Unlike Start-Job, Start-ThreadJob doesn't respect a Set-PSBreakpoint -Command call in connection with Debug-Job

[mklement0]

Prerequisites

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• Make sure you are able to repro it on the latest version
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Steps to reproduce

• When using Set-PSBreakpoint -Command from a background (child process-based) job, the Set-PSBreakpoint -Command is honored (assuming that the job is already in the Running state - see Background jobs (Start-Job) and ForEach-Object -AsJob -Parallel, in combination with Debug-Job, prematurely report being in the Running state, before being ready for debugging PowerShell#21258): the breakpoint suspends execution until the Debug-Job call connects.

• By contrast, with a thread job, that doesn't work: the thread job runs to completion, irrespective of the break point; the same applies to ForEach-Object -AsJob -Parallel.

Write-Verbose -Verbose 'Creating a job that uses `Set-PSBreakpoint -Command foo`'
# NOTE: If you substitute `Start-Job` on the next line, the behavior is as expected.
$job = Start-ThreadJob {

  function foo {
    'hi'
  }
  
  Set-PSBreakpoint -Command foo

  foo

} 

Write-Verbose -Verbose 'Waiting an arbitrary amount of time (e.g., 3 seconds)...'
Start-Sleep 3

Write-Verbose -Verbose 'Initiating debugging...'
$job | Debug-Job

# Clean up.
$job | Remove-Job -Force

Expected behavior

Hit Command breakpoint on 'foo'

At line:3 char:16
+   function foo {
+

That is, the break point should be honored, irrespective of when Debug-Job is invoked,
and the debugger should be entered.

This is indeed how it works with a Start-Job (child process-based) job.

Actual behavior

Debug-Job: /path/to/some.ps1:42
Line |
  19 |  $job | Debug-Job
     |         ~~~~~~~~~
     | The provided job and all child jobs were examined but no jobs were found that could be debugged.  In order to debug a job or child job the job must support debugging and
     | also be in a running state.

That is, the thread job ran to completion without honoring the break point, and the attempt to call Debug-Job came too late.

Error details

No response

Environment data

PowerShell 7.5.0-preview.3

Version

2.0.3, as shipped with PowerShell Core v7.5.0-preview.3

Visuals

No response