Friday, August 03, 2018

PSReadline V2 Can Break PowerShell Profile Scripts in Latest Insider's RS5 Preview

The Windows Insider programme provides access to the latest pre-release versions of Windows 10 and Windows Server 2019. Earlier this week, Microsoft released a new preview of what is coming with Windows 10 RS5. This build, 17728.1000, contains an updated version of the module PSReadLine. PowerShell uses this module to enable you to, inter alia, set the colours of tokens in the PowerShell command console.

I love this feature, as it allows me to override the default colours that PowerShell uses. One particular issue for me is that the colours can look less good when displaying on some of the lower quality projectors I get stuck with!  One example - the parameter name token is set, by default, to gray. Displaying from my laptop, this has been hard to see at some sites. So I just added this line to my profile:
Set-PSReadlineOption -TokenKind Parameter -ForegroundColor Cyan
Simple and this is highly useful for me ainsome places I teach. However, with the latest release of the RS5 preview, Microsoft has  now included an updated version of PSReadline (2.0 vs 1.2). Taking the new version was done to enable a fix to an accessibility issue. If you run PowerShell after the upgrade, you might see this error when you run PowerShell:

This is both a breaking change and one not described in the release notes. And, if you use Bing or Google to search for Set-PSReadLine, the page at shows the old version of the cmdlet - you need to dive into the actual PSReadLine repository (ie the modules 'source' code!) to discover the answer.

The solution is simple - change that line to:
Set-PSReadLineOption -Colors @{"parameter" = [ConsoleColor]::Cyan}
I've opened issues at, the PsRadline repo and with the Insider's programme, so hopefully going forward this issue is no longer an issue.