Nested ForEach-Object -Parallel

Prerequisites

• I have written a descriptive issue title.
• I have searched all open and closed issues to ensure it has not already been reported.
• I have read the troubleshooting guide.
• I am sure this issue is with the extension itself and does not reproduce in a standalone PowerShell instance.
• I have verified that I am using the latest version of Visual Studio Code and the PowerShell extension.
• If this is a security issue, I have read the security issue reporting guidance.

Summary

I am expecting the same behaviour between the PowerShell Extension terminal and the standard PowerShell terminal.

It appears that there is a scoping issue or not cleaning up of variable names within the PowerShell Extension terminal.

PowerShell Version

Name                           Value
----                           -----
PSVersion                      7.4.1
PSEdition                      Core
GitCommitId                    7.4.1
OS                             Microsoft Windows 10.0.20348
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

Name             : ConsoleHost
Version          : 7.4.1
InstanceId       : 1a36e6cd-b018-4307-8cf6-1068ec5a11bf
UI               : System.Management.Automation.Internal.Host.InternalHostUserInterface
CurrentCulture   : en-US
CurrentUICulture : en-US
PrivateData      : Microsoft.PowerShell.ConsoleHost+ConsoleColorProxy
DebuggerEnabled  : True
IsRunspacePushed : False
Runspace         : System.Management.Automation.Runspaces.LocalRunspace

Visual Studio Code Version

1.86.2
903b1e9d8990623e3d7da1df3d33db3e42d80eda
x64

Extension Version

ms-vscode.powershell@2024.3.0

Steps to Reproduce

Test.ps1

Param (
    [int]$MaxConcurrentJobs = 2
)

$Tasks = @(
    @{
        Type    = 'PC'
        Actions = @(
            @{
                ComputerName = 'PC1'
                Result       = $null
            }
            @{
                ComputerName = 'PC2'
                Result       = $null
            }
        )
    }
    @{
        Type    = 'SERVER'
        Actions = @(
            @{
                ComputerName = 'SERVER1'
                Result       = $null
            }
            @{
                ComputerName = 'SERVER2'
                Result       = $null
            }
        )
    }
)

$outerScriptBlock = {
    $task = $_

    $innerScriptBlock = {
        $action = $_

        if (-not $MaxConcurrentJobs) {
            $task = $using:task
        }

        $action.Result = '{0} - {1}' -f $task.Type, $action.ComputerName
    }

    $innerForeachParams = @{
        Process = $innerScriptBlock
    }

    if (-not $MaxConcurrentJobs) {
        $innerForeachParams = @{
            Parallel      = $innerScriptBlock
            ThrottleLimit = $using:MaxConcurrentJobs
        }
    }

    $task.Actions | ForEach-Object @innerForeachParams
}

$foreachParams = @{
    Process = $outerScriptBlock
}

if ($MaxConcurrentJobs -gt 1) {
    $foreachParams = @{
        Parallel      = $outerScriptBlock
        ThrottleLimit = $MaxConcurrentJobs
    }
}

$Tasks | ForEach-Object @foreachParams

$Tasks.Actions.Result

Execute in terminal PowerShell Extension:

Step 1

• Open file Test.ps1 with $MaxConcurrentJobs = 1 and press F5 # no error
• Open file Test.ps1 with $MaxConcurrentJobs = 2 and press F5 # no error

Step 2

& 'T:\Test\Brecht\PowerShell\Test.ps1' -MaxConcurrentJobs 2 # no error 

Execute in a standard PowerShell 7 terminal:

Step 1

& 'T:\Test\Brecht\PowerShell\Test.ps1' -MaxConcurrentJobs 1 # no error

Step 2

& 'T:\Test\Brecht\PowerShell\Test.ps1' -MaxConcurrentJobs 2 # ERROR

Visuals

No response

Logs

No response

Start with the Test.ps1 reproduction and run it from the PowerShell Extension terminal and a standard PowerShell 7 terminal using MaxConcurrentJobs values of 1 and 2. Trace the extension's terminal or debugging entry point to determine why nested ForEach-Object -Parallel scoping differs. Done means the same script has consistent behavior in both terminals.