This has been happening for over a year.

• Every letter typed filters the completion list and so the list control is re-filled
• When doing so, the variable tracking the current focused item is reset here
• Due to this, the code to smartly skip re-rendering the focused item is never reached.
  https://github.com/Microsoft/vscode/blob/622eab8bebbe5a7b228cf890fc3ca1665a49bcf1/src/vs/editor/contrib/suggest/suggestWidget.ts#L581-L583

The root cause, is that the variable tracking the current focused item is reset. This was done in a35c7da. @joaomoreno Do you recall the reason for this change?

I would suggest the fix to be ac12c69, but am not sure if we should take this for April

My commit message and related issue #23408 seem to be very helpful. I can't even imagine how broken it was 🐛

Serious now: I'm not sure. The suggest widget used to narrow down suggestions by itself, without asking the provider to narrow down, except if the provider returns an incomplete result. I can only reason that in that case, showSuggestions would only be called on the initial population of results; while further "narrow downs" wouldn't pass through that code pass. It seems that even narrowing down now uses showSuggestions, so that assumption is misleading.

@jrieken thoughts?

Don't reset the item when it's the same completion model?

That works. Pushing this to May as there is no visible user impact of this issue.

Don't reset the item when it's the same completion model?

The completion model differs for each keystroke if there is a completion provider giving result of the incomplete kind. So checking the completion model doesn't always work

Pushed another fix 2e0a564 which doesn't rely on the completion model.

Moving this bug for June for another round of verification.