Option -module does not work anymore for protoc-gen-grpc-gateway v2

[olivierlemasle]

🐛 Bug Report

The option module fails for protoc-gen-grpc-gateway v2.

Actually, the issue is that the module prefix is removed a first time by protoc-gen-grpc-gateway, then protogen attempts to remove the prefix a second time. It then fails with an error "generated file does not match prefix".

To Reproduce

1. Create a service file service.proto:

   syntax = "proto3";
   package your.service.v1;
   option go_package = "github.com/yourorg/yourproject/your/service/v1";
   message StringMessage {
     string value = 1;
   }
   service YourService {
     rpc Echo(StringMessage) returns (StringMessage) {}
   }

2. Generate protobuf definitions and go-grpc with option module=:

   protoc -I . \
      --go_out . \
      --go_opt module=github.com/yourorg/yourproject \
      --go-grpc_out . \
      --go-grpc_opt module=github.com/yourorg/yourproject \
      service.proto
   

   It generates definitions in the right directory:
   

3. Then, use protoc-gen-grpc-gateway with the same module= option:

   protoc -I . \
      --grpc-gateway_out . \
       --grpc-gateway_opt module=github.com/yourorg/yourproject \
      --grpc-gateway_opt logtostderr=true \
      --grpc-gateway_opt generate_unbound_methods=true \
      service.proto
   

   It fails with:

   --grpc-gateway_out: your/service/v1/service.pb.gw.go: generated file does not match prefix "github.com/yourorg/yourproject"
   

Expected behavior

I'd expect the last command to generate your/service/v1/service_grpc.pb.go.

Actual Behavior

See above

Your Environment

Fedora 32

➜  protoc --version
libprotoc 3.11.2
➜  protoc-gen-go-grpc -version
protoc-gen-go-grpc 1.0

[olivierlemasle]

Created PR #1754 to fix it