PSNotApplyErrorActionToStderr does not work as expected with ForEach-Object -Parallel

Steps to reproduce

Enable PSNotApplyErrorActionToStderr - no longer needed

$ErrorActionPreference = 'Stop'
@(1,2,3) | ForEach-Object -Parallel { cmd.exe /c "echo $_ >&2" }

Expected behavior

Process all records, with no error records produced:

1
2
3

Actual behavior

Stops after first record, produces an error record for native command stderr:

1 # in red

Environment data

Name                           Value
----                           -----
PSVersion                      7.1.0
PSEdition                      Core
GitCommitId                    7.1.0
OS                             Microsoft Windows 10.0.20206
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

[aelij]

@PaulHigin I’ve investigated it a bit, and it doesn’t seem that the issue is about experimental features at all:

1 | ForEach-Object -Parallel { Get-ExperimentalFeature PSNotApplyErrorActionToStderr }

yields:

Name                                Enabled Source                              Description
----                                ------- ------                              -----------
PSNotApplyErrorActionToStderr          True PSEngine                            Don't have $ErrorActionPreference affect stderr output

I think the problem is in NativeCommandProcessor and how it handles output from background processes. So it should work regardless of the suggested -UseCurrentState.

This code gets executed only in parallel:

https://github.com/PowerShell/PowerShell/blob/4a09585fe72c3679e23a1aa047b23ac827609c55/src/System.Management.Automation/engine/NativeCommandProcessor.cs#L657-L673

So please reopen as it’s definitely unrelated to the other issue.

[msftbot[bot]]

This issue has been marked as duplicate and has not had any activity for 1 day. It has been closed for housekeeping purposes.