add safe home assistant error handling

tests/api/test_entities.py

@@ -2,6 +2,7 @@ from collections.abc import Sequence
 
 from fastapi.testclient import TestClient
 
+from app.ha.exceptions import HaTimeoutError
 from app.ha.models import HaEntitySummary
 from app.ha.reader import HaReader
 from app.main import app
@@ -15,6 +16,14 @@ class FakeHaReader(HaReader):
         return [HaEntitySummary(entity_id="sensor.temperature", domain="sensor")]
 
 
+class TimeoutHaReader(HaReader):
+    def __init__(self) -> None:
+        pass
+
+    def read_entities(self) -> Sequence[HaEntitySummary]:
+        raise HaTimeoutError("contains internal details that must not leak")
+
+
 def test_openapi_docs_are_available() -> None:
     with TestClient(app) as client:
         response = client.get("/docs")
@@ -44,3 +53,11 @@ def test_entities_returns_503_without_home_assistant_config() -> None:
             delattr(app.state, "ha_reader")
         response = client.get("/v1/entities")
     assert response.status_code == 503
+
+
+def test_entities_maps_ha_errors_without_leaking_details() -> None:
+    with TestClient(app) as client:
+        app.state.ha_reader = TimeoutHaReader()
+        response = client.get("/v1/entities")
+    assert response.status_code == 504
+    assert response.json() == {"detail": "Home Assistant request timed out."}