Use case

Arguably, it might be easier for users if an empty Dict is returned instead of None for path_parameters in APIGatewayProxyEventV2, for example.

Instead of:

@event_source(data_class=APIGatewayProxyEventV2)
def lambda_handler(event: APIGatewayProxyEventV2, context) -> None:
    parameters = event.path_parameters or {}
    handle(parameters["id"])

it would become:

@event_source(data_class=APIGatewayProxyEventV2)
def lambda_handler(event: APIGatewayProxyEventV2, context) -> None:
    handle(event.path_parameters["id"])

Ultimately this approach could be followed for any return value that is either an Optional[Dict] or an Optional[List], returning an empty Dict or List instead of None in all cases:

• utilities/data_classes/api_gateway_proxy_event.py
  • APIGatewayEventAuthorizer
    • def claims(self) -> Dict[str, Any]
    • def scopes(self) -> List[str]
  • APIGatewayProxyEvent
    • def multi_value_query_string_parameters(self) -> Dict[str, List[str]]
    • def path_parameters(self) -> Dict[str, str]
    • def stage_variables(self) -> Dict[str, str]
  • RequestContextV2AuthorizerIam
    • def cognito_amr(self) -> List[str]
  • RequestContextV2Authorizer
    • def jwt_claim(self) -> Dict[str, Any]
    • def jwt_scopes(self) -> List[str]
    • def get_lambda(self) -> Dict[str, Any]
  • APIGatewayProxyEventV2
    • def cookies(self) -> List[str]
    • def path_parameters(self) -> Dict[str, str]
    • def stage_variables(self) -> Dict[str, str]

and so on...

The bottom line is: Does it matter for users to differentiate between None and an empty Dict or List for any Event Source Data Classe property? If it does for a particular one, it an exception to a rule or the rule?

This change would be backwards compatible with the previous code.

This approach was already implemented in only one place so far, as far as I could check:

• utilities/data_classes/common.py
  • BaseProxyEvent
    • def headers(self) -> Dict[str, str]

Solution/User Experience

Solution can be the same as for the headers in the BaseProxyEvent:

Alternative solutions

No response

Acknowledgment

• This feature request meets Powertools for AWS Lambda (Python) Tenets
• Should this be considered in other Powertools for AWS Lambda languages? i.e. Java, TypeScript, and .NET