PowerShell Predicting with Style

I've been using the PSReadline module for years in PowerShell. I especially loved it when the module added inline command prediction based on your history. You would start typing a command and the module would search your saved history and suggest an inline completion.

In my PowerShell profile I enable and configure this feature.

Set-PSReadLineOption -PredictionSource History -colors @{
    InlinePrediction = "$([char]27)[4;92m"
}

Recently, Microsoft updated the PSReadline module to version 2.2.2. You can install it from the PowerShell Gallery. If you've never updated the module, you will need to actually install it.

Install-Module PSReadline -force

This is because PSReadline ships with PowerShell. Once you've installed a newer version, you can use Update-Module to keep it up to date.

The newer version brings an alternate prediction view style. You can now specify a list view.

Set-PSReadLineOption -PredictionViewStyle ListView

Arrow down to the selection you want, and press Enter. It may not seem like much, but it is little things like this that save time throughout your day and remove a bit of command-line friction.

Toggle Style

What I have found is that sometimes I want inline prediction and sometimes I want a list. But I don't want to be constantly running Set-PSReadlineOption. Although with command prediction, I guess it wouldn't be too bad. Instead, I wrote a PowerShell function that by default toggles the prediction view style.

Function Set-PredictionView {
    [cmdletbinding(SupportsShouldProcess)]
    [alias("spv", 'sview')]
    [OutputType("none")]
    Param(
        [Parameter(Position = 0, HelpMessage = "Specify the prediction style. Toggle will switch to the unused style.")]
        [ValidateSet("List", "InLine", "Toggle")]
        [string]$View = "Toggle",
        [switch]$Passthru
    )

    Try {
        Switch ($View) {
            "List" { $style = "ListView" }
            "Inline" { $style = "InLineView" }
            "Toggle" {
                Switch ((Get-PSReadLineOption).PredictionViewStyle) {
                    "InLineview" {
                        $style = "ListView"
                    }
                    "ListView" {
                        $style = "InLineView"
                    }
                    Default {
                        #fail safe action. This should never happen.
                        Write-Warning "Could not determine a view style. Are you running PSReadline v2.2.2 or later?"
                    }
                } #nested switch
            } #toggle
        } #switch view

        if ($style -AND ($PSCmdlet.ShouldProcess($style, "Set prediction view style"))) {
            Set-PSReadLineOption -PredictionViewStyle $style
            if ($Passthru) {
                Get-PredictionView
            }
        }
    } #try
    Catch {
        Write-Warning "There was a problem. Could not determine a view style. Are you running PSReadline v2.2.2 or later? $($_.exception.message)."
    }
} #end function

This code requires PSReadline version 2.2.2 or later. You can use the function to easily set a view style.

I set the default "style" to toggle between List and Inline. If I'm using List, the function will toggle the style to Inline and vice versa. Or I can explicitly set a style.

Set-predictionview List

Get View Settings

Of course, if I'm setting something I should have a function to get something.

Function Get-PredictionView {
    [cmdletbinding()]
    [OutputType('PSPredictionView')]
    [alias('gview')]
    Param()

    #define escape character based on PowerShell version
    if ($IsCoreCLR) {
        $e = '`e'
    }
    else {
        $e = '[char]0x1b)'
    }

    #get prediction related PSReadline options
    $options = Get-PSReadLineOption | Select-Object PredictionSource, PredictionViewStyle, ListPredictionColor,
    ListPredictionSelectedColor, InlinePredictionColor

    #create a new PSPredictionView object
    [PSCustomObject]@{
        PSTypeName        = "PSPredictionView"
        Source            = $options.PredictionSource
        Style             = $options.PredictionViewStyle
        ListColor         = "{0}$e{1}$([char]27)[0m" -f $options.ListPredictionColor, ($options.ListPredictionColor -replace [char]27, "")
        ListSelectedColor = "{0}$e{1}$([char]27)[0m" -f $options.ListPredictionSelectedColor, ($options.ListPredictionSelectedColor -replace [char]27, "")
        InlineColor       = "{0}$e{1}$([char]27)[0m" -f $options.InlinePredictionColor, ($options.InlinePredictionColor -replace [char]27, "")
    }

} #end function

This function is called when running Set-PredictionView -passthru.

The functions have aliases which make them very easy to use from the console. With only a few keystrokes I can toggle between list and inline views. Talk about reducing friction!

Summary

If you aren't using this PSReadline feature, you are missing out. I am aware that there is a potential security risk because the History option stores commands in a plain text file, so some people choose not to use it. But if you do, I hope you'll give these commands a try and let me know what you think.

Later that day...

I guess Microsoft must have also thought you might want to toggle between views. I never looked, but thanks to friends on Twitter, you can also press F2 to toggle between inline and list prediction views. I guess you don't really need my Set function unless you've re-mapped F2 to something else. You should run Get-PSReadlineKeyHandler to see what else you might be missing out on!