[Python] typing for `bytes` in typespec

[msyyc]

According to https://typespec.io/docs/getting-started/typespec-for-openapi-dev/, openapi {"type": string; "format": binary} equals to typespec bytes

However, python emitter emit the former to BinaryType whose typing is IO while the latter to ByteArraySchema whose typing is bytes.

Context

the issue is reported by @catalinaperalta who is helping migrate loadtesting to typespec.

• loadtesting swagger: https://github.com/Azure/azure-rest-api-specs/blob/3e27c70e7c02c07b458bc0e94716c3d82d3fdd19/specification/loadtestservice/data-plane/Microsoft.LoadTestService/stable/2022-11-01/loadtestservice.json#L291-L297
• loadtesting typespec: https://github.com/Azure/azure-rest-api-specs/blob/ab2a9e7b3df919d5195c98fc539e6257e5f27995/specification/loadtestservice/LoadTestService/routes.tsp#L70-L99

[msyyc]

To keep backward compatibility for migration, maybe we could add overload BinaryType for ByteArraySchema.

[catalinaperalta]

@msyyc so in this case you suggest that the team patches the method in patch.py for python?

[msyyc]

@msyyc so in this case you suggest that the team patches the method in patch.py for python?

We are still in discussion and I update you with final decision after tomorrow. Thanks!

[msyyc]

Update: @catalinaperalta, python emitter will add overload with IO for it to keep compatibility and the SDK API will look like:

@overlaod def op(body: IO, ...): ...

@overload def op(body: bytes, ...): ...

def op(body: Union[IO, bytes], ...): ...

If python emitter can't catch up with service team's ETA, they could patch if for now.

[catalinaperalta]

Thanks for the update @msyyc! Do you have an ETA for when this will be checked in?

[msyyc]

Since typespec is going to GA before end of March, language emitters including python emitter are busy in other necessary items for GA. So I am not sure about whether we have spare time to fix it for now. I will keep track and update for this issue.