Add support for Notebooks to LSP

[dbaeumer]

Notebooks are getting more and more popular. We should investigate if we can provide first class support for notebooks in LSP.

A first possible draft can be found here: https://github.com/microsoft/vscode-languageserver-node/blob/78ee13a4bafdd831411dd3fb66c8083d3c8ca9b1/protocol/src/common/proposed.notebooks.md#L1

[rchiodo]

LGTM.

[michaelmesser]

Will servers be notified when a cell is evaluated?

[dbaeumer]

@michaelmesser We discussed this and it is not part of the current proposal. But I think it would be easy to add if clients support it.

[chrisjsewell]

Heya, thanks for the added support!

It's all great, except I've had one issue, in https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#notebookDocument_synchronization:

Cell text documents have an URI however servers should not rely on any format for this URI

Is there something we can do about this?

The use case is that,
many language servers perform some form of analysis on files not opened by the client (e.g. https://github.com/microsoft/pyright on Python module files), then allow these to be referenced in e.g. definition lookups, returning the standard file URI scheme in the Definition data returned to the client.

What if you know the notebook "path+cell index+position range" of a definition, say for an ID in a Markdown cell, and want to return this to the client.
How can you do this in a client-agnostic way?

Happy to open in another issue?

---

On a side note, I can't for the life of me find where in the code base of vscode cell URI is actually computed e.g. vscode-notebook-cell:/path/to/Untitled.ipynb#W2sZmlsZQ%3D%3D?

Obviously the 2 refers to the cell index, and I worked out that ZmlsZQ%3D%3D is actually file (after URL decoding, then base64 encoding) 🤷

---

edit: well at least I found how this is generated: https://github.com/microsoft/vscode/blob/81d2ccccc9c153e088df3f3805f8255d36f82f90/src/vs/workbench/contrib/notebook/common/notebookCommon.ts#L537

but yeh, some form of common, cross-client, schema would be great

[dbaeumer]

@chrisjsewell I see your desire for this, but it would require editors to follow the LSP specification which is very hard to achieve. This is why in LSP we don't enforce URI formats.

I will close the issue since the notebook support got added in 3.17. @chrisjsewell please feel free to open another issue for the URI request.