Syntax Highlighting for Julia in VS Code not working at all and broken in VS Code Insider

I reported this issue first on Julia discourse here: https://discourse.julialang.org/t/running-julia-jupyter-notebooks-inside-vscode/47421/13?u=manuel_bergmann I am copying this over here:

I am currently on the stable version 1.53.2 of VSCode with Julia 1.5.3 and I have the exact same issues with it as described previously in the thread: Code runs, but no syntax highlighting and also only old UI. Installed versions:

• VSCode (stable) 1.53.2
• Julia (on the system): 1.5.3
• Julia VS extension: 1.1.32
• Jupyter VS extension: v2021.2.603412351
• Platform: Windows 10
• Running: Locally
• Python: 3.8.2

Again, with the current VS Code Insider version this works. Kinda. The syntax highlighting in many cases seems broken, especially string interpolations.

• VSCode (insider) 1.55.0
• Julia (on the system): 1.5.3
• Julia VS extension: 1.1.37
• Jupyter VS extension: v2021.4.641214696
• Platform: Windows 10
• Running: Locally
• Python: 3.8.2

Note the 2pi marked red as well as the syntax highlighting for the string interpolation being broken. All those things work in regular .jl files in VS Code however:

Out of interest I tried the string interpolation in nteract as well and here it was completely broken too (but in a different way):

Am I missing something?

[rchiodo]

I closed and saved the notebook after I set the syntax to Julia for every cell and after reopening it, every cell was set to Python again

This is actually a known issue. This bug here: https://github.com/microsoft/vscode-jupyter/issues/5148

[rchiodo]

I’m going to enter a new issue for this part:

A notebook created with current stable VS Code will integrate the following metadata, regardless of what kernel was used:

 "metadata": {
  "language_info": {
   "codemirror_mode": {
    "name": "ipython",
    "version": 3
   },
   "file_extension": ".py",
   "mimetype": "text/x-python",
   "name": "python",
   "nbconvert_exporter": "python",
   "pygments_lexer": "ipython3",
   "version": 3
  },
  "orig_nbformat": 2,
  "kernelspec": {
   "name": "julia-1.5",
   "display_name": "Julia 1.5.3",
   "language": "julia"
  }
 },

I want to make sure our insiders version is not doing the same thing.