Color detection error in WSL in Windows Terminal

[meowgorithm]

This could be user error, but I'm noticing that, while termenv will correctly detect TrueColor in Windows Terminal, it incorrectly detects ANSI256, in WSL.

Given this code...

package main

import (
        "fmt"

        "github.com/muesli/termenv"
)

func main() {
        p := func() string {
                switch termenv.ColorProfile() {
                case termenv.TrueColor:
                        return "TrueColor"
                case termenv.ANSI256:
                        return "ANSI256"
                case termenv.ANSI:
                        return "ANSI"
                case termenv.Ascii:
                        return "Ascii"
                default:
                        return "(Undetected)"
                }
        }()

        fmt.Printf("Termenv detected profile: %s\n", p)
}

...I get the following output. The first line shows example.exe running in PowerShell and then in WSL.

[muesli]

I'll see if we can reliably detect WSL inside Windows Terminal and add a special case for its TrueColor support.

[Delta456]

To know if WSL is being used inside Windows Terminal. One can do:

// Detect WSL as it has True Color support
	wsl, err := ioutil.ReadFile("/proc/sys/kernel/osrelease")
	// Additional check needed for Mac Os as it doesn't have "/proc/" folder
	if err != nil && !errors.Is(err, os.ErrNotExist) {
		log.Fatal(err)
	}
	// Lowercasing every content inside "/proc/sys/kernal/osrelease"
	// because it gives "Microsoft" for WSL and "microsoft" for WSL 2
	// so no need of checking twice
	if string(wsl) != "" {
		wslLower := strings.ToLower(string(wsl))
               // Also check if the terminal used is Windows Terminal
		if strings.Contains(wslLower, "Microsoft") && os.GetEnv("WT_SESSION") != 0 {
			return terminfo.ColorLevelMillions
		}
	}

@muesli I can work on this issue.