Mqtt fix issue with displaying non UTF-8 payload (#67471)

* Mqtt fix issue with displaying non UTF-8 payload

* None or binary

* Casting and additional test

* casting

homeassistant/components/mqtt/__init__.py

@@ -1206,20 +1206,29 @@ async def websocket_subscribe(hass, connection, msg):
 
     async def forward_messages(mqttmsg: ReceiveMessage):
         """Forward events to websocket."""
+        try:
+            payload = cast(bytes, mqttmsg.payload).decode(
+                DEFAULT_ENCODING
+            )  # not str because encoding is set to None
+        except (AttributeError, UnicodeDecodeError):
+            # Convert non UTF-8 payload to a string presentation
+            payload = str(mqttmsg.payload)
+
         connection.send_message(
             websocket_api.event_message(
                 msg["id"],
                 {
                     "topic": mqttmsg.topic,
-                    "payload": mqttmsg.payload,
+                    "payload": payload,
                     "qos": mqttmsg.qos,
                     "retain": mqttmsg.retain,
                 },
             )
         )
 
+    # Perform UTF-8 decoding directly in callback routine
     connection.subscriptions[msg["id"]] = await async_subscribe(
-        hass, msg["topic"], forward_messages
+        hass, msg["topic"], forward_messages, encoding=None
     )
 
     connection.send_message(websocket_api.result_message(msg["id"]))

tests/components/mqtt/test_init.py

@@ -1647,6 +1647,7 @@ async def test_mqtt_ws_subscription(hass, hass_ws_client, mqtt_mock):
 
     async_fire_mqtt_message(hass, "test-topic", "test1")
     async_fire_mqtt_message(hass, "test-topic", "test2")
+    async_fire_mqtt_message(hass, "test-topic", b"\xDE\xAD\xBE\xEF")
 
     response = await client.receive_json()
     assert response["event"]["topic"] == "test-topic"
@@ -1656,6 +1657,10 @@ async def test_mqtt_ws_subscription(hass, hass_ws_client, mqtt_mock):
     assert response["event"]["topic"] == "test-topic"
     assert response["event"]["payload"] == "test2"
 
+    response = await client.receive_json()
+    assert response["event"]["topic"] == "test-topic"
+    assert response["event"]["payload"] == "b'\\xde\\xad\\xbe\\xef'"
+
     # Unsubscribe
     await client.send_json({"id": 8, "type": "unsubscribe_events", "subscription": 5})
     response = await client.receive_json()