RunInTerminal Request strategy

[GustavEikaas]

Hi there,

I randomly stumbled upon this repository while checking out some netcoredbg stuff. It looks really cool! I'm not sure if this will be helpful, but I am currently building C# "IDE tooling" for Neovim.

I recently had some users asking about runInTerminal support because they wanted to use methods like System.Console.ReadLine(), which I ended up building on top of netcoredbg. I figured if you are considering implementing runInTerminal for this project, you might run into the exact same issue I did: How the heck do you pause the external terminal process long enough to properly attach the debugger?

I ended up using a .NET Startup Hook to solve this and just wanted to share the idea. Here is the full PR if you are interested in seeing how it works.

I am definitely better at C# than C++, but if I can help out in any way, please don't hesitate to ask. Currently, I am bundling netcoredbg with my server, but perhaps I can bundle this project in the future!

internal static class StartupHook
{
  public static void Initialize()
  {
    var pipeName = ReadAndDiscardHookPipe();
    RemoveStartupHookEnvironment();

    if (string.IsNullOrEmpty(pipeName)) return;

    using var client = new NamedPipeClientStream(".", pipeName, PipeDirection.InOut);
    client.Connect(5000);

    var pid = Environment.ProcessId;
    var pidBytes = BitConverter.GetBytes(pid);
    client.Write(pidBytes, 0, pidBytes.Length);
    client.Flush();
    client.ReadByte();
  }

  private static string? ReadAndDiscardHookPipe()
  {
    const string envVarName = "EASY_DOTNET_HOOK_PIPE";
    var pipeName = Environment.GetEnvironmentVariable(envVarName);
    Environment.SetEnvironmentVariable(envVarName, null);
    return pipeName;
  }

  private static void RemoveStartupHookEnvironment()
  {
    var currentHooks = Environment.GetEnvironmentVariable("DOTNET_STARTUP_HOOKS");
    if (string.IsNullOrEmpty(currentHooks)) return;

    var hooksList = currentHooks.Split(Path.PathSeparator);

    var remainingHooks = string.Join(Path.PathSeparator.ToString(), hooksList.Skip(1));

    Environment.SetEnvironmentVariable("DOTNET_STARTUP_HOOKS", string.IsNullOrEmpty(remainingHooks) ? null : remainingHooks);
  }
}

[viewizard]

Hi,

hmm interesting... you are using Startup Hook, netcoredbg use it for Hot Reload stuff, but I was never happy about load into debggee process some code that don't belong to debuggee process and execute it.

I am planning implement "RunInTerminal" in future (not sure about details now, need more time for investigation), but now should fix some old issues and finally refactor code for future development (not sure when Samsung will be interested in netcoredbg and I will back to netcoredbg development again and move some changes from dncdbg into it, at least my PL don't mind about this, but now I only fixing bugs in netcoredbg that I found during dncdbg development :))).

[GustavEikaas]

Hmm yeah I agree that injecting code is kinda hacky. I tried to make it as non-intrusive as possible. My first implementation was done using DOTNET_DefaultDiagnosticPortSuspend=1 and Microsoft.Diagnostics.NETCore.Client. Which I guess is equally hacky but doesnt involve loading a custom dll. I got it to work but I struggled with breaking on the first line of the program. Probably a race condition I guess

[viewizard]

I see, at this moment we don't have debugger API to catch child managed process that started by terminal or other program, only start debuggee process itself or attach to it, so, any approach from this side will looks like hacky.

My personal view about "external terminal" for now - provide "server" side in debugger, so, if user need interaction with debuggee process this could be done via local tcp port, that easy to use with something like Netcat/Ncat program or via simple "client" that could be launched in terminal and just read/write data.

[viewizard]

I finally have some good news regarding this issue. I've spent some time analyzing and implementing a few approaches, and here is what dncdbg currently supports (https://github.com/viewizard/dncdbg/blob/master/docs/inputting_text.md):

• Internal console: Uses an Evaluate Request when the process is not at a Stop Event.
• Remote console: As mentioned above, the debugger starts a TCP socket that you can connect to even before the application launches.
• External terminal: Utilizes the Windows API (CreateProcessW + CREATE_NEW_CONSOLE creation flag) and currently works only on Windows.

Since diagnostics (dbgshim code) is now part of our codebase (third_party), I will try to implement the external terminal for Linux and macOS as well. However, it's still unclear how feasible this is and whether it will succeed.

[GustavEikaas]

Thats awesome! Let me know if you need any help with testing