PR Summary

Fixes #23950.

PR Context

When a native process writes a line to stderr, PowerShell wraps it in an ErrorRecord. Users often want to merge the stdout and stderr streams, at which point they need to convert the ErrorRecord from stderr back to a string. However, before this PR, an ErrorRecord with an empty exception message string stringifies to the name of the exception (System.Management.Automation.RemoteException for this specific scenario), which requires the user to use various workarounds (e.g. grabbing .Exception.Message manually) to get the original string.

Reproduction:

$(try {throw ""} catch {$_}) | % {"$_"} # System.Management.Automation.RuntimeException

This PR makes .ToString() behave consistently even for empty exception messages, so just running .ToString() on items from stderr should be enough to get back the original strings. While this is technically a breaking change, I'm pretty sure it falls into bucket 3 (unlikely gray area).

PR Checklist

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• Breaking changes
  • None
  • OR
  • Experimental feature(s) needed
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• User-facing changes
  • Not Applicable
  • OR
  • Documentation needed
    - [ ] Issue filed:
• 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.
  • OR
  • I have considered the user experience from a tooling perspective and opened an issue in the relevant tool repository. This may include:
    • Impact on PowerShell Editor Services which is used in the PowerShell extension for VSCode
      (which runs in a different PS Host).
      • Issue filed:
    • Impact on Completions (both in the console and in editors) - one of PowerShell's most powerful features.
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    • Impact on PSScriptAnalyzer (which provides linting & formatting in the editor extensions).
      • Issue filed:
    • Impact on EditorSyntax (which provides syntax highlighting with in VSCode, GitHub, and many other editors).
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