Specified cast is not valid when $VerbosePreference is a string

[dreaburn]

When the $VerbosePreference variable has been explicitly set to a string, the BeginProcessing function throws an InvalidCastException.

This can be fixed by either getting PowerShell to cast like this:
[System.Management.Automation.LanguagePrimitives]::ConvertTo("Continue", [System.Management.Automation.ActionPreference])
or doing an [Enum]::Parse.

Repro:

function foo {
    [CmdletBinding()] param()

    $VerbosePreference = "Continue"
    $VerbosePreference.GetType().FullName
    1 | Split-Pipeline -Count 1 -Script {}
}
foo
$error[0] | fl * -Force

Result:

System.String
Split-Pipeline : Specified cast is not valid.
At line:6 char:13
+         1 | Split-Pipeline -Count 1 -Script {}
+             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    + CategoryInfo          : NotSpecified: (:) [Split-Pipeline], InvalidCastException
    + FullyQualifiedErrorId : System.InvalidCastException,SplitPipeline.SplitPipelineCommand



PSMessageDetails      : 
Exception             : System.InvalidCastException: Specified cast is not valid.
                           at SplitPipeline.SplitPipelineCommand.BeginProcessing()
                           at System.Management.Automation.Cmdlet.DoBeginProcessing()
                           at System.Management.Automation.CommandProcessorBase.DoBegin()
TargetObject          : 
CategoryInfo          : NotSpecified: (:) [Split-Pipeline], InvalidCastException
FullyQualifiedErrorId : System.InvalidCastException,SplitPipeline.SplitPipelineCommand
ErrorDetails          : 
InvocationInfo        : System.Management.Automation.InvocationInfo
ScriptStackTrace      : at foo, <No file>: line 6
                        at <ScriptBlock>, <No file>: line 8
PipelineIterationInfo : {}

[nightroman]

This is an interesting issue, rather PowerShell issue, but Split-Pipeline should take this into account, yes. Will do.

What would you suggest to do in this case:

$VerbosePreference = "Garbage"

PowerShell allows this.

[nightroman]

N.B. Some time ago I submitted a similar issue to Connect 692892. It is closed as postponed, whatever this means.

[dreaburn]

Thanks for linking that Connect, that's interesting. It looks like this issue is caused by PowerShell not strongly typing the preference variables in new scopes.
I'd suggest in that case, you mirror normal PowerShell behavior, it seems to treat an invalid value the same as 'SilentlyContinue'.
I think you could also just remove the Verbose handling, it seems to me that the output would be the same, although it would cost a few unnecessary string.Formats if Verbose was not enabled.

[nightroman]

Fixed in v1.5.2. If there are any issues feel free to reopen.

Later on I will also document this issue in PowerShellTraps.

[nightroman]

Documented as Local-ActionPreference.