Bug: DataclassSerializer cannot save datetime/UUID fields and does not rebuild nested dataclasses on replay

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Desde 1/11/2026.

Avaliação

Dificuldade
3/5
Tempo estimado
1-2 dias
Facilidade para iniciantes
75/100
Tipo de issue
Bug
Clareza
Claramente especificada
Status de atividade
Ativa
Stack de tecnologia
python
Domínio
backend

Direção de pesquisa

Read AGENTS.md for test commands. Edit aws_lambda_powertools/utilities/idempotency/serialization/dataclass.py: make to_dict emit ISO strings and str for UUID, and have from_dict rebuild nested dataclasses via dataclasses.fields(). Add tests in tests/functional/idempotency/_boto3/test_idempotency.py verifying round-trip of UUID/datetime and nested dataclass equality. Done when replayed value equals original.

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Descrição

bug good first issue help wanted idempotency

[!WARNING]
For contributors, human or agent. Comment here to claim this issue and wait for the assignment before opening a PR; if two PRs show up, the assignee's stays. AI-assisted work is welcome, say so in the PR and tell us how you verified it: run the tests yourself and paste what you saw, do not describe runs you did not do. Read AGENTS.md first, it has the commands and the rules the CI enforces. This goes into 3.41.0.

Expected Behaviour

DataclassSerializer saves a dataclass result that contains datetime or UUID fields, and rebuilds nested dataclasses on replay, so the replayed value equals the original.

Current Behaviour

to_dict returns dataclasses.asdict(data) unchanged and save_success dumps it with the plain JSON encoder, which has no datetime/UUID support, so the first call fails with IdempotencyPersistenceLayerError (and then hits the stuck INPROGRESS record described in the companion issue for item 4). This is the same class of bug fixed for Pydantic in #8569. Separately, from_dict does self.__model(**data), so nested dataclasses come back as plain dicts on replay.

Code snippet
import uuid
from dataclasses import dataclass
from datetime import datetime
from aws_lambda_powertools.utilities.idempotency import idempotent_function
from aws_lambda_powertools.utilities.idempotency.serialization.dataclass import DataclassSerializer

@dataclass
class Item:
    sku: str

@dataclass
class Order:
    id: uuid.UUID
    created: datetime
    item: Item

@idempotent_function(data_keyword_argument="order", persistence_store=layer, output_serializer=DataclassSerializer)
def process(order: dict) -> Order:
    return Order(id=uuid.uuid4(), created=datetime(2026, 1, 1), item=Item(sku="x"))

process(order={"id": 1})  # IdempotencyPersistenceLayerError: Object of type UUID is not JSON serializable
# with only str fields: first call Order(item=Item(sku='x')), replay Order(item={'sku': 'x'})
Possible Solution

In aws_lambda_powertools/utilities/idempotency/serialization/dataclass.py: make to_dict produce JSON-safe values (ISO strings for datetime/date, str for UUID), and in from_dict rebuild nested dataclasses from dataclasses.fields() type hints (and lists of them). Tests in tests/functional/idempotency/_boto3/test_idempotency.py: a dataclass with UUID and datetime round-trips through save and replay, and a nested dataclass comes back as the dataclass, not a dict.

Item 6 of the Idempotency audit in #8603. No AWS resources needed.

Powertools for AWS Lambda (Python) version

latest

AWS Lambda function runtime

3.13

Packaging format used

PyPi

Debugging logs

No response

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