Reactions sometimes counted multiple times in the buttons below messages

[jryans]

Not sure of the cause yet, but I have seen (and others have reported) that reactions can be counted twice in the row of buttons below a message.

There are not duplicate reaction events in the timeline when this happens. Refreshing Riot makes the problem go away. Somehow, the Relations structure for the event ends up with several copies of seemingly the same event.

It be best to have a clear reproduction case... Without that, the best I can imagine is just strengthening Relations to ignore events with the same ID as one it already has... It would still be best to understand what's actually going wrong.

[anoadragon453]

Issue with screenshot and rageshake: #11710

[ara4n]

I'm pretty sure this is because of https://github.com/matrix-org/matrix-doc/pull/1849/files#diff-07b4d0d635f906073d643f758ae283bdR194.

[tredondo]

@jryans: I could reliably reproduce reacting twice with the same emoji to a given message in #13586. Not sure if that is a dupe of this issue, but @turt2live seems to believe so.

[jryans]

@jryans: I could reliably reproduce reacting twice with the same emoji to a given message in #13586. Not sure if that is a dupe of this issue, but @turt2live seems to believe so.

Looks like that's in fact a separate issue with different emoji character sequences. In any case, thanks for reporting.

[bwindels]

Given that at the time of writing, element web aggregates reactions completely client-side, this must be a client bug. Events in https://github.com/matrix-org/matrix-js-sdk/blob/develop/src/models/relations.js are deduplicated by using a Set, which compares object references to determine identity. So if somehow a reaction snuck in and wasn't deduplicated with an event object we already know about, this could easily happen.