[SOLVED] XML to console using StringWriter expanding variables rather than writing strings literally

XML to console using StringWriter expanding variables rather than writing strings literally

I have been using this function to dump XML to the console for review as I work on code to do some extensive XML manipulation, and for the most part it works as expected.

function Write-PxXmlToConsole {
    param (
        [Xml.XmlNode]$Xml
    )
    
    if ($Xml -is [Xml.XmlDocument]) {
        $xmlDocument = $Xml
    } else {
        $xmlDocument = [Xml.XmlDocument]::new()
        $newElement = $xmlDocument.ImportNode($Xml, $True)
        [Void]$xmlDocument.AppendChild($newElement)
    }

    $stringWriter = [System.IO.StringWriter]::new()
    $xmlWriter = [System.Xml.XmlTextWriter]::new($stringWriter)
    $xmlWriter.Formatting = "indented"

    $xmlDocument.WriteTo($xmlWriter)
    $xmlWriter.Flush()
    $stringWriter.Flush()

    Write-Host $stringWriter.ToString()
    Write-Host
}

However, it seems that somewhere in the [System.IO.StringWriter] variables are getting expanded. Because when my XML looks like this

$xml = [Xml]@"
<Pattern>$key.Value</Pattern>
"@
Write-PxXmlToConsole $xml

I get <Pattern>Autodesk Revit 2019.Value</Pattern> as output because somewhere in this session the variable $key got populated. And if I start a new session I will get <Pattern>.Value</Pattern>. A bit of a pain, and I can't seem to find anything here that suggests a setting that would suppress this behavior.

Solution

Variables are getting expanded during creation of [Xml] with double quotes:

$xml = [Xml]@"
<Pattern>$key.Value</Pattern>
"@
Write-Host $xml.Pattern
Write-PxXmlToConsole $xml

.Value
<Pattern>.Value</Pattern>

The output is different when single quotes are used:

$xml = [Xml]@'
<Pattern>$key.Value</Pattern>
'@
Write-Host $xml.Pattern
Write-PxXmlToConsole $xml

$key.Value
<Pattern>$key.Value</Pattern>