Add logging quickly to an existing set of powershell scripts - powershell

Question

I've got a collection of powershell scripts, some of which call others. Some of these subscripts can also be called on their own as needed. How can I quickly add logging to all of the scripts so that any script invocation results in a log file for later examination?
There are a number of questions dealing with logging with some great answers, like this one. But I wanted to see what we could come up with that:
required minimal touching of the existing powershell files
automatically dealt with script A.ps1 calling script B.ps1. If you call
A.ps1, A.ps1 needs to start and finish the logging. But if you call B.ps1
directly, B.ps1 does.
I came up with my answer below, and wanted to share and see if there were other ideas on how to approach this, or suggestions for improvement on my answer.

Answer 1

The support code I write (further down) allows for just adding the following to each ps1 file. It automatically gives me logging regardless of if a script is called at top-level or by another script:
#any params for script
. "$PSScriptRoot\ps_support.ps1"
StartTranscriptIfAppropriate
try
{
#all of the original script
}
finally
{
ConditionalStopTranscript
}
The code that powers this is in ps_support.ps1, sitting next to my collection of powershell files that need logging. It uses Get-Variable and Set-Variable to manipulate a couple variables at the caller's scope level:
Logging__TranscriptStarted is normal so sub-scopes can see that
logging is already happening and not try to start it again.
Logging__TranscriptStartedPrivate is private so a scope can know if
it is responsible for stopping the logging.
Here is ps_support.ps1:
Set-Variable -name TranscriptStartedPropertyName -opt ReadOnly -value 'Logging__TranscriptStarted'
Set-Variable -name TranscriptStartedPrivatePropertyName -opt ReadOnly -value 'Logging__TranscriptStartedPrivate'
function StartTranscriptIfAppropriate
{
$transcriptStarted = [bool](Get-Variable -name $TranscriptStartedPropertyName -ErrorAction Ignore)
if (-not $transcriptStarted)
{
$callstack = get-pscallstack
$fullPath = $callstack[$callstack.count-2].ScriptName
$name = Split-Path -Path $fullPath -Leaf
$directory = Split-Path -Path $fullPath
$logDirectory = [IO.Path]::GetFullPath("$directory\..\scripts_logs")
md -force $logDirectory | out-null
$logFinalPath = "$logDirectory\$(Get-Date -Format o | foreach {$_ -replace ":", "."})_$name.log"
Set-Variable -scope 1 -name $TranscriptStartedPropertyName -value $True
Set-Variable -scope 1 -option private -name $TranscriptStartedPrivatePropertyName -value $True
Start-Transcript $logFinalPath | Write-Host
}
$immediateCallerPath = Get-Variable -scope 1 -name PSCommandPath -ValueOnly
Write-Host "Starting script at $immediateCallerPath"
}
function ConditionalStopTranscript
{
$immediateCallerPath = Get-Variable -scope 1 -name PSCommandPath -ValueOnly
Write-Host "Stopping script at $immediateCallerPath"
$transcriptStartedByMe = [bool](Get-Variable -scope 1 -name $TranscriptStartedPrivatePropertyName -ErrorAction Ignore)
if ($transcriptStartedByMe)
{
Stop-Transcript | Write-Host
}
}