Powershell: resolve path that might not exist?

Join-Path (Resolve-Path .) newdir\newfile.txt

When Resolve-Path fails due to the file not existing, the fully resolved path is accessible from the thrown error object.

You can use a function like the following to fix Resolve-Path and make it work like you expect.

function Force-Resolve-Path {
    <#
    .SYNOPSIS
        Calls Resolve-Path but works for files that don't exist.
    .REMARKS
        From http://devhawk.net/blog/2010/1/22/fixing-powershells-busted-resolve-path-cmdlet
    #>
    param (
        [string] $FileName
    )

    $FileName = Resolve-Path $FileName -ErrorAction SilentlyContinue `
                                       -ErrorVariable _frperror
    if (-not($FileName)) {
        $FileName = $_frperror[0].TargetObject
    }

    return $FileName
}

I think you're on the right path. Just use [Environment]::CurrentDirectory to set .NET's notion of the process's current dir e.g.:

[Environment]::CurrentDirectory = $pwd
[IO.Path]::GetFullPath(".\xyz")

You want:

c:\path\exists\> $ExecutionContext.SessionState.Path.GetUnresolvedProviderPathFromPSPath(".\nonexist\foo.txt")

returns:

c:\path\exists\nonexists\foo.txt

This has the advantage of working with PSPaths, not native filesystem paths. A PSPath may not map 1-1 to a filesystem path, for example if you mount a psdrive with a multi-letter drive name.

What's a pspath?

ps c:\> new-psdrive temp filesystem c:\temp
...
ps c:\> cd temp:
ps temp:\> 

temp:\ is a drive-qualified pspath that maps to a win32 (native) path of c:\temp.

-Oisin