From d88421ab03e72a6c7f69ca38a57b4b6212f1bc82 Mon Sep 17 00:00:00 2001
From: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>
Date: Tue, 9 Jul 2019 13:43:08 +0100
Subject: [PATCH] Include the original event in /relations (#5626)

When asking for the relations of an event, include the original event in the response. This will mostly be used for efficiently showing edit history, but could be useful in other circumstances.
---
 changelog.d/5626.feature                     | 1 +
 synapse/rest/client/v2_alpha/relations.py    | 8 +++++---
 synapse/storage/relations.py                 | 2 +-
 tests/rest/client/v2_alpha/test_relations.py | 5 +++++
 4 files changed, 12 insertions(+), 4 deletions(-)
 create mode 100644 changelog.d/5626.feature

diff --git a/changelog.d/5626.feature b/changelog.d/5626.feature
new file mode 100644
index 000000000000..5ef793b943a0
--- /dev/null
+++ b/changelog.d/5626.feature
@@ -0,0 +1 @@
+Include the original event when asking for its relations.
diff --git a/synapse/rest/client/v2_alpha/relations.py b/synapse/rest/client/v2_alpha/relations.py
index 8e362782cc3c..458afd135f96 100644
--- a/synapse/rest/client/v2_alpha/relations.py
+++ b/synapse/rest/client/v2_alpha/relations.py
@@ -145,9 +145,9 @@ def on_GET(self, request, room_id, parent_id, relation_type=None, event_type=Non
             room_id, requester.user.to_string()
         )
 
-        # This checks that a) the event exists and b) the user is allowed to
-        # view it.
-        yield self.event_handler.get_event(requester.user, room_id, parent_id)
+        # This gets the original event and checks that a) the event exists and
+        # b) the user is allowed to view it.
+        event = yield self.event_handler.get_event(requester.user, room_id, parent_id)
 
         limit = parse_integer(request, "limit", default=5)
         from_token = parse_string(request, "from")
@@ -173,10 +173,12 @@ def on_GET(self, request, room_id, parent_id, relation_type=None, event_type=Non
         )
 
         now = self.clock.time_msec()
+        original_event = yield self._event_serializer.serialize_event(event, now)
         events = yield self._event_serializer.serialize_events(events, now)
 
         return_value = result.to_dict()
         return_value["chunk"] = events
+        return_value["original_event"] = original_event
 
         defer.returnValue((200, return_value))
 
diff --git a/synapse/storage/relations.py b/synapse/storage/relations.py
index 1b01934c19e8..9954bc094f8d 100644
--- a/synapse/storage/relations.py
+++ b/synapse/storage/relations.py
@@ -60,7 +60,7 @@ def to_dict(self):
 class RelationPaginationToken(object):
     """Pagination token for relation pagination API.
 
-    As the results are order by topological ordering, we can use the
+    As the results are in topological order, we can use the
     `topological_ordering` and `stream_ordering` fields of the events at the
     boundaries of the chunk as pagination tokens.
 
diff --git a/tests/rest/client/v2_alpha/test_relations.py b/tests/rest/client/v2_alpha/test_relations.py
index 6bb7d926385e..58c69518520d 100644
--- a/tests/rest/client/v2_alpha/test_relations.py
+++ b/tests/rest/client/v2_alpha/test_relations.py
@@ -126,6 +126,11 @@ def test_basic_paginate_relations(self):
             channel.json_body["chunk"][0],
         )
 
+        # We also expect to get the original event (the id of which is self.parent_id)
+        self.assertEquals(
+            channel.json_body["original_event"]["event_id"], self.parent_id
+        )
+
         # Make sure next_batch has something in it that looks like it could be a
         # valid token.
         self.assertIsInstance(