Try to create tab completion for the PSDeploy DSL.

PSdeploy.Argumentcompleter.ps1

Function PSDeployCompletion 
{
    param( $commandName, $parameterName, $wordToComplete, $commandAst, $fakeBoundParameter)

    $CommandTree = Get-CompletionPrivateData -Key PSDeployCompletionCommandTree
    if ($null -eq $CommandTree) {
        
        $CommandTree = & {
            New-CommandTree  -Completion FromSource -ToolTip 'Source'  -Argument
            New-CommandTree  -Completion To -ToolTip 'Destination' -Argument
            New-CommandTree  -Completion Tagged -ToolTip 'Tags to use for the deployment' -Argument

            New-CommandTree -Completion WithOptions -ToolTip 'options for the deployment' -SubCommands {
                New-CommandTree -Completion Test -tooltip 'test'
            }
        }

        Set-CompletionPrivateData -Key PSDeployCompletionCommandTree -Value $commandTree
    }

    Get-CommandTreeCompletion $wordToComplete $commandAst $commandTree
}


Register-ArgumentCompleter `
    -Command 'By' `
    -ParameterName 'ScriptBlock' `
    -Description 'Complete arguments to a Deployment' `
    -ScriptBlock $function:PSDeployCompletion