Python Code Generator bug

[abaldeva]

What version of gRPC and what language are you using?

1.4.2 - python

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

Windows 10.

What did you do?

Invoked following command line
E:\work\experimental\grpc-example\bin\protoc.exe --proto_path=. --proto_path=E:\work\experimental\protobuf\3.3.2/src --grpc_out=E:\work\experimental\grpc-example\build\pc64\grpc-example\flattened/gen/python --plugin=protoc-gen-grpc=E:\work\experimental\grpc-example/bin/grpc_python_plugin.exe component\greeter\greeterslave_grpcservice.proto

What did you expect to see?

Generate python service code

What did you see instead?

Error - component/greeter/greeterslave_grpcservice_pb2.py: Tried to insert into file that doesn't exist.

Note: The error goes away if I add
--python_out=E:\work\experimental\grpc-example\build\pc64\grpc-example\flattened/gen/python to the above command line.

I call this a bug because none of the other languages (I tested C++, C#, Ruby, JS, PHP) need --python_out arg when running grpc code generator plugin and I found no documentation reference that calls python as an exception.

Thanks.

[nathanielmanistaatgoogle]

In our upcoming 1.7 release we've changed the code generator behavior to by default no longer insert into the _pb2.py file assumed to be present and available. In the meantime it sounds like the behavior you want is what is currently (pre-1.7) available using the (not-exactly-accurately-named) grpc_2_0 code generator flag. Take a look at this change to see the default behavior flip and this test to get a sense of how the code generator works in each case.

[abaldeva]

Okay, I'll try it out with 1.7. Just one thing I'd like to add. The _pb2.py files were indeed present in the problematic case as I was running a 2-step code generation (first for protobuf and second for grpc).

Thanks.

[nathanielmanistaatgoogle]

Regarding "The _pb2.py files were indeed present in the problematic case as I was running a 2-step code generation (first for protobuf and second for grpc)": I think that's expected, and counterintuitive and unhelpful, which is why we're changing the default to the more sensible behavior.