Generate OnIdle event only if the editing buffer is empty

[daxian-dbw]

PR Summary

Generate OnIdle event only if the editing buffer is empty. But if there is any other event subscribers, we still run the dummy pipeline to allow potential event handling.

OnIdle event by definition is not an event that need urgent processing, and sometimes it's used by module/script to output a message, e.g. Az.Predictor uses it to write out a ask-for-survey message. Having this event to fire when the user already input something in the buffer is not a good experience for the user. See the following screenshot as an example.

With this PR, we generate the OnIdle event only if the editing buffer is empty. But for any other event subscribers, we still run the dummy pipeline to allow potential event processing for them even if the editing buffer is not empty.

PR Checklist

• PR has a meaningful title
  • Use the present tense and imperative mood when describing your changes
• Summarized changes
• Make sure you've added one or more new tests
• Make sure you've tested these changes in terminals that PowerShell is commonly used in (i.e. conhost.exe, Windows Terminal, Visual Studio Code Integrated Terminal, etc.)
• User-facing changes
  • Not Applicable
  • OR
  • Documentation needed at PowerShell-Docs
    • Doc Issue filed: PSReadLine: OnIdle event is fired only when the editing buffer is empty MicrosoftDocs/PowerShell-Docs#8270

Microsoft Reviewers: Open in CodeFlow

[ghost]

🎉 v2.2.0-beta4 has been released which incorporates this pull request. 🎉

[lzybkr]

I understand the issue you are trying to address, I'm not sure this is the right fix. For example, without PSReadLine, the experience is still ugly.

I think it'd be better to find a better solution than using OnIdle for any sort of UI experience.

[daxian-dbw]

Right, totally agree that using OnIdle event for UI experience is far from desired. The good news is that Az.Predictor depends on PSReadLine to work :)

[lzybkr]

Fine, but this change will probably affect people not using Az.Predictor. People will randomly see their OnIdle events not firing and not understand the root cause, or waste a lot of time tracking down it down.

[daxian-dbw]

Yes, that's absolutely possible. But I think the impact should be quite low, as OnIdle event will be fired when there's a timeout and the buffer is empty, and that situation happens a lot. I will keep an eye on the feedback, and I can revert this change if there is a scenario that got blocked by this change.

[daxian-dbw]

I also opened the doc issue MicrosoftDocs/PowerShell-Docs#8270 to have this behavior documented (not now, but I will submit a doc PR after a while if there is no feedback about this change).

[lzybkr]

I would also mention it as a low risk breaking change in the release notes for better visibility.

[daxian-dbw]

Done, updated the GitHub release page: https://github.com/PowerShell/PSReadLine/releases/tag/v2.2.0-beta4