Allow opt-out of the named-pipe listener using an environment variable by daxian-dbw · Pull Request #26086

Allow opt-out of the named-pipe listener using an environment variable by daxian-dbw · Pull Request #26086 · PowerShell/PowerShell

PR Summary

Fix #11599

The named-pipe listener is created for all PowerShell instances today (including scenarios where apps host PowerShell). On Linux platforms, this causes the named pipe files left behind uncleaned when PowerShell terminates abruptly.

This PR includes changes to allow opt-out of the named-pipe listener using the environment variable POWERSHELL_DIAGNOSTICS_OPTOUT.

For reference, .NET has the environment variable DOTNET_EnableDiagnostics for disabling the debugger, the profiler, and EventPipe diagnostics (enabled by default).

PR Checklist

PR has a meaningful title
- Use the present tense and imperative mood when describing your changes
Summarized changes
Make sure all .h, .cpp, .cs, .ps1 and .psm1 files have the correct copyright header
This PR is ready to merge. If this PR is a work in progress, please open this as a Draft Pull Request and mark it as Ready to Review when it is ready to merge.
Breaking changes
- None
- OR
- Experimental feature(s) needed
  - Experimental feature name(s):
User-facing changes
- Not Applicable
- OR
- Documentation needed
  - Issue filed: Allow opt-out of the named-pipe listener using the environment variable 'POWERSHELL_DIAGNOSTICS_OPTOUT' MicrosoftDocs/PowerShell-Docs#12403
Testing - New and feature
- N/A or can only be tested interactively
- OR
- Make sure you've added a new test if existing tests do not effectively test the code changed

daxian-dbw added the CL-Engine

Indicates that a PR should be marked as an engine change in the Change Log

label

Sep 23, 2025


		var boolStr = str.AsSpan();

		if (boolStr.Length == 1)

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Could you possibly use SequenceEqual possibly with or without StringComparer.OrdinalIgnoreCase to avoid the individual length and char checks. I assume .NET has all the necessary logic to make that performant and you could make this a lot simpler by doing something like

ReadOnlySpan<char> true1 = ['1'];
ReadOnlySpan<char> trueYes = ['y', 'e', 's'];
ReadOnlySpan<char> trueTrue = ['t', 'r', 'u', 'e'];

// Repeat for false checks

var boolStr = str.AsSpan()
if (boolStr.SequenceEquals(true1, StringComparer.OrdinalIgnoreCase) ||
    boolStr.SequenceEquals(trueYes, StringComparer.OrdinalIgnoreCase ||
    ...)
{
    return true;
}

// Repeat for false checks and default
...

Not sure if stackalloc'ing one big span with all the options and slicing it would be more efficient or not but that's probably in micro-optimising territory.

Edit: Ah I see this has been copied from elsewhere.

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Yes, this is copied from Telemetry.cs. I will keep it as is in this PR as this one will be included in the next preview and the following RC. But I will submit a separate PR to make this optimization change.

/azp run PowerShell-Windows-Packaging-CI, PowerShell-CI-linux-packaging

Azure Pipelines could not run because the pipeline triggers exclude this branch/path.

@iSazonov I guess you clicked the "Update branch" button. There were unrelated test failures after merging the master branch, so I have to revert that (force pushed the original 2 commits again). Please approve again once all CIs pass, thank you!

Oh, sorry! It seems the button is too near to scroll bar.

I restarted CIs and the WindowStyle test fail again. :-(

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LGTM!

/azp run PowerShell-CI-linux-packaging, PowerShell-Windows-Packaging-CI

Azure Pipelines could not run because the pipeline triggers exclude this branch/path.

The failing tests are as following. They are not related to the changes and consistently fail for all CIs starting from 9/26.
I will merge the PR regardless of those 3 failures.

  Describing WindowStyle argument
    [-] -WindowStyle Normal should work on Windows
      Expected exactly 'Normal', but got Hidden.
      1044:             $showCmd | Should -BeExactly $WindowStyle
      at <ScriptBlock>, D:\a\PowerShell\PowerShell\test\powershell\Host\ConsoleHost.Tests.ps1: line 1044
    [-] -WindowStyle Minimized should work on Windows
      Expected exactly 'Minimized', but got Hidden.
      1044:             $showCmd | Should -BeExactly $WindowStyle
      at <ScriptBlock>, D:\a\PowerShell\PowerShell\test\powershell\Host\ConsoleHost.Tests.ps1: line 1044
    [-] -WindowStyle Maximized should work on Windows
      Expected exactly 'Maximized', but got Hidden.
      1044:             $showCmd | Should -BeExactly $WindowStyle
      at <ScriptBlock>, D:\a\PowerShell\PowerShell\test\powershell\Host\ConsoleHost.Tests.ps1: line 1044

[UPDATE] I cannot bypass the policy to merge the PR with failing tests. The 3 tests are disabled now in master branch, and I will rebase the PR against the master branch.

/azp run PowerShell-CI-linux-packaging, PowerShell-Windows-Packaging-CI

Azure Pipelines could not run because the pipeline triggers exclude this branch/path.

Should the new env variable be documented?

SIRMARGIN pushed a commit to SIRMARGIN/PowerShell that referenced this pull request

Dec 12, 2025