Powershell: Multiple parameters for a TabExpansion++ ArgumentCompleter - powershell

Question

I am working on a function to schedule a user's home drive transfer, I am going to use TabExpansion++ to allow the user to autocomplete the server name, which is populated from a CSV file. There will be parameters for both OldServer and NewServer.
Is it possible with TabExpansion++ to specify more than one parameter for a single autocompleter?
Here is what I have:
function HomeDriveSiteCompletion {
[ArgumentCompleter(
Parameter = 'OldServer',
Command = { 'Schedule-HomeTransfer' },
Description = 'Home drive transfer tool server name autocomplete')]
param($commandName,$parameterName,$wordToComplete,$commandAst,$fakeBoundParameter)
Import-Csv -Path $Global:ServersList | % {New-CompletionResult -ToolTip $_.Site -completiontext $_.Site}
}
Which works fine for OldServer. If I can save code by specifying both parameters in the same place, that would be ideal. I have tried both
Parameter = #('OldServer','NewServer')
and
Parameter = { 'OldServer','NewServer' }
Neither of which worked. Is there another way I could make this work?

Answer 1

Questions like this are why I love this site. I have not used TabExpansion++, but I have done some tab expansion stuff for parameters. I couldn't remember if I'd run into this exact question before so I went looking and discovered something that I haven't encountered in the PowerShell world before, DynamicParam. How have I not seen this before? The levels of awesome of it for situations like this are right off the charts! What it allows you to do is not declare a parameter, but then add that parameter before the actual scriptblock of the function, and do scripty kinds of things for validation of that parameter.
I asked Google for a little help, and it pointed me to this SO question (where Shay Levy gives the accepted answer recommending TabExpansion++), but the next answer goes on about DynamicParam. So I looked that up and found this blog on Microsoft's site that explains it further. Basically for your needs you would do something like:
DynamicParam {
$SrvList = Import-CSV $Global:ServerList | Select -Expand Site
$ParamNames = #('OldServer','NewServer')
#Create Param Dictionary
$ParamDictionary = new-object -Type System.Management.Automation.RuntimeDefinedParameterDictionary
ForEach($Name in $ParamNames){
#Create a container for the new parameter's various attributes, like Manditory, HelpMessage, etc that usually goes in the [Parameter()] part
$ParamAttribCollecton = new-object -Type System.Collections.ObjectModel.Collection[System.Attribute]
#Create each attribute
$ParamAttrib = new-object System.Management.Automation.ParameterAttribute
$ParamAttrib.Mandatory = $true
$ParamAttrib.HelpMessage = "Enter a server name"
#Create ValidationSet to make tab-complete work
$ParamValSet = New-Object -type System.Management.Automation.ValidateSetAttribute($SrvList)
#Add attributes and validationset to the container
$ParamAttribCollecton.Add($ParamAttrib)
$ParamAttribCollecton.Add($ParamValSet)
#Create the actual parameter, then add it to the Param Dictionary
$MyParam = new-object -Type System.Management.Automation.RuntimeDefinedParameter($Name, [String], $ParamAttribCollecton)
$ParamDictionary.Add($Name, $MyParam)
}
#Return the param dictionary so the function can add the parameters to itself
return $ParamDictionary
}
That would add the OldServer and NewServer parameters to your function. Both would tab-complete the servers listed in the Site column of the CSV located at $global:ServerList. Sure, it's not as short and sweet as TabExpansion++'s context, but on the other hand it does not require any additional modules or anything to be loaded on the system since it is all self contained and only using basic PowerShell features.
Now, that adds the parameters, but it doesn't actually assign them to variables, so we'll have to do that in the Begin part of the function. We'll list the parameters in PSBoundParameters.Keys and check if a variable already exists in the current scope, and if not we'll make one in the current scope, so as to mess with anything outside of the function. So, with a basic parameter of -User, the two dynamic parameters, and the addition of the variables for the dynamic parameters, we're looking at something like this for your function:
Function Schedule-HomeTransfer{
[CmdletBinding()]
Param([string]$User)
DynamicParam {
$SrvList = Import-CSV $Global:ServerList | Select -Expand Site
$ParamNames = #('OldServer','NewServer')
#Create Param Dictionary
$ParamDictionary = new-object -Type System.Management.Automation.RuntimeDefinedParameterDictionary
ForEach($Name in $ParamNames){
#Create a container for the new parameter's various attributes, like Manditory, HelpMessage, etc that usually goes in the [Parameter()] part
$ParamAttribCollecton = new-object -Type System.Collections.ObjectModel.Collection[System.Attribute]
#Create each attribute
$ParamAttrib = new-object System.Management.Automation.ParameterAttribute
$ParamAttrib.Mandatory = $true
$ParamAttrib.HelpMessage = "Enter a server name"
#Create ValidationSet to make tab-complete work
$ParamValSet = New-Object -type System.Management.Automation.ValidateSetAttribute($SrvList)
#Add attributes and validationset to the container
$ParamAttribCollecton.Add($ParamAttrib)
$ParamAttribCollecton.Add($ParamValSet)
#Create the actual parameter, then add it to the Param Dictionary
$MyParam = new-object -Type System.Management.Automation.RuntimeDefinedParameter($Name, [String], $ParamAttribCollecton)
$ParamDictionary.Add($Name, $MyParam)
}
#Return the param dictionary so the function can add the parameters to itself
return $ParamDictionary
}
Begin{$PSBoundParameters.Keys | Where{!(Get-Variable -name $_ -Scope 0 -ErrorAction SilentlyContinue)} | ForEach{New-Variable -Name $_ -Value $PSBoundParameters[$_]}}
Process{
"You chose to move $User from $OldServer to $NewServer"
}
}
That right there will allow for tab completion on -OldServer and -NewServer, and when I set $global:ServerList to "C:\Temp\new.csv' and populated that with a 'Site' column having 3 values, those popped right up for me to select (in the ISE it actually pops up a list to choose from, not just tab completion like in the console).