Fix Duco diagnostics crash on connection error

homeassistant/components/duco/diagnostics.py

@@ -2,14 +2,17 @@
 
 from __future__ import annotations
 
-import asyncio
 from dataclasses import asdict
 from typing import Any
 
+from duco.exceptions import DucoConnectionError
+
 from homeassistant.components.diagnostics import async_redact_data
 from homeassistant.const import CONF_HOST
 from homeassistant.core import HomeAssistant
+from homeassistant.exceptions import HomeAssistantError
 
+from .const import DOMAIN
 from .coordinator import DucoConfigEntry
 
 TO_REDACT = {
@@ -32,11 +35,15 @@ async def async_get_config_entry_diagnostics(
     board = asdict(coordinator.board_info)
     board.pop("time")
 
-    lan_info, duco_diags, write_remaining = await asyncio.gather(
-        coordinator.client.async_get_lan_info(),
-        coordinator.client.async_get_diagnostics(),
-        coordinator.client.async_get_write_req_remaining(),
-    )
+    try:
+        lan_info = await coordinator.client.async_get_lan_info()
+        duco_diags = await coordinator.client.async_get_diagnostics()
+        write_remaining = await coordinator.client.async_get_write_req_remaining()
+    except DucoConnectionError as err:
+        raise HomeAssistantError(
+            translation_domain=DOMAIN,
+            translation_key="connection_error",
+        ) from err
 
     return async_redact_data(
         {

homeassistant/components/duco/strings.json

@@ -87,6 +87,9 @@
     "cannot_connect": {
       "message": "An error occurred while trying to connect to the Duco instance: {error}"
     },
+    "connection_error": {
+      "message": "Could not connect to the Duco device."
+    },
     "failed_to_set_state": {
       "message": "Failed to set ventilation state: {error}"
     },

tests/components/duco/test_diagnostics.py

@@ -2,12 +2,16 @@
 
 from __future__ import annotations
 
+from http import HTTPStatus
 from unittest.mock import AsyncMock
 
+from duco.exceptions import DucoConnectionError
 import pytest
 from syrupy.assertion import SnapshotAssertion
 
+from homeassistant.components.diagnostics import DOMAIN as DIAGNOSTICS_DOMAIN
 from homeassistant.core import HomeAssistant
+from homeassistant.setup import async_setup_component
 
 from tests.common import MockConfigEntry
 from tests.components.diagnostics import get_diagnostics_for_config_entry
@@ -27,3 +31,28 @@ async def test_diagnostics(
         await get_diagnostics_for_config_entry(hass, hass_client, mock_config_entry)
         == snapshot
     )
+
+
+@pytest.mark.usefixtures("init_integration")
+@pytest.mark.parametrize(
+    "failing_method",
+    ["async_get_lan_info", "async_get_diagnostics", "async_get_write_req_remaining"],
+)
+async def test_diagnostics_connection_error(
+    hass: HomeAssistant,
+    hass_client: ClientSessionGenerator,
+    mock_config_entry: MockConfigEntry,
+    mock_duco_client: AsyncMock,
+    failing_method: str,
+) -> None:
+    """Test that a connection error during diagnostics returns a 500 response."""
+    getattr(mock_duco_client, failing_method).side_effect = DucoConnectionError(
+        "Server disconnected"
+    )
+    assert await async_setup_component(hass, DIAGNOSTICS_DOMAIN, {})
+    await hass.async_block_till_done()
+    client = await hass_client()
+    response = await client.get(
+        f"/api/diagnostics/config_entry/{mock_config_entry.entry_id}"
+    )
+    assert response.status == HTTPStatus.INTERNAL_SERVER_ERROR