Avoid creating more than one room when inviting multiple people at once

Previously, when initiating a call by calling multiple people, only
the first person would get the call while all the others would briefly
show a "pending" status but never get the call.

This would happen because `ActiveCall` was trying to a create a different
room for each person called, because the original room creation hadn't finished
and so a `ModelHandle<Room>` wasn't being store in the active call.

With this commit, only one room can be created at any given time and further
invites have to wait until that room creation is done.

crates/call/src/call.rs

@@ -6,6 +6,7 @@ use std::sync::Arc;
 use anyhow::{anyhow, Result};
 use client::{proto, Client, TypedEnvelope, User, UserStore};
 use collections::HashSet;
+use futures::{future::Shared, FutureExt};
 use postage::watch;
 
 use gpui::{
@@ -33,6 +34,7 @@ pub struct IncomingCall {
 /// Singleton global maintaining the user's participation in a room across workspaces.
 pub struct ActiveCall {
     room: Option<(ModelHandle<Room>, Vec<Subscription>)>,
+    pending_room_creation: Option<Shared<Task<Result<ModelHandle<Room>, Arc<anyhow::Error>>>>>,
     location: Option<WeakModelHandle<Project>>,
     pending_invites: HashSet<u64>,
     incoming_call: (
@@ -56,6 +58,7 @@ impl ActiveCall {
     ) -> Self {
         Self {
             room: None,
+            pending_room_creation: None,
             location: None,
             pending_invites: Default::default(),
             incoming_call: watch::channel(),
@@ -124,45 +127,74 @@ impl ActiveCall {
         initial_project: Option<ModelHandle<Project>>,
         cx: &mut ModelContext<Self>,
     ) -> Task<Result<()>> {
-        let client = self.client.clone();
-        let user_store = self.user_store.clone();
         if !self.pending_invites.insert(called_user_id) {
             return Task::ready(Err(anyhow!("user was already invited")));
         }
-
         cx.notify();
-        cx.spawn(|this, mut cx| async move {
-            let invite = async {
-                if let Some(room) = this.read_with(&cx, |this, _| this.room().cloned()) {
-                    let initial_project_id = if let Some(initial_project) = initial_project {
-                        Some(
-                            room.update(&mut cx, |room, cx| {
-                                room.share_project(initial_project, cx)
-                            })
+
+        let room = if let Some(room) = self.room().cloned() {
+            Some(Task::ready(Ok(room)).shared())
+        } else {
+            self.pending_room_creation.clone()
+        };
+
+        let invite = if let Some(room) = room {
+            cx.spawn_weak(|_, mut cx| async move {
+                let room = room.await.map_err(|err| anyhow!("{:?}", err))?;
+
+                let initial_project_id = if let Some(initial_project) = initial_project {
+                    Some(
+                        room.update(&mut cx, |room, cx| room.share_project(initial_project, cx))
                             .await?,
-                        )
-                    } else {
-                        None
-                    };
-
-                    room.update(&mut cx, |room, cx| {
-                        room.call(called_user_id, initial_project_id, cx)
-                    })
-                    .await?;
+                    )
                 } else {
-                    let room = cx
-                        .update(|cx| {
-                            Room::create(called_user_id, initial_project, client, user_store, cx)
-                        })
-                        .await?;
-
-                    this.update(&mut cx, |this, cx| this.set_room(Some(room), cx))
-                        .await?;
+                    None
                 };
 
-                Ok(())
-            };
+                room.update(&mut cx, |room, cx| {
+                    room.call(called_user_id, initial_project_id, cx)
+                })
+                .await?;
 
+                anyhow::Ok(())
+            })
+        } else {
+            let client = self.client.clone();
+            let user_store = self.user_store.clone();
+            let room = cx
+                .spawn(|this, mut cx| async move {
+                    let create_room = async {
+                        let room = cx
+                            .update(|cx| {
+                                Room::create(
+                                    called_user_id,
+                                    initial_project,
+                                    client,
+                                    user_store,
+                                    cx,
+                                )
+                            })
+                            .await?;
+
+                        this.update(&mut cx, |this, cx| this.set_room(Some(room.clone()), cx))
+                            .await?;
+
+                        anyhow::Ok(room)
+                    };
+
+                    let room = create_room.await;
+                    this.update(&mut cx, |this, _| this.pending_room_creation = None);
+                    room.map_err(Arc::new)
+                })
+                .shared();
+            self.pending_room_creation = Some(room.clone());
+            cx.foreground().spawn(async move {
+                room.await.map_err(|err| anyhow!("{:?}", err))?;
+                anyhow::Ok(())
+            })
+        };
+
+        cx.spawn(|this, mut cx| async move {
             let result = invite.await;
             this.update(&mut cx, |this, cx| {
                 this.pending_invites.remove(&called_user_id);