Clean up cancelled SSE wait tasks

repub/datastar.py

@@ -169,20 +169,23 @@ async def render_stream(
                 return
             queue_task = asyncio.create_task(queue.get())
             shutdown_task = asyncio.create_task(shutdown_event.wait())
-            done, pending = await asyncio.wait(
+            try:
+                done, _pending = await asyncio.wait(
                     {queue_task, shutdown_task},
                     return_when=asyncio.FIRST_COMPLETED,
                 )
-            for task in pending:
-                task.cancel()
-            for task in pending:
-                with suppress(asyncio.CancelledError):
-                    await task
                 if shutdown_task in done:
-                with suppress(asyncio.CancelledError):
-                    await queue_task
                     return
                 event_name = queue_task.result()
+            finally:
+                for task in (queue_task, shutdown_task):
+                    if not task.done():
+                        task.cancel()
+                for task in (queue_task, shutdown_task):
+                    if task.done() and not task.cancelled():
+                        continue
+                    with suppress(asyncio.CancelledError):
+                        await task
         last_event_id, event = await render_sse_event(
             render,
             last_event_id=last_event_id,

tests/test_web.py

@@ -575,6 +575,39 @@ def test_render_stream_stops_when_shutdown_is_requested() -> None:
     asyncio.run(run())
 
 
+def test_render_stream_cleans_up_child_tasks_when_cancelled() -> None:
+    async def run() -> None:
+        queue = RefreshBroker().subscribe()
+        shutdown_event = asyncio.Event()
+
+        async def render() -> str:
+            return '<main id="morph">queue</main>'
+
+        stream = render_stream(
+            queue,
+            render,
+            render_on_connect=False,
+            shutdown_event=shutdown_event,
+        )
+        next_event = asyncio.create_task(anext(stream))
+        await asyncio.sleep(0)
+        next_event.cancel()
+
+        with pytest.raises(asyncio.CancelledError):
+            await next_event
+
+        await asyncio.sleep(0)
+
+        pending = tuple(
+            task
+            for task in asyncio.all_tasks()
+            if task is not asyncio.current_task() and not task.done()
+        )
+        assert pending == ()
+
+    asyncio.run(run())
+
+
 def test_render_dashboard_shows_dashboard_information_architecture(
     monkeypatch, tmp_path: Path
 ) -> None: