feat(base): Add RoomUpdates::iter_all_room_ids.

This patch adds the `RoomUpdates::iter_all_room_ids` method, to iterate
over all IDs of rooms that have received an update.

crates/matrix-sdk-base/src/sync.rs

@@ -80,6 +80,80 @@ pub struct RoomUpdates {
     pub knocked: BTreeMap<OwnedRoomId, KnockedRoomUpdate>,
 }
 
+impl RoomUpdates {
+    /// Iterate over all room IDs, from [`RoomUpdates::left`],
+    /// [`RoomUpdates::joined`], [`RoomUpdates::invited`] and
+    /// [`RoomUpdates::knocked`].
+    fn iter_all_room_ids(&self) -> impl Iterator<Item = &OwnedRoomId> {
+        self.left
+            .keys()
+            .chain(self.joined.keys())
+            .chain(self.invited.keys())
+            .chain(self.knocked.keys())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use std::collections::BTreeMap;
+
+    use assert_matches::assert_matches;
+    use ruma::room_id;
+
+    use super::{
+        InvitedRoomUpdate, JoinedRoomUpdate, KnockedRoomUpdate, LeftRoomUpdate, RoomUpdates,
+    };
+
+    #[test]
+    fn test_room_updates_iter_all_room_ids() {
+        let room_id_0 = room_id!("!r0");
+        let room_id_1 = room_id!("!r1");
+        let room_id_2 = room_id!("!r2");
+        let room_id_3 = room_id!("!r3");
+        let room_id_4 = room_id!("!r4");
+        let room_id_5 = room_id!("!r5");
+        let room_id_6 = room_id!("!r6");
+        let room_id_7 = room_id!("!r7");
+        let room_updates = RoomUpdates {
+            left: {
+                let mut left = BTreeMap::new();
+                left.insert(room_id_0.to_owned(), LeftRoomUpdate::default());
+                left.insert(room_id_1.to_owned(), LeftRoomUpdate::default());
+                left
+            },
+            joined: {
+                let mut joined = BTreeMap::new();
+                joined.insert(room_id_2.to_owned(), JoinedRoomUpdate::default());
+                joined.insert(room_id_3.to_owned(), JoinedRoomUpdate::default());
+                joined
+            },
+            invited: {
+                let mut invited = BTreeMap::new();
+                invited.insert(room_id_4.to_owned(), InvitedRoomUpdate::default());
+                invited.insert(room_id_5.to_owned(), InvitedRoomUpdate::default());
+                invited
+            },
+            knocked: {
+                let mut knocked = BTreeMap::new();
+                knocked.insert(room_id_6.to_owned(), KnockedRoomUpdate::default());
+                knocked.insert(room_id_7.to_owned(), KnockedRoomUpdate::default());
+                knocked
+            },
+        };
+
+        let mut iter = room_updates.iter_all_room_ids();
+        assert_matches!(iter.next(), Some(room_id) => assert_eq!(room_id, room_id_0));
+        assert_matches!(iter.next(), Some(room_id) => assert_eq!(room_id, room_id_1));
+        assert_matches!(iter.next(), Some(room_id) => assert_eq!(room_id, room_id_2));
+        assert_matches!(iter.next(), Some(room_id) => assert_eq!(room_id, room_id_3));
+        assert_matches!(iter.next(), Some(room_id) => assert_eq!(room_id, room_id_4));
+        assert_matches!(iter.next(), Some(room_id) => assert_eq!(room_id, room_id_5));
+        assert_matches!(iter.next(), Some(room_id) => assert_eq!(room_id, room_id_6));
+        assert_matches!(iter.next(), Some(room_id) => assert_eq!(room_id, room_id_7));
+        assert!(iter.next().is_none());
+    }
+}
+
 #[cfg(not(tarpaulin_include))]
 impl fmt::Debug for RoomUpdates {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {