Support ConPTY as an replacement to STDIO redirection in System.Diagnostics.Process

[wfjsw]

In 2018 Windows released Windows Pseudo Console (ConPTY) and I am looking for ways to integrate it into some of my subprocesses.

I quickly find out that:

1. I cannot turn a PROCESS_ALL_ACCESS handle into a Process object, if I were to occupy the handle by CreateProcess on my own. The only way I can do it right now is to firstly convert the handle to a PID, then use the GetProcessById to create the Process object. In this process it involves OpenProcess with PROCESS_ALL_ACCESS which in turn requires SeDebugPrivilege. This is bad and error-prone.
2. To use ConPTY I have to use STARTUPINFOEX and put something inside, instead of STARTUPINFO, but nevertheless even the STARTUPINFO is beyond my control.

To implement it I end up cloning the entire Process.Start() flow to make the modification, though I don't really have much idea on how to make it better.

[alexrp]

There is a general trend of people needing more control over process creation. Related issues:

• [API Proposal]: ProcessStartInfo.CreateSuspended, Process.Resume #94127
• [API Proposal]: Process constructor from SafeProcessHandle #71595
• [API Proposal]: ProcessStartInfo.CreationFlags (for Windows only) #71515
• Make Process.Start have a option to change handle inheritance #13943