Only import MQTT in MySensors once it is set up (#183290)

Co-authored-by: Claude <noreply@anthropic.com>

homeassistant/components/mysensors/config_flow.py

@@ -10,11 +10,6 @@ from awesomeversion import (
 )
 import probatio
 
-from homeassistant.components.mqtt import (
-    DOMAIN as MQTT_DOMAIN,
-    valid_publish_topic,
-    valid_subscribe_topic,
-)
 from homeassistant.config_entries import ConfigEntry, ConfigFlow, ConfigFlowResult
 from homeassistant.const import CONF_DEVICE
 from homeassistant.core import callback
@@ -34,6 +29,7 @@ from .const import (
     CONF_TOPIC_OUT_PREFIX,
     CONF_VERSION,
     DOMAIN,
+    MQTT_DOMAIN,
     ConfGatewayType,
 )
 from .gateway import MQTT_COMPONENT, is_serial_port, is_socket_address, try_connect
@@ -211,6 +207,11 @@ class MySensorsConfigFlowHandler(ConfigFlow, domain=DOMAIN):
         if MQTT_DOMAIN not in self.hass.config.components:
             return self.async_abort(reason="mqtt_required")
 
+        from homeassistant.components.mqtt import (  # noqa: PLC0415
+            valid_publish_topic,
+            valid_subscribe_topic,
+        )
+
         gw_type = self._gw_type = CONF_GATEWAY_TYPE_MQTT
         errors: dict[str, str] = {}
 

homeassistant/components/mysensors/const.py

@@ -5,6 +5,9 @@ from typing import Final, Literal, TypedDict
 
 from homeassistant.const import Platform
 
+# MQTT is only imported once it is set up, as it is heavy to load
+MQTT_DOMAIN: Final = "mqtt"
+
 ATTR_DEVICES: Final = "devices"
 ATTR_GATEWAY_ID: Final = "gateway_id"
 ATTR_NODE_ID: Final = "node_id"

homeassistant/components/mysensors/gateway.py

@@ -11,12 +11,6 @@ from typing import Any
 from mysensors import BaseAsyncGateway, Message, Sensor, get_const, mysensors
 import probatio
 
-from homeassistant.components.mqtt import (
-    DOMAIN as MQTT_DOMAIN,
-    ReceiveMessage as MQTTReceiveMessage,
-    async_publish,
-    async_subscribe,
-)
 from homeassistant.const import CONF_DEVICE, EVENT_HOMEASSISTANT_STOP
 from homeassistant.core import Event, HomeAssistant, callback
 from homeassistant.helpers import config_validation as cv
@@ -35,6 +29,7 @@ from .const import (
     CONF_TOPIC_IN_PREFIX,
     CONF_TOPIC_OUT_PREFIX,
     CONF_VERSION,
+    MQTT_DOMAIN,
     ConfGatewayType,
 )
 from .handler import HANDLERS
@@ -176,6 +171,12 @@ async def _get_gateway(
         if MQTT_DOMAIN not in hass.config.components:
             return None
 
+        from homeassistant.components.mqtt import (  # noqa: PLC0415
+            ReceiveMessage as MQTTReceiveMessage,
+            async_publish,
+            async_subscribe,
+        )
+
         def pub_callback(topic: str, payload: str, qos: int, retain: bool) -> None:
             """Call MQTT publish function."""
             hass.async_create_task(async_publish(hass, topic, payload, qos, retain))

tests/components/mysensors/test_gateway.py

@@ -1,13 +1,26 @@
 """Test function in gateway.py."""
 
-from unittest.mock import patch
+from unittest.mock import AsyncMock, MagicMock, patch
 
 import probatio
 import pytest
 
+from homeassistant.components.mysensors.const import (
+    CONF_GATEWAY_TYPE,
+    CONF_GATEWAY_TYPE_MQTT,
+    CONF_RETAIN,
+    CONF_TOPIC_IN_PREFIX,
+    CONF_TOPIC_OUT_PREFIX,
+    CONF_VERSION,
+    DOMAIN,
+)
 from homeassistant.components.mysensors.gateway import is_serial_port
+from homeassistant.const import CONF_DEVICE
 from homeassistant.core import HomeAssistant
 
+from tests.common import MockConfigEntry, async_fire_mqtt_message
+from tests.typing import MqttMockHAClient
+
 
 @pytest.mark.parametrize(
     ("port", "expect_valid"),
@@ -31,3 +44,42 @@ def test_is_serial_port_windows(
             assert not expect_valid
         else:
             assert expect_valid
+
+
+async def test_mqtt_gateway(hass: HomeAssistant, mqtt_mock: MqttMockHAClient) -> None:
+    """Test the MQTT gateway subscribes and publishes through MQTT."""
+    entry = MockConfigEntry(
+        domain=DOMAIN,
+        data={
+            CONF_GATEWAY_TYPE: CONF_GATEWAY_TYPE_MQTT,
+            CONF_DEVICE: "mqtt",
+            CONF_VERSION: "2.3",
+            CONF_TOPIC_IN_PREFIX: "in",
+            CONF_TOPIC_OUT_PREFIX: "out",
+            CONF_RETAIN: False,
+        },
+    )
+    entry.add_to_hass(hass)
+    with (
+        patch("mysensors.task.OTAFirmware", autospec=True),
+        patch("mysensors.task.load_fw", autospec=True),
+        patch("mysensors.task.Persistence", autospec=True) as persistence_class,
+    ):
+        persistence = persistence_class.return_value
+        persistence.schedule_save_sensors = AsyncMock()
+        persistence.safe_load_sensors = MagicMock()
+        persistence.save_sensors = MagicMock()
+        assert await hass.config_entries.async_setup(entry.entry_id)
+        await hass.async_block_till_done()
+
+        subscribed_topics = [
+            call.args[0] for call in mqtt_mock.async_subscribe.call_args_list
+        ]
+        assert "in/+/+/3/+/+" in subscribed_topics
+
+        # A time request is answered by publishing the current time
+        async_fire_mqtt_message(hass, "in/1/255/3/0/1", "")
+        await hass.async_block_till_done()
+
+    published_topics = [call.args[0] for call in mqtt_mock.async_publish.call_args_list]
+    assert "out/1/255/3/0/1" in published_topics