Parameter discovery snippet pollutes error reporting

[briantist]

This snippet to discover the parameters:

foreach($h in $MyInvocation.MyCommand.Parameters.GetEnumerator()) {
    try {
        $key = $h.Key
        $val = Get-Variable -Name $key -ValueOnly -ErrorAction Stop
        if (([String]::IsNullOrEmpty($val) -and (!$PSBoundParameters.ContainsKey($key)))) {
            throw "A blank value that wasn't supplied by the user."
        }
        $params[$key] = $val
    } catch {}
}

is using exceptions in a bad way (tsk tsk). This has some nasty side effects.

First, if pollutes the $Error variable, which is a bad thing for anyone who wants to use it.

I think I could work around this by something like $Error.RemoveAt(0) in the snippet's catch block.

---

The other problem I only just noticed in using automatic transcription. All of those errors show up as lines in the transcript, like so:

PS>TerminatingError(Get-Variable): "The running command stopped because the preference variable "ErrorActionPreference" or common parameter is set to Stop: Cannot find a variable with the name 'Verbose'."
>> TerminatingError(Get-Variable): "The running command stopped because the preference variable "ErrorActionPreference" or common parameter is set to Stop: Cannot find a variable with the name 'Debug'."
>> TerminatingError(Get-Variable): "The running command stopped because the preference variable "ErrorActionPreference" or common parameter is set to Stop: Cannot find a variable with the name 'ErrorAction'."
>> TerminatingError(Get-Variable): "The running command stopped because the preference variable "ErrorActionPreference" or common parameter is set to Stop: Cannot find a variable with the name 'WarningAction'."
>> TerminatingError(Get-Variable): "The running command stopped because the preference variable "ErrorActionPreference" or common parameter is set to Stop: Cannot find a variable with the name 'InformationAction'."
>> TerminatingError(Get-Variable): "The running command stopped because the preference variable "ErrorActionPreference" or common parameter is set to Stop: Cannot find a variable with the name 'ErrorVariable'."
>> TerminatingError(Get-Variable): "The running command stopped because the preference variable "ErrorActionPreference" or common parameter is set to Stop: Cannot find a variable with the name 'WarningVariable'."
>> TerminatingError(Get-Variable): "The running command stopped because the preference variable "ErrorActionPreference" or common parameter is set to Stop: Cannot find a variable with the name 'InformationVariable'."
>> TerminatingError(Get-Variable): "The running command stopped because the preference variable "ErrorActionPreference" or common parameter is set to Stop: Cannot find a variable with the name 'OutVariable'."
>> TerminatingError(Get-Variable): "The running command stopped because the preference variable "ErrorActionPreference" or common parameter is set to Stop: Cannot find a variable with the name 'OutBuffer'."
>> TerminatingError(Get-Variable): "The running command stopped because the preference variable "ErrorActionPreference" or common parameter is set to Stop: Cannot find a variable with the name 'PipelineVariable'."
>> TerminatingError(Get-Variable): "The running command stopped because the preference variable "ErrorActionPreference" or common parameter is set to Stop: Cannot find a variable with the name 'WhatIf'."
>> TerminatingError(Get-Variable): "The running command stopped because the preference variable "ErrorActionPreference" or common parameter is set to Stop: Cannot find a variable with the name 'Confirm'."

This really sucks.

I'd like to rewrite the snippet in a way that doesn't (ab)use exceptions, to solve both problems.