Polyglot VSCode thinks F# notebooks generated by FSharp.Formatting are C# notebooks

Describe the bug

1. This is probably the same issue as #2289, and it breaks all documentation notebooks previously created by F# Formatting.
2. For new F# notebooks, I can do a PR to update the F# Formatting library to generate F# notebooks with the metadata that the Polyglot notebooks extension wants. What metadata should we add?

Details follow:

The F# Formatting Library generates .NET interactive notebooks. The VSCode extension previously recognized the code cells as F#, but now the polyglot extension converts them to C#. As far as I can tell it’s necessary to manually go through every cell and change it to F# (not practical). This breaks all documentation notebooks previously created by F# Formatting.

For example, the extension now thinks the F# code in this notebook from the F# Data Library is C# code:

Regarding metadata … A simple notebook generated by the F# formatting tool looks like this below in json and is what used to work with the old VSCode extension.

        {
            "cells": [
          {
           "cell_type": "code",
           "metadata": {},
            "execution_count": 1, "outputs": [],
           "source": ["let x = 100\n"]
          }
,
          {
           "cell_type": "code",
           "metadata": {},
            "execution_count": 2, "outputs": [],
           "source": ["let y = 100\n"]
          }],
            "metadata": {
            "kernelspec": {"display_name": ".NET (F#)", "language": "F#", "name": ".net-fsharp"},
            "langauge_info": {
        "file_extension": ".fs",
        "mimetype": "text/x-fsharp",
        "name": "C#",
        "pygments_lexer": "fsharp",
        "version": "4.5"
        }
        },
            "nbformat": 4,
            "nbformat_minor": 1
        }

From experimentation, it looks like if we change "metadata": {} in code cells to what I have here then the cells are recognized as being F# code. Is this correct, is there anything else that you suggest?

 "metadata": {
    "dotnet_interactive": {
     "language": "fsharp"
    },
    "polyglot_notebook": {
     "kernelName": "fsharp"
    }
   }

Please complete the following:

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

.NET Interactive Version: 1.0.360602+9bf026dabac44a6256a65168fa93dcb7e2edcca4 Library version: 1.0.0-beta.22606.2+9bf026dabac44a6256a65168fa93dcb7e2edcca4 Build date: 2023-01-31T11:33:36.0115292Z

Screenshots

If applicable, add screenshots to help explain your problem.

[brettfo]

@nhirschey we published a new extension to our insiders channel, can you give it a shot to see if it fixes this issue? You’ll need to install VS Code - Insiders and then install the extension like normal, it should automatically pick up the correct version, which should be 1.0.4108061.

[nhirschey]

@brettfo yes I checked docs from a few repos and it’s fixed in the insiders version of VS Code. Thank you!