python-betterproto Expose request metadata in the generated ```ServiceBase```

service Echo {
  rpc Echo(EchoRequest) returns (EchoResponse);
  // rpc EchoStream(EchoRequest) returns (stream EchoStreamResponse);
}

The generated servicer code generates the code but does not expose the request metadata as a parameter.

class EchoService(EchoBase):
    async def echo(self, value: str, extra_times: int) -> "EchoResponse":
        return value

    async def echo_stream(
        self, value: str, extra_times: int
    ) -> AsyncIterator["EchoStreamResponse"]:
        for _ in range(extra_times):
            yield value

The request metadata is really important since it works like headers in rest-api requests, so this is where a client could add authentication tokens, and also where other metadata could be injected by interceptors for instance.

May 14 '21 08:05 bettdouglas

I have a PR for this: #234 Feedback welcome.

May 19 '21 00:05 iamnoah

@iamnoah I've trying generating the echo service, using the example above gives this error

python -m grpc_tools.protoc -I . --python_betterproto_out=lib echo.proto

gives this exception

--python_betterproto_out: protoc-gen-python_betterproto: Plugin failed with status code 1.

I am on python 3.8 and environment variables are

betterproto @ git+https://github.com/hack-edu/python-betterproto.git@02e41afd09f0050a10fea764b15279b82cdd6e6b
grpcio==1.37.1
grpcio-tools==1.37.1
grpclib==0.4.1
h2==4.0.0
hpack==4.0.0
hyperframe==6.0.1
multidict==5.1.0
protobuf==3.17.0
python-dateutil==2.8.1
six==1.16.0

which i installed via pip install git+https://github.com/hack-edu/python-betterproto.git

May 19 '21 11:05 bettdouglas

@bettdouglas try pip install git+https://github.com/hack-edu/python-betterproto.git@with-stream-hooks black jinja2

My PR is from a branch, it looks like you installed master, which is unchanged.

Also, installing the plugin from the repo doesn't pickup the compiler dependencies:

> protoc-gen-python_betterproto
Unable to import `black` from betterproto plugin! Please ensure that you've installed betterproto as `pip install "betterproto[compiler]"` so that compiler dependencies are included.

Which is why I added black and jinja2.

May 20 '21 03:05 iamnoah

Are there any other suggestions on this issue? I forked betterproto and did something similar to @iamnoah's solution, but if there is a better practice suggested by the community, I'd love to learn about it.

Thanks all!