Start-Job -PSVersion 5.1 does not include the Windows Powershell module user path when run in PSIC terminal

[JustinGrote]

Issue Type: Bug

Reproduce

In PSIC terminal:

Start-Job -PSVersion '5.1' -ScriptBlock {$ENV:PSModulePath} | Receive-Job -Wait

Expected

PSModulePath contains $HOME\Documents\WindowsPowershell\Modules

Actual

Only contains system folders and the powershell preview extension modules folder
C:\Program Files\WindowsPowerShell\Modules;C:\WINDOWS\system32\WindowsPowerShell\v1.0\Modules;c:\Users\JGrote\.vscode-insiders\extensions\ms-vscode.powershell-preview-2021.5.0\modules

Workaround

Add back to PSModulePath as first step in the job

Extension version: 2021.5.0
VS Code version: Code - Insiders 1.57.0-insider (fe1eafc80c07608de52a2f9c99fee103dea77f5e, 2021-06-04T12:21:40.077Z)
OS version: Windows_NT x64 10.0.19043

System Info

Item	Value
CPUs	AMD Ryzen 7 4700U with Radeon Graphics (8 x 1996)
GPU Status	2d_canvas: enabled gpu_compositing: enabled multiple_raster_threads: enabled_on oop_rasterization: enabled opengl: enabled_on rasterization: enabled skia_renderer: enabled_on video_decode: enabled vulkan: disabled_off webgl: enabled webgl2: enabled
Load (avg)	undefined
Memory (System)	15.36GB (4.84GB free)
Process Argv	--folder-uri file:///c%3A/Users/JGrote/Projects/PowerConfig --crash-reporter-id 4453efaa-0821-4555-88e2-3de8bad9109e
Screen Reader	no
VM	0%

A/B Experiments

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pythonvsuse255:30303025
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[andyleejordan]

Thanks @JustinGrote. I can reproduce this in my integrated console, but only when using PowerShell 7 in the IC, it does not reproduce in PowerShell 5.1. @rjmholt cannot reproduce it, so this bug feels a bit tricky. @PaulHigin is there anything we should know about within the remoting context that Start-Job uses that may cause the environment not to be successfully propagated (after the pruning I expect happens when PSVersion is set)?

[PaulHigin]

I don't think Start-Job is doing anything special. It runs the job script in a separate child process, which should pick up environment from the parent. I know @SteveL-MSFT has spent time with $PSModulePath under different start up conditions, and may have an idea.

[andyleejordan]

This is a weird scenario because we're starting in PowerShell 7, which has an incompatible PSModulePath environment variable, and so it cannot be passed as-is when Start-Job -PSVersion '5.1' is used. Based on testing, pwsh itself is doing something to either reset or trim that environment variable before starting the PowerShell 5.1 process, but when used from the IC, a part of that logic appears to be missing.

[JustinGrote]

@andschwa I vaguely remember something about there being this kind of logic added when calling powershell.exe from a pwsh.exe window, because it would bring along its PSModulePath env variable and screw up powershell.exe. Maybe this logic still occurs even when doing a start-job even though its not necessary because it's a completely separate space.

@SteveL-MSFT may recall the issue, I think it was pwsh 7.0 timeframe.