectTest;

public static class ConsoleOutput
{
    public static void ConsoleOut()
    {
        Out.WriteLine("This is a message from 'Console.Out.WriteLine'.");
    }
    
    public static void ConsoleError()
    {
        Error.WriteLine("This is a message from 'Console.Error.WriteLine'.");
    }
}

And then try to call it within Python with:

import os
import io
import sys
from contextlib import redirect_stdout, redirect_stderr
from pythonnet import load

load('coreclr')


def init_dlls() -> None:
    import clr
    dll_path = os.path.join(
        '..', 'PythonConsoleRedirectTest', 'bin', 'Release', 'net7.0')
    clr.AddReference(os.path.join(dll_path, 'PythonConsoleRedirectTest'))


def execute_csharp() -> None:
    from PythonConsoleRedirectTest import ConsoleOutput

    console_error = None

    with redirect_stderr(io.StringIO()) as ferr:
        sys.stderr.write("This is a message from 'sys.stderr'.")
        ConsoleOutput.ConsoleError()

        console_error = ferr.getvalue()

    print(f"\n{console_error}")


if __name__ == "__main__":
    init_dlls()
    execute_csharp()

The current out put of this is:

This is a message from 'Console.Error.WriteLine'.

This is a message from 'sys.stderr'.

But I would expect it to be the following if the redirection was working as expected:

This is a message from 'sys.stderr'.
This is a message from 'Console.Error.WriteLine'.

I may be missing something with how the IO streams work between C# and Python so and advice would be appreciated.