Synapse sends empty `m.push_rules` account_data in initial sync

[t3chguy]

Description

As per title. The spec lists a number of ordered default rules which must be present, and they are via the push rules API but missing in the corresponding account_data event.

Steps to reproduce

• inspect initial sync response

Homeserver

matrix.org

Synapse Version

1.102.0rc1

Installation Method

I don't know

Database

I don't know

Workers

I don't know

Platform

I don't know

Configuration

I don't know

Relevant log output

I don't know

Anything else that would be useful to know?

https://matrix-client.matrix.org/_matrix/client/v3/sync?filter=%7B%22room%22%3A%7B%22timeline%22%3A%7B%22unread_thread_notifications%22%3Atrue%2C%22limit%22%3A20%7D%2C%22state%22%3A%7B%22lazy_load_members%22%3Atrue%7D%7D%7D&timeout=0&_cacheBuster=1709907549083 for anyone wishing to sleuth logs @webdevguru_github:matrix.org

[erikjohnston]

The user in question has m.push_rules set to {} in account_data table. Somehow.

The easiest fix here would be to switch things around so the calculated push rules trump whatever is in account data:

synapse/synapse/handlers/sync.py

Lines 1951 to 1956 in 892cbd0

	global_account_data = {
	AccountDataTypes.PUSH_RULES: await self._push_rules_handler.push_rules_for_user(
	sync_config.user
	),
	**all_global_account_data,
	}

And/or make a background update to delete such entries from account_data.

We should also double check that there is no longer anyway of actually setting m.push_rules account data nowadays.

[erikjohnston]

There are roughly 1.2k users on matrix.org with an m.push_rules account data, most of them have full push rules in them but some have them empty.

c.f. SELECT * FROM account_data WHERE account_data_type = 'm.push_rules';

[erikjohnston]

The easiest fix here would be to switch things around so the calculated push rules trump whatever is in account data

We actually used to do this, but the condition got swapped in matrix-org/synapse#16325, so this is a regression from v1.93.0