Add test that drops the node in an async context

.. as tokio tends to panic if dropping a runtime in an async context and
we're not super careful. Here, we add some test coverage for this edge
case in Rust tests.

Author: tnull

src/lib.rs

@@ -680,10 +680,10 @@ impl Node {
 		log_debug!(self.logger, "Stopped chain sources.");
 
 		// Wait until all background tasks (mod LDK's background processor) are done.
-		let runtime_handle = runtime.handle();
+		let runtime_2 = Arc::clone(&runtime);
 		if let Some(mut tasks) = self.background_tasks.lock().unwrap().take() {
 			tokio::task::block_in_place(move || {
-				runtime_handle.block_on(async {
+				runtime_2.block_on(async {
 					loop {
 						let timeout_fut = tokio::time::timeout(
 							Duration::from_secs(BACKGROUND_TASK_SHUTDOWN_TIMEOUT_SECS),
@@ -721,10 +721,9 @@ impl Node {
 		if let Some(background_processor_task) =
 			self.background_processor_task.lock().unwrap().take()
 		{
-			let runtime_handle = runtime.handle();
 			let abort_handle = background_processor_task.abort_handle();
 			let timeout_res = tokio::task::block_in_place(move || {
-				runtime_handle.block_on(async {
+				runtime.block_on(async {
 					tokio::time::timeout(
 						Duration::from_secs(LDK_EVENT_HANDLER_SHUTDOWN_TIMEOUT_SECS),
 						background_processor_task,

tests/integration_tests_rust.rs

@@ -1381,3 +1381,14 @@ fn facade_logging() {
 		validate_log_entry(entry);
 	}
 }
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 1)]
+async fn drop_in_async_context() {
+	let (_bitcoind, electrsd) = setup_bitcoind_and_electrsd();
+	let chain_source = TestChainSource::Esplora(&electrsd);
+	let seed_bytes = vec![42u8; 64];
+
+	let config = random_config(true);
+	let node = setup_node(&chain_source, config, Some(seed_bytes));
+	node.stop().unwrap();
+}