Measure-GremlinCharacter

SYNOPSIS

Rule to detect invisible or visually deceptive Unicode characters (gremlins).

SYNTAX

Measure-GremlinCharacter [-Token] <Token[]> [-ProgressAction <ActionPreference>] [<CommonParameters>]

DESCRIPTION

This rule detects Unicode characters that are invisible or visually similar to legitimate characters, such as zero-width spaces, bidirectional overrides, and curly quotes. These characters can introduce subtle bugs or security issues that are nearly impossible to see in an editor.

Severity levels reflect how dangerous the character is:

• Error - Bidirectional overrides, zero-width spaces, and control characters that can actively obscure code intent or enable Trojan-source attacks.
• Warning - Typographic characters (curly quotes, en dash) that are unlikely to be intentional in source code and may cause parse errors.
• Information - Characters like non-breaking spaces that are rarely intentional but generally harmless.

Inspired by the vscode-gremlins extension.

EXAMPLES

EXAMPLE 1

Measure-GremlinCharacter -Token $Token

This will check if the given Token contains any gremlin characters.

PARAMETERS

-Token

The token to check for gremlin characters.

Type: Token[]
Parameter Sets: (All)
Aliases:

Required: True
Position: 1
Default value: None
Accept pipeline input: False
Accept wildcard characters: False

-ProgressAction

{{ Fill ProgressAction Description }}

Type: ActionPreference
Parameter Sets: (All)
Aliases: proga

Required: False
Position: Named
Default value: None
Accept pipeline input: False
Accept wildcard characters: False

CommonParameters

This cmdlet supports the common parameters: -Debug, -ErrorAction, -ErrorVariable, -InformationAction, -InformationVariable, -OutVariable, -OutBuffer, -PipelineVariable, -Verbose, -WarningAction, and -WarningVariable. For more information, see about_CommonParameters.

INPUTS

[System.Management.Automation.Language.Token]

OUTPUTS

[Microsoft.Windows.PowerShell.ScriptAnalyzer.Generic.DiagnosticRecord[]]

NOTES

Inspired by https://github.com/nhoizey/vscode-gremlins

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