PowerShell Core and Why Bleeding-Edge Isn’t Always Exciting - Part 1
When I learned about PowerShell Core, I was a few months into diving deep into Windows PowerShell. I had already written a few scripts that I would consider “advanced” in some way, one of which being an earlier version of my script to install WinDbg from the Win10 SDK. In the following chunk of code from that script, I scrape the link to download the setup executable from the Windows 10 SDK webpage:
# Get the download link
$url = 'https://developer.microsoft.com/en-US/windows/downloads/windows-10-sdk'
try {
$response = Invoke-WebRequest -Uri $url -ErrorAction "Stop"
}
catch {
$PSCmdlet.ThrowTerminatingError($PSItem)
}
$downloadUrl = $response `
| Select-Object -ExpandProperty "Links" `
| Where-Object {$PSItem.innerText -eq 'Download the .EXE'} `
| Select-Object -ExpandProperty "href"
$downloadUrl = 'https:' + $downloadUrl
On the latest version of Windows PowerShell (5.1 as of writing), filtering the Links works just fine. When testing this script on Core (version 6.0+) for the first time, I discovered the innerText property doesn’t exist and I got a shell full of errors. Super.
As it turns out, things can change between versions of software. Who knew? Mark Kraus has a great blog post about his work on the web cmdlet API change from System.Net.WebRequest to System.Net.Http.HttpClient in PowerShell Core. After a bit of Get-Member-ing around with Invoke-WebRequest, I was able to determine this fix:
# No longer working on PS 6.0
<# $downloadUrl = $response `
| Select-Object -ExpandProperty "Links" `
| Where-Object {$PSItem.innerText -eq 'Download the .EXE'} `
| Select-Object -ExpandProperty "href" #>
# PS 6.0 Conversion
$downloadUrl = $response `
| Select-Object -ExpandProperty "Links" `
| Where-Object {$PSItem.outerHTML.Contains('Download the .EXE')} `
| Select-Object -ExpandProperty "href"
$downloadUrl = 'https:' + $downloadUrl
Of course, this was an intentional difference between Windows PowerShell and PowerShell Core. What about an unintentional difference? Part 2 will come soon, hopefully; as soon as a pull request that I have open is closed!
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