grpc-dump prints warning if message definition contains a map

[shinderuk]

WARN[0075] Failed to search for unknown fields in message =proto_decoder error="failed to enrich decode descriptor: unknown nested field type map[interface {}]interface {}"

Nevertheless map is dumped correctly.

Steps to reproduce:

1. Start greeter_server

$ ~/go/bin/greeter_server
...

2. Download helloworld.proto to proto/helloworld/helloworld.proto
3. Edit helloworld.proto and add a map field to HelloRequest:

message HelloRequest {
  string name = 1;
  map<string, string> foo = 2;
}

4. Start grpc-dump:

$ ~/go/bin/grpc-dump -port 8980 -destination localhost:50051 -proto_roots proto
...

5. Call SayHello with grpc_cli, first without, then with a map:

$ grpc_cli -remotedb=false -proto_path proto -protofiles helloworld/helloworld.proto \
    call localhost:8980 helloworld.Greeter/SayHello 'name:"world"'
...
$ grpc_cli -remotedb=false -proto_path proto -protofiles helloworld/helloworld.proto \
    call localhost:8980 helloworld.Greeter/SayHello 'name:"world" foo{key:"abc" value:"123"}'
...

6. grpc-dump prints warnings, but dumps everything correctly:

WARN[0003] Failed to search for unknown fields in message  =proto_decoder error="failed to enrich decode descriptor: unknown nested field type map[interface {}]interface {}"
{"service":"helloworld.Greeter","method":"SayHello","messages":[{"message_origin":"client","raw_message":"CgV3b3JsZA==","message":{"name":"world"},"timestamp":"2020-03-31T23:47:27.013997+03:00"},{"message_origin":"server","raw_message":"CgtIZWxsbyB3b3JsZA==","message":{"message":"Hello world"},"timestamp":"2020-03-31T23:47:27.014589+03:00"}],"metadata":{":authority":["localhost:8980"],"accept-encoding":["identity,gzip"],"content-type":["application/grpc"],"grpc-accept-encoding":["identity,deflate,gzip"],"user-agent":["grpc-c++/1.19.1 grpc-c/7.0.0 (osx; chttp2; gold)"],"via":["HTTP/2.0 127.0.0.1:8980"]},"metadata_response_headers":{"content-type":["application/grpc"]},"metadata_response_trailers":{}}
WARN[0075] Failed to search for unknown fields in message  =proto_decoder error="failed to enrich decode descriptor: unknown nested field type map[interface {}]interface {}"
{"service":"helloworld.Greeter","method":"SayHello","messages":[{"message_origin":"client","raw_message":"CgV3b3JsZBIKCgNhYmMSAzEyMw==","message":{"name":"world","foo":{"abc":"123"}},"timestamp":"2020-03-31T23:48:38.287028+03:00"},{"message_origin":"server","raw_message":"CgtIZWxsbyB3b3JsZA==","message":{"message":"Hello world"},"timestamp":"2020-03-31T23:48:38.28725+03:00"}],"metadata":{":authority":["localhost:8980"],"accept-encoding":["identity,gzip"],"content-type":["application/grpc"],"grpc-accept-encoding":["identity,deflate,gzip"],"user-agent":["grpc-c++/1.19.1 grpc-c/7.0.0 (osx; chttp2; gold)"],"via":["HTTP/2.0 127.0.0.1:8980"]},"metadata_response_headers":{"content-type":["application/grpc"]},"metadata_response_trailers":{}}

Workaround

In proto-files for grpc-dump replace map with repeated MapEntry field.
See: https://developers.google.com/protocol-buffers/docs/proto3#backwards-compatibility