address lints and lock more granularly in do_get

Author: robtandy

src/flight_service/do_get.rs

@@ -91,7 +91,10 @@ impl ArrowFlightEndpoint {
         let key = doget
             .stage_key
             .ok_or(Status::invalid_argument("DoGet is missing the stage key"))?;
-        let once_stage = self.stages.entry(key).or_default();
+        let once_stage = {
+            let entry = self.stages.entry(key).or_default();
+            Arc::clone(&entry)
+        };
 
         let (state, stage) = once_stage
             .get_or_try_init(|| async {

src/flight_service/service.rs

@@ -34,7 +34,8 @@ pub struct StageKey {
 pub struct ArrowFlightEndpoint {
     pub(super) channel_manager: Arc<ChannelManager>,
     pub(super) runtime: Arc<RuntimeEnv>,
-    pub(super) stages: DashMap<StageKey, OnceCell<(SessionState, Arc<ExecutionStage>)>>,
+    #[allow(clippy::type_complexity)]
+    pub(super) stages: DashMap<StageKey, Arc<OnceCell<(SessionState, Arc<ExecutionStage>)>>>,
     pub(super) session_builder: Arc<dyn SessionBuilder + Send + Sync>,
 }