From 147a1b1124467bf23b1130c246ed6e81f6b9550e Mon Sep 17 00:00:00 2001
From: Patrick Cloke <patrickc@matrix.org>
Date: Tue, 11 Oct 2022 09:34:52 -0400
Subject: [PATCH 1/2] Return the main timeline for events which are not part of
 a thread.

---
 synapse/push/bulk_push_rule_evaluator.py    |  2 +-
 synapse/storage/databases/main/relations.py | 12 +++++++-----
 2 files changed, 8 insertions(+), 6 deletions(-)

diff --git a/synapse/push/bulk_push_rule_evaluator.py b/synapse/push/bulk_push_rule_evaluator.py
index eced182fd571..8b6b93aebc70 100644
--- a/synapse/push/bulk_push_rule_evaluator.py
+++ b/synapse/push/bulk_push_rule_evaluator.py
@@ -292,7 +292,7 @@ async def action_for_event_by_user(
             else:
                 # Since the event has not yet been persisted we check whether
                 # the parent is part of a thread.
-                thread_id = await self.store.get_thread_id(relation.parent_id) or "main"
+                thread_id = await self.store.get_thread_id(relation.parent_id)
 
         # It's possible that old room versions have non-integer power levels (floats or
         # strings). Workaround this by explicitly converting to int.
diff --git a/synapse/storage/databases/main/relations.py b/synapse/storage/databases/main/relations.py
index 116abef9de10..4e15bd0bdaa5 100644
--- a/synapse/storage/databases/main/relations.py
+++ b/synapse/storage/databases/main/relations.py
@@ -28,7 +28,7 @@
 
 import attr
 
-from synapse.api.constants import RelationTypes
+from synapse.api.constants import MAIN_TIMELINE, RelationTypes
 from synapse.events import EventBase
 from synapse.storage._base import SQLBaseStore
 from synapse.storage.database import LoggingTransaction, make_in_list_sql_clause
@@ -830,7 +830,7 @@ def _get_event_relations(
         )
 
     @cached()
-    async def get_thread_id(self, event_id: str) -> Optional[str]:
+    async def get_thread_id(self, event_id: str) -> str:
         """
         Get the thread ID for an event. This considers multi-level relations,
         e.g. an annotation to an event which is part of a thread.
@@ -840,7 +840,7 @@ async def get_thread_id(self, event_id: str) -> Optional[str]:
 
         Returns:
             The event ID of the root event in the thread, if this event is part
-            of a thread. None, otherwise.
+            of a thread. "main", otherwise.
         """
         # Since event relations form a tree, we should only ever find 0 or 1
         # results from the below query.
@@ -855,13 +855,15 @@ async def get_thread_id(self, event_id: str) -> Optional[str]:
             ) SELECT relates_to_id FROM related_events WHERE relation_type = 'm.thread';
         """
 
-        def _get_thread_id(txn: LoggingTransaction) -> Optional[str]:
+        def _get_thread_id(txn: LoggingTransaction) -> str:
             txn.execute(sql, (event_id,))
             # TODO Should we ensure there's only a single result here?
             row = txn.fetchone()
             if row:
                 return row[0]
-            return None
+
+            # If no thread was found, it is part of the main timeline.
+            return MAIN_TIMELINE
 
         return await self.db_pool.runInteraction("get_thread_id", _get_thread_id)
 

From 6b922c9e0fc3dd35d87e7eebab6b9d273d95ff5d Mon Sep 17 00:00:00 2001
From: Patrick Cloke <patrickc@matrix.org>
Date: Tue, 11 Oct 2022 12:04:36 -0400
Subject: [PATCH 2/2] Newsfragment

---
 changelog.d/14140.feature | 1 +
 1 file changed, 1 insertion(+)
 create mode 100644 changelog.d/14140.feature

diff --git a/changelog.d/14140.feature b/changelog.d/14140.feature
new file mode 100644
index 000000000000..5d0ae16e131b
--- /dev/null
+++ b/changelog.d/14140.feature
@@ -0,0 +1 @@
+Support for thread-specific notifications & receipts ([MSC3771](https://github.com/matrix-org/matrix-spec-proposals/pull/3771) and [MSC3773](https://github.com/matrix-org/matrix-spec-proposals/pull/3773)).