Excess re-rendering causes waiting times after cell completion

[Happypig375]

Describe the bug

for (var i = 0; i <= 100; i++) System.Console.WriteLine(i);

It is expected that such a small number of console writes would complete instantly. Indeed it does, however, excess re-rendering takes place immediately afterwards, costing additional seconds. This waiting time grows with the number of console writes, which is undesirable especially when used inside a loop.

It seems that a render function is called every time console output changes. It would probably be a lot faster if it buffered the output and just rendered it when the end of the cell is reached.

Please complete the following:

Which version of .NET Interactive are you using? (In a notebook, run the #!about magic command. ):

• OS
  • [ ] Windows 11
  • [x] Windows 10
  • [ ] macOS
  • [ ] Linux (Please specify distro)
  • [ ] iOS
  • [ ] Android
• Frontend
  • [ ] Jupyter Notebook
  • [ ] Jupyter Lab
  • [ ] nteract
  • [x] Visual Studio Code
  • [ ] Visual Studio Code Insiders
  • [ ] Visual Studio
  • [ ] Other (please specify)

[Happypig375]

This is the .dib file equivalent to https://github.com/dotnet/interactive/issues/1832. This issue has been fixed months ago, but the issue still persists.

[bisen2]

For the solution of buffering output and only rendering at the end, it would probably need to be an opt-in feature to avoid breaking code that may rely on having output written before the cell is done:

printfn "Beginning long computation"
let result = longComputation()
printfn "Done"

Maybe a magic command would be a good way to say that you want a specific cell to only render once at the end?

[jonsequitur]

This bug isn't related to the file format. The root cause is different from #1832. This appears to be due to a change in VS Code rendering but we haven't pinned it down yet.

@brettfo