Revert "Leave out optional keys from /sync (#9919)" (#9940)

This reverts commit e9eb3549d32a6f93d07de8dbd5e1ebe54c8d8278.

4 files changed, 50 insertions, 51 deletions

diff --git a/changelog.d/9919.feature b/changelog.d/9919.feature
deleted file mode 100644
index 07747505d2..0000000000
--- a/changelog.d/9919.feature
+++ /dev/null
@@ -1 +0,0 @@
-Omit empty fields from the `/sync` response.  Contributed by @deepbluev7.
diff --git a/synapse/rest/client/v2_alpha/sync.py b/synapse/rest/client/v2_alpha/sync.py
index 5f85653330..95ee3f1b84 100644
--- a/synapse/rest/client/v2_alpha/sync.py
+++ b/synapse/rest/client/v2_alpha/sync.py
@@ -14,7 +14,6 @@
 
 import itertools
 import logging
-from collections import defaultdict
 from typing import TYPE_CHECKING, Tuple
 
 from synapse.api.constants import PresenceState
@@ -230,49 +229,24 @@ class SyncRestServlet(RestServlet):
         )
 
         logger.debug("building sync response dict")
-
-        response: dict = defaultdict(dict)
-        response["next_batch"] = await sync_result.next_batch.to_string(self.store)
-
-        if sync_result.account_data:
-            response["account_data"] = {"events": sync_result.account_data}
-        if sync_result.presence:
-            response["presence"] = SyncRestServlet.encode_presence(
-                sync_result.presence, time_now
-            )
-
-        if sync_result.to_device:
-            response["to_device"] = {"events": sync_result.to_device}
-
-        if sync_result.device_lists.changed:
-            response["device_lists"]["changed"] = list(sync_result.device_lists.changed)
-        if sync_result.device_lists.left:
-            response["device_lists"]["left"] = list(sync_result.device_lists.left)
-
-        if sync_result.device_one_time_keys_count:
-            response[
-                "device_one_time_keys_count"
-            ] = sync_result.device_one_time_keys_count
-        if sync_result.device_unused_fallback_key_types:
-            response[
-                "org.matrix.msc2732.device_unused_fallback_key_types"
-            ] = sync_result.device_unused_fallback_key_types
-
-        if joined:
-            response["rooms"]["join"] = joined
-        if invited:
-            response["rooms"]["invite"] = invited
-        if archived:
-            response["rooms"]["leave"] = archived
-
-        if sync_result.groups.join:
-            response["groups"]["join"] = sync_result.groups.join
-        if sync_result.groups.invite:
-            response["groups"]["invite"] = sync_result.groups.invite
-        if sync_result.groups.leave:
-            response["groups"]["leave"] = sync_result.groups.leave
-
-        return response
+        return {
+            "account_data": {"events": sync_result.account_data},
+            "to_device": {"events": sync_result.to_device},
+            "device_lists": {
+                "changed": list(sync_result.device_lists.changed),
+                "left": list(sync_result.device_lists.left),
+            },
+            "presence": SyncRestServlet.encode_presence(sync_result.presence, time_now),
+            "rooms": {"join": joined, "invite": invited, "leave": archived},
+            "groups": {
+                "join": sync_result.groups.join,
+                "invite": sync_result.groups.invite,
+                "leave": sync_result.groups.leave,
+            },
+            "device_one_time_keys_count": sync_result.device_one_time_keys_count,
+            "org.matrix.msc2732.device_unused_fallback_key_types": sync_result.device_unused_fallback_key_types,
+            "next_batch": await sync_result.next_batch.to_string(self.store),
+        }
 
     @staticmethod
     def encode_presence(events, time_now):
diff --git a/tests/rest/client/v2_alpha/test_sync.py b/tests/rest/client/v2_alpha/test_sync.py
index 74be5176d0..dbcbdf159a 100644
--- a/tests/rest/client/v2_alpha/test_sync.py
+++ b/tests/rest/client/v2_alpha/test_sync.py
@@ -37,7 +37,35 @@ class FilterTestCase(unittest.HomeserverTestCase):
         channel = self.make_request("GET", "/sync")
 
         self.assertEqual(channel.code, 200)
-        self.assertIn("next_batch", channel.json_body)
+        self.assertTrue(
+            {
+                "next_batch",
+                "rooms",
+                "presence",
+                "account_data",
+                "to_device",
+                "device_lists",
+            }.issubset(set(channel.json_body.keys()))
+        )
+
+    def test_sync_presence_disabled(self):
+        """
+        When presence is disabled, the key does not appear in /sync.
+        """
+        self.hs.config.use_presence = False
+
+        channel = self.make_request("GET", "/sync")
+
+        self.assertEqual(channel.code, 200)
+        self.assertTrue(
+            {
+                "next_batch",
+                "rooms",
+                "account_data",
+                "to_device",
+                "device_lists",
+            }.issubset(set(channel.json_body.keys()))
+        )
 
 
 class SyncFilterTestCase(unittest.HomeserverTestCase):
diff --git a/tests/server_notices/test_resource_limits_server_notices.py b/tests/server_notices/test_resource_limits_server_notices.py
index 3245aa91ca..d46521ccdc 100644
--- a/tests/server_notices/test_resource_limits_server_notices.py
+++ b/tests/server_notices/test_resource_limits_server_notices.py
@@ -306,9 +306,8 @@ class TestResourceLimitsServerNoticesWithRealRooms(unittest.HomeserverTestCase):
 
         channel = self.make_request("GET", "/sync?timeout=0", access_token=tok)
 
-        self.assertNotIn(
-            "rooms", channel.json_body, "Got invites without server notice"
-        )
+        invites = channel.json_body["rooms"]["invite"]
+        self.assertEqual(len(invites), 0, invites)
 
     def test_invite_with_notice(self):
         """Tests that, if the MAU limit is hit, the server notices user invites each user
@@ -365,8 +364,7 @@ class TestResourceLimitsServerNoticesWithRealRooms(unittest.HomeserverTestCase):
             # We could also pick another user and sync with it, which would return an
             # invite to a system notices room, but it doesn't matter which user we're
             # using so we use the last one because it saves us an extra sync.
-            if "rooms" in channel.json_body:
-                invites = channel.json_body["rooms"]["invite"]
+            invites = channel.json_body["rooms"]["invite"]
 
         # Make sure we have an invite to process.
         self.assertEqual(len(invites), 1, invites)