refactor(timeline): add more logs when we couldn't create an embedded event

This should help figuring out why some thread's latest replies are
marked as "unsupported events".

Author: bnjbvr

crates/matrix-sdk-ui/src/timeline/controller/state_transaction.rs

@@ -558,6 +558,7 @@ impl<'a, P: RoomDataProvider> TimelineStateTransaction<'a, P> {
 
     // Attempt to load a thread's latest reply as an embedded timeline item, either
     // using the event cache or the storage.
+    #[instrument(skip(self, room_data_provider))]
     async fn fetch_latest_thread_reply(
         &mut self,
         event_id: &EventId,

crates/matrix-sdk-ui/src/timeline/event_handler.rs

@@ -194,8 +194,7 @@ impl TimelineAction {
 
     /// Create a new [`TimelineAction`] from a given remote event.
     ///
-    /// The return value may be `None` if handling the event (be it a new item
-    /// or an aggregation) is not supported for this event type.
+    /// The return value may be `None` if the event was a redacted reaction.
     #[allow(clippy::too_many_arguments)]
     pub async fn from_event<P: RoomDataProvider>(
         event: AnySyncTimelineEvent,

crates/matrix-sdk-ui/src/timeline/event_item/content/reply.rs

@@ -133,15 +133,24 @@ impl EmbeddedEvent {
         )
         .await;
 
-        let Some(TimelineAction::AddItem { content }) = action else {
-            // The event can't be represented as a standalone timeline item.
-            return Ok(None);
-        };
+        match action {
+            Some(TimelineAction::AddItem { content }) => {
+                let sender_profile = TimelineDetails::from_initial_value(
+                    room_data_provider.profile_from_user_id(&sender).await,
+                );
+                Ok(Some(Self { content, sender, sender_profile, timestamp, identifier }))
+            }
 
-        let sender_profile = TimelineDetails::from_initial_value(
-            room_data_provider.profile_from_user_id(&sender).await,
-        );
+            Some(TimelineAction::HandleAggregation { kind, .. }) => {
+                // The event can't be represented as a standalone timeline item.
+                warn!("embedded event is an aggregation: {}", kind.debug_string());
+                Ok(None)
+            }
 
-        Ok(Some(Self { content, sender, sender_profile, timestamp, identifier }))
+            None => {
+                warn!("embedded event lead to no action (neither an aggregation nor a new item)");
+                Ok(None)
+            }
+        }
     }
 }