Styjun

Is it possible, using PowerShell, to use splatting from hashtable when the hashtable contains more entries that the function accepts ?

My use case is to have config objects I pass from one function to another. However, all functions does not require same parameters.

Ex:

function Process-Something
 param(
 [Parameter()]
 [string]$Owner
 )




function Process-SomethingElse
 param(
 [Parameter()]
 [string]$Owner,
 [Parameter()]
 [int]$x,
 [Parameter()]
 [int]$y

 )



$config = @
 "Owner" = "Bart Simpson"
 "X" = 10
 "Y" = 20


Process-Something @config
Process-SomethingElse @config

It fails with these error:

Process-Something : Cannot find a matching parameter « Y ».

The idea is to avoid specifying individual properties for each functions.

As @Ansgar is stating in the comments, the whole idea of having defined your parameters, is to get validation. When you are splatting parameters to your function, you are forcing them to the function. So if a given property of your hashtable doesn't exist as a parameter, you will get an error - just like it is intended.

What you can do, is going into a PSCustomObject and utilize the pipe. If you set all you parameters to accept value from the pipeline, using property name (ValueFromPipelineByPropertyName = $true), then you can actually get the desired behavior.

First I'm redefining your different functions, to have the ValueFromPipelineByPropertyName = $true parameter attribute configured.

function Process-Something
 param(
 [Parameter(ValueFromPipelineByPropertyName = $true)]
 [string]$Owner
 )

 $PSBoundParameters


function Process-SomethingElse
 param(
 [Parameter(ValueFromPipelineByPropertyName = $true)]
 [string]$Owner,
 [Parameter(ValueFromPipelineByPropertyName = $true)]
 [int]$x,
 [Parameter(ValueFromPipelineByPropertyName = $true)]
 [int]$y

 )

 $PSBoundParameters
 

With that in place, I'm able to create a hashtable like your example, convert it to a PSCustomObject, and now I can pipe that new object to the different methods and have them pick up only the properties that they need.

I included the PSBoundParameters to showcase that they get what they expect.
Testing is done like this:

$config = @
 "Owner" = "Bart Simpson"
 "X" = 10
 "Y" = 20


$psConfig = [PSCustomObject]$config

$psConfig | Process-Something

$psConfig | Process-SomethingElse