fix(room_preview): Return room preview info based on local data for banned rooms too

Any remote endpoint would just return a `403` status code so we have no other choice than trusting the local room info we already have.

Author: jmartinesp

crates/matrix-sdk/src/client/mod.rs

@@ -1155,16 +1155,20 @@ impl Client {
         };
 
         if let Some(room) = self.get_room(&room_id) {
-            // The cached data can only be trusted if the room is joined: for invite and
-            // knock rooms, no updates will be received for the rooms after the invite/knock
-            // action took place so we may have very out to date data for important fields
-            // such as `join_rule`
-            if room.state() == RoomState::Joined {
-                return Ok(RoomPreview::from_joined(&room).await);
+            // The cached data can only be trusted if the room state is joined or
+            // banned: for invite and knock rooms, no updates will be received
+            // for the rooms after the invite/knock action took place so we may
+            // have very out to date data for important fields such as
+            // `join_rule`. For left rooms, the homeserver should return the latest info.
+            match room.state() {
+                RoomState::Joined | RoomState::Banned => {
+                    return Ok(RoomPreview::from_known_room(&room).await);
+                }
+                RoomState::Left | RoomState::Invited | RoomState::Knocked => {}
             }
         }
 
-        RoomPreview::from_not_joined(self, room_id, room_or_alias_id, via).await
+        RoomPreview::from_remote_room(self, room_id, room_or_alias_id, via).await
     }
 
     /// Resolve a room alias to a room id and a list of servers which know

crates/matrix-sdk/src/room_preview.rs

@@ -126,8 +126,12 @@ impl RoomPreview {
         }
     }
 
-    /// Create a room preview from a known room we've joined.
-    pub(crate) async fn from_joined(room: &Room) -> Self {
+    /// Create a room preview from a known room.
+    ///
+    /// Note this shouldn't be used with invited or knocked rooms, since the
+    /// local info may be out of date and no longer represent the latest room
+    /// state.
+    pub(crate) async fn from_known_room(room: &Room) -> Self {
         let is_direct = room.is_direct().await.ok();
 
         let display_name = room.display_name().await.ok().map(|name| name.to_string());
@@ -143,7 +147,7 @@ impl RoomPreview {
     }
 
     #[instrument(skip(client))]
-    pub(crate) async fn from_not_joined(
+    pub(crate) async fn from_remote_room(
         client: &Client,
         room_id: OwnedRoomId,
         room_or_alias_id: &RoomOrAliasId,