Invoke-Expression and Invoke-Command: redirecting the error stream to the success stream discards error output

Note that the symptom only occurs when redirecting to another stream, either via 2>&1 or *>&1.

By contrast, redirecting to a file works as expected.

Steps to reproduce

Run the following Pester test:

# Create a string with a command that writes to all streams.
$cmd = '1; write-error 2; write-warning 3; write-verbose -vb 4; write-debug -debug 5; write-information -infa continue 6'
# Make sure that all streams can be directed to the success output stream (1).
(Invoke-Expression $cmd *>&1).Count | Should -Be 6

Note: the same applies to (at least local use of) Invoke-Command: (Invoke-Command ([scriptblock]::create($cmd)) *>&1).Count | Should -Be 6

The workaround is enclosure in (...), but it comes at the expense of losing streaming behavior. ( (Invoke-Expression $cmd) *>&1).Count | Should -Be 6

Expected behavior

The test should pass - all 6 streams should show up in the success output stream.

Actual behavior

Expected 6, but got 5.

That is, the error output was quietly discarded, as you 'll see if you run the command inside (...) in isolation

Environment data

PowerShell Core 7.0.0-preview.3
Windows PowerShell v5.1.18362.145 on Microsoft Windows 10 Pro (64-bit; Version 1903, OS Build: 18362.295)

[onlyann]

@mklement0 Somehow, it wasn’t working in a PowerShell Core console but was fine on Windows PowerShell. Now that I try to reproduce, it works in both. I must have been doing something stupid… Thank you @mklement0 for your help!

[PHeonix25]

Just ran into this myself wondering where Write-Error output went!? Thanks for making the issue!

My $PSVersionTable for reference:

Name                           Value
----                           -----
PSVersion                      7.1.0
PSEdition                      Core
GitCommitId                    7.1.0
OS                             Microsoft Windows 10.0.19042
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0