Hi @jambar42 - can you use a parameter name here? E.g. Write-Output -InputObject ... or $propertiesAsStrings | Write-Output -NoEnumerate?

I've tried both of the suggestions listed above and both return the same results. The act of piping the object or feeding it into -InputObject both cause enumeration resulting in a failed LCM call to the Get method.

Invoke-DscResource -Name WindowsOptionalFeature -Method Get -ModuleName PSDSCResources -Property @{Name = 'HyperVisorPlatform'; Ensure = 'Present'}
A general error occurred that is not covered by a more specific error code.
+ CategoryInfo : NotSpecified: (root/Microsoft/...gurationManager:String) [], CimException
+ FullyQualifiedErrorId : MI RESULT 1
+ PSComputerName : localhost

Another option that may work is to make the output of line 58 always be an array.

That is really strange. We have a standard that we must only used named parameters, rather than positional. Specifying a parameter name shouldn't have changed the behavior here. I don't know what could have caused that.

What you could try is casting the value to an array in the return - although not sure this would work either:

return @($propertiesAsStrings)

Here are my results using the various outputs from Convert-CustomPropertyArrayToStringArray. So far, I've only found the first to return an empty array directly from this function. If you have other methods of ensuring this function always returns an array, even if empty I am curious to see them.

Write-Output $propertiesAsStrings -NoEnumerate

(Convert-CustomPropertyArrayToStringArray -CustomProperties @()).GetType()

IsPublic IsSerial Name BaseType
True True String[] System.Array

Write-Output -InputObject $propertiesAsStrings -NoEnumerate

(Convert-CustomPropertyArrayToStringArray -CustomProperties @()).GetType()

You cannot call a method on a null-valued expression.
At line:1 char:1
(Convert-CustomPropertyArrayToStringArray -CustomProperties @()).GetT ...
CategoryInfo : InvalidOperation: (:) [], RuntimeException
FullyQualifiedErrorId : InvokeMethodOnNull

return @($propertiesAsStrings)

(Convert-CustomPropertyArrayToStringArray -CustomProperties @()).GetType()

You cannot call a method on a null-valued expression.
At line:1 char:1
(Convert-CustomPropertyArrayToStringArray -CustomProperties @()).GetT ...
CategoryInfo : InvalidOperation: (:) [], RuntimeException
FullyQualifiedErrorId : InvokeMethodOnNull

The other option would be to adjust the calling of this function, however I don't think this is as clean and doesn't fit well with being unit tested.

[System.String[]]$CustomProperties =  Convert-CustomPropertyArrayToStringArray `
-CustomProperties $windowsOptionalFeatureProperties.CustomProperties

$windowsOptionalFeatureResource = @{ 
     LogPath = $windowsOptionalFeatureProperties.LogPath 
     Ensure = Convert-FeatureStateToEnsure -State $windowsOptionalFeatureProperties.State 
     CustomProperties = $CustomProperties
     Name = $windowsOptionalFeatureProperties.FeatureName 
     LogLevel = $windowsOptionalFeatureProperties.LogLevel 
     Description = $windowsOptionalFeatureProperties.Description 
     DisplayName = $windowsOptionalFeatureProperties.DisplayName 
 }