feat(idempotency): Fix when delete_record raise a KeyError

Fix a KeyError when we an error happens and local_cache is True and the cache is empty

Author: Michael Brewer

Diff for: aws_lambda_powertools/utilities/idempotency/persistence/base.py

@@ -272,7 +272,8 @@ def _retrieve_from_cache(self, idempotency_key: str):
     def _delete_from_cache(self, idempotency_key: str):
         if not self.use_local_cache:
             return
-        del self._cache[idempotency_key]
+        if idempotency_key in self._cache:
+            del self._cache[idempotency_key]
 
     def save_success(self, event: Dict[str, Any], result: dict) -> None:
         """

Diff for: tests/functional/idempotency/test_idempotency.py

@@ -627,3 +627,14 @@ def test_user_local_disabled(persistence_store):
     # THEN raise AttributeError
     # AND don't have a _cache attribute
     assert not hasattr("persistence_store", "_cache")
+
+
+@pytest.mark.parametrize("persistence_store", [{"use_local_cache": True}], indirect=True)
+def test_delete_from_cache_when_empty(persistence_store):
+    # GIVEN use_local_cache is True AND the local cache is empty
+    try:
+        # WHEN we _delete_from_cache
+        persistence_store._delete_from_cache("key_does_not_exist")
+    except KeyError:
+        # THEN we should not get a KeyError
+        pytest.fail("KeyError should not happen")