Tighten list_users() to trust Core's auth/list contract

Core's config/auth/list WS command always returns a list, never None.
Replace the silent `if not raw: return []` (which also swallowed empty
lists) with an assert, remove the dead AuthListUsersNoneResponseError
exception class, and document the HomeAssistantWSError contract in the
docstring.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

supervisor/exceptions.py

@@ -620,18 +620,6 @@ class AuthListUsersError(AuthError, APIUnknownSupervisorError):
     message_template = "Can't request listing users on Home Assistant"
 
 
-class AuthListUsersNoneResponseError(AuthError, APIInternalServerError):
-    """Auth error if listing users returned invalid None response."""
-
-    error_key = "auth_list_users_none_response_error"
-    message_template = "Home Assistant returned invalid response of `{none}` instead of a list of users. Check Home Assistant logs for details (check with `{logs_command}`)"
-    extra_fields = {"none": "None", "logs_command": "ha core logs"}
-
-    def __init__(self, logger: Callable[..., None] | None = None) -> None:
-        """Initialize exception."""
-        super().__init__(None, logger)
-
-
 class AuthInvalidNonStringValueError(AuthError, APIUnauthorized):
     """Auth error if something besides a string provided as username or password."""
 

supervisor/homeassistant/module.py

@@ -568,10 +568,12 @@ class HomeAssistant(FileConfiguration, CoreSysAttributes):
                 self._data[attr] = data[attr]
 
     async def list_users(self) -> list[HomeAssistantUser]:
-        """Fetch list of all users from Home Assistant Core via WebSocket."""
+        """Fetch list of all users from Home Assistant Core via WebSocket.
+
+        Raises HomeAssistantWSError on WebSocket connection/communication failure.
+        """
         raw: list[dict[str, Any]] | None = await self.websocket.async_send_command(
             {ATTR_TYPE: "config/auth/list"}
         )
-        if not raw:
-            return []
+        assert raw is not None
         return [HomeAssistantUser.from_dict(data) for data in raw]

tests/api/test_auth.py

@@ -189,18 +189,6 @@ async def test_list_users_ws_error(
     assert "Can't request listing users on Home Assistant: fail" in caplog.text
 
 
-async def test_list_users_none_response(
-    api_client: TestClient,
-    ha_ws_client: AsyncMock,
-):
-    """Test None response from WS returns empty user list."""
-    ha_ws_client.async_send_command.return_value = None
-    resp = await api_client.get("/auth/list")
-    assert resp.status == 200
-    result = await resp.json()
-    assert result["data"]["users"] == []
-
-
 @pytest.mark.parametrize(
     ("field", "api_client"),
     [("username", TEST_ADDON_SLUG), ("user", TEST_ADDON_SLUG)],

tests/homeassistant/test_module.py

@@ -59,9 +59,10 @@ async def test_load(
 
 
 async def test_list_users_none(coresys: CoreSys, ha_ws_client: AsyncMock):
-    """Test list users returning none does not fail."""
+    """Test list users asserts on unexpected None response from Core."""
     ha_ws_client.async_send_command.return_value = None
-    assert await coresys.homeassistant.list_users() == []
+    with pytest.raises(AssertionError):
+        await coresys.homeassistant.list_users()
 
 
 async def test_write_pulse_error(coresys: CoreSys, caplog: pytest.LogCaptureFixture):