Gets the parameters for a command from the default parameter set

Get-CommandParameter.ps1

function Get-CommandParameter {
    param (
        [Parameter(Mandatory = $true)]
        [String]$Command,

        [Switch]$GetDefaultValues
    )
    
    $defaultParams = @(
        [System.Management.Automation.Internal.CommonParameters].GetProperties().Name
        [System.Management.Automation.Internal.ShouldProcessParameters].GetProperties().Name
        [System.Management.Automation.Internal.TransactionParameters].GetProperties().Name
    )    
    
    # Get command information and go through each parameter
    try {
        $commandInfo = Get-Command $Command -ErrorAction Stop

        if ($commandInfo) {
            if ($commandInfo.ParameterSets.Count -eq 1) {
                $parameterSetName = $commandInfo.ParameterSets[0].Name
            }
            else {
                $parameterSetName = $commandInfo.ParameterSets.Where{ $_.IsDefault }.Name
            }
            $parameters = $commandInfo.ParameterSets.Where{ $_.Name -eq $parameterSetName }.Parameters |
                Where-Object { 
                $_.Name -notin $defaultParams -and 
                -not $_.Attributes.Where{
                    $_ -is [Parameter] -and
                    -not $_.ParameterSetName -eq $parameterSetName }.DontShow
            } |
                Select-Object *, DefaultValue, @{n = 'ValidValues'; e = {
                    if ($validateSet = $_.Attributes | Where-Object { $_ -is [System.Management.Automation.ValidateSetAttribute] }) {
                        $validateSet.ValidValues
                    }
                    elseif ($_.ParameterType.BaseType -eq [Enum]) {
                        [Enum]::GetNames($_.ParameterType)
                    }
                }
            }
            if ($GetDefaultValues) {
                if ($commandInfo.CommandType -eq 'Cmdlet') {
                    $typeInstance = New-Object $commandInfo.ImplementingType

                    foreach ($parameter in $parameters) {
                        if ($null -ne $typeInstance.($parameter.Name)) {
                            $parameter.DefaultValue = $typeInstance.($parameter.Name)
                        }
                    }
                }
                elseif ($commandInfo.CommandType -in 'Function', 'ExternalScript') {
                    $defaultValues = @{}
                    foreach ($parameter in $commandInfo.ScriptBlock.Ast.Body.ParamBlock.Parameters) {
                        if ($parameter.DefaultValue) {
                            try {
                                $defaultValues.($parameter.Name.VariablePath.UserPath) = $parameter.DefaultValue.SafeGetValue()
                            }
                            catch {
                                # Ignore errors raised by this
                            }
                        }
                    }
                    foreach ($parameter in $parameters) {
                        if ($defaultValues.ContainsKey($parameter.Name)) {
                            $parameter.DefaultValue = $defaultValues.($parameter.Name)
                        }
                    }
                }
            }
            $parameters
        }
    }
    catch {
        throw
    }
}

A PS2 compatible version of this https://gist.github.com/indented-automation/56405ea6940f747c7b309e8b522bdeb4