Argument completer for Spectre.Cli

Register.ps1

Register-ArgumentCompleter -Native -CommandName myapp -ScriptBlock {
    param($commandName, $wordToComplete, $cursorPosition)
        $split = $wordToComplete.ToString().Split()
        $command = [system.String]::Join("_", $split[1..$split.Length])
        $position = ($cursorPosition-$split[0].Length - 1);
        myapp complete --position $position "$command" | ForEach-Object {
           [System.Management.Automation.CompletionResult]::new($_, $_, 'ParameterValue', $_)
        }
}