Description
Runtime:
Python (but could apply to all languages that support decorators and lack existing libraries for event source data classes)
Is your feature request related to a problem? Please describe
Originally raises in the following issue: aws-powertools/powertools-lambda-python#434
Constructing a data class from an existing event could be cleaner, and tools like MyPy would complain about change the type of event
def lambda_handler(event: Dict[str, Any], context: LambdaContext) -> Dict[str, Any]:
event: APIGatewayProxyEventV2 = APIGatewayProxyEventV2(event)
...and the more version would mean an floating event variable:
```python
def lambda_handler(_event: Dict[str, Any], context: LambdaContext) -> Dict[str, Any]:
event = APIGatewayProxyEventV2(_event)
...Describe the solution you'd like
Creating a thin decorator like event_source which just constructors an instance of the passed in class type would fix this.
@event_source(data_class=APIGatewayProxyEventV2)
def lambda_handler(event: APIGatewayProxyEventV2, context: LambdaContext) -> Dict[str, Any]:
...Describe alternatives you've considered
N/A
If you provide guidance, is this something you'd like to contribute?
Implementation see: aws-powertools/powertools-lambda-python#442
Additional context
Note, to make this work in combination with the idempotent decorator we should allow for the generation of the idempotent key when combined with the @event_source decorator, otherwise there will be a type error when trying to generate the json. Example code which would raise a TypeError:
persistence_layer = DynamoDBPersistenceLayer(table_name="IdempotencyTable")
@event_source(data_class=APIGatewayProxyEventV2)
@idempotent(persistence_store=persistence_layer)
def lambda_handler(event: APIGatewayProxyEventV2, context):
assert isinstance(event, APIGatewayProxyEventV2)
...Fortunately this would be a simple fix:
if hasattr(data, "raw_event"):
data = data.raw_event
hashed_data = self.hash_function(json.dumps(data, cls=Encoder).encode())