Slow OnAutoInsert for brace completion

[gundermanc]

Describe the bug: Typing '\n' in a C# block in Razor results in slow brace completion edits, which can feel somewhat jarring.

Version used: e.g. VS2022 17.2 Preview 3

To reproduce: Steps to reproduce the behavior:

1. Create a new Blazor app
2. Open Index.razor
3. Add a C# block @{}
4. Type some {} inside of the c# block.
5. Press ENTER

Expected behavior: Brace completion completes immediately.

Actual behavior: It seems to consistently take 1-2 seconds. Possib

le dupe of #5617?

[gundermanc]

Related VS language server client protocol issue: https://devdiv.visualstudio.com/DevDiv/_workitems/edit/1488456.

@NTaylorMullen any recommendations on what to do when LS is slow like this?

• Option 1 - cancel if the caret has moved.
• Option 2 - cancel if some timeout elapses (1-2 seconds?)
• Option 3 - apply the edit anyways at the original location
• Option 4 - apply the edit anyways at caret position, but only if it got there via typing.

I'm leaning toward option 4, as scrolling away and seeing the text suddenly change 2-3 seconds later is a bit jarring.

**cc: ** @dibarbet

[dibarbet]

For whatever it is worth, Roslyn perf appears to be acceptable - with a p99.9 of 1.2-1.5s and p90 of 25ms

[NTaylorMullen]

Razor definitely seem to be where the slowdown comes in but nothing like 1-2s. Based on telemetry the worst case scenario averages around 673ms but the 90th percentile is around 180ms. I wouldn't be surprised if it was Razor's formatting perf influencing this

[gundermanc]

nothing like 1-2s

The one other possibility is that our switch to main thread is so low priority it's delayed. I'll look into that..

[allisonchou]

@gundermanc Is there any update on this issue?