Warning about unused PSNativeCommandArgumentPassing preference variable

[0xfeeddeadbeef]

Steps to reproduce

Save this script to a file test.ps1:

$PSNativeCommandArgumentPassing = 'Legacy'

'Hello, World!'

Call Invoke-ScriptAnalyzer cmdlet:

Invoke-ScriptAnalyzer -Path .\test.ps1

Expected behavior

Empty output; no warnings.

$PSNativeCommandArgumentPassing is a preference variable.

I'm aware that I can suppress this warnings by applying [Diagnostics.CodeAnalysis.SuppressMessageAttribute('PSUseDeclaredVarsMoreThanAssignments','')] attribute, but it is wrong, because I still want to receive warnings about other unused variables.

Actual behavior

RuleName                            Severity     ScriptName Line  Message
--------                            --------     ---------- ----  -------
PSUseDeclaredVarsMoreThanAssignment Warning      test.ps1   1     The variable 'PSNativeCommandArgumentPassing' is assigned
s                                                                 but never used.

Environment data

> $PSVersionTable

Name                           Value
----                           -----
PSVersion                      7.5.0
PSEdition                      Core
GitCommitId                    7.5.0
OS                             Microsoft Windows 10.0.20348
Platform                       Win32NT
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

> (Get-Module -ListAvailable PSScriptAnalyzer).Version | ForEach-Object { $_.ToString() }

1.24.0

[SamErde]

Yep. It's the little things like this that sting. I sometimes work around it by adding a line like [void]$PSNativeCommandArgumentPassing or Write-Verbose $PSNativeCommandArgumentPassing but you're right that it shouldn't be necessary for preference variables. Does PSScriptAnalyzer maintain a list of ignored variable names for the PSUseDeclaredVarsMoreThanAssignment test?

[bergmeister]

We have a list of excluded special variables, it seems that variable is new and needs to be added:

PSScriptAnalyzer/Engine/SpecialVars.cs

Line 169 in 2287a13

internal static readonly string[] OtherInitializedVariables = new string[]