vscode.dev cell languages not working properly

[alyssajotice]

Version: 1.64.2
Commit: f80445a
Date: 2022-02-09T22:00:24.333Z
Browser: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/98.0.4758.80 Safari/537.36 Edg/98.0.1108.50
OS Version: Windows 11

I am working on Live Share notebook support in vscode.dev. Notebook cell language modes are not working properly on web. When the guest opens a cell, the language identifier is displayed rather than the language itself. No language services are present and the cell is not able to be run. Changing the cell to a built-in language type solves the problem. We do not have this issue on the desktop client.

This gif shows the language showing up as the incorrect name and not being able to run it. The host is able to run the cell:

This gif shows that when you change the language to CSS, the cell becomes enabled and you can run it:

When the guest opens the notebook, we return an object that has NotebookData. Each cell in the list has a languageId that would be dotnet-interactive.csharp in this example. How can we get these cell types to show up properly on web?

cc @rebornix

[rebornix]

@alyssajotice I think this happens when there is no such language defined on the guest client/machine, the dotnet-interactive.csharp is contributed by the .NET notebook extension, which is not mirrored in on the guest client. I wonder if we need a plugin model for Live Share, with which the .NET notebook can tell Live Share what language configurations should be synced to the guest.

[alyssajotice]

I see. Why don't we see this issue with the desktop extension?

[roblourens]

I'm assuming the .NET interactive extension is not installed in the browser, because it's not web enabled. So to get the same behavior, Live Share would have to contribute this language configuration in a browser client, that's what @rebornix is suggesting. Or it would be even better if the .NET interactive extension could be installed in a browser.

[alyssajotice]

Thanks @roblourens. I will see if .NET has plans to be browser-friendly any time soon. Can you explain more how I could contribute the language configuration?

[roblourens]

Not a notebook-specific concept - what happens when a host opens a file with some custom language from an extension, and the guest does not have that language extension installed?

[alyssajotice]

We currently do not have this feature. I will update our docs to require both guest and host to have the custom cell extension if they want to join/share. And encourage extensions to have a browser-friendly version. Thank you!