Get a powershell script's location, optionally through symlink

It's a little clunky, but use the common $PSCommandPath to get the script pathname, then try to look up what it links to. If there's no result then $PSCommandPath is the answer. Otherwise check if it's an absolute link target path; if it is then that is the answer. Otherwise join the path of the symlink with its target. Finally Resolve-Path is used to "remove" the relative part of the merged pathname.

Function Get-RealScriptPath() {
  # Get script path and name
  $ScriptPath = $PSCommandPath

  # Attempt to extract link target from script pathname
  $link_target = Get-Item $ScriptPath | Select-Object -ExpandProperty Target

  # If it's not a link ..
  If(-Not($link_target)) {
    # .. then the script path is the answer.
    return $ScriptPath
  }

  # If the link target is absolute ..
  $is_absolute = [System.IO.Path]::IsPathRooted($link_target)
  if($is_absolute) {
    # .. then it is the answer.
    return $link_target
  }

  # At this point:
  # - we know that script was launched from a link
  # - the link target is probably relative (depending on how accurate
  #   IsPathRooted() is).
  # Try to make an absolute path by merging the script directory and the link
  # target and then normalize it through Resolve-Path.
  $joined = Join-Path $PSScriptRoot $link_target
  $resolved = Resolve-Path -Path $joined
  return $resolved
}

Function Get-ScriptDirectory() {
  $ScriptPath = Get-RealScriptPath
  $ScriptDir = Split-Path -Parent $ScriptPath
  return $ScriptDir
}

$ScriptDir = Get-ScriptDirectory