Protocol Buffer Code Generation Skill

Generate C++ and Python code from Protocol Buffer (.proto) service and message definitions.

Prerequisites

• ORDER_PARSER_PROCESSOR_ROOT environment variable must be set
• protoc compiler must be installed
• For C++: grpc_cpp_plugin must be available
• For Python: grpc_tools.protoc must be installed

Instructions

1. Verify ORDER_PARSER_PROCESSOR_ROOT is set
2. Determine which language to generate (C++, Python, or both)
3. Generate gRPC service files first, then message files
4. Report success or any errors encountered

C++ Code Generation

Generate gRPC Services (C++)

protoc -I$ORDER_PARSER_PROCESSOR_ROOT/proto \
  --cpp_out=$ORDER_PARSER_PROCESSOR_ROOT/generated/cpp/messages/ \
  --grpc_out=$ORDER_PARSER_PROCESSOR_ROOT/generated/cpp/ \
  --plugin=protoc-gen-grpc=`which grpc_cpp_plugin` \
  $(find $ORDER_PARSER_PROCESSOR_ROOT/proto/services/ -iname "*.proto")

Note: The --cpp_out is in messages/ directory while --grpc_out is in root cpp/ - this is intentional and works correctly.

Generate Protobuf Messages (C++)

protoc -I$ORDER_PARSER_PROCESSOR_ROOT/proto/messages \
  --cpp_out=$ORDER_PARSER_PROCESSOR_ROOT/generated/cpp/messages/ \
  $(find $ORDER_PARSER_PROCESSOR_ROOT/proto/messages/ -iname "*.proto")

Python Code Generation

Generate gRPC Services (Python)

python3 -m grpc_tools.protoc \
  --proto_path=$ORDER_PARSER_PROCESSOR_ROOT/proto \
  --python_out=$ORDER_PARSER_PROCESSOR_ROOT/generated/python/ \
  --pyi_out=$ORDER_PARSER_PROCESSOR_ROOT/generated/python/ \
  --grpc_python_out=$ORDER_PARSER_PROCESSOR_ROOT/generated/python/ \
  $(find $ORDER_PARSER_PROCESSOR_ROOT/proto/services/ -iname "*.proto")

Generate Protobuf Messages (Python)

python3 -m grpc_tools.protoc \
  --proto_path=$ORDER_PARSER_PROCESSOR_ROOT/proto \
  --python_out=$ORDER_PARSER_PROCESSOR_ROOT/generated/python/ \
  $(find $ORDER_PARSER_PROCESSOR_ROOT/proto/messages/ -iname "*.proto")

Generated File Locations

C++ Generated Files

• Services: generated/cpp/services/*.pb.cc and *.pb.h
• Messages: generated/cpp/messages/*.pb.cc and *.pb.h
• gRPC stubs: generated/cpp/services/*.grpc.pb.cc and *.grpc.pb.h

Python Generated Files

• Services: generated/python/*_pb2.py and *_pb2_grpc.py
• Messages: generated/python/*_pb2.py
• Type stubs: generated/python/*_pb2.pyi

Common Commands

Generate All (C++ and Python)

Run all four commands in sequence:

1. C++ gRPC services
2. C++ protobuf messages
3. Python gRPC services
4. Python protobuf messages

Generate Only C++

Run only the two C++ commands

Generate Only Python

Run only the two Python commands

Proto File Organization

• Services: proto/services/*.proto - gRPC service definitions
• Messages: proto/messages/*.proto - Message structure definitions

Common Issues

• ORDER_PARSER_PROCESSOR_ROOT not set: Export it in your shell profile
• protoc not found: Install Protocol Buffers compiler
• grpc_cpp_plugin not found: Install gRPC C++ plugin
• grpc_tools not found: Install Python package: pip install grpcio-tools
• Import errors in proto files: Check that proto paths are correct and imports use relative paths

Important Notes

• Order matters: Generate services before messages (services may depend on messages)
• C++ quirk: The --cpp_out for services goes to messages/ but --grpc_out goes to root cpp/ - this is correct
• Regenerate after proto changes: Always regenerate when modifying .proto files
• CMake integration:
  • CMake does NOT handle gRPC proto file generation automatically
  • CMake does handle ANTLR .g4 file generation automatically
  • For proto files, use this skill to manually generate code before building

Workflow

1. Modify .proto files in proto/services/ or proto/messages/
2. Run this proto-gen skill to generate C++/Python code
3. Run the build skill to compile the project with updated generated code

Success Criteria

• All proto files compile without errors
• Generated files appear in generated/cpp/ and/or generated/python/
• No import errors or missing dependencies
• Generated code compiles successfully with the project