PR Summary

Fix #15651

PowerShell automatically adds 'Out-Default -Transcript' to the end of pipeline when it's transcribing and invoked via API. When -Transcript is specified, objects passed through are transcribed but are not passed ahead to the host.

The PowerShell sub-kernel actually already adds Out-Default to pass output to host, however, we have to use Out-Default2 as the name due to a limitation in the native command processor. Since we are using Out-Default2, PowerShell believes it doesn't have the Out-Default command at the end, and thus adds Out-Default -Transcript automatically, which prevents sending anything to the host and hence you don't see output from PowerShell sub-kernel when the transcription is turned on.

This needs to be fixed in the InvokeHelper() method, to not just check for the Out-Default name, but also check whether the ImplementingType is typeof(OutDefaultCommand).

This PR also refactors the code a bit, to calculate needToAddOutDefault only if PowerShell is transcribing.

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 and is not Work in Progress.
  • If the PR is work in progress, please add the prefix WIP: or [ WIP ] to the beginning of the title (the WIP bot will keep its status check at Pending while the prefix is present) and remove the prefix when the PR is ready.
• Breaking changes
  • None
  • OR
  • Experimental feature(s) needed
    • Experimental feature name(s):
• User-facing changes
  • Not Applicable
  • OR
  • Documentation needed
    • Issue filed:
• 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
• Tooling
  • I have considered the user experience from a tooling perspective and don't believe tooling will be impacted.