Start-Process on Unix: trying to launch / open a nonexistent file doesn't trigger an error

Note: Windows is not affected.

Steps to reproduce

# Fails on macOS and Linux - no statement-terminating error occurs.
{ Start-Process nosuch } | Should -Throw

If you run Start-Process nosuch directly, a system error message that cannot be captured prints directly to stderr:

• Ubuntu:

"gio: file:///.../nosuch: Error when getting information for file “/.../nosuch”: No such file or directory"

• macOS:

The file /.../nosuch does not exist.

Expected behavior

The test should succeed.

Actual behavior

The test fails, because no statement-terminating error is triggered, even though no such file in the current directory / no such executable in the path exists.

Expected an exception, to be thrown, but no exception was thrown.

Environment data

PowerShell Core v7.2.0-preview.4 on macOS 10.15.7
PowerShell Core v7.2.0-preview.4 on Ubuntu 18.04.5 LTS

[SteveL-MSFT]

The way Start-Process works is it tries to find the target first. If it’s not found, and no arguments were provided, then it tries UseShellExecute = true. At this point, it’s all handled by the dotnet runtime. Dotnet relies on xdg-open on Linux and open on macOS. You can try this by running open foo on macOS and you’ll see the stderr message. It appears that dotnet runtime writes this directly to the console and thus you can’t actually redirect. Created https://github.com/dotnet/runtime/issues/49788

[joeyaiello]

Seems like a reasonable ask to me, barring difficulty of implementation