Edited messages appear twice in fulltext search

[S7evinK]

When a message is edited, they appear twice in the results of /search. While Element Web seems to aggregate the results and only returns one results, Element Android returns both. This may be a bit confusing.

IMO, Dendrite should only return the latest message.

The responsible code for this: https://github.com/matrix-org/dendrite/blob/14a6c100977be6484eec419fdc8f496eb27b0677/syncapi/consumers/roomserver.go#L593-L627

We'd need to check if m.relates.to in content contains a rel_type of m.replace and then delete the event_id from the fulltext index before indexing the new event.

[adnull]

Hi! I'd like to take this.

[S7evinK]

Sure, go for it! :)

[S7evinK]

Fixed with #3363.