Static typing: type inconsistency with BaseEnvelope and DictWrapper

Static type checker used

{“label”=>“mypy (project’s standard)”}

AWS Lambda function runtime

{“label”=>“3.8”}

AWS Lambda Powertools for Python version

1.20.2

Static type checker info

Argument 1 to “APIGatewayProxyEvent” has incompatible type “Union[Dict[str, Any], Any, None]”; expected "Dict[str, Any]"mypy(error)

Code snippet

class SomeEnvelope(BaseEnvelope):

    def parse(self, data: Optional[Union[Dict[str, Any], Any]], model: Type[Model]) -> Optional[Model]:

        parsed_env = APIGatewayProxyEvent(data)
        data = dict(
            headers=parsed_env.headers or {},
            http_method=parsed_env.http_method,
            path=parsed_env.path,
            path_parameters=parsed_env.path_parameters or {},
            query_parameters=parsed_env.query_string_parameters or {},
            body=json.loads(parsed_env.body) if parsed_env.body else None,
        )
        return self._parse(data=data, model=model)

Possible Solution

update DictWrapper into receiving Optional[Union[Dict[str, Any], Any]]

[heitorlessa]

hey @heitorlessa, just tested with the latest version 1.25.7 and I’m still getting the same error.

I’ve checked ant the problem seems to be on the __ini__ of DictWrapper.

APIGatewayProxyEvent --> BaseProxyEvent --> DictWrapper

This is DictWrapper’s __init__ on latest version:

def __init__(self, data: Dict[str, Any]): self._data = data

Let’s take a step back: what are you trying to achieve? Mypy and the types are correct, as you’re accidentally using the incorrect class - APIGatewayProxyEvent instead of APIGatewayProxyEventModel which is a Pydantic model in itself.

from aws_lambda_powertools.utilities.parser.models import APIGatewayProxyEventModel
# Or if using HTTP API with v2 payload
# from aws_lambda_powertools.utilities.parser.models import APIGatewayProxyEventV2Model

Understanding what you’re after will help us provide a more accurate solution.

Look forward to hearing from you 😃

[michaelbrewer]

@heitorlessa @efrquerido - but APIGatewayProxyEvent (aws_lambda_powertools/utilities/data_classes/api_gateway_proxy_event.py) was built to except the original raw dict event and not the Pydantic version.

If you are using Pydantic, then why not stick to ApiGatewayEnvelope (aws_lambda_powertools/utilities/parser/envelopes/apigw.py), but if you still want both, then maybe convert data to a dict?