[Bug]: Duplicate "entangled" collaboration cursors in Yjs fragments across parent doc & sibling subdocs

[ideosyncretic]

Affected Packages

extension-collaboration-cursor, extension-collaboration, react

Version(s)

2.4.0

Bug Description

When using Liveblocks and Yjs subdocuments, TipTap collaboration cursors on fragments become duplicated (appearing in other fragments) and "entangled" (moving in tandem) across the parent Y.Doc and sibling subdocs, depending on the length of fragment content.

cursor.bug.2.screens.mp4

Browser Used

Chrome

Code Example URL

https://github.com/ideosyncretic/liveblocks-tiptap-yjs-subdocs-collabcursor

Expected Behavior

Collaboration cursor state should not sync to unrelated fragments.

Additional Context (Optional)

• The issue persists with different Y.Doc shapes, whether the fragments are top-level types or in nested Y.Maps.
• The attached code example is a Kanban board where the project Board is the parent Y.Doc, Lists are subdocs.
  • 
• We have only tested this with Liveblocks as Yjs provider, because other providers do not support subdocuments.

Dependency Updates

• Yes, I've updated all my dependencies.

[andrictham]

I went spelunking through the source code for extension-collaboration-cursor, and the origin of this bug seems to be y-prosemirror’s cursor plugin, which doesn’t support subdocuments, and has a broken implementation for cursorStateField.

Here is a related issue reported in that repo: yjs/y-prosemirror#86

And a stale PR which fixes it, but wasn’t yet merged: yjs/y-prosemirror#86

When this issue is resolved in y-prosemirror, then extension-collaboration-cursor needs to expose cursorStateField as an option so the user can configure it, and pass in the guid of the related subdoc.

This should then resolve the issue.

Edit: I filed a PR to y-prosemirror here: yjs/y-prosemirror#159. Once this is merged, it should be possible to update extension-collaboration-cursor to expose the cursorStateField, and anyone who uses subdocuments can use it to properly namespace cursors by their subdoc’s guid.