Add a `$PSAssignedParameters` automatic variable

[DevOpsJeremy]

Summary of the new feature / enhancement

There is currently a $PSBoundParameters automatic variable which includes any parameters/values passed to the command. But this variable doesn't include parameters which have default values. There are times when users want any assigned parameter key/values passed to another function--including any default values if the user didn't pass a value to that parameter. Basically any parameter variables which hold a value, whether that value was provided by the user or a default value.

I'd like to propose a $PSAssignedParameters automatic variable which includes any parameters with assigned values, whether they be bound parameters passed by the user, or parameters not passed by the user, but with default values.

Current functionality:

PS > function Get-BoundParameters {
    param (
        $Param1 = "This is param1",
        $Param2,
        $Param3
    )
    [PSCustomObject] $PSBoundParameters
}
PS > Get-BoundParameters -Param2 "This is param2"

Param2
------
This is param2

Currently, only $Param2 is returned, whereas the desired result (for the proposed $PSAssignedParameters variable) is that both $Param1 and $Param2 are returned, since both variables have assigned values--$Param1 from the default value, and $Param2 from the value passed by the user.

Proposed technical implementation details (optional)

Desired functionality:

PS > function Get-AssignedParameters {
    param (
        $Param1 = "This is param1",
        $Param2,
        $Param3
    )
    [PSCustomObject] $PSAssignedParameters
}
PS > Get-AssignedParameters -Param2 "This is param2"

Param1         Param2
------         ------
This is param1 This is param2

The $PSAssignedParameters automatic variable would hold any parameters which have assigned values, whether that value was assigned by the user during runtime, or it's a default value. In this example, it returns $Param1 with the default value and $Param2 with the user-provided value, but doesn't return $Param3 because it doesn't have a value at all.

Possible challenges / considerations

• How to approach switch/boolean parameters. If the switch/boolean is unused, should it be included in the $PSAssignedParameters hash with a $false value, or should it not be included at all?
• How to handle dynamic parameters

[StartAutomating]

@DevOpsJeremy thanks for submitting this!

@SteveL-MSFT this is something @Jaykul and I have discussed many times as being desired and valuable.

It greatly streamlines the process of splatting down to a command.

This stated the way this would work best is as a list of names of parameters that were assigned. This would make it easier to filter an existing dictionary into a new splat.

[mklement0]

Good suggestion, but your issue is a duplicate of this issue (from 2017, alas):

• Suggestion: Also include parameter default values in $PSBoundParameters or provide a similar variable that does #3285

[DevOpsJeremy]

@mklement0 ah you're right. That's a shame it's been outstanding this long, it would be a really valuable feature.

[237dmitry]

And what could be practical use? If the parameter has a default value then this parameter is already assigned and can be used without checking whether it is present or not. What is the logic in this?

[DevOpsJeremy]

@237dmitry if a number of parameter key/values are being passed to another cmdlet via splatting, the params with default values need to be manually added to the follow-on cmdlet since they aren't included in $PSBoundParameters. With $PSAssignedParameters (or a similar functionality), any parameters with values would be included without additional code needed for handling default values.

[DevOpsJeremy]

Closing due to duplicate of #3285