[BUG]: Powershell@2 Impossible to ignore specific warning output

[arc-hbas]

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Task name

Powershell

Task version

2

Issue Description

When using the PowerShell@2 task and enabling showWarnings, it becomes impossible to specifically ignore a single warning, even if WarningAction is set to Ignore or SilentlyContinue. Other "hacks", such as using redirect operator 3> to redirect warning output stream to file or $null, have not been successful to workaround this issue. This potentially causes massive log clutter when you still want to surface warning output to the pipeline summary view, but would like to disregard some of the non-important ones.

Running below example YAML pipeline, all of the warnings are still surfaced:

I thought surely the 3> redirect would work, but alas it doesn't. Thus far I have been unable to find any sort of workaround. Warnings are helpful, but only when they're relevant. Sometimes we call system level or pre-built cmdlets and cannot expect them to only print out relevant warnings (from our perspective at least).

Environment type (Please select at least one enviroment where you face this issue)

• Self-Hosted
• Microsoft Hosted
• VMSS Pool
• Container

Azure DevOps Server type

dev.azure.com (formerly visualstudio.com)

Azure DevOps Server Version (if applicable)

No response

Operation system

Windows

Relevant log output

...
WARNING: a) Default: Shows = true & Expected = true
##[warning]a) Default: Shows = true & Expected = true
##[warning]b) SilentlyContinue: Shows = true & Expected = false
##[warning]c) Ignore: Shows = true & Expected = false
##[warning]d) 3> redirect $null: Shows = true & Expected = false
##[warning]e) 3> redirect file: Shows = true & Expected = false


Finishing: Test PS

Full task logs with system.debug enabled

No response

Repro steps

trigger:
- none

pool:
  vmImage: windows-latest

steps:

- task: PowerShell@2
  displayName: Test PS
  inputs:
    targetType: 'inline'
    showWarnings: true
    script: |      
      # Should print and does
      Write-Warning "a) Default: Shows = true & Expected = true" 

      # Should NOT print but does
      Write-Warning "b) SilentlyContinue: Shows = true & Expected = false" -WarningAction SilentlyContinue

      # Should NOT print but does
      Write-Warning "c) Ignore: Shows = true & Expected = false" -WarningAction Ignore

      # Should NOT print but does
      Write-Warning "d) 3> redirect `$null: Shows = true & Expected = false" 3> $null

      # Should NOT print but does
      Write-Warning "e) 3> redirect file: Shows = true & Expected = false" 3> out.txt

[rishabhmalikMS]

Why This Happens

1. Write-Warning Behavior:
   o The -WarningAction parameter is command-specific and determines how the warning is handled at the time it is generated (e.g., displayed, suppressed).
   o However, this parameter is not stored in the WarningRecord object that represents the warning.
2. WarningRecord Object:
   o When a warning is generated, it is represented as a System.Management.Automation.WarningRecord object.
   o This object contains properties like:
   • Message: The warning message.
   • InvocationInfo: Information about the command that generated the warning which does not have warningAction related details.
   o Missing Information: The WarningRecord does not include any details about the -WarningAction parameter or how the warning was handled.
3. Observable Collection:
   o When warnings are captured using -WarningVariable and stored in an observable collection, only the WarningRecord objects are stored.
   o Since the WarningRecord does not include -WarningAction, it is impossible to determine the action that was passed to Write-Warning.

Implications
• You cannot directly determine the -WarningAction value that was passed to Write-Warning by inspecting the WarningRecord object.
• This limitation makes it not feasible to display warning in conditional manner