Improve panic safety and queue performance

lib/queue.rs

@@ -46,6 +46,7 @@ impl ThreadQueue {
         Ok(id)
     }
 
+    #[inline]
     pub fn drain_items<'outer, 'lua>(
         &'outer self,
         lua: &'lua Lua,
@@ -56,11 +57,17 @@ impl ThreadQueue {
         self.queue.try_iter().map(|stored| stored.into_inner(lua))
     }
 
+    #[inline]
     pub async fn wait_for_item(&self) {
         if self.queue.is_empty() {
             self.event.listen().await;
         }
     }
+
+    #[inline]
+    pub fn is_empty(&self) -> bool {
+        self.queue.is_empty()
+    }
 }
 
 /**

lib/runtime.rs

@@ -5,6 +5,7 @@ use std::{
     process::ExitCode,
     rc::{Rc, Weak as WeakRc},
     sync::{Arc, Weak as WeakArc},
+    thread::panicking,
 };
 
 use futures_lite::prelude::*;
@@ -417,7 +418,10 @@ impl<'lua> Runtime<'lua> {
 
                 // Empty executor = we didn't spawn any new Lua tasks
                 // above, and there are no remaining tasks to run later
-                if local_exec.is_empty() {
+                if local_exec.is_empty()
+                    && self.queue_spawn.is_empty()
+                    && self.queue_defer.is_empty()
+                {
                     break;
                 }
             }
@@ -445,6 +449,16 @@ impl<'lua> Runtime<'lua> {
 
 impl Drop for Runtime<'_> {
     fn drop(&mut self) {
+        if panicking() {
+            // Do not cause further panics if already panicking, as
+            // this may abort the program instead of safely unwinding
+            self.lua.remove_app_data::<SpawnedThreadQueue>();
+            self.lua.remove_app_data::<DeferredThreadQueue>();
+            self.lua.remove_app_data::<ThreadErrorCallback>();
+            self.lua.remove_app_data::<ThreadResultMap>();
+            self.lua.remove_app_data::<Exit>();
+        } else {
+            // In any other case we panic if metadata was removed incorrectly
             self.lua
                 .remove_app_data::<SpawnedThreadQueue>()
                 .expect(ERR_METADATA_REMOVED);
@@ -462,3 +476,4 @@ impl Drop for Runtime<'_> {
                 .expect(ERR_METADATA_REMOVED);
         }
     }
+}