Send both updated and outdated fields on gateway 'message update' events

[MrAugu]

Now, I know that this suggestion would be a burden to implement on discord, but hear me out:

Currently if discord bots want to listen for update events and also do an action with the old information they have to cache all of the old information themselves. This is not an issue for user update, guild update, member update, channel update, thread update because that information is already cached anyway as it's required for operational purposes and the amount of those objects is pale by comparison to the message objects. If, for example, bots want to listen for changes in messages: say for a log, or other purposes - they need to cache those messages in memory in case of a possible update, this is extremely unfeasible because:

• in a single channel there could be thousands of messages in a channel in a short interval of time and therefore we have to limit the amount of messages to cache in a single channel if you don't want your resource usage to skyrocket really quickly
• once the bot reboots for maintenance or applying updates all of the messages sent previous to the shard's ready state are gone because the old objects are not present in the empty/very recent cache and cannot determine what was changed within the object

Therefore, 'range of sight' for being able to determine changes in a message is extremely limited up the last few hundred send in a channel after the bot last restarted; this suggestion would allow us to save a lot of resources by being able to drop the message cache; and this would be an amazing thing.

To be noted that I'm fully aware of the implications of this feature request: it would be more costly on the discord side; it would create an inconsistency in the gateway update event model that we see thought the API and it would slightly increase the message update event payload size.

[Capt-Brunch]

This can all be handled by the bot itself with better cache management, though. I'd argue that actions occuring on the message update event that require the previous version of that message are absurdly rare. So, you're asking Discord to re-engineer a process in a very costly way, to use up additional bandwidth for everyone to basically double the size of all message update events received, for something that serves a very limited purpose and can already be handled by better cache management on the side of bots that actually need these functions.

[MinnDevelopment]

additional bandwidth for everyone

This is untrue since message intents they will not contain any user data, and you can simply turn the events off. It is almost impossible to handle message updates with cache if your bot just started and has an empty cache, you also cannot expect bots to keep track of all messages ever sent in a server. Your "cache management" solution is unfeasible in a lot of cases that you don't seem to consider.

[SinisterRectus]

To clarify, is this about receiving the message object before it was updated or receiving a full message object on MESSAGE_UPDATE?

[MrAugu]

It's about both receiving the message object/partial message object with the contents before it was updated; and a message object/partial message object with the contents after they were updated in the same event's payload. At most, only the old fields that were updated would even need to be sent.

[Myst82015]

I can only agree with MrAugu on that topic. It definitly makes more sense this way even if it means an increased payload size.

Another possible solution in my opinion is (like Augu mentioned above) to only receive the modified fields of the old message so you can compare it to the new message. This would result in a lower payload size so Discord would also be satisfied :) .

Using partials doesn't help since you need to fetch the message and since the messageId of oldMessage and newMessage are the same you only fetch the new one which makes the logging system obsolete.

[kaplego]

The server sould do this:

• Store temporary the old message
• Edit the message
• If the message was edited:
  Send the event with (old message, new message)
• Delete old message

[MrAugu]

[NovaFox161]

Discord does not, and likely never will send old data. It is up to the library/bot to implement a runtime cache to handle old data. Several libraries already do this and if the bot is online and has the old data cached, it can be referenced.

And at discord's scale and due to eventual consistency, this would fall apart and lead to progressively inaccurate past states being sent depending on which server happens to process the update and if there were updates before that one.
If someone edits a message twice very quickly, it's entirely possible 2 different servers would get that update before sending it out to the gateway, meaning they'd be sending out the same previous state.

Unrelated: bumping a 5 day old thread is bad etiquette.