Debugging / unloading PowerShell Cmdlet

Anytime I see something like this:

It is very unhandy to close the powershell, rebuild the dll and then reopen a new powershell, cd to the dll path (usually deeply nested), re-import it again, start the command to debut, and so on for every single debugging session...

I immediately think, "I should create a script to do these tasks for me".

There are solutions. You can start a second PowerShell (like another answer suggested). Another solution is to use a script to do some work for you, and to top it off, you can add this to your VS project.

Create a script in your profile to start PowerShell

function Start-DebugPowerShell
{
    PowerShell -NoProfile -NoExit -Command {
        function prompt {
            $newPrompt = "$pwd.Path [DEBUG]"
            Write-Host -NoNewline -ForegroundColor Yellow $newPrompt
            return '> '
        }
    }
}
Set-Alias -Name sdp -Value Start-DebugPowerShell

Edit debug settings for your Cmdlet project

Start external program:

C:\Windows\System32\WindowsPowerShell\v1.0\powershell.exe

Command line arguments:

-NoProfile -NoExit -Command "Import-Module .\MyCoolCmdlet.dll"

Debug your Module

Now from Visual Studio, start debugger with F5, and you have a new PowerShell window with your Cmdlet loaded, and you can debug it however you like.

Use the 'sdp' alias from any PowerShell window

Since the Start-DebugPowerShell function is in our profile and we gave it an alias sdp, you can use this to start a second instance of PowerShell anytime you need it.

I used a helper powershell script which did most of it for me.

    $module = 'AccessLogParser'
    Push-Location $PSScriptroot

    dotnet build -o $PSScriptRoot\output\$module\bin
    Import-Module "$PSScriptRoot\Output\$module\bin\$module.dll"
    $VerbosePreference = $DebugPreference="continue"
    Write-Debug "$pid - $($PSVersionTable.PSVersion)"

with two options in launch config, the helper outputs the current process ID in which terminal process (bottom part of the vscode) is running, and I can select that PID in the dropdown when I launch debugger. Helpful when you want to develop something for old v5 powershell as well as v7 (pwsh.exe) version.

 {
            "name": ".NET Framework Attach",
            "type": "clr",
            "request": "attach",
            "processId": "${command:pickProcess}"
        },
        {
            "name": ".NET Core Attach",
            "type": "coreclr",
            "request": "attach",
            "processId": "${command:pickProcess}"
        }

<edit: this is now doc'd fully for pwsh and powershell.exe at https://learn.microsoft.com/en-us/powershell/scripting/dev-cross-plat/vscode/using-vscode-for-debugging-compiled-cmdlets - this doc discusses the DLL lock issue /edit>

To add to @kory-gill's answer, this is my launch.json:

{
    "name": ".NET Core Launch (console)",
    "type": "coreclr",
    "request": "launch",
    "preLaunchTask": "build",
    "cwd": "${workspaceFolder}",
    "program": "pwsh",
    "args": [
        "-NoExit",
        "-NoProfile",
        "-Command",
        "ipmo ${workspaceFolder}/DependencyTree/bin/Debug/netstandard2.0/DependencyTree.dll",
    ],
    "console": "integratedTerminal",
    "stopAtEntry": false
}

My project is called DependencyTree. Substitute your own project name.

The -NoProfile is important for me because my profile is large and breaks the debugger.

More generally, I have PSReadline set up, and you should too, to persist history across terminal sessions. So I can Ctrl-R and summon any command I have typed for a long way back. With that configured, the following is useful when working interactively with compiled or Powershell classes, and also when working with non-exported members of a module:

1. Use your keyboard shortcuts to create and delete terminals. In VS Code, terminals should be considered disposable.
2. $host.ExitNestedPrompt(); $Module = ipmo .\DependencyTree.psd1 -Force -PassThru; & $Module {$host.EnterNestedPrompt()}

The & $Module { ... } trick runs that scriptblock inside the module scope. Very useful for wizards ;-)