"Ignoring duplicate event" is logged each time the sdk sends an event

[BurnyBoi]

Describe the bug
I have an image bot that sends an image based on user input. I've noticed since updating to a recent matrix-js-sdk that whenever I send an event with the SDK, it logs a line that says EventTimelineSet.addLiveEvent: ignoring duplicate event $event_id, where $event_id is the event sent by the sdk.

To Reproduce
This is the simplified version of the code I am using with matrix-js-sdk 19.3.0 to reproduce the issue:

const sdk = require("matrix-js-sdk");
const matrixcs = require("matrix-js-sdk/lib/matrix");
const request = require('request');
matrixcs.request(request);

const log = require('loglevel');
const { logger} = require('matrix-js-sdk/lib/logger');
logger.setLevel(log.levels.INFO, false);

var myUserId = "@test:matrix.example.com";
var myAccessToken = "syt_token";
var matrixClient = sdk.createClient({
    baseUrl: "https://matrix.example.com",
    accessToken: myAccessToken,
    userId: myUserId
});

matrixClient.on("Room.timeline", function(event, room, toStartOfTimeline) {

	if (event.getType() === "m.room.message" && event.getContent().body.indexOf("!cot") === 0) {
                matrixClient.sendImageMessage(room.roomId, "mxc://matrix.org/SZcQxxckvdxdzbIeiSurDEng", {"mimetype": "image/png"}, "cot.png", null);
        }

});

matrixClient.startClient({initialSyncLimit: 0});

Once running, invite the account to a test room, then send !cot in the room with any other account.

Expected behavior
The "ignoring duplicate event" line shouldn't get logged.

Actual behavior
This is the output I get when sending !cot in the room and having the bot send the image:

$ node ./test.js
EventTimelineSet.addLiveEvent: ignoring duplicate event $-W_XVQn5UotOvWC3F7-gZfaWc5Boim3hI28labr-8ys

Desktop (please complete the following information):

• OS: Arch Linux
• Browser Firefox
• Version 103

[3nprob]

If this is indeed a bug it might be from #2587 (comment) and #2586

[3nprob]

So the currently broken deepCompare is now called in

matrix-js-sdk/src/sync.ts

Line 629 in 209c6a4

filterId = await this.client.getOrCreateFilter(getFilterName(this.client.credentials.userId), filter);

so it looks related indeed.

@t3chguy not sure why you were removed as reviewer on #2586 as it concerns code you were directly calling there as mentioned in this comment prior to #2587 being merged.

(Aside but I find it kind of wild that this underlying bug has been unnoticed for >6y and I only discovered it by chance when browsing the code, filing the bug and fix 23 minutes before the PR triggering it was opened 🤯 )

[3nprob]

Sorry, realized now you are on v19.3.0, which does not contain the recent changes referred to. If the previous version uses deepCompare in a similar way it could be the same underlying bug - have not confirmed that.

[t3chguy]

@3nprob yes, sync.ts has been using filterId = await this.client.getOrCreateFilter(getFilterName(this.client.credentials.userId), filter); before my recent commits.