plugins/pscolor/src/module/src/private/Get-CallerPreference.ps1

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function Get-CallerPreference {
    <#
    .Synopsis
       Fetches "Preference" variable values from the caller's scope.
    .DESCRIPTION
       Script module functions do not automatically inherit their caller's variables, but they can be
       obtained through the $PSCmdlet variable in Advanced Functions. This function is a helper function
       for any script module Advanced Function; by passing in the values of $ExecutionContext.SessionState
       and $PSCmdlet, Get-CallerPreference will set the caller's preference variables locally.
    .PARAMETER Cmdlet
       The $PSCmdlet object from a script module Advanced Function.
    .PARAMETER SessionState
       The $ExecutionContext.SessionState object from a script module Advanced Function. This is how the
       Get-CallerPreference function sets variables in its callers' scope, even if that caller is in a different
       script module.
    .PARAMETER Name
       Optional array of parameter names to retrieve from the caller's scope. Default is to retrieve all
       Preference variables as defined in the about_Preference_Variables help file (as of PowerShell 4.0)
       This parameter may also specify names of variables that are not in the about_Preference_Variables
       help file, and the function will retrieve and set those as well.
    .EXAMPLE
       Get-CallerPreference -Cmdlet $PSCmdlet -SessionState $ExecutionContext.SessionState
 
       Imports the default PowerShell preference variables from the caller into the local scope.
    .EXAMPLE
       Get-CallerPreference -Cmdlet $PSCmdlet -SessionState $ExecutionContext.SessionState -Name 'ErrorActionPreference','SomeOtherVariable'
 
       Imports only the ErrorActionPreference and SomeOtherVariable variables into the local scope.
    .EXAMPLE
       'ErrorActionPreference','SomeOtherVariable' | Get-CallerPreference -Cmdlet $PSCmdlet -SessionState $ExecutionContext.SessionState
 
       Same as Example 2, but sends variable names to the Name parameter via pipeline input.
    .INPUTS
       String
    .OUTPUTS
       None. This function does not produce pipeline output.
    .LINK
       about_Preference_Variables
    #>


    [CmdletBinding(DefaultParameterSetName = 'AllVariables')]
    param (
        [Parameter(Mandatory = $true)]
        [ValidateScript({ $_.GetType().FullName -eq 'System.Management.Automation.PSScriptCmdlet' })]
        $Cmdlet,

        [Parameter(Mandatory = $true)]
        [System.Management.Automation.SessionState]$SessionState,

        [Parameter(ParameterSetName = 'Filtered', ValueFromPipeline = $true)]
        [string[]]$Name
    )

    begin {
        $filterHash = @{}
    }
    
    process {
        if ($null -ne $Name)
        {
            foreach ($string in $Name)
            {
                $filterHash[$string] = $true
            }
        }
    }

    end {
        # List of preference variables taken from the about_Preference_Variables help file in PowerShell version 4.0

        $vars = @{
            'ErrorView' = $null
            'FormatEnumerationLimit' = $null
            'LogCommandHealthEvent' = $null
            'LogCommandLifecycleEvent' = $null
            'LogEngineHealthEvent' = $null
            'LogEngineLifecycleEvent' = $null
            'LogProviderHealthEvent' = $null
            'LogProviderLifecycleEvent' = $null
            'MaximumAliasCount' = $null
            'MaximumDriveCount' = $null
            'MaximumErrorCount' = $null
            'MaximumFunctionCount' = $null
            'MaximumHistoryCount' = $null
            'MaximumVariableCount' = $null
            'OFS' = $null
            'OutputEncoding' = $null
            'ProgressPreference' = $null
            'PSDefaultParameterValues' = $null
            'PSEmailServer' = $null
            'PSModuleAutoLoadingPreference' = $null
            'PSSessionApplicationName' = $null
            'PSSessionConfigurationName' = $null
            'PSSessionOption' = $null

            'ErrorActionPreference' = 'ErrorAction'
            'DebugPreference' = 'Debug'
            'ConfirmPreference' = 'Confirm'
            'WhatIfPreference' = 'WhatIf'
            'VerbosePreference' = 'Verbose'
            'WarningPreference' = 'WarningAction'
        }

        foreach ($entry in $vars.GetEnumerator()) {
            if (([string]::IsNullOrEmpty($entry.Value) -or -not $Cmdlet.MyInvocation.BoundParameters.ContainsKey($entry.Value)) -and
                ($PSCmdlet.ParameterSetName -eq 'AllVariables' -or $filterHash.ContainsKey($entry.Name))) {
                
                $variable = $Cmdlet.SessionState.PSVariable.Get($entry.Key)
                
                if ($null -ne $variable) {
                    if ($SessionState -eq $ExecutionContext.SessionState) {
                        Set-Variable -Scope 1 -Name $variable.Name -Value $variable.Value -Force -Confirm:$false -WhatIf:$false
                    }
                    else {
                        $SessionState.PSVariable.Set($variable.Name, $variable.Value)
                    }
                }
            }
        }

        if ($PSCmdlet.ParameterSetName -eq 'Filtered') {
            foreach ($varName in $filterHash.Keys) {
                if (-not $vars.ContainsKey($varName)) {
                    $variable = $Cmdlet.SessionState.PSVariable.Get($varName)
                
                    if ($null -ne $variable)
                    {
                        if ($SessionState -eq $ExecutionContext.SessionState)
                        {
                            Set-Variable -Scope 1 -Name $variable.Name -Value $variable.Value -Force -Confirm:$false -WhatIf:$false
                        }
                        else
                        {
                            $SessionState.PSVariable.Set($variable.Name, $variable.Value)
                        }
                    }
                }
            }
        }
    }
}