AvoidAssignmentToAutomaticVariable

Severity Level: Warning

Default state: Always enabled

Description

Avoid using automatic variable names in your functions and parameters. This rule detects assignments to automatic variables and parameter names that use automatic variable names. PowerShell automatically defines variables that store internal state information and manages them on its own. Even though you can override many automatic variables, doing so can have unexpected effects for users and make your code harder to maintain and debug.

Reserve automatic variables for PowerShell's internal use only, and rely on them only to read state information.

To learn more, see about_Automatic_Variables.

Example

Noncompliant

The variable $Error is an automatic variable that exists in the global scope and should therefore never be used as a variable or parameter name.

function foo($Error){ }

function Get-CustomErrorMessage($ErrorMessage){ $Error = "Error occurred: $ErrorMessage" }

Compliant

function Get-CustomErrorMessage($ErrorMessage){ $FinalErrorMessage = "Error occurred: $ErrorMessage" }

Configure rule

This rule is always enabled and isn't configurable. Use one of the following methods to avoid using this rule:

• Create a custom rule configuration file to include only the rules you want or exclude the rules you don't want.
• Add the appropriate rule suppression attributes to your code to suppress the rule for specific code blocks. For more information, see the Suppressing rules section of Using PSScriptAnalyzer.