refactor: Log sync persistent-store close errors instead of returning them

Store.close() previously returned the close error as Optional[Exception],
which the only caller (FDv2.stop) discarded, so a failed close was
silently lost. It now logs a warning and returns None. Closing happens at
shutdown, where there is no caller left to react to the error.

Author: jsonbailey

ldclient/impl/datasystem/store.py

@@ -521,7 +521,7 @@ def __mapping(data: Dict[str, ModelEntity]) -> Dict[str, Dict[str, Any]]:
                     return e
         return None
 
-    def close(self) -> Optional[Exception]:
+    def close(self) -> None:
         """Close the store and any persistent store if configured."""
         with self._lock:
             if self._persistent_store is not None:
@@ -532,8 +532,7 @@ def close(self) -> Optional[Exception]:
                     if callable(close):
                         close()
                 except Exception as e:
-                    return e
-        return None
+                    log.warning("Error closing the persistent store: %s", e)
 
     def get_data_store_status_provider(self) -> Optional[DataStoreStatusProvider]:
         """Get the data store status provider for the persistent store, if configured."""

ldclient/testing/impl/datasystem/test_fdv2_persistence.py

@@ -845,3 +845,25 @@ def test_variation_does_not_throw_when_persistent_store_errors_during_warm_start
         for record in caplog.records
         if record.levelname == "ERROR"
     )
+
+
+def test_persistent_store_close_logs_and_swallows_error(caplog):
+    """A persistent-store close error is logged as a warning, not raised."""
+    from ldclient.impl.datasystem.store import Store
+    from ldclient.impl.listeners import Listeners
+
+    class ClosingFailsStore(StubFeatureStore):
+        def close(self):
+            raise RuntimeError("close boom")
+
+    store = Store(Listeners(), Listeners())
+    store.with_persistence(ClosingFailsStore(), True, None)
+
+    # close() must log the error rather than raise it.
+    store.close()
+
+    assert any(
+        "Error closing the persistent store" in record.message
+        for record in caplog.records
+        if record.levelname == "WARNING"
+    )