AsyncServerInterceptor fails when non-existent service is invoked

[anuraaga]

What versions of the following are you using?

• python: 3.11
• grpc-interceptor: 0.15.3
• grpcio: 1.59.2
• protobuf: 4.24.4

What operating system (Linux, Windows,...) and version?

Mac

What did you do?

Define an AsyncServerInterceptor and query the server with grpcurl.

What did you expect to see?

Service is executed

What did you see instead?

AttributeError: 'NoneType' object has no attribute 'unary_unary'

Anything else we should know about your project / environment?

This happens because next_handler is None here if the requested service doesn't exist

https://github.com/d5h-foss/grpc-interceptor/blob/master/src/grpc_interceptor/server.py#L123

This effectively makes it not possible to use grpcurl which first queries with non-alpha reflection API before falling back to alpha one if it's not implemented. But the internal server error is not handled with that fallback it seems.

[metasyn]

So interesting - I just found this today - also from using grpcurl. I was able to fix it I think by adding:

if next_handler is None:
    return

right here: https://github.com/d5h-foss/grpc-interceptor/blob/master/src/grpc_interceptor/server.py#L123

Which is what the non-async one does here:
https://github.com/d5h-foss/grpc-interceptor/blob/master/src/grpc_interceptor/server.py#L55-L57

[dan-hipschman]

Good find, thank you! I've been busy with work but will get to this when I have time. Or happy to review a PR if you'd like to take a stab at it.

[anuraaga]

Thanks @dan-hipschman @metasyn I have sent #48 to fix, it was nice seeing there was already a test that just needed to be parameterized

[d5h]

Thanks again for the fix! The release is out now.