Maintenance: Revisit return types of `BaseProvider`

[dreamorosi]

Summary

BaseProvider was the first base class implemented for the new Parameters utility.

At the time, it was not yet known what each AWS SDK provider would return. For instance DynamoDBProvider might return different types than SSMProvider, so the types in BaseProvider have been intentionally left generic.

This issue serves to track the task that will have to be carried out after all providers have been implemented.

Why is this needed?

To enforce strong typing to the values returned by the utility, whenever possible.

Which area does this relate to?

Parameters

Solution

No response

Acknowledgment

• This request meets Lambda Powertools Tenets
• Should this be considered in other Lambda Powertools languages? i.e. Python, Java

[shdq]

AppConfig API returns Uint8Array, and the python implementation of the AppConfig provider implicitly converts it to a string. I did the same for now, but we have the transformValue function in the BaseProvider, which I think should do that. Correct me if I'm wrong – the result for the end user is to get raw data (binary) or transformed value to the end type, which is json for AppConfig.

EDIT: related PR from python powertools
I think it is just the wrong return type of the function def _get(self, name: str, **sdk_options) -> str: and it actually returns binary. I looked at docs of Configuration is StreamingBody which is response type and app config in python powertools return type is binary.

[dreamorosi]

My understanding is that, whenever the user specifies a transform when calling get, we should apply that transform and return the corresponding type. If no transform is specified, we can return as-is. If a transform has to be applied, then yes, it should be handled by the transformValue method from the BaseProvider, this applies to all providers.

I don't have 100% confidence on this, but I think your assessment is correct, and the return type on the Python's function might be wrong. Looking at the docs section for this method, the type annotation seems to be bytes:

# Retrieve a single secret
value: bytes = appconf_provider.get("my_conf")

I think it's worth opening an issue on the Python's repo so that it can be looked at be fixed. If instead we both understood it wrong, then they can clarify what's the expected behavior :)