Log unhandled loop exception traces when asyncio debug is on (#57602)

homeassistant/runner.py

@@ -5,6 +5,7 @@ import asyncio
 import dataclasses
 import logging
 import threading
+import traceback
 from typing import Any
 
 from homeassistant import bootstrap
@@ -86,9 +87,15 @@ def _async_loop_exception_handler(_: Any, context: dict[str, Any]) -> None:
     if exception := context.get("exception"):
         kwargs["exc_info"] = (type(exception), exception, exception.__traceback__)
 
-    logging.getLogger(__package__).error(
+    logger = logging.getLogger(__package__)
-        "Error doing job: %s", context["message"], **kwargs  # type: ignore
+    if source_traceback := context.get("source_traceback"):
-    )
+        stack_summary = "".join(traceback.format_list(source_traceback))
+        logger.error(
+            "Error doing job: %s: %s", context["message"], stack_summary, **kwargs  # type: ignore
+        )
+        return
+
+    logger.error("Error doing job: %s", context["message"], **kwargs)  # type: ignore
 
 
 async def setup_and_run_hass(runtime_config: RuntimeConfig) -> int:

tests/ignore_uncaught_exceptions.py

@@ -1,5 +1,11 @@
 """List of tests that have uncaught exceptions today. Will be shrunk over time."""
 IGNORE_UNCAUGHT_EXCEPTIONS = [
+    (
+        # This test explicitly throws an uncaught exception
+        # and should not be removed.
+        "tests.test_runner",
+        "test_unhandled_exception_traceback",
+    ),
     (
         "test_homeassistant_bridge",
         "test_homeassistant_bridge_fan_setup",

tests/test_runner.py

@@ -117,3 +117,23 @@ def test_run_does_not_block_forever_with_shielded_task(hass, tmpdir, caplog):
     assert (
         "Task could not be canceled and was still running after shutdown" in caplog.text
     )
+
+
+async def test_unhandled_exception_traceback(hass, caplog):
+    """Test an unhandled exception gets a traceback in debug mode."""
+
+    async def _unhandled_exception():
+        raise Exception("This is unhandled")
+
+    try:
+        hass.loop.set_debug(True)
+        asyncio.create_task(_unhandled_exception())
+    finally:
+        hass.loop.set_debug(False)
+
+    await asyncio.sleep(0)
+    await asyncio.sleep(0)
+
+    assert "Task exception was never retrieved" in caplog.text
+    assert "This is unhandled" in caplog.text
+    assert "_unhandled_exception" in caplog.text