Fix mqtt callback exception logging (#118138)

* Fix mqtt callback exception logging

* Improve code

* Add test

homeassistant/components/mqtt/client.py

@@ -835,8 +835,13 @@ class MQTT:
         msg: ReceiveMessage,
     ) -> str:
         """Return a string with the exception message."""
+        # if msg_callback is a partial we return the name of the first argument
+        if isinstance(msg_callback, partial):
+            call_back_name = getattr(msg_callback.args[0], "__name__")  # type: ignore[unreachable]
+        else:
+            call_back_name = getattr(msg_callback, "__name__")
         return (
-            f"Exception in {msg_callback.__name__} when handling msg on "
+            f"Exception in {call_back_name} when handling msg on "
             f"'{msg.topic}': '{msg.payload}'"  # type: ignore[str-bytes-safe]
         )
 

tests/components/mqtt/test_init.py

@@ -4,6 +4,7 @@ import asyncio
 from collections.abc import Generator
 from copy import deepcopy
 from datetime import datetime, timedelta
+from functools import partial
 import json
 import logging
 import socket
@@ -2912,8 +2913,8 @@ async def test_message_callback_exception_gets_logged(
     await mqtt_mock_entry()
 
     @callback
-    def bad_handler(*args) -> None:
-        """Record calls."""
+    def bad_handler(msg: ReceiveMessage) -> None:
+        """Handle callback."""
         raise ValueError("This is a bad message callback")
 
     await mqtt.async_subscribe(hass, "test-topic", bad_handler)
@@ -2926,6 +2927,40 @@ async def test_message_callback_exception_gets_logged(
     )
 
 
+@pytest.mark.no_fail_on_log_exception
+async def test_message_partial_callback_exception_gets_logged(
+    hass: HomeAssistant,
+    caplog: pytest.LogCaptureFixture,
+    mqtt_mock_entry: MqttMockHAClientGenerator,
+) -> None:
+    """Test exception raised by message handler."""
+    await mqtt_mock_entry()
+
+    @callback
+    def bad_handler(msg: ReceiveMessage) -> None:
+        """Handle callback."""
+        raise ValueError("This is a bad message callback")
+
+    def parial_handler(
+        msg_callback: MessageCallbackType,
+        attributes: set[str],
+        msg: ReceiveMessage,
+    ) -> None:
+        """Partial callback handler."""
+        msg_callback(msg)
+
+    await mqtt.async_subscribe(
+        hass, "test-topic", partial(parial_handler, bad_handler, {"some_attr"})
+    )
+    async_fire_mqtt_message(hass, "test-topic", "test")
+    await hass.async_block_till_done()
+
+    assert (
+        "Exception in bad_handler when handling msg on 'test-topic':"
+        " 'test'" in caplog.text
+    )
+
+
 async def test_mqtt_ws_subscription(
     hass: HomeAssistant,
     hass_ws_client: WebSocketGenerator,