How to pause a powershell script until a debugger attaches - powershell

Question

I have an application which allows you to run a user provided PowerShell script. I want inject some code at the top of the script to pause the running script on the first line, and wait for a debugger (ie, PowerShell ISE) to attach.
A good example of what I want to achieve is how DSC pauses and waits for you to attach:
PS C:\> Enable-DscDebug -BreakAll
PS C:\> Start-DscConfiguration .\temp\DSCTestClass -wait -force
WARNING: [DEV-14257-44]: [DSCEngine] Warning LCM is in Debug 'ResourceScriptBreakAll' mode. Resource script processing will be stopped to wait for PowerShe1l script debugger to attach.
WARNING: [DEV-14257-44]: [[FileResource]file] Resource is waiting for PowerShell script debugger to attach. Use the following commands to begin debugging this resource script:
Enter-PSSession -ComputerName DEV-14257-44 -Credential <credentials>
Enter-PSHostProcess -Id 596 -AppDomainName DscPsPluginWkr_AppDomain
Debug-Runspace -Id 4
(this example from https://blogs.msdn.microsoft.com/powershell/2016/03/14/debugging-powershell-dsc-class-resources/)
Unfortunately, when I try and setup a similar kind of wait, powershell.exe automatically launches the command line debugger:
Given the file test.ps1:
set-psbreakpoint -script "test.ps1" -line 4
write-host "pid is $pid"
write-host "Pausing for debugger to attach"
write-host "Paused waiting for debugger to attach"
When I run it (even in -noninteractive mode), it launches the command line debugger:
PS C:\temp\PowershellDebugging> powershell -file .\test.ps1 -noninteractive
ID Script Line Command Variable Action
-- ------ ---- ------- -------- ------
0 test.ps1 4
pid is 13228
Pausing for debugger to attach
Entering debug mode. Use h or ? for help.
Hit Line breakpoint on 'C:\temp\PowershellDebugging\test.ps1:6'
At C:\temp\PowershellDebugging\test.ps1:6 char:1
+ write-host "Paused waiting for debugger to attach"
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[DBG]: PS C:\temp\PowershellDebugging>
How can I get PowerShell to break/pause execution without launching the command line debugger?
EDIT:
The script that is being executed only exists for a short time (it is written to disk, executed, then cleaned up). Also, the powershell.exe instance that runs it only exists for a short time - there is no long running process to manually attach to and set breakpoints on before execution.

Answer 1

After getting some help from the PowerShell team (thanks!), it turns out the key is using New-RunSpace. Normally, if you just execute a script, it will run in the default RunSpace, and that will have the built-in PowerShell debugger already attached.
The following demonstrates how to use it:
# create a fake script that simulates the user provided scrip
#'
Write-Output "Starting Test"
1..20 | foreach {
Write-Output "I Love PowerShell!"
}
Write-Output "Test Complete"
'# | Set-Content -Path c:\temp\Test.ps1
# create a launcher script
#'
Write-Output "Process Id: $pid"
$ps = [powershell]::Create([System.Management.Automation.RunspaceMode]::NewRunspace)
Write-Output "Runspace Id: $($ps.Runspace.Id)"
$ps.AddScript(‘Wait-Debugger; C:\temp\Test.ps1’).Invoke()
'# | Set-Content -Path c:\temp\LaunchTestInNewRunspace.ps1
# run the launch script
PS C:\> powershell -File c:\temp\LaunchTestInNewRunspace.ps1
Process Id: 14288
Runspace Id: 2
In another window:
# in another window
PS C:\> Enter-PSHostProcess -Id 14288
[Process:14288]: PS C:\> Debug-RunSpace -Id 2
Debugging Runspace: Runspace2
To end the debugging session type the 'Detach' command at the debugger
prompt, or type 'Ctrl+C' otherwise.
Entering debug mode. Use h or ? for help.
At line:1 char:16
+ Wait-Debugger; C:\temp\Test.ps1
+ ~~~~~~~~~~~~~~~~
This breaks into the debugger, ready to step into Test.ps1.