Powershell: Redirected stderr output causes $? to be set to $false, even if the process exit code is 0

[mklement0]

PR https://github.com/PowerShell/PowerShell/pull/13361 missed one aspect of what is was trying to fix, namely what was originally reported in #10512:

How $? is set in an external-program call should solely depend on the process exit code, irrespective of whether there is stderr output and _whether or not stderr output is redirected_.

It is the latter that's still a problem, which matters primarily with respect to && and ||:

# On Unix
PS> sh -c 'ls nosuch; :' 2>$null || 'why did I get here?'
why did I get here?

Steps to reproduce

# On Unix
sh -c 'ls nosuch; :' 2>$null; $? | Should -BeTrue

Expected behavior

The test should succeed:

Since the _exit code_ of the sh command is 0, $? should be $true - irrespective of the presence of stderr output, _whether redirected or not_.

Actual behavior

The test fails, because the presence of _redirected_ stderr output unexpectedly set $? to `$false

Expected $true, but got $false.

Environment data

PowerShell Core 7.1.0-preview.5

[SteveL-MSFT]

Since @PowerShell/powershell-committee agreed that stderr is not an indicator of an error, it makes sense to not set $? to false.

[msftbot[bot]]

:tada:This issue was addressed in #13395, which has now been successfully released as v7.1.0-preview.7.:tada:

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