348 lines
13 KiB
Python
348 lines
13 KiB
Python
# Copyright 2014-2016 OpenMarket Ltd
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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from typing import TYPE_CHECKING, Optional, Union
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import attr
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from frozendict import frozendict
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from synapse.appservice import ApplicationService
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from synapse.events import EventBase
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from synapse.logging.context import make_deferred_yieldable, run_in_background
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from synapse.types import StateMap
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if TYPE_CHECKING:
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from synapse.storage.databases.main import DataStore
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@attr.s(slots=True)
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class EventContext:
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"""
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Holds information relevant to persisting an event
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Attributes:
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rejected: A rejection reason if the event was rejected, else False
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_state_group: The ID of the state group for this event. Note that state events
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are persisted with a state group which includes the new event, so this is
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effectively the state *after* the event in question.
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For a *rejected* state event, where the state of the rejected event is
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ignored, this state_group should never make it into the
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event_to_state_groups table. Indeed, inspecting this value for a rejected
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state event is almost certainly incorrect.
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For an outlier, where we don't have the state at the event, this will be
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None.
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Note that this is a private attribute: it should be accessed via
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the ``state_group`` property.
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state_group_before_event: The ID of the state group representing the state
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of the room before this event.
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If this is a non-state event, this will be the same as ``state_group``. If
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it's a state event, it will be the same as ``prev_group``.
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If ``state_group`` is None (ie, the event is an outlier),
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``state_group_before_event`` will always also be ``None``.
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prev_group: If it is known, ``state_group``'s prev_group. Note that this being
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None does not necessarily mean that ``state_group`` does not have
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a prev_group!
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If the event is a state event, this is normally the same as ``prev_group``.
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If ``state_group`` is None (ie, the event is an outlier), ``prev_group``
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will always also be ``None``.
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Note that this *not* (necessarily) the state group associated with
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``_prev_state_ids``.
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delta_ids: If ``prev_group`` is not None, the state delta between ``prev_group``
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and ``state_group``.
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app_service: If this event is being sent by a (local) application service, that
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app service.
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_current_state_ids: The room state map, including this event - ie, the state
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in ``state_group``.
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(type, state_key) -> event_id
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FIXME: what is this for an outlier? it seems ill-defined. It seems like
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it could be either {}, or the state we were given by the remote
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server, depending on $THINGS
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Note that this is a private attribute: it should be accessed via
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``get_current_state_ids``. _AsyncEventContext impl calculates this
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on-demand: it will be None until that happens.
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_prev_state_ids: The room state map, excluding this event - ie, the state
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in ``state_group_before_event``. For a non-state
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event, this will be the same as _current_state_events.
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Note that it is a completely different thing to prev_group!
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(type, state_key) -> event_id
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FIXME: again, what is this for an outlier?
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As with _current_state_ids, this is a private attribute. It should be
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accessed via get_prev_state_ids.
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"""
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rejected = attr.ib(default=False, type=Union[bool, str])
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_state_group = attr.ib(default=None, type=Optional[int])
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state_group_before_event = attr.ib(default=None, type=Optional[int])
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prev_group = attr.ib(default=None, type=Optional[int])
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delta_ids = attr.ib(default=None, type=Optional[StateMap[str]])
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app_service = attr.ib(default=None, type=Optional[ApplicationService])
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_current_state_ids = attr.ib(default=None, type=Optional[StateMap[str]])
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_prev_state_ids = attr.ib(default=None, type=Optional[StateMap[str]])
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@staticmethod
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def with_state(
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state_group,
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state_group_before_event,
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current_state_ids,
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prev_state_ids,
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prev_group=None,
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delta_ids=None,
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):
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return EventContext(
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current_state_ids=current_state_ids,
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prev_state_ids=prev_state_ids,
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state_group=state_group,
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state_group_before_event=state_group_before_event,
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prev_group=prev_group,
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delta_ids=delta_ids,
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)
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async def serialize(self, event: EventBase, store: "DataStore") -> dict:
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"""Converts self to a type that can be serialized as JSON, and then
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deserialized by `deserialize`
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Args:
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event (FrozenEvent): The event that this context relates to
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Returns:
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dict
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"""
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# We don't serialize the full state dicts, instead they get pulled out
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# of the DB on the other side. However, the other side can't figure out
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# the prev_state_ids, so if we're a state event we include the event
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# id that we replaced in the state.
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if event.is_state():
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prev_state_ids = await self.get_prev_state_ids()
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prev_state_id = prev_state_ids.get((event.type, event.state_key))
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else:
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prev_state_id = None
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return {
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"prev_state_id": prev_state_id,
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"event_type": event.type,
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"event_state_key": event.state_key if event.is_state() else None,
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"state_group": self._state_group,
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"state_group_before_event": self.state_group_before_event,
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"rejected": self.rejected,
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"prev_group": self.prev_group,
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"delta_ids": _encode_state_dict(self.delta_ids),
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"app_service_id": self.app_service.id if self.app_service else None,
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}
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@staticmethod
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def deserialize(storage, input):
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"""Converts a dict that was produced by `serialize` back into a
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EventContext.
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Args:
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storage (Storage): Used to convert AS ID to AS object and fetch
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state.
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input (dict): A dict produced by `serialize`
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Returns:
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EventContext
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"""
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context = _AsyncEventContextImpl(
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# We use the state_group and prev_state_id stuff to pull the
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# current_state_ids out of the DB and construct prev_state_ids.
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storage=storage,
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prev_state_id=input["prev_state_id"],
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event_type=input["event_type"],
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event_state_key=input["event_state_key"],
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state_group=input["state_group"],
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state_group_before_event=input["state_group_before_event"],
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prev_group=input["prev_group"],
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delta_ids=_decode_state_dict(input["delta_ids"]),
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rejected=input["rejected"],
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)
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app_service_id = input["app_service_id"]
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if app_service_id:
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context.app_service = storage.main.get_app_service_by_id(app_service_id)
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return context
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@property
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def state_group(self) -> Optional[int]:
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"""The ID of the state group for this event.
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Note that state events are persisted with a state group which includes the new
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event, so this is effectively the state *after* the event in question.
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For an outlier, where we don't have the state at the event, this will be None.
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It is an error to access this for a rejected event, since rejected state should
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not make it into the room state. Accessing this property will raise an exception
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if ``rejected`` is set.
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"""
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if self.rejected:
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raise RuntimeError("Attempt to access state_group of rejected event")
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return self._state_group
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async def get_current_state_ids(self) -> Optional[StateMap[str]]:
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"""
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Gets the room state map, including this event - ie, the state in ``state_group``
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It is an error to access this for a rejected event, since rejected state should
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not make it into the room state. This method will raise an exception if
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``rejected`` is set.
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Returns:
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Returns None if state_group is None, which happens when the associated
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event is an outlier.
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Maps a (type, state_key) to the event ID of the state event matching
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this tuple.
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"""
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if self.rejected:
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raise RuntimeError("Attempt to access state_ids of rejected event")
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await self._ensure_fetched()
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return self._current_state_ids
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async def get_prev_state_ids(self):
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"""
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Gets the room state map, excluding this event.
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For a non-state event, this will be the same as get_current_state_ids().
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Returns:
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dict[(str, str), str]|None: Returns None if state_group
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is None, which happens when the associated event is an outlier.
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Maps a (type, state_key) to the event ID of the state event matching
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this tuple.
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"""
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await self._ensure_fetched()
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return self._prev_state_ids
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def get_cached_current_state_ids(self):
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"""Gets the current state IDs if we have them already cached.
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It is an error to access this for a rejected event, since rejected state should
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not make it into the room state. This method will raise an exception if
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``rejected`` is set.
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Returns:
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dict[(str, str), str]|None: Returns None if we haven't cached the
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state or if state_group is None, which happens when the associated
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event is an outlier.
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"""
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if self.rejected:
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raise RuntimeError("Attempt to access state_ids of rejected event")
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return self._current_state_ids
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async def _ensure_fetched(self):
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return None
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@attr.s(slots=True)
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class _AsyncEventContextImpl(EventContext):
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"""
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An implementation of EventContext which fetches _current_state_ids and
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_prev_state_ids from the database on demand.
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Attributes:
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_storage (Storage)
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_fetching_state_deferred (Deferred|None): Resolves when *_state_ids have
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been calculated. None if we haven't started calculating yet
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_event_type (str): The type of the event the context is associated with.
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_event_state_key (str): The state_key of the event the context is
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associated with.
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_prev_state_id (str|None): If the event associated with the context is
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a state event, then `_prev_state_id` is the event_id of the state
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that was replaced.
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"""
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# This needs to have a default as we're inheriting
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_storage = attr.ib(default=None)
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_prev_state_id = attr.ib(default=None)
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_event_type = attr.ib(default=None)
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_event_state_key = attr.ib(default=None)
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_fetching_state_deferred = attr.ib(default=None)
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async def _ensure_fetched(self):
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if not self._fetching_state_deferred:
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self._fetching_state_deferred = run_in_background(self._fill_out_state)
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return await make_deferred_yieldable(self._fetching_state_deferred)
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async def _fill_out_state(self):
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"""Called to populate the _current_state_ids and _prev_state_ids
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attributes by loading from the database.
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"""
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if self.state_group is None:
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return
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self._current_state_ids = await self._storage.state.get_state_ids_for_group(
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self.state_group
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)
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if self._event_state_key is not None:
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self._prev_state_ids = dict(self._current_state_ids)
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key = (self._event_type, self._event_state_key)
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if self._prev_state_id:
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self._prev_state_ids[key] = self._prev_state_id
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else:
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self._prev_state_ids.pop(key, None)
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else:
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self._prev_state_ids = self._current_state_ids
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def _encode_state_dict(state_dict):
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"""Since dicts of (type, state_key) -> event_id cannot be serialized in
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JSON we need to convert them to a form that can.
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"""
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if state_dict is None:
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return None
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return [(etype, state_key, v) for (etype, state_key), v in state_dict.items()]
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def _decode_state_dict(input):
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"""Decodes a state dict encoded using `_encode_state_dict` above"""
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if input is None:
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return None
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return frozendict({(etype, state_key): v for etype, state_key, v in input})
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