Bug: idempotent functions return None on replay when the stored response is falsy (0, False, "", [], {}) #8700

serialized_response = self.output_serializer.from_dict(response_dict) if response_dict else None

from aws_lambda_powertools.utilities.idempotency import idempotent_function
from aws_lambda_powertools.utilities.idempotency.exceptions import (
    IdempotencyItemAlreadyExistsError,
    IdempotencyItemNotFoundError,
)
from aws_lambda_powertools.utilities.idempotency.persistence.base import BasePersistenceLayer, DataRecord


class InMemoryPersistenceLayer(BasePersistenceLayer):
    def __init__(self):
        super().__init__()
        self.records = {}

    def _get_record(self, idempotency_key) -> DataRecord:
        if idempotency_key not in self.records:
            raise IdempotencyItemNotFoundError
        return self.records[idempotency_key]

    def _put_record(self, data_record: DataRecord) -> None:
        if data_record.idempotency_key in self.records:
            raise IdempotencyItemAlreadyExistsError
        self.records[data_record.idempotency_key] = data_record

    def _update_record(self, data_record: DataRecord) -> None:
        self.records[data_record.idempotency_key] = data_record

    def _delete_record(self, data_record: DataRecord) -> None:
        self.records.pop(data_record.idempotency_key, None)


persistence_layer = InMemoryPersistenceLayer()


@idempotent_function(data_keyword_argument="order", persistence_store=persistence_layer)
def count_items(order):
    return len(order["items"])


order = {"order_id": "o-1", "items": []}
print(count_items(order=order))  # 0
print(count_items(order=order))  # None, expected 0

serialized_response = self.output_serializer.from_dict(response_dict) if response_dict is not None else None