Show all joinable rooms in the spaces summary. (#10298)

Previously only world-readable rooms were shown. This means that
rooms which are public, knockable, or invite-only with a pending invitation,
are included in a space summary. It also applies the same logic to
the experimental room version from MSC3083 -- if a user has access
to the proper allowed rooms then it is shown in the spaces summary.

This change is made per MSC3173 allowing stripped state of a room to
be shown to any potential room joiner.

changelog.d/10298.feature

@@ -0,0 +1 @@
+The spaces summary API now returns any joinable rooms, not only rooms which are world-readable.

changelog.d/10305.feature

@@ -0,0 +1 @@
+The spaces summary API now returns any joinable rooms, not only rooms which are world-readable.

synapse/handlers/space_summary.py

@@ -24,6 +24,7 @@
     EventContentFields,
     EventTypes,
     HistoryVisibility,
+    JoinRules,
     Membership,
     RoomTypes,
 )
@@ -150,14 +151,21 @@ async def get_space_summary(
                     # The room should only be included in the summary if:
                     #     a. the user is in the room;
                     #     b. the room is world readable; or
-                    #     c. the user is in a space that has been granted access to
-                    #        the room.
+                    #     c. the user could join the room, e.g. the join rules
+                    #        are set to public or the user is in a space that
+                    #        has been granted access to the room.
                     #
                     # Note that we know the user is not in the root room (which is
                     # why the remote call was made in the first place), but the user
                     # could be in one of the children rooms and we just didn't know
                     # about the link.
-                    include_room = room.get("world_readable") is True
+
+                    # The API doesn't return the room version so assume that a
+                    # join rule of knock is valid.
+                    include_room = (
+                        room.get("join_rules") in (JoinRules.PUBLIC, JoinRules.KNOCK)
+                        or room.get("world_readable") is True
+                    )
 
                     # Check if the user is a member of any of the allowed spaces
                     # from the response.
@@ -420,9 +428,8 @@ async def _is_room_accessible(
 
         It should be included if:
 
-        * The requester is joined or invited to the room.
-        * The requester can join without an invite (per MSC3083).
-        * The origin server has any user that is joined or invited to the room.
+        * The requester is joined or can join the room (per MSC3173).
+        * The origin server has any user that is joined or can join the room.
         * The history visibility is set to world readable.
 
         Args:
@@ -441,13 +448,39 @@ async def _is_room_accessible(
 
         # If there's no state for the room, it isn't known.
         if not state_ids:
+            # The user might have a pending invite for the room.
+            if requester and await self._store.get_invite_for_local_user_in_room(
+                requester, room_id
+            ):
+                return True
+
             logger.info("room %s is unknown, omitting from summary", room_id)
             return False
 
         room_version = await self._store.get_room_version(room_id)
 
-        # if we have an authenticated requesting user, first check if they are able to view
-        # stripped state in the room.
+        # Include the room if it has join rules of public or knock.
+        join_rules_event_id = state_ids.get((EventTypes.JoinRules, ""))
+        if join_rules_event_id:
+            join_rules_event = await self._store.get_event(join_rules_event_id)
+            join_rule = join_rules_event.content.get("join_rule")
+            if join_rule == JoinRules.PUBLIC or (
+                room_version.msc2403_knocking and join_rule == JoinRules.KNOCK
+            ):
+                return True
+
+        # Include the room if it is peekable.
+        hist_vis_event_id = state_ids.get((EventTypes.RoomHistoryVisibility, ""))
+        if hist_vis_event_id:
+            hist_vis_ev = await self._store.get_event(hist_vis_event_id)
+            hist_vis = hist_vis_ev.content.get("history_visibility")
+            if hist_vis == HistoryVisibility.WORLD_READABLE:
+                return True
+
+        # Otherwise we need to check information specific to the user or server.
+
+        # If we have an authenticated requesting user, check if they are a member
+        # of the room (or can join the room).
         if requester:
             member_event_id = state_ids.get((EventTypes.Member, requester), None)
 
@@ -470,9 +503,11 @@ async def _is_room_accessible(
                     return True
 
         # If this is a request over federation, check if the host is in the room or
-        # is in one of the spaces specified via the join rules.
+        # has a user who could join the room.
         elif origin:
-            if await self._event_auth_handler.check_host_in_room(room_id, origin):
+            if await self._event_auth_handler.check_host_in_room(
+                room_id, origin
+            ) or await self._store.is_host_invited(room_id, origin):
                 return True
 
             # Alternately, if the host has a user in any of the spaces specified
@@ -490,18 +525,10 @@ async def _is_room_accessible(
                     ):
                         return True
 
-        # otherwise, check if the room is peekable
-        hist_vis_event_id = state_ids.get((EventTypes.RoomHistoryVisibility, ""), None)
-        if hist_vis_event_id:
-            hist_vis_ev = await self._store.get_event(hist_vis_event_id)
-            hist_vis = hist_vis_ev.content.get("history_visibility")
-            if hist_vis == HistoryVisibility.WORLD_READABLE:
-                return True
-
         logger.info(
-            "room %s is unpeekable and user %s is not a member / not allowed to join, omitting from summary",
+            "room %s is unpeekable and requester %s is not a member / not allowed to join, omitting from summary",
             room_id,
-            requester,
+            requester or origin,
         )
         return False
 
@@ -535,6 +562,7 @@ async def _build_room_entry(self, room_id: str) -> JsonDict:
             "canonical_alias": stats["canonical_alias"],
             "num_joined_members": stats["joined_members"],
             "avatar_url": stats["avatar"],
+            "join_rules": stats["join_rules"],
             "world_readable": (
                 stats["history_visibility"] == HistoryVisibility.WORLD_READABLE
             ),

synapse/storage/databases/main/roommember.py

@@ -703,13 +703,22 @@ async def _get_joined_profiles_from_event_ids(self, event_ids: Iterable[str]):
 
     @cached(max_entries=10000)
     async def is_host_joined(self, room_id: str, host: str) -> bool:
+        return await self._check_host_room_membership(room_id, host, Membership.JOIN)
+
+    @cached(max_entries=10000)
+    async def is_host_invited(self, room_id: str, host: str) -> bool:
+        return await self._check_host_room_membership(room_id, host, Membership.INVITE)
+
+    async def _check_host_room_membership(
+        self, room_id: str, host: str, membership: str
+    ) -> bool:
         if "%" in host or "_" in host:
             raise Exception("Invalid host name")
 
         sql = """
             SELECT state_key FROM current_state_events AS c
             INNER JOIN room_memberships AS m USING (event_id)
-            WHERE m.membership = 'join'
+            WHERE m.membership = ?
                 AND type = 'm.room.member'
                 AND c.room_id = ?
                 AND state_key LIKE ?
@@ -722,7 +731,7 @@ async def is_host_joined(self, room_id: str, host: str) -> bool:
         like_clause = "%:" + host
 
         rows = await self.db_pool.execute(
-            "is_host_joined", None, sql, room_id, like_clause
+            "is_host_joined", None, sql, membership, room_id, like_clause
         )
 
         if not rows: