observe does not work for Y.Map of Y.Arrays

[eberberich]

Checklist

• [x] Are you reporting a bug? Use github issues for bug reports and feature requests. For general questions, please use https://discuss.yjs.dev/
• [x] Try to report your issue in the correct repository. Yjs consists of many modules. When in doubt, report it to https://github.com/yjs/yjs/issues/

Describe the bug

The observe callback for (a) nested Y.Array(s) in a Y.Map is not executed when indexeddb persistence is in place.

To Reproduce

Run the attached minimal example persistence-problem.zip

• npm install
• npm run dev
• Open http://localhost:5173/
  • The div showing the length goes up (the console shows that yArray.observe callback is executed) - with every interval callback in the code
• Uncomment the line // const persistence = new IndexeddbPersistence(dbName, ydoc);
  • Page automatically reloads (vite) - all works as before
  • Reload the page multiple times
  • The yArray starts from an empty array now, instead of adding to the existing array
  • Most of the time the div showing the length is stuck now (you can see in the console, that the callback is NOT called anymore) - sometimes the counting up works - but still: always starts from an empty array

Search in index.js for PROBLEM 1/2/3 to find the code places

Expected behavior

The observe callbacks for the nested arrays work, and the nested arrays do not start from scratch upon page reloads!

Environment Information

• Browser: Firefox 128
• "y-indexeddb": "9.0.12", "yjs": "13.6.18"

• [x] This issue is a blocker for my project.

[eberberich]

Here is a video

https://github.com/user-attachments/assets/c2668655-e1d8-422e-8b73-6334d0fac544

[eberberich]

Any ideas here?

[dmonad]

I looked through the source code of your app (which I normally don't do), and it seems that you are overwriting the data on every load. You register event listeners on Y.Arrays that you overwrite when you enable persistence.