Merge branch 'develop' into babolivier/mark_unread

1 files changed, 203 insertions, 141 deletions

diff --git a/synapse/events/snapshot.py b/synapse/events/snapshot.py
index acbcbeeced..7c5f620d09 100644
--- a/synapse/events/snapshot.py
+++ b/synapse/events/snapshot.py
@@ -12,104 +12,124 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+from typing import Optional, Union
 
 from six import iteritems
 
+import attr
 from frozendict import frozendict
 
 from twisted.internet import defer
 
+from synapse.appservice import ApplicationService
 from synapse.logging.context import make_deferred_yieldable, run_in_background
+from synapse.types import StateMap
 
 
-class EventContext(object):
+@attr.s(slots=True)
+class EventContext:
     """
+    Holds information relevant to persisting an event
+
     Attributes:
-        state_group (int|None): state group id, if the state has been stored
-            as a state group. This is usually only None if e.g. the event is
-            an outlier.
-        rejected (bool|str): A rejection reason if the event was rejected, else
-            False
-
-        push_actions (list[(str, list[object])]): list of (user_id, actions)
-            tuples
-
-        prev_group (int): Previously persisted state group. ``None`` for an
-            outlier.
-        delta_ids (dict[(str, str), str]): Delta from ``prev_group``.
-            (type, state_key) -> event_id. ``None`` for an outlier.
-
-        prev_state_events (?): XXX: is this ever set to anything other than
-            the empty list?
-
-        _current_state_ids (dict[(str, str), str]|None):
-            The current state map including the current event. None if outlier
-            or we haven't fetched the state from DB yet.
-            (type, state_key) -> event_id
+        rejected: A rejection reason if the event was rejected, else False
+
+        _state_group: The ID of the state group for this event. Note that state events
+            are persisted with a state group which includes the new event, so this is
+            effectively the state *after* the event in question.
+
+            For a *rejected* state event, where the state of the rejected event is
+            ignored, this state_group should never make it into the
+            event_to_state_groups table. Indeed, inspecting this value for a rejected
+            state event is almost certainly incorrect.
+
+            For an outlier, where we don't have the state at the event, this will be
+            None.
+
+            Note that this is a private attribute: it should be accessed via
+            the ``state_group`` property.
+
+        state_group_before_event: The ID of the state group representing the state
+            of the room before this event.
+
+            If this is a non-state event, this will be the same as ``state_group``. If
+            it's a state event, it will be the same as ``prev_group``.
+
+            If ``state_group`` is None (ie, the event is an outlier),
+            ``state_group_before_event`` will always also be ``None``.
+
+        prev_group: If it is known, ``state_group``'s prev_group. Note that this being
+            None does not necessarily mean that ``state_group`` does not have
+            a prev_group!
+
+            If the event is a state event, this is normally the same as ``prev_group``.
+
+            If ``state_group`` is None (ie, the event is an outlier), ``prev_group``
+            will always also be ``None``.
+
+            Note that this *not* (necessarily) the state group associated with
+            ``_prev_state_ids``.
+
+        delta_ids: If ``prev_group`` is not None, the state delta between ``prev_group``
+            and ``state_group``.
+
+        app_service: If this event is being sent by a (local) application service, that
+            app service.
+
+        _current_state_ids: The room state map, including this event - ie, the state
+            in ``state_group``.
 
-        _prev_state_ids (dict[(str, str), str]|None):
-            The current state map excluding the current event. None if outlier
-            or we haven't fetched the state from DB yet.
             (type, state_key) -> event_id
 
-        _fetching_state_deferred (Deferred|None): Resolves when *_state_ids have
-            been calculated. None if we haven't started calculating yet
+            FIXME: what is this for an outlier? it seems ill-defined. It seems like
+            it could be either {}, or the state we were given by the remote
+            server, depending on $THINGS
 
-        _event_type (str): The type of the event the context is associated with.
-            Only set when state has not been fetched yet.
+            Note that this is a private attribute: it should be accessed via
+            ``get_current_state_ids``. _AsyncEventContext impl calculates this
+            on-demand: it will be None until that happens.
 
-        _event_state_key (str|None): The state_key of the event the context is
-            associated with. Only set when state has not been fetched yet.
+        _prev_state_ids: The room state map, excluding this event - ie, the state
+            in ``state_group_before_event``. For a non-state
+            event, this will be the same as _current_state_events.
 
-        _prev_state_id (str|None): If the event associated with the context is
-            a state event, then `_prev_state_id` is the event_id of the state
-            that was replaced.
-            Only set when state has not been fetched yet.
-    """
+            Note that it is a completely different thing to prev_group!
 
-    __slots__ = [
-        "state_group",
-        "rejected",
-        "prev_group",
-        "delta_ids",
-        "prev_state_events",
-        "app_service",
-        "_current_state_ids",
-        "_prev_state_ids",
-        "_prev_state_id",
-        "_event_type",
-        "_event_state_key",
-        "_fetching_state_deferred",
-    ]
-
-    def __init__(self):
-        self.prev_state_events = []
-        self.rejected = False
-        self.app_service = None
+            (type, state_key) -> event_id
 
-    @staticmethod
-    def with_state(
-        state_group, current_state_ids, prev_state_ids, prev_group=None, delta_ids=None
-    ):
-        context = EventContext()
+            FIXME: again, what is this for an outlier?
 
-        # The current state including the current event
-        context._current_state_ids = current_state_ids
-        # The current state excluding the current event
-        context._prev_state_ids = prev_state_ids
-        context.state_group = state_group
+            As with _current_state_ids, this is a private attribute. It should be
+            accessed via get_prev_state_ids.
+    """
 
-        context._prev_state_id = None
-        context._event_type = None
-        context._event_state_key = None
-        context._fetching_state_deferred = defer.succeed(None)
+    rejected = attr.ib(default=False, type=Union[bool, str])
+    _state_group = attr.ib(default=None, type=Optional[int])
+    state_group_before_event = attr.ib(default=None, type=Optional[int])
+    prev_group = attr.ib(default=None, type=Optional[int])
+    delta_ids = attr.ib(default=None, type=Optional[StateMap[str]])
+    app_service = attr.ib(default=None, type=Optional[ApplicationService])
 
-        # A previously persisted state group and a delta between that
-        # and this state.
-        context.prev_group = prev_group
-        context.delta_ids = delta_ids
+    _current_state_ids = attr.ib(default=None, type=Optional[StateMap[str]])
+    _prev_state_ids = attr.ib(default=None, type=Optional[StateMap[str]])
 
-        return context
+    @staticmethod
+    def with_state(
+        state_group,
+        state_group_before_event,
+        current_state_ids,
+        prev_state_ids,
+        prev_group=None,
+        delta_ids=None,
+    ):
+        return EventContext(
+            current_state_ids=current_state_ids,
+            prev_state_ids=prev_state_ids,
+            state_group=state_group,
+            state_group_before_event=state_group_before_event,
+            prev_group=prev_group,
+            delta_ids=delta_ids,
+        )
 
     @defer.inlineCallbacks
     def serialize(self, event, store):
@@ -128,7 +148,7 @@ class EventContext(object):
         # the prev_state_ids, so if we're a state event we include the event
         # id that we replaced in the state.
         if event.is_state():
-            prev_state_ids = yield self.get_prev_state_ids(store)
+            prev_state_ids = yield self.get_prev_state_ids()
             prev_state_id = prev_state_ids.get((event.type, event.state_key))
         else:
             prev_state_id = None
@@ -137,74 +157,93 @@ class EventContext(object):
             "prev_state_id": prev_state_id,
             "event_type": event.type,
             "event_state_key": event.state_key if event.is_state() else None,
-            "state_group": self.state_group,
+            "state_group": self._state_group,
+            "state_group_before_event": self.state_group_before_event,
             "rejected": self.rejected,
             "prev_group": self.prev_group,
             "delta_ids": _encode_state_dict(self.delta_ids),
-            "prev_state_events": self.prev_state_events,
             "app_service_id": self.app_service.id if self.app_service else None,
         }
 
     @staticmethod
-    def deserialize(store, input):
+    def deserialize(storage, input):
         """Converts a dict that was produced by `serialize` back into a
         EventContext.
 
         Args:
-            store (DataStore): Used to convert AS ID to AS object
+            storage (Storage): Used to convert AS ID to AS object and fetch
+                state.
             input (dict): A dict produced by `serialize`
 
         Returns:
             EventContext
         """
-        context = EventContext()
+        context = _AsyncEventContextImpl(
+            # We use the state_group and prev_state_id stuff to pull the
+            # current_state_ids out of the DB and construct prev_state_ids.
+            storage=storage,
+            prev_state_id=input["prev_state_id"],
+            event_type=input["event_type"],
+            event_state_key=input["event_state_key"],
+            state_group=input["state_group"],
+            state_group_before_event=input["state_group_before_event"],
+            prev_group=input["prev_group"],
+            delta_ids=_decode_state_dict(input["delta_ids"]),
+            rejected=input["rejected"],
+        )
 
-        # We use the state_group and prev_state_id stuff to pull the
-        # current_state_ids out of the DB and construct prev_state_ids.
-        context._prev_state_id = input["prev_state_id"]
-        context._event_type = input["event_type"]
-        context._event_state_key = input["event_state_key"]
+        app_service_id = input["app_service_id"]
+        if app_service_id:
+            context.app_service = storage.main.get_app_service_by_id(app_service_id)
 
-        context._current_state_ids = None
-        context._prev_state_ids = None
-        context._fetching_state_deferred = None
+        return context
 
-        context.state_group = input["state_group"]
-        context.prev_group = input["prev_group"]
-        context.delta_ids = _decode_state_dict(input["delta_ids"])
+    @property
+    def state_group(self) -> Optional[int]:
+        """The ID of the state group for this event.
 
-        context.rejected = input["rejected"]
-        context.prev_state_events = input["prev_state_events"]
+        Note that state events are persisted with a state group which includes the new
+        event, so this is effectively the state *after* the event in question.
 
-        app_service_id = input["app_service_id"]
-        if app_service_id:
-            context.app_service = store.get_app_service_by_id(app_service_id)
+        For an outlier, where we don't have the state at the event, this will be None.
 
-        return context
+        It is an error to access this for a rejected event, since rejected state should
+        not make it into the room state. Accessing this property will raise an exception
+        if ``rejected`` is set.
+        """
+        if self.rejected:
+            raise RuntimeError("Attempt to access state_group of rejected event")
+
+        return self._state_group
 
     @defer.inlineCallbacks
-    def get_current_state_ids(self, store):
-        """Gets the current state IDs
+    def get_current_state_ids(self):
+        """
+        Gets the room state map, including this event - ie, the state in ``state_group``
+
+        It is an error to access this for a rejected event, since rejected state should
+        not make it into the room state. This method will raise an exception if
+        ``rejected`` is set.
 
         Returns:
             Deferred[dict[(str, str), str]|None]: Returns None if state_group
                 is None, which happens when the associated event is an outlier.
+
                 Maps a (type, state_key) to the event ID of the state event matching
                 this tuple.
         """
+        if self.rejected:
+            raise RuntimeError("Attempt to access state_ids of rejected event")
 
-        if not self._fetching_state_deferred:
-            self._fetching_state_deferred = run_in_background(
-                self._fill_out_state, store
-            )
-
-        yield make_deferred_yieldable(self._fetching_state_deferred)
-
+        yield self._ensure_fetched()
         return self._current_state_ids
 
     @defer.inlineCallbacks
-    def get_prev_state_ids(self, store):
-        """Gets the prev state IDs
+    def get_prev_state_ids(self):
+        """
+        Gets the room state map, excluding this event.
+
+        For a non-state event, this will be the same as get_current_state_ids().
 
         Returns:
             Deferred[dict[(str, str), str]|None]: Returns None if state_group
@@ -212,65 +251,88 @@ class EventContext(object):
                 Maps a (type, state_key) to the event ID of the state event matching
                 this tuple.
         """
-
-        if not self._fetching_state_deferred:
-            self._fetching_state_deferred = run_in_background(
-                self._fill_out_state, store
-            )
-
-        yield make_deferred_yieldable(self._fetching_state_deferred)
-
+        yield self._ensure_fetched()
         return self._prev_state_ids
 
     def get_cached_current_state_ids(self):
         """Gets the current state IDs if we have them already cached.
 
+        It is an error to access this for a rejected event, since rejected state should
+        not make it into the room state. This method will raise an exception if
+        ``rejected`` is set.
+
         Returns:
             dict[(str, str), str]|None: Returns None if we haven't cached the
             state or if state_group is None, which happens when the associated
             event is an outlier.
         """
+        if self.rejected:
+            raise RuntimeError("Attempt to access state_ids of rejected event")
 
         return self._current_state_ids
 
+    def _ensure_fetched(self):
+        return defer.succeed(None)
+
+
+@attr.s(slots=True)
+class _AsyncEventContextImpl(EventContext):
+    """
+    An implementation of EventContext which fetches _current_state_ids and
+    _prev_state_ids from the database on demand.
+
+    Attributes:
+
+        _storage (Storage)
+
+        _fetching_state_deferred (Deferred|None): Resolves when *_state_ids have
+            been calculated. None if we haven't started calculating yet
+
+        _event_type (str): The type of the event the context is associated with.
+
+        _event_state_key (str): The state_key of the event the context is
+            associated with.
+
+        _prev_state_id (str|None): If the event associated with the context is
+            a state event, then `_prev_state_id` is the event_id of the state
+            that was replaced.
+    """
+
+    # This needs to have a default as we're inheriting
+    _storage = attr.ib(default=None)
+    _prev_state_id = attr.ib(default=None)
+    _event_type = attr.ib(default=None)
+    _event_state_key = attr.ib(default=None)
+    _fetching_state_deferred = attr.ib(default=None)
+
+    def _ensure_fetched(self):
+        if not self._fetching_state_deferred:
+            self._fetching_state_deferred = run_in_background(self._fill_out_state)
+
+        return make_deferred_yieldable(self._fetching_state_deferred)
+
     @defer.inlineCallbacks
-    def _fill_out_state(self, store):
+    def _fill_out_state(self):
         """Called to populate the _current_state_ids and _prev_state_ids
         attributes by loading from the database.
         """
         if self.state_group is None:
             return
 
-        self._current_state_ids = yield store.get_state_ids_for_group(self.state_group)
-        if self._prev_state_id and self._event_state_key is not None:
+        self._current_state_ids = yield self._storage.state.get_state_ids_for_group(
+            self.state_group
+        )
+        if self._event_state_key is not None:
             self._prev_state_ids = dict(self._current_state_ids)
 
             key = (self._event_type, self._event_state_key)
-            self._prev_state_ids[key] = self._prev_state_id
+            if self._prev_state_id:
+                self._prev_state_ids[key] = self._prev_state_id
+            else:
+                self._prev_state_ids.pop(key, None)
         else:
             self._prev_state_ids = self._current_state_ids
 
-    @defer.inlineCallbacks
-    def update_state(
-        self, state_group, prev_state_ids, current_state_ids, prev_group, delta_ids
-    ):
-        """Replace the state in the context
-        """
-
-        # We need to make sure we wait for any ongoing fetching of state
-        # to complete so that the updated state doesn't get clobbered
-        if self._fetching_state_deferred:
-            yield make_deferred_yieldable(self._fetching_state_deferred)
-
-        self.state_group = state_group
-        self._prev_state_ids = prev_state_ids
-        self.prev_group = prev_group
-        self._current_state_ids = current_state_ids
-        self.delta_ids = delta_ids
-
-        # We need to ensure that that we've marked as having fetched the state
-        self._fetching_state_deferred = defer.succeed(None)
-
 
 def _encode_state_dict(state_dict):
     """Since dicts of (type, state_key) -> event_id cannot be serialized in