Since Synapse 1.76.0, any module which registers a `on_new_event`
callback would brick the ability to join remote rooms.
This is because this callback tried to get the full state of the room,
which would end up in a deadlock.
Related:
https://github.com/matrix-org/synapse-auto-accept-invite/issues/18
The following module would brick the ability to join remote rooms:
```python
from typing import Any, Dict, Literal, Union
import logging
from synapse.module_api import ModuleApi, EventBase
logger = logging.getLogger(__name__)
class MyModule:
def __init__(self, config: None, api: ModuleApi):
self._api = api
self._config = config
self._api.register_third_party_rules_callbacks(
on_new_event=self.on_new_event,
)
async def on_new_event(self, event: EventBase, _state_map: Any) -> None:
logger.info(f"Received new event: {event}")
@staticmethod
def parse_config(_config: Dict[str, Any]) -> None:
return None
```
This is technically a breaking change, as we are now passing partial
state on the `on_new_event` callback.
However, this callback was broken for federated rooms since 1.76.0, and
local rooms have full state anyway, so it's unlikely that it would
change anything.
