fix(sdk): Latest Event lazy-loads the Room Event Cache

Cargo.toml

@@ -25,7 +25,9 @@ as_variant = "1.3.0"
 assert-json-diff = "2.0.2"
 assert_matches = "1.5.0"
 assert_matches2 = "0.1.2"
+async_cell = "0.2.3"
 async-compat = "0.2.5"
+async-once-cell = "0.5.4"
 async-rx = "0.1.3"
 # Bumping this to 0.3.6 produces a test failure because the semantic between the
 # versions changed subtly: https://github.com/matrix-org/matrix-rust-sdk/issues/4599

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

@@ -56,6 +56,13 @@ impl LatestEventValue {
             Self::None | Self::Remote(_) => false,
         }
     }
+
+    /// Check whether the [`LatestEventValue`] is not set, i.e. [`None`].
+    ///
+    /// [`None`]: LatestEventValue::None
+    pub fn is_none(&self) -> bool {
+        matches!(self, Self::None)
+    }
 }
 
 /// Represents the value for [`LatestEventValue::Remote`].

crates/matrix-sdk-ui/Cargo.toml

@@ -36,7 +36,7 @@ experimental-encrypted-state-events = [
 as_variant.workspace = true
 async-rx.workspace = true
 async-stream.workspace = true
-async_cell = "0.2.3"
+async_cell.workspace = true
 bitflags.workspace = true
 chrono.workspace = true
 eyeball.workspace = true

crates/matrix-sdk-ui/tests/integration/room_list_service.rs

@@ -1876,7 +1876,7 @@ async fn test_room_sorting() -> Result<(), Error> {
     // Now, let's define a filter.
     dynamic_entries.set_filter(Box::new(new_filter_non_left()));
 
-    // Assert rooms are sorted by recency and by name!.
+    // Assert rooms are sorted by recency and by name!
     assert_entries_batch! {
         [stream]
         reset [
@@ -1925,7 +1925,7 @@ async fn test_room_sorting() -> Result<(), Error> {
                     "timeline": [{
                         "content": {
                               "body": "foo",
-                              "msgtype": "m.text"
+                              "msgtype": "m.text",
                           },
                           "event_id": "$ev7",
                           "origin_server_ts": 7,
@@ -2015,7 +2015,7 @@ async fn test_room_sorting() -> Result<(), Error> {
     // | 3     | !r4     | 5       |      |
     // | 4     | !r3     | 4       |      |
 
-    // The Latest Events are updated.
+    // Rooms are individually updated.
     assert_entries_batch! {
         [stream]
         set [ 1 ] [ "!r0:bar.org" ];
@@ -2086,19 +2086,7 @@ async fn test_room_sorting() -> Result<(), Error> {
 
     assert_entries_batch! {
         [stream]
-        insert [ 3 ] [ "!r6:bar.org" ];
-        end;
-    };
-
-    // The Latest Event is updated.
-    assert_entries_batch! {
-        [stream]
-        set [ 3 ] [ "!r6:bar.org" ];
-        end;
-    };
-    assert_entries_batch! {
-        [stream]
-        set [ 3 ] [ "!r6:bar.org" ];
+        insert [ 1 ] [ "!r6:bar.org" ];
         end;
     };
 
@@ -2113,6 +2101,18 @@ async fn test_room_sorting() -> Result<(), Error> {
     // | 4     | !r4     | 5       |      |
     // | 5     | !r3     | 4       |      |
 
+    // Rooms are individually updated.
+    assert_entries_batch! {
+        [stream]
+        set [ 1 ] [ "!r6:bar.org" ];
+        end;
+    };
+    assert_entries_batch! {
+        [stream]
+        set [ 1 ] [ "!r6:bar.org" ];
+        end;
+    };
+
     assert_entries_batch! {
         [stream]
         remove [ 5 ];
@@ -2131,17 +2131,22 @@ async fn test_room_sorting() -> Result<(), Error> {
     // | 4     | !r1     | 6       | Aaa  |
     // | 5     | !r4     | 5       |      |
 
-    // The Latest Events are updated.
+    // Rooms are individually updated.
     assert_entries_batch! {
         [stream]
-        set [ 4 ] [ "!r6:bar.org" ];
+        set [ 2 ] [ "!r6:bar.org" ];
         end;
     };
     assert_entries_batch! {
         [stream]
         set [ 0 ] [ "!r3:bar.org" ];
         end;
     };
+    assert_entries_batch! {
+        [stream]
+        set [ 2 ] [ "!r6:bar.org" ];
+        end;
+    };
 
     assert_pending!(stream);
 

crates/matrix-sdk/CHANGELOG.md

@@ -26,6 +26,9 @@ All notable changes to this project will be documented in this file.
 
 ### Bugfix
 
+- Latest Event is lazier: a `RoomLatestEvents` can be registered even if its
+  associated `RoomEventCache` isn't created yet.
+  ([#5947](https://github.com/matrix-org/matrix-rust-sdk/pull/5947))
 - Allow granting of QR login to a new client whose device ID is not a base64
   encoded Curve25519 public key.
   ([#5940](https://github.com/matrix-org/matrix-rust-sdk/pull/5940))

crates/matrix-sdk/Cargo.toml

@@ -86,6 +86,7 @@ assert_matches2 = { workspace = true, optional = true }
 async-channel = "2.5.0"
 async-stream.workspace = true
 async-trait.workspace = true
+async-once-cell.workspace = true
 axum = { version = "0.8.4", optional = true }
 bytes = "1.11.0"
 bytesize = "2.3.0"