Add an admin API to get the current room state (#9168)

This could arguably replace the existing admin API for `/members`, however that is out of scope of this change.

This sort of endpoint is ideal for moderation use cases as well as other applications, such as needing to retrieve various bits of information about a room to perform a task (like syncing power levels between two places). This endpoint exposes nothing more than an admin would be able to access with a `select *` query on their database.

changelog.d/9168.feature

@@ -0,0 +1 @@
+Add an admin API for retrieving the current room state of a room.

docs/admin_api/rooms.md

@@ -368,6 +368,36 @@ Response:
 }
 ```
 
+# Room State API
+
+The Room State admin API allows server admins to get a list of all state events in a room.
+
+The response includes the following fields:
+
+* `state` - The current state of the room at the time of request.
+
+## Usage
+
+A standard request:
+
+```
+GET /_synapse/admin/v1/rooms/<room_id>/state
+
+{}
+```
+
+Response:
+
+```json
+{
+  "state": [
+    {"type": "m.room.create", "state_key": "", "etc": true},
+    {"type": "m.room.power_levels", "state_key": "", "etc": true},
+    {"type": "m.room.name", "state_key": "", "etc": true}
+  ]
+}
+```
+
 # Delete Room API
 
 The Delete Room admin API allows server admins to remove rooms from server

synapse/handlers/message.py

@@ -174,7 +174,7 @@ class MessageHandler:
                 raise NotFoundError("Can't find event for token %s" % (at_token,))
 
             visible_events = await filter_events_for_client(
-                self.storage, user_id, last_events, filter_send_to_client=False
+                self.storage, user_id, last_events, filter_send_to_client=False,
             )
 
             event = last_events[0]

synapse/rest/admin/__init__.py

@@ -44,6 +44,7 @@ from synapse.rest.admin.rooms import (
     MakeRoomAdminRestServlet,
     RoomMembersRestServlet,
     RoomRestServlet,
+    RoomStateRestServlet,
     ShutdownRoomRestServlet,
 )
 from synapse.rest.admin.server_notice_servlet import SendServerNoticeServlet
@@ -213,6 +214,7 @@ def register_servlets(hs, http_server):
     """
     register_servlets_for_client_rest_resource(hs, http_server)
     ListRoomRestServlet(hs).register(http_server)
+    RoomStateRestServlet(hs).register(http_server)
     RoomRestServlet(hs).register(http_server)
     RoomMembersRestServlet(hs).register(http_server)
     DeleteRoomRestServlet(hs).register(http_server)

synapse/rest/admin/rooms.py

@@ -292,6 +292,45 @@ class RoomMembersRestServlet(RestServlet):
         return 200, ret
 
 
+class RoomStateRestServlet(RestServlet):
+    """
+    Get full state within a room.
+    """
+
+    PATTERNS = admin_patterns("/rooms/(?P<room_id>[^/]+)/state")
+
+    def __init__(self, hs: "HomeServer"):
+        self.hs = hs
+        self.auth = hs.get_auth()
+        self.store = hs.get_datastore()
+        self.clock = hs.get_clock()
+        self._event_serializer = hs.get_event_client_serializer()
+
+    async def on_GET(
+        self, request: SynapseRequest, room_id: str
+    ) -> Tuple[int, JsonDict]:
+        requester = await self.auth.get_user_by_req(request)
+        await assert_user_is_admin(self.auth, requester.user)
+
+        ret = await self.store.get_room(room_id)
+        if not ret:
+            raise NotFoundError("Room not found")
+
+        event_ids = await self.store.get_current_state_ids(room_id)
+        events = await self.store.get_events(event_ids.values())
+        now = self.clock.time_msec()
+        room_state = await self._event_serializer.serialize_events(
+            events.values(),
+            now,
+            # We don't bother bundling aggregations in when asked for state
+            # events, as clients won't use them.
+            bundle_aggregations=False,
+        )
+        ret = {"state": room_state}
+
+        return 200, ret
+
+
 class JoinRoomAliasServlet(RestServlet):
 
     PATTERNS = admin_patterns("/join/(?P<room_identifier>[^/]*)")

tests/rest/admin/test_room.py

@@ -1180,6 +1180,21 @@ class RoomTestCase(unittest.HomeserverTestCase):
         )
         self.assertEqual(channel.json_body["total"], 3)
 
+    def test_room_state(self):
+        """Test that room state can be requested correctly"""
+        # Create two test rooms
+        room_id = self.helper.create_room_as(self.admin_user, tok=self.admin_user_tok)
+
+        url = "/_synapse/admin/v1/rooms/%s/state" % (room_id,)
+        channel = self.make_request(
+            "GET", url.encode("ascii"), access_token=self.admin_user_tok,
+        )
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+        self.assertIn("state", channel.json_body)
+        # testing that the state events match is painful and not done here. We assume that
+        # the create_room already does the right thing, so no need to verify that we got
+        # the state events it created.
+
 
 class JoinAliasRoomTestCase(unittest.HomeserverTestCase):