RestartableSession

RestartableSession is a PowerShell module to instantly and properly reflect the code changes to the module or script you are making. It helps you perform quick interactive testing on the console.

ScriptModuleIteration.mp4

If you have written a PowerShell module, you might have got into some situations where you had to restart the PowerShell session to reflect your code changes, such as changes to classes imported by using module, and C# classes added by Add-Type. It's annoying if you have to manually restart the session and import the module every time but with RestartableSession, you can make the process automatic.

Requirements

This module has been tested on:

• Windows 10, Windows 11 and Ubuntu 20.04
• Windows PowerShell 5.1 and PowerShell 7.3

Warning It only runs on the ConsoleHost and does not support Windows PowerShell ISE Host or Visual Studio Code Host.

Installation

RestartableSession is available on the PowerShell Gallery. You can install the module with the following command:

Install-Module -Name RestartableSession -Scope CurrentUser

Usage

Basic flow

By calling Enter-RSSession, you enter a restartable session. The specified script block is called every time the session is restarted. RS(n) is added to the prompt to indicate that you are in a restartable session and how many times you restarted the session.

PS C:\> Enter-RSSession -OnStart {'Hello'}
Hello
RS(1) PS C:\> 

Inside the restartable session, you can restart the session by calling Restart-RSSession function.

RS(1) PS C:\> Restart-RSSession
Hello
RS(2) PS C:\> 

Start-RSRestartFileWatcher is used to automatically call Restart-RSSession on file saves.

RS(2) PS C:\> Start-RSRestartFileWatcher -Path D:\ScriptModuleTest -IncludeSubdirectories

Finally, when you've done with the module development, you can return to the caller session by Exit-RSSession.

RS(2) PS C:\> Exit-RSSession
PS C:\>

OnStart and OnEnd

OnStart script block is called at the start of an RSSession and OnEnd script block is called at the end of the RSSession. The script blocks are called in a newly created session so if you want to pass variables of the caller session, you have to pass them through OnStartArgumentList or OnEndArgumentList. All the variables and functions defined in OnStart are visible in the session because it is executed in the session scope.

PS C:\> Enter-RSSession -OnStart {$var = 99} -OnEnd {$var}
RS(1) PS C:\> $var
99
RS(1) PS C:\> Exit-RSSession
99
PS C:\>

Showing Process ID to attach debuggers

By adding ShowProcessId switch to Enter-RSSession, the process ID of the restartable session is shown in the prompt which makes it easier to attach a debugger from VSCode.

PS C:\> Enter-RSSession -ShowProcessId
RS(1)[19264] PS C:\> Restart-RSSession
RS(2)[5860] PS C:\> Exit-RSSession
PS C:\>

Use Cases

Script Module development

Assuming that all the code used for the module is placed under one directory, you can set up a auto-reloading console by calling this function.

function StartScriptModuleDevelopment($ModuleDirectory)
{
    $onStart = {
        param($dir)
        Import-Module $dir
        Start-RSRestartFileWatcher -Path $dir -IncludeSubdirectories
    }
    Enter-RSSession -OnStart $onStart -OnStartArgumentList $ModuleDirectory -ShowProcessId
}

Script Class Module development

If the module exports classes, you need using module statement to import the module. In order to use using module inside a script block, you have to create the script block from a string. The video at the top of this page was made using this function.

function StartScriptClassModuleDevelopment($ModuleDirectory)
{
    $scriptBlockString = 
@'
    using module {0}
    Start-RSRestartFileWatcher -Path {0} -IncludeSubdirectories
'@
    $onStart = [ScriptBlock]::Create($scriptBlockString -f $ModuleDirectory)
    Enter-RSSession -OnStart $onStart -ShowProcessId
}

Binary Module development

$OnStart script block could be anything so you can even build a .Net project once the code has been changed and reload the dll. The session is restarted at the source code change so there is no dll blocking issue.

function StartBinaryModuleDevelopment($DotNetProjectDirectory, $DllPath)
{
    $onStart = {
        param($projectDir, $dll)
        dotnet build $projectDir
        Import-Module $dll
        Start-RSRestartFileWatcher -Path $projectDir -IncludeSubdirectories
    }
    Enter-RSSession -OnStart $onStart -OnStartArgumentList $DotNetProjectDirectory, $DllPath -ShowProcessId
}

BinaryModuleIteration.mp4

Changelog

Changelog is available here