Fix race condition when UpdateChannel message is received while fetching participants for previous update

Co-authored-by: Mikayla <mikayla@zed.dev>

crates/client/src/channel_store.rs

@@ -4,11 +4,13 @@ use anyhow::anyhow;
 use anyhow::Result;
 use collections::HashMap;
 use collections::HashSet;
+use futures::channel::mpsc;
 use futures::Future;
 use futures::StreamExt;
 use gpui::{AsyncAppContext, Entity, ModelContext, ModelHandle, Task};
 use rpc::{proto, TypedEnvelope};
 use std::sync::Arc;
+use util::ResultExt;
 
 pub type ChannelId = u64;
 pub type UserId = u64;
@@ -20,10 +22,12 @@ pub struct ChannelStore {
     channel_participants: HashMap<ChannelId, Vec<Arc<User>>>,
     channels_with_admin_privileges: HashSet<ChannelId>,
     outgoing_invites: HashSet<(ChannelId, UserId)>,
+    update_channels_tx: mpsc::UnboundedSender<proto::UpdateChannels>,
     client: Arc<Client>,
     user_store: ModelHandle<UserStore>,
     _rpc_subscription: Subscription,
     _watch_connection_status: Task<()>,
+    _update_channels: Task<()>,
 }
 
 #[derive(Clone, Debug, PartialEq)]
@@ -62,6 +66,7 @@ impl ChannelStore {
         let rpc_subscription =
             client.add_message_handler(cx.handle(), Self::handle_update_channels);
 
+        let (update_channels_tx, mut update_channels_rx) = mpsc::unbounded();
         let mut connection_status = client.status();
         let watch_connection_status = cx.spawn_weak(|this, mut cx| async move {
             while let Some(status) = connection_status.next().await {
@@ -89,10 +94,23 @@ impl ChannelStore {
             channel_participants: Default::default(),
             channels_with_admin_privileges: Default::default(),
             outgoing_invites: Default::default(),
+            update_channels_tx,
             client,
             user_store,
             _rpc_subscription: rpc_subscription,
             _watch_connection_status: watch_connection_status,
+            _update_channels: cx.spawn_weak(|this, mut cx| async move {
+                while let Some(update_channels) = update_channels_rx.next().await {
+                    if let Some(this) = this.upgrade(&cx) {
+                        let update_task = this.update(&mut cx, |this, cx| {
+                            this.update_channels(update_channels, cx)
+                        });
+                        if let Some(update_task) = update_task {
+                            update_task.await.log_err();
+                        }
+                    }
+                }
+            }),
         }
     }
 
@@ -159,13 +177,14 @@ impl ChannelStore {
             let channel_id = channel.id;
 
             this.update(&mut cx, |this, cx| {
-                this.update_channels(
+                let task = this.update_channels(
                     proto::UpdateChannels {
                         channels: vec![channel],
                         ..Default::default()
                     },
                     cx,
                 );
+                assert!(task.is_none());
 
                 // This event is emitted because the collab panel wants to clear the pending edit state
                 // before this frame is rendered. But we can't guarantee that the collab panel's future
@@ -287,13 +306,14 @@ impl ChannelStore {
                 .channel
                 .ok_or_else(|| anyhow!("missing channel in response"))?;
             this.update(&mut cx, |this, cx| {
-                this.update_channels(
+                let task = this.update_channels(
                     proto::UpdateChannels {
                         channels: vec![channel],
                         ..Default::default()
                     },
                     cx,
                 );
+                assert!(task.is_none());
 
                 // This event is emitted because the collab panel wants to clear the pending edit state
                 // before this frame is rendered. But we can't guarantee that the collab panel's future
@@ -375,8 +395,10 @@ impl ChannelStore {
         _: Arc<Client>,
         mut cx: AsyncAppContext,
     ) -> Result<()> {
-        this.update(&mut cx, |this, cx| {
-            this.update_channels(message.payload, cx);
+        this.update(&mut cx, |this, _| {
+            this.update_channels_tx
+                .unbounded_send(message.payload)
+                .unwrap();
         });
         Ok(())
     }
@@ -385,7 +407,7 @@ impl ChannelStore {
         &mut self,
         payload: proto::UpdateChannels,
         cx: &mut ModelContext<ChannelStore>,
-    ) {
+    ) -> Option<Task<Result<()>>> {
         if !payload.remove_channel_invitations.is_empty() {
             self.channel_invitations
                 .retain(|channel| !payload.remove_channel_invitations.contains(&channel.id));
@@ -470,6 +492,11 @@ impl ChannelStore {
             }
         }
 
+        cx.notify();
+        if payload.channel_participants.is_empty() {
+            return None;
+        }
+
         let mut all_user_ids = Vec::new();
         let channel_participants = payload.channel_participants;
         for entry in &channel_participants {
@@ -480,11 +507,10 @@ impl ChannelStore {
             }
         }
 
-        // TODO: Race condition if an update channels messages comes in while resolving avatars
         let users = self
             .user_store
             .update(cx, |user_store, cx| user_store.get_users(all_user_ids, cx));
-        cx.spawn(|this, mut cx| async move {
+        Some(cx.spawn(|this, mut cx| async move {
             let users = users.await?;
 
             this.update(&mut cx, |this, cx| {
@@ -509,10 +535,7 @@ impl ChannelStore {
                 cx.notify();
             });
             anyhow::Ok(())
-        })
-        .detach();
-
-        cx.notify();
+        }))
     }
 
     fn channel_path_sorting_key<'a>(

crates/client/src/channel_store_tests.rs

@@ -139,7 +139,8 @@ fn update_channels(
     message: proto::UpdateChannels,
     cx: &mut AppContext,
 ) {
-    channel_store.update(cx, |store, cx| store.update_channels(message, cx));
+    let task = channel_store.update(cx, |store, cx| store.update_channels(message, cx));
+    assert!(task.is_none());
 }
 
 #[track_caller]