Improve exception handling for subscriber credential refresh (#637)

* Improve exception handling for subscriber credential refresh

* Address spelling error

google_nest_sdm/google_nest_subscriber.py

@@ -13,7 +13,7 @@
 
 from aiohttp.client_exceptions import ClientError
 from google.api_core.exceptions import GoogleAPIError, NotFound, Unauthenticated
-from google.auth.exceptions import RefreshError
+from google.auth.exceptions import RefreshError, GoogleAuthError, TransportError
 from google.auth.transport.requests import Request
 from google.cloud import pubsub_v1
 from google.oauth2.credentials import Credentials
@@ -119,6 +119,26 @@ def _validate_topic_name(topic_name: str) -> None:
         )
 
 
+def refresh_creds(creds: Credentials) -> Credentials:
+    """Refresh credentials.
+
+    This is not part of the subscriber API, exposed only to facilitate testing.
+    """
+    try:
+        creds.refresh(Request())
+    except RefreshError as err:
+        raise AuthException(f"Authentication refresh failure: {err}") from err
+    except TransportError as err:
+        raise SubscriberException(
+            f"Connectivity error during authentication refresh: {err}"
+        ) from err
+    except GoogleAuthError as err:
+        raise SubscriberException(
+            f"Error during authentication refresh: {err}"
+        ) from err
+    return creds
+
+
 class AbstractSubscriberFactory(ABC):
     """Abstract class for creating a subscriber, to facilitate testing."""
 
@@ -232,7 +252,7 @@ def _delete_subscription(
         subscription_name: str,
     ) -> None:
         """Deletes a subscription."""
-        creds = self._refresh_creds(creds)
+        creds = refresh_creds(creds)
         subscriber = pubsub_v1.SubscriberClient(credentials=creds)
         _LOGGER.debug(f"Deleting subscription '{subscription_name}'")
         subscriber.delete_subscription(subscription=subscription_name)
@@ -265,22 +285,14 @@ def callback_wrapper(message: pubsub_v1.subscriber.message.Message) -> None:
                 callback_wrapper,
             )
 
-    def _refresh_creds(self, creds: Credentials) -> Credentials:
-        """Refresh credentials."""
-        try:
-            creds.refresh(Request())
-        except RefreshError as err:
-            raise AuthException(f"Access token failure: {err}") from err
-        return creds
-
     def _new_subscriber(
         self,
         creds: Credentials,
         subscription_name: str,
         callback_wrapper: Callable[[pubsub_v1.subscriber.message.Message], None],
     ) -> pubsub_v1.subscriber.futures.StreamingPullFuture:
         """Issue a command to verify subscriber creds are correct."""
-        creds = self._refresh_creds(creds)
+        creds = refresh_creds(creds)
         subscriber = pubsub_v1.SubscriberClient(credentials=creds)
         subscription = subscriber.get_subscription(subscription=subscription_name)
         if subscription.topic:

tests/test_google_nest_subscriber.py

@@ -3,10 +3,11 @@
 import asyncio
 import json
 from typing import Any, Awaitable, Callable, Dict, Optional
-from unittest.mock import create_autospec
+from unittest.mock import create_autospec, Mock
 
 import aiohttp
 import pytest
+from google.auth.exceptions import RefreshError, GoogleAuthError, TransportError
 from google.api_core.exceptions import ClientError, Unauthenticated
 from google.cloud import pubsub_v1
 from google.oauth2.credentials import Credentials
@@ -23,6 +24,7 @@
     AbstractSubscriberFactory,
     GoogleNestSubscriber,
     get_api_env,
+    refresh_creds,
 )
 
 from .conftest import DeviceHandler, EventCallback, StructureHandler, assert_diagnostics
@@ -92,6 +94,33 @@ async def make_subscriber(
     return make_subscriber
 
 
+async def test_refresh_creds() -> None:
+    """Test low level refresh errors."""
+    mock_refresh = Mock()
+    mock_creds = Mock()
+    mock_creds.refresh = mock_refresh
+    refresh_creds(mock_creds)
+    assert mock_refresh.call_count == 1
+
+
+@pytest.mark.parametrize(
+    ("raised", "expected"),
+    [
+        (RefreshError(), AuthException),
+        (TransportError(), SubscriberException),
+        (GoogleAuthError(), SubscriberException),
+    ],
+)
+async def test_refresh_creds_error(raised: Exception, expected: Any) -> None:
+    """Test low level refresh errors."""
+    mock_refresh = Mock()
+    mock_refresh.side_effect = raised
+    mock_creds = Mock()
+    mock_creds.refresh = mock_refresh
+    with pytest.raises(expected):
+        refresh_creds(mock_creds)
+
+
 async def test_subscribe_no_events(
     device_handler: DeviceHandler,
     structure_handler: StructureHandler,