powershell/PSUseConsistentParameterSetName

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Description

1. Missing DefaultParameterSetName - Warns when parameter sets are used but no default is specified
2. Multiple parameter declarations - Detects when a parameter is declared multiple times in the same parameter set. This is ultimately a runtime exception - this check helps catch it sooner.
3. Case mismatch between DefaultParameterSetName and ParameterSetName - Ensures consistent casing
4. Case mismatch between different ParameterSetName values - Ensures all references to the same parameter set use identical casing
5. Parameter set names containing newlines - Warns against using newline characters in parameter set names

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How

• Use a DefaultParameterSetName when defining multiple parameter sets
• Ensure consistent casing between DefaultParameterSetName and ParameterSetName values
• Use identical casing for all references to the same parameter set name
• Avoid declaring the same parameter multiple times in a single parameter set
• Do not use newline characters in parameter set names

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Examples

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Problematic code

# Missing DefaultParameterSetName
function Get-Data {
    [CmdletBinding()]
    param(
        [Parameter(ParameterSetName='ByName')]
        [string]$Name,

        [Parameter(ParameterSetName='ByID')]
        [int]$ID
    )
}

# Case mismatch between DefaultParameterSetName and ParameterSetName
function Get-Data {
    [CmdletBinding(DefaultParameterSetName='ByName')]
    param(
        [Parameter(ParameterSetName='byname')]
        [string]$Name,

        [Parameter(ParameterSetName='ByID')]
        [int]$ID
    )
}

# Inconsistent casing between ParameterSetName values
function Get-Data {
    [CmdletBinding(DefaultParameterSetName='ByName')]
    param(
        [Parameter(ParameterSetName='ByName')]
        [string]$Name,

        [Parameter(ParameterSetName='byname')]
        [string]$DisplayName
    )
}

# Multiple parameter declarations in same set
function Get-Data {
    param(
        [Parameter(ParameterSetName='ByName')]
        [Parameter(ParameterSetName='ByName')]
        [string]$Name
    )
}

# Parameter set name with newline
function Get-Data {
    param(
        [Parameter(ParameterSetName="Set`nOne")]
        [string]$Name
    )
}

​

Correct code

# Proper parameter set configuration
function Get-Data {
    [CmdletBinding(DefaultParameterSetName='ByName')]
    param(
        [Parameter(ParameterSetName='ByName', Mandatory)]
        [string]$Name,

        [Parameter(ParameterSetName='ByName')]
        [Parameter(ParameterSetName='ByID')]
        [string]$ComputerName,

        [Parameter(ParameterSetName='ByID', Mandatory)]
        [int]$ID
    )
}

​

Configuration

Rules = @{
    PSUseConsistentParameterSetName  = @{
        Enable = $true
    }
}

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Parameters

• Enable: bool (Default value is $false) Enable or disable the rule during ScriptAnalyzer invocation.

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Notes

• Parameter set names are case-sensitive in PowerShell, making this different from most other PowerShell elements
• The first occurrence of a parameter set name in your code is treated as the canonical casing
• Parameters without [Parameter()] attributes are automatically part of all parameter sets
• It’s a PowerShell best practice to always specify a DefaultParameterSetName when using parameter sets

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Source