fix rejoin after quit (#10100)

Release Notes:

- collab: Fixed rejoining channels quickly after a restart

crates/gpui/src/executor.rs

@@ -219,11 +219,17 @@ impl BackgroundExecutor {
                         if let Some(test) = self.dispatcher.as_test() {
                             if !test.parking_allowed() {
                                 let mut backtrace_message = String::new();
+                                let mut waiting_message = String::new();
                                 if let Some(backtrace) = test.waiting_backtrace() {
                                     backtrace_message =
                                         format!("\nbacktrace of waiting future:\n{:?}", backtrace);
                                 }
-                                panic!("parked with nothing left to run\n{:?}", backtrace_message)
+                                if let Some(waiting_hint) = test.waiting_hint() {
+                                    waiting_message = format!("\n  waiting on: {}\n", waiting_hint);
+                                }
+                                panic!(
+                                    "parked with nothing left to run{waiting_message}{backtrace_message}",
+                                )
                             }
                         }
 
@@ -354,6 +360,12 @@ impl BackgroundExecutor {
         self.dispatcher.as_test().unwrap().forbid_parking();
     }
 
+    /// adds detail to the "parked with nothing let to run" message.
+    #[cfg(any(test, feature = "test-support"))]
+    pub fn set_waiting_hint(&self, msg: Option<String>) {
+        self.dispatcher.as_test().unwrap().set_waiting_hint(msg);
+    }
+
     /// in tests, returns the rng used by the dispatcher and seeded by the `SEED` environment variable
     #[cfg(any(test, feature = "test-support"))]
     pub fn rng(&self) -> StdRng {

crates/gpui/src/platform/test/dispatcher.rs

@@ -36,6 +36,7 @@ struct TestDispatcherState {
     is_main_thread: bool,
     next_id: TestDispatcherId,
     allow_parking: bool,
+    waiting_hint: Option<String>,
     waiting_backtrace: Option<Backtrace>,
     deprioritized_task_labels: HashSet<TaskLabel>,
     block_on_ticks: RangeInclusive<usize>,
@@ -54,6 +55,7 @@ impl TestDispatcher {
             is_main_thread: true,
             next_id: TestDispatcherId(1),
             allow_parking: false,
+            waiting_hint: None,
             waiting_backtrace: None,
             deprioritized_task_labels: Default::default(),
             block_on_ticks: 0..=1000,
@@ -132,6 +134,14 @@ impl TestDispatcher {
         self.state.lock().allow_parking = false
     }
 
+    pub fn set_waiting_hint(&self, msg: Option<String>) {
+        self.state.lock().waiting_hint = msg
+    }
+
+    pub fn waiting_hint(&self) -> Option<String> {
+        self.state.lock().waiting_hint.clone()
+    }
+
     pub fn start_waiting(&self) {
         self.state.lock().waiting_backtrace = Some(Backtrace::new_unresolved());
     }

crates/gpui/src/platform/test/platform.rs

@@ -69,6 +69,7 @@ impl TestPlatform {
             .multiple_choice
             .pop_front()
             .expect("no pending multiple choice prompt");
+        self.background_executor().set_waiting_hint(None);
         tx.send(response_ix).ok();
     }
 
@@ -76,8 +77,10 @@ impl TestPlatform {
         !self.prompts.borrow().multiple_choice.is_empty()
     }
 
-    pub(crate) fn prompt(&self) -> oneshot::Receiver<usize> {
+    pub(crate) fn prompt(&self, msg: &str, detail: Option<&str>) -> oneshot::Receiver<usize> {
         let (tx, rx) = oneshot::channel();
+        self.background_executor()
+            .set_waiting_hint(Some(format!("PROMPT: {:?} {:?}", msg, detail)));
         self.prompts.borrow_mut().multiple_choice.push_back(tx);
         rx
     }

crates/gpui/src/platform/test/window.rs

@@ -159,8 +159,8 @@ impl PlatformWindow for TestWindow {
     fn prompt(
         &self,
         _level: crate::PromptLevel,
-        _msg: &str,
-        _detail: Option<&str>,
+        msg: &str,
+        detail: Option<&str>,
         _answers: &[&str],
     ) -> Option<futures::channel::oneshot::Receiver<usize>> {
         Some(
@@ -169,7 +169,7 @@ impl PlatformWindow for TestWindow {
                 .platform
                 .upgrade()
                 .expect("platform dropped")
-                .prompt(),
+                .prompt(msg, detail),
         )
     }