simplistic direnv for powershell in ~100 loc

direnv.ps1

function Initialize-Direnv {
    if($env:DIRENV_AUTH_FILE){
        if(-not (test-path $env:DIRENV_AUTH_FILE)) { return "Auth file unreadable: $env:DIRENV_AUTH_FILE" }
        # stole this stuff from https://github.com/lzybkr/PSReadLine/blob/master/PSReadLine/SamplePSReadlineProfile.ps1
        $global:DIRENV = [System.Collections.ArrayList]@(
            $last = ''
            $lines = ''
            foreach ($line in [System.IO.File]::ReadLines($env:DIRENV_AUTH_FILE))
            {
                if ($lines)
                {
                    $line = "$lines`n$line"
                    $lines = ''
                }

                if (($line -cne $last) -and (!$pattern -or ($line -match $pattern)))
                {
                    $last = $line
                    $line
                }
            }
        )
    }
}

function Load-Direnv {
    if ($global:DIRENV){
        # Direnv enabled
        $this_envrc = $pwd.path + "\.envrc"
        if ((test-path $this_envrc) -and
            ((gc -raw $this_envrc).Length -ne 0)){
            # .envrc exists and is not empty
            if ($global:DIRENV -ccontains $pwd.path){
                # this .envrc has been whitelisted
                try {
                    # it's not empty, use it in a very unsafe way
                    iex (gc -raw $this_envrc)
                }
                catch {
                    Write-Warning "Invalid $this_envrc"
                }
            } else {
                # .envrc not whitelisted
                Write-Warning ".envrc found in current directory but not authorized. Ignoring"
                Write-Warning "use Add-Direnv $pwd.path to whitelist"
            }
        }
    } else {
        # no DIRENV var, thus uninitialized
        Initialize-Direnv
    }
}

function Add-Direnv($dir=$pwd.path) {
    Add-Content $env:DIRENV_AUTH_FILE $dir
    Initialize-direnv
}

function Remove-Direnv($dir=$pwd.path) {
    $global:DIRENV.Remove($dir)
    Set-Content $env:DIRENV_AUTH_FILE $global:DIRENV
    Initialize-Direnv
}

# Bash style: cd -
function cd {
    if ($args[0] -eq '-') {
        $pwd=$OLDPWD;
    } else {
        $pwd=$args[0];
    }

    $tmp=Get-Location;

    if ($pwd) {
        Set-Location $pwd;
    }

    Set-Variable -Name OLDPWD -Value $tmp -Scope global;

    if($global:DIRENV) {
        Load-Direnv
    }
}

if((get-command cd).CommandType -eq 'Alias'){
    remove-item alias:cd
}

$env:DIRENV_AUTH_FILE=(join-path $env:HOME _direnv.txt)
echo $null >> $env:DIRENV_AUTH_FILE

Initialize-Direnv