Hangs on Windows when launched as a subprocess with no console window

[adamralph]

Description

On Windows, when openapi-changes is launched as a subprocess with no console window, the process hangs indefinitely. This affects any command, including a bare openapi-changes invocation with no arguments.

Launching subprocesses with no console window is common when running from GUI applications, background services, CI agents, or tools that orchestrate multiple CLI processes without flashing console windows.

This is Windows-specific. SysProcAttr.CreationFlags only exists in Windows-specific source files, so the repro code won't compile on other platforms. In .NET, CreateNoWindow compiles on all platforms but has no effect on macOS or Linux.

Reproduction

package main

import (
	"os"
	"os/exec"
	"syscall"
)

func main() {
	cmd := exec.Command("openapi-changes")
	cmd.SysProcAttr = &syscall.SysProcAttr{
		CreationFlags: 0x08000000, // CREATE_NO_WINDOW
	}
	cmd.Stdout = os.Stdout
	err := cmd.Run() // hangs indefinitely
	if err != nil {
		panic(err)
	}
}

The equivalent in .NET (where this was originally discovered). In .NET, both CreateNoWindow and RedirectStandardInput must be true to trigger the hang (when RedirectStandardInput is false, the child inherits the parent's stdin handle rather than getting a pipe):

using System.Diagnostics;

using var process = new Process();
process.StartInfo.FileName = "openapi-changes";
process.StartInfo.UseShellExecute = false;
process.StartInfo.RedirectStandardInput = true;
process.StartInfo.CreateNoWindow = true;
process.Start();
process.WaitForExit(); // hangs indefinitely

Expected Behaviour

The process runs to completion and exits.

Actual Behaviour

The process hangs indefinitely and never exits.

Workaround

Set PB33F_DARK_BACKGROUND=1 (or 0 for light).

Environment

• openapi-changes v0.2.6
• Windows (the CREATE_NO_WINDOW flag is Windows-specific)

Context

Found while investigating adamralph/simple-exec#843

[adamralph]

The hang appears to be related to terminal background color detection during startup. It looks like lipgloss.HasDarkBackground sends an ANSI query to the terminal and waits for a response and when there's no console window, that response never arrives.

The workaround works because DetectDarkBackground in doctor checks for the PB33F_DARK_BACKGROUND env var before calling lipgloss.HasDarkBackground. When the env var is set, the terminal query is skipped entirely.

[michael-wolfenden]

To provide some additional context, the issue first started appearing in v0.1.1.

[daveshanley]

investigating.