String Expansion Scoping... Wat?

Test-StringExpansionScoping.ps1

$MyObjGlobal = [PSCustomObject]@{
    PSTypeName = 'MyObj'
    Prop1 = 'Value1'
}

$MyObjFunction = [PSCustomObject]@{
    PSTypeName = 'MyObj'
    Prop1 = 'Value1'
}

$Test = 'In Global'

$MyObjGlobal | Add-Member -Name Expand -MemberType ScriptMethod -Value {param([string]$string) return $ExecutionContext.InvokeCommand.ExpandString($string)} 
$String = 'Test: $Test'

' '
' '
' '
' '
'----------------------------------'

$MyObjGlobal.Expand($String)

function DumbFunction ($GlobalObj, $FunctionObj, $String) {
    $Test = 'In Dumb Function'
    $GlobalObj.Expand($string)
    $FunctionObj | Add-Member -Name Expand -MemberType ScriptMethod -Value {param([string]$string) return $ExecutionContext.InvokeCommand.ExpandString($string)} 
    $FunctionObj.Expand($string)
}
'----------------------------------'
DumbFunction $MyObjGlobal $MyObjFunction $String

function Test-AdvFunction {
    [CmdletBinding()]
    param (
        $MyObjGlobal,
        $MyObjFunction,
        $String
    )
    end {
        $Test = 'In Advanced Function'
        $MyObjGlobal.Expand($string)
        $MyObjFunction | Add-Member -Name Expand -MemberType ScriptMethod -Value {param([string]$string) return $ExecutionContext.InvokeCommand.ExpandString($string)} 
        $MyObjFunction.Expand($string)
    }
}
$MyObjFunction = [PSCustomObject]@{
    PSTypeName = 'MyObj'
    Prop1 = 'Value1'
}
'----------------------------------'
Test-AdvFunction -MyObjGlobal $MyObjGlobal -MyObjFunction $MyObjFunction -String $String

$Module = New-Module {
    $Test = 'In Module'
    $MyModuleObj = [PSCustomObject]@{
        PSTypeName = 'MyObj'
        Prop1 = 'Value1'
    }
    $MyModuleObj | Add-Member -Name Expand -MemberType ScriptMethod -Value {param([string]$string) return $ExecutionContext.InvokeCommand.ExpandString($string)}

    $MyModuleFunctionObj = [PSCustomObject]@{
        PSTypeName = 'MyObj'
        Prop1 = 'Value1'
    }

    $MyModuleFunctionObj2 = [PSCustomObject]@{
        PSTypeName = 'MyObj'
        Prop1 = 'Value1'
    }

    $MyModuleFunctionObj3 = [PSCustomObject]@{
        PSTypeName = 'MyObj'
        Prop1 = 'Value1'
    }

    function ModuleDumbFunction ($GlobalObj, $FunctionObj, $String) {
        $Test = 'In Module Dumb Function'
        $GlobalObj.Expand($string)
        $FunctionObj | Add-Member -Name Expand -MemberType ScriptMethod -Value {param([string]$string) return $ExecutionContext.InvokeCommand.ExpandString($string)} 
        $FunctionObj.Expand($string)
        $Script:MyModuleObj.Expand($string)
        $Script:MyModuleFunctionObj | Add-Member -Name Expand -MemberType ScriptMethod -Value {param([string]$string) return $ExecutionContext.InvokeCommand.ExpandString($string)} 
        $Script:MyModuleFunctionObj.Expand($String)
    }
    Export-ModuleMember -Function ModuleDumbFunction
    function Test-ModuleAdvFunction {
        [CmdletBinding()]
        param (
            $MyObjGlobal,
            $MyObjFunction,
            $String
        )
        end {
            $Test = 'In Module Advanced Function'
            $MyObjGlobal.Expand($string)
            $MyObjFunction | Add-Member -Name Expand -MemberType ScriptMethod -Value {param([string]$string) return $ExecutionContext.InvokeCommand.ExpandString($string)} 
            $MyObjFunction.Expand($string)
            $Script:MyModuleObj.Expand($string)
            $Script:MyModuleFunctionObj2 | Add-Member -Name Expand -MemberType ScriptMethod -Value {param([string]$string) return $ExecutionContext.InvokeCommand.ExpandString($string)} 
            $Script:MyModuleFunctionObj2.Expand($String)
        }
    }
    Export-ModuleMember -Function Test-ModuleAdvFunction

    function Get-UpdatedObject {
        [CmdletBinding()]
        param (
            $Object
        )
        end {
            $Test = 'In Get-UpdatedObject'
            $Object | Add-Member -Name Expand -MemberType ScriptMethod -Value {param([string]$string) return $ExecutionContext.InvokeCommand.ExpandString($string)} -PassThru
            $Script:MyModuleObj
            $Script:MyModuleFunctionObj3 | Add-Member -Name Expand -MemberType ScriptMethod -Value {param([string]$string) return $ExecutionContext.InvokeCommand.ExpandString($string)} -PassThru
            [PSCustomObject]@{
                PSTypeName = 'MyObj'
                Prop1 = 'Value1'
            }  | Add-Member -Name Expand -MemberType ScriptMethod -Value {param([string]$string) return $ExecutionContext.InvokeCommand.ExpandString($string)} -PassThru
        }
    }
    Export-ModuleMember -Function Get-UpdatedObject
}

Import-Module $Module

'----------------------------------'
$MyObjFunction = [PSCustomObject]@{
    PSTypeName = 'MyObj'
    Prop1 = 'Value1'
}
ModuleDumbFunction $MyObjGlobal $MyObjFunction $String

'----------------------------------'
$MyObjFunction = [PSCustomObject]@{
    PSTypeName = 'MyObj'
    Prop1 = 'Value1'
}
Test-ModuleAdvFunction -MyObjGlobal $MyObjGlobal -MyObjFunction $MyObjFunction -String $String

'-----------------------------------'
$MyObjFunction = [PSCustomObject]@{
    PSTypeName = 'MyObj'
    Prop1 = 'Value1'
}
$out = Get-UpdatedObject -Object $MyObjFunction 
$out.Expand($String)

<# OUtput:
----------------------------------
Test: In Global
----------------------------------
Test: In Dumb Function
Test: In Dumb Function
----------------------------------
Test: In Advanced Function
Test: In Advanced Function
----------------------------------
Test: In Global
Test: In Module Dumb Function
Test: In Module Dumb Function
Test: In Module Dumb Function
----------------------------------
Test: In Global
Test: In Module Advanced Function
Test: In Module Advanced Function
Test: In Module Advanced Function
-----------------------------------
Test: In Module
Test: In Module
Test: In Module
Test: In Module
#>