Can not delete items from a partykit persisted store

[clentfort]

Describe the bug

When using the partykit persister deletes are not written to the persisted database. Delete items reappear after a reconnect. See also this Discord message with a repo h

I have modified my partykit server to inspect the log messages like so

import { TinyBasePartyKitServer } from 'tinybase/persisters/persister-partykit-server';

export default class PartyKitServer extends TinyBasePartyKitServer {
	async onMessage(
		...params: Parameters<TinyBasePartyKitServer['onMessage']>
	): Promise<void> {
		console.log('onMessage', params[0]);
		return super.onMessage(...params);
	}

	async onRequest(
		...params: Parameters<TinyBasePartyKitServer['onRequest']>
	): Promise<ReturnType<TinyBasePartyKitServer['onRequest']>> {
		console.log('onRequest', params[0]);
		return super.onRequest(...params);
	}
}

When creating/deleting items I see the following in my partykit server logs.

// After add
onMessage s[{"feeding-sessions":{"1767445910545":{"durationInSeconds":2,"endTime":"2026-01-03T13:11:52.395Z"}}},{},1]
// After a delete
onMessage s[{"feeding-sessions":{}},{},1]

I did not

(Nevermind the stupid data schema please)

Your Example Website or App

https://discord.com/channels/1027918215323590676/1057696796404629720/1285757436803813416

Steps to Reproduce the Bug or Issue

No response

Expected behavior

Items are removed from the partykit store

Screenshots or Videos

No response

Platform

tinybase 7.3.1

Additional context

No response

[clentfort]

I tried downgrading all the way to v5 (couldnt try v4 with my apps code as the API has changed between v4 and v5 so that it would no longer build). Even in v5 the deleting did not work.

[clentfort]

Did some more digging by stepping through with a debugger on the client site:

When sending the data to partykit via https://github.com/tinyplex/tinybase/blob/main/src/persisters/persister-partykit-client/index.ts#L65 changes looks something like this

Array(3) [ {…}, {}, 1 ]
  0: Object { "feeding-sessions": {…} }
    "feeding-sessions": Object { 1767445910545: undefined }
    <prototype>: Object { … }
  1: Object {  }
  2: 1
  length: 3
  <prototype>: Array []

The culprit is 1767445910545: undefined. The message is constructed via construct, which internally calls JSON.stringify. JSON.stringify drops any property that is undefined. So the message we are sending is basically empty.

I dont know the project well enough to know the appropriate fix. The easiest would probably to set a magic value or simply null where undefined is used now. While debugging I tried replacing the undefined with null before serializing the message and that did not delete the item.

and sorry for braindumping all this in this issue, hope it's helpful