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Remove allow_no_prev_events option (MSC2716 cleanup) #18676

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Merged
merged 4 commits into from
Jul 15, 2025
Merged

Remove allow_no_prev_events option (MSC2716 cleanup) #18676

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18ecd98
Remove `allow_no_prev_events` option
MadLittleMods Jul 11, 2025
a706b7b
Add changelog
MadLittleMods Jul 11, 2025
85a9149
Remove extra related changes
MadLittleMods Jul 11, 2025
e1276f8
Merge branch 'develop' into madlittlemods/remove-allow_no_prev_events
MadLittleMods Jul 15, 2025
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1 change: 1 addition & 0 deletions changelog.d/18676.misc
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
Remove unused `allow_no_prev_events` option when creating an event.
40 changes: 5 additions & 35 deletions synapse/handlers/message.py
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Original file line number Diff line number Diff line change
Expand Up @@ -568,7 +568,6 @@ async def create_event(
requester: Requester,
event_dict: dict,
txn_id: Optional[str] = None,
allow_no_prev_events: bool = False,
prev_event_ids: Optional[List[str]] = None,
auth_event_ids: Optional[List[str]] = None,
state_event_ids: Optional[List[str]] = None,
Expand All @@ -594,10 +593,6 @@ async def create_event(
requester
event_dict: An entire event
txn_id
allow_no_prev_events: Whether to allow this event to be created an empty
list of prev_events. Normally this is prohibited just because most
events should have a prev_event and we should only use this in special
cases (previously useful for MSC2716).
prev_event_ids:
the forward extremities to use as the prev_events for the
new event.
Expand Down Expand Up @@ -717,7 +712,6 @@ async def create_event(
event, unpersisted_context = await self.create_new_client_event(
builder=builder,
requester=requester,
allow_no_prev_events=allow_no_prev_events,
prev_event_ids=prev_event_ids,
auth_event_ids=auth_event_ids,
state_event_ids=state_event_ids,
Expand Down Expand Up @@ -945,7 +939,6 @@ async def create_and_send_nonmember_event(
self,
requester: Requester,
event_dict: dict,
allow_no_prev_events: bool = False,
prev_event_ids: Optional[List[str]] = None,
state_event_ids: Optional[List[str]] = None,
ratelimit: bool = True,
Expand All @@ -962,10 +955,6 @@ async def create_and_send_nonmember_event(
Args:
requester: The requester sending the event.
event_dict: An entire event.
allow_no_prev_events: Whether to allow this event to be created an empty
list of prev_events. Normally this is prohibited just because most
events should have a prev_event and we should only use this in special
cases (previously useful for MSC2716).
prev_event_ids:
The event IDs to use as the prev events.
Should normally be left as None to automatically request them
Expand Down Expand Up @@ -1051,7 +1040,6 @@ async def create_and_send_nonmember_event(
return await self._create_and_send_nonmember_event_locked(
requester=requester,
event_dict=event_dict,
allow_no_prev_events=allow_no_prev_events,
prev_event_ids=prev_event_ids,
state_event_ids=state_event_ids,
ratelimit=ratelimit,
Expand All @@ -1065,7 +1053,6 @@ async def _create_and_send_nonmember_event_locked(
self,
requester: Requester,
event_dict: dict,
allow_no_prev_events: bool = False,
prev_event_ids: Optional[List[str]] = None,
state_event_ids: Optional[List[str]] = None,
ratelimit: bool = True,
Expand Down Expand Up @@ -1097,7 +1084,6 @@ async def _create_and_send_nonmember_event_locked(
requester,
event_dict,
txn_id=txn_id,
allow_no_prev_events=allow_no_prev_events,
prev_event_ids=prev_event_ids,
state_event_ids=state_event_ids,
outlier=outlier,
Expand Down Expand Up @@ -1180,7 +1166,6 @@ async def create_new_client_event(
self,
builder: EventBuilder,
requester: Optional[Requester] = None,
allow_no_prev_events: bool = False,
prev_event_ids: Optional[List[str]] = None,
auth_event_ids: Optional[List[str]] = None,
state_event_ids: Optional[List[str]] = None,
Expand All @@ -1200,10 +1185,6 @@ async def create_new_client_event(
Args:
builder:
requester:
allow_no_prev_events: Whether to allow this event to be created an empty
list of prev_events. Normally this is prohibited just because most
events should have a prev_event and we should only use this in special
cases (previously useful for MSC2716).
prev_event_ids:
the forward extremities to use as the prev_events for the
new event.
Expand Down Expand Up @@ -1241,7 +1222,6 @@ async def create_new_client_event(
if state_event_ids is not None:
# Do a quick check to make sure that prev_event_ids is present to
# make the type-checking around `builder.build` happy.
# prev_event_ids could be an empty array though.
assert prev_event_ids is not None

temp_event = await builder.build(
Expand Down Expand Up @@ -1269,24 +1249,14 @@ async def create_new_client_event(
else:
prev_event_ids = await self.store.get_prev_events_for_room(builder.room_id)

# We now ought to have some `prev_events` (unless it's a create event).
#
# Do a quick sanity check here, rather than waiting until we've created the
# event and then try to auth it (which fails with a somewhat confusing "No
# create event in auth events")
if allow_no_prev_events:
# We allow events with no `prev_events` but it better have some `auth_events`
assert (
builder.type == EventTypes.Create
# Allow an event to have empty list of prev_event_ids
# only if it has auth_event_ids.
or auth_event_ids
), (
"Attempting to create a non-m.room.create event with no prev_events or auth_event_ids"
)
else:
# we now ought to have some prev_events (unless it's a create event).
assert builder.type == EventTypes.Create or prev_event_ids, (
"Attempting to create a non-m.room.create event with no prev_events"
)
assert builder.type == EventTypes.Create or len(prev_event_ids) > 0, (
"Attempting to create an event with no prev_events"
)

if for_batch:
assert prev_event_ids is not None
Expand Down
21 changes: 1 addition & 20 deletions synapse/handlers/room_member.py
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Original file line number Diff line number Diff line change
Expand Up @@ -388,11 +388,11 @@ async def ratelimit_invite(

async def _local_membership_update(
self,
*,
requester: Requester,
target: UserID,
room_id: str,
membership: str,
allow_no_prev_events: bool = False,
prev_event_ids: Optional[List[str]] = None,
state_event_ids: Optional[List[str]] = None,
depth: Optional[int] = None,
Expand All @@ -414,11 +414,6 @@ async def _local_membership_update(
desired membership event.
room_id:
membership:

allow_no_prev_events: Whether to allow this event to be created an empty
list of prev_events. Normally this is prohibited just because most
events should have a prev_event and we should only use this in special
cases (previously useful for MSC2716).
prev_event_ids: The event IDs to use as the prev events
state_event_ids:
The full state at a given event. This was previously used particularly
Expand Down Expand Up @@ -486,7 +481,6 @@ async def _local_membership_update(
"origin_server_ts": origin_server_ts,
},
txn_id=txn_id,
allow_no_prev_events=allow_no_prev_events,
prev_event_ids=prev_event_ids,
state_event_ids=state_event_ids,
depth=depth,
Expand Down Expand Up @@ -583,7 +577,6 @@ async def update_membership(
new_room: bool = False,
require_consent: bool = True,
outlier: bool = False,
allow_no_prev_events: bool = False,
prev_event_ids: Optional[List[str]] = None,
state_event_ids: Optional[List[str]] = None,
depth: Optional[int] = None,
Expand All @@ -607,10 +600,6 @@ async def update_membership(
outlier: Indicates whether the event is an `outlier`, i.e. if
it's from an arbitrary point and floating in the DAG as
opposed to being inline with the current DAG.
allow_no_prev_events: Whether to allow this event to be created an empty
list of prev_events. Normally this is prohibited just because most
events should have a prev_event and we should only use this in special
cases (previously useful for MSC2716).
prev_event_ids: The event IDs to use as the prev events
state_event_ids:
The full state at a given event. This was previously used particularly
Expand Down Expand Up @@ -680,7 +669,6 @@ async def update_membership(
new_room=new_room,
require_consent=require_consent,
outlier=outlier,
allow_no_prev_events=allow_no_prev_events,
prev_event_ids=prev_event_ids,
state_event_ids=state_event_ids,
depth=depth,
Expand All @@ -703,7 +691,6 @@ async def update_membership_locked(
new_room: bool = False,
require_consent: bool = True,
outlier: bool = False,
allow_no_prev_events: bool = False,
prev_event_ids: Optional[List[str]] = None,
state_event_ids: Optional[List[str]] = None,
depth: Optional[int] = None,
Expand All @@ -729,10 +716,6 @@ async def update_membership_locked(
outlier: Indicates whether the event is an `outlier`, i.e. if
it's from an arbitrary point and floating in the DAG as
opposed to being inline with the current DAG.
allow_no_prev_events: Whether to allow this event to be created an empty
list of prev_events. Normally this is prohibited just because most
events should have a prev_event and we should only use this in special
cases (previously useful for MSC2716).
prev_event_ids: The event IDs to use as the prev events
state_event_ids:
The full state at a given event. This was previously used particularly
Expand Down Expand Up @@ -933,7 +916,6 @@ async def update_membership_locked(
)
# InviteRule.IGNORE is handled at the sync layer.

# An empty prev_events list is allowed as long as the auth_event_ids are present
if prev_event_ids is not None:
return await self._local_membership_update(
requester=requester,
Expand All @@ -942,7 +924,6 @@ async def update_membership_locked(
membership=effective_membership_state,
txn_id=txn_id,
ratelimit=ratelimit,
allow_no_prev_events=allow_no_prev_events,
prev_event_ids=prev_event_ids,
state_event_ids=state_event_ids,
depth=depth,
Expand Down
66 changes: 5 additions & 61 deletions tests/handlers/test_message.py
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Original file line number Diff line number Diff line change
Expand Up @@ -204,46 +204,19 @@ def test_duplicated_txn_id_one_call(self) -> None:
self.assertEqual(len(events), 2)
self.assertEqual(events[0].event_id, events[1].event_id)

def test_when_empty_prev_events_allowed_create_event_with_empty_prev_events(
def test_reject_event_with_empty_prev_events(
self,
) -> None:
"""When we set allow_no_prev_events=True, should be able to create a
event without any prev_events (only auth_events).
"""
# Create a member event we can use as an auth_event
memberEvent, _ = self._create_and_persist_member_event()

# Try to create the event with empty prev_events bit with some auth_events
event, _ = self.get_success(
self.handler.create_event(
self.requester,
{
"type": EventTypes.Message,
"room_id": self.room_id,
"sender": self.requester.user.to_string(),
"content": {"msgtype": "m.text", "body": random_string(5)},
},
# Empty prev_events is the key thing we're testing here
prev_event_ids=[],
# But with some auth_events
auth_event_ids=[memberEvent.event_id],
# Allow no prev_events!
allow_no_prev_events=True,
)
)
self.assertIsNotNone(event)

def test_when_empty_prev_events_not_allowed_reject_event_with_empty_prev_events(
self,
) -> None:
"""When we set allow_no_prev_events=False, shouldn't be able to create a
event without any prev_events even if it has auth_events. Expect an
exception to be raised.
Shouldn't be able to create an event without any `prev_events` even if it has
`auth_events`. Expect an exception to be raised.
"""
# Create a member event we can use as an auth_event
memberEvent, _ = self._create_and_persist_member_event()

# Try to create the event with empty prev_events but with some auth_events
#
# We expect the test to fail because empty prev_events are not allowed
self.get_failure(
self.handler.create_event(
self.requester,
Expand All @@ -257,35 +230,6 @@ def test_when_empty_prev_events_not_allowed_reject_event_with_empty_prev_events(
prev_event_ids=[],
# But with some auth_events
auth_event_ids=[memberEvent.event_id],
# We expect the test to fail because empty prev_events are not
# allowed here!
allow_no_prev_events=False,
),
AssertionError,
)

def test_when_empty_prev_events_allowed_reject_event_with_empty_prev_events_and_auth_events(
self,
) -> None:
"""When we set allow_no_prev_events=True, should be able to create a
event without any prev_events or auth_events. Expect an exception to be
raised.
"""
# Try to create the event with empty prev_events and empty auth_events
self.get_failure(
self.handler.create_event(
self.requester,
{
"type": EventTypes.Message,
"room_id": self.room_id,
"sender": self.requester.user.to_string(),
"content": {"msgtype": "m.text", "body": random_string(5)},
},
prev_event_ids=[],
# The event should be rejected when there are no auth_events
auth_event_ids=[],
# Allow no prev_events!
allow_no_prev_events=True,
),
AssertionError,
)
Expand Down
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