Invoke code in caller scope by manipulating the session state, like in Pester

InCallerScope.ps1

function Set-ScriptBlockScope
{
    [CmdletBinding()]
    param (
        [Parameter(Mandatory = $true)]
        [scriptblock]
        $ScriptBlock,

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

    $flags = [System.Reflection.BindingFlags]'Instance,NonPublic'

    $SessionStateInternal = $SessionState.GetType().GetProperty('Internal', $flags).GetValue($SessionState, $null)

    $SessionStateInternal | Add-Member -Value "caller" -MemberType NoteProperty -Name "ScopeName" -Force

    [scriptblock].GetProperty('SessionStateInternal', $flags).SetValue($ScriptBlock, $SessionStateInternal, $null)
}

function Get-ScriptBlockScope
{
    [CmdletBinding()]
    param (
        [Parameter(Mandatory = $true)]
        [scriptblock]
        $ScriptBlock)

    $flags = [System.Reflection.BindingFlags]'Instance,NonPublic'

    [scriptblock].GetProperty('SessionStateInternal', $flags).GetValue($ScriptBlock) | select ScopeName
}

function InCallerScope { 
    [cmdletbinding()]
    param($sb)

    Set-ScriptBlockScope -ScriptBlock $sb -SessionState ( $PSCmdlet.SessionState )
   

    &$sb
}



remove-item 'function:\mine' -ea 0
remove-item 'alias:\gg' -ea 0

# make one extra scope so we can see that the alias is not defined in script scope
&{
    function ext { 'external' }
    $sb = { 
        function mine () { "just define it" }
        set-alias -Name gg -Value ext -Scope 2
    }    

    InCallerScope $sb

    Get-ScriptBlockScope -ScriptBlock $sb

    mine # <- not defined, but if the code executed directly in the caller scope it would be executed
    gg

    (Get-Alias gg -Scope 0  | Out-String)

}