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/collab/src/tests/integration_tests.rs

@@ -334,6 +334,134 @@ async fn test_basic_calls(
     );
 }
 
+#[gpui::test(iterations = 10)]
+async fn test_calling_multiple_users_simultaneously(
+    deterministic: Arc<Deterministic>,
+    cx_a: &mut TestAppContext,
+    cx_b: &mut TestAppContext,
+    cx_c: &mut TestAppContext,
+    cx_d: &mut TestAppContext,
+) {
+    deterministic.forbid_parking();
+    let mut server = TestServer::start(&deterministic).await;
+
+    let client_a = server.create_client(cx_a, "user_a").await;
+    let client_b = server.create_client(cx_b, "user_b").await;
+    let client_c = server.create_client(cx_c, "user_c").await;
+    let client_d = server.create_client(cx_d, "user_d").await;
+    server
+        .make_contacts(&mut [
+            (&client_a, cx_a),
+            (&client_b, cx_b),
+            (&client_c, cx_c),
+            (&client_d, cx_d),
+        ])
+        .await;
+
+    let active_call_a = cx_a.read(ActiveCall::global);
+    let active_call_b = cx_b.read(ActiveCall::global);
+    let active_call_c = cx_c.read(ActiveCall::global);
+    let active_call_d = cx_d.read(ActiveCall::global);
+
+    // Simultaneously call user B and user C from client A.
+    let b_invite = active_call_a.update(cx_a, |call, cx| {
+        call.invite(client_b.user_id().unwrap(), None, cx)
+    });
+    let c_invite = active_call_a.update(cx_a, |call, cx| {
+        call.invite(client_c.user_id().unwrap(), None, cx)
+    });
+    b_invite.await.unwrap();
+    c_invite.await.unwrap();
+
+    let room_a = active_call_a.read_with(cx_a, |call, _| call.room().unwrap().clone());
+    deterministic.run_until_parked();
+    assert_eq!(
+        room_participants(&room_a, cx_a),
+        RoomParticipants {
+            remote: Default::default(),
+            pending: vec!["user_b".to_string(), "user_c".to_string()]
+        }
+    );
+
+    // Call client D from client A.
+    active_call_a
+        .update(cx_a, |call, cx| {
+            call.invite(client_d.user_id().unwrap(), None, cx)
+        })
+        .await
+        .unwrap();
+    deterministic.run_until_parked();
+    assert_eq!(
+        room_participants(&room_a, cx_a),
+        RoomParticipants {
+            remote: Default::default(),
+            pending: vec![
+                "user_b".to_string(),
+                "user_c".to_string(),
+                "user_d".to_string()
+            ]
+        }
+    );
+
+    // Accept the call on all clients simultaneously.
+    let accept_b = active_call_b.update(cx_b, |call, cx| call.accept_incoming(cx));
+    let accept_c = active_call_c.update(cx_c, |call, cx| call.accept_incoming(cx));
+    let accept_d = active_call_d.update(cx_d, |call, cx| call.accept_incoming(cx));
+    accept_b.await.unwrap();
+    accept_c.await.unwrap();
+    accept_d.await.unwrap();
+
+    deterministic.run_until_parked();
+
+    let room_b = active_call_b.read_with(cx_b, |call, _| call.room().unwrap().clone());
+    let room_c = active_call_c.read_with(cx_c, |call, _| call.room().unwrap().clone());
+    let room_d = active_call_d.read_with(cx_d, |call, _| call.room().unwrap().clone());
+    assert_eq!(
+        room_participants(&room_a, cx_a),
+        RoomParticipants {
+            remote: vec![
+                "user_b".to_string(),
+                "user_c".to_string(),
+                "user_d".to_string(),
+            ],
+            pending: Default::default()
+        }
+    );
+    assert_eq!(
+        room_participants(&room_b, cx_b),
+        RoomParticipants {
+            remote: vec![
+                "user_a".to_string(),
+                "user_c".to_string(),
+                "user_d".to_string(),
+            ],
+            pending: Default::default()
+        }
+    );
+    assert_eq!(
+        room_participants(&room_c, cx_c),
+        RoomParticipants {
+            remote: vec![
+                "user_a".to_string(),
+                "user_b".to_string(),
+                "user_d".to_string(),
+            ],
+            pending: Default::default()
+        }
+    );
+    assert_eq!(
+        room_participants(&room_d, cx_d),
+        RoomParticipants {
+            remote: vec![
+                "user_a".to_string(),
+                "user_b".to_string(),
+                "user_c".to_string(),
+            ],
+            pending: Default::default()
+        }
+    );
+}
+
 #[gpui::test(iterations = 10)]
 async fn test_room_uniqueness(
     deterministic: Arc<Deterministic>,