Powershell: SWITCH statement overrides automatic variable $_

[yecril71pl]

Steps to reproduce

1 | % { SWITCH (0) { DEFAULT { $_ } } }

Expected behavior

1

Actual behavior

0

Environment data

Name                           Value
----                           -----
PSVersion                      7.0.1
PSEdition                      Core
GitCommitId                    7.0.1
OS                             Microsoft Windows 10.0.18363
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

[yecril71pl]

Workaround:
powershell 1 | % { SWITCH (0) { DEFAULT { $INPUT } } }

[thlac]

I don't think this is an issue, the switch statement sets $PSItem to the value passed into the switch which is 0 in this case.

[yecril71pl]

This behaviour is undocumented. The automatic variable $_ is documented to be set by commands, the SWITCH statement is not a command.

[thlac]

Ah right, the switch statement is documented to set it, but it does look to be inconsistent with the documentation regarding $PSItem/$_

[KalleOlaviNiemitalo]

Related to https://github.com/MicrosoftDocs/PowerShell-Docs/issues/5096.

[iSazonov]

The design is explicitly documented now.

[msftbot[bot]]

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