PR Summary

This fixes a possible race condition during abrupt (Ctrl+C) stop of foreach -parallel, where a powerShell object does not get disposed.

PR Context

The powershell.dispose() method is not thread safe and so we prevent it from being called twice during an asynchronous stop command (Ctrl+C). This change add an extra condition to allow a normally completing thread to dispose a powershell object after stop has been commanded.

PR Checklist

• PR has a meaningful title
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• Summarized changes
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• This PR is ready to merge and is not Work in Progress.
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• Breaking changes
  • None
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  • Experimental feature(s) needed
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• User-facing changes
  • Not Applicable
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  • Documentation needed
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• Testing - New and feature
  • N/A or can only be tested interactively
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  • Make sure you've added a new test if existing tests do not effectively test the code changed
• Tooling
  • I have considered the user experience from a tooling perspective and don't believe tooling will be impacted.
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  • I have considered the user experience from a tooling perspective and enumerated concerns in the summary. This may include:
    • Impact on PowerShell Editor Services which is used in the PowerShell extension for VSCode (which runs in a different PS Host).
    • Impact on Completions (both in the console and in editors) - one of PowerShell's most powerful features.
    • Impact on PSScriptAnalyzer (which provides linting & formatting in the editor extensions).
    • Impact on EditorSyntax (which provides syntax highlighting with in VSCode, GitHub, and many other editors).