MoonBit protobuf generator

This is the protobuf compiler for MoonBit, consisting of the compiler plugin written in Go and the runtime library.

The compiler and the runtime library are not published yet. To use this protobuf generator:

1. Clone this repository
2. Build the compiler plugin with moon build -C cli
3. Generate the MoonBit output. You can either add the compiled plugin to your PATH, or specify it with the --plugin option:
   • Add to PATH: PATH=".:$PATH" protoc --mbt_out=. --mbt_opt=paths=source_relative,project_name=gen-proto3 src/test/reader/proto3.proto
   • Or use --plugin: protoc --plugin=protoc-gen-mbt=protoc-gen-mbt.exe --mbt_out=. --mbt_opt=paths=source_relative,project_name=gen-proto3 src/test/reader/proto3.proto Note: project_name must match the output directory name (e.g., gen-proto3), and the directory must exist.
4. Use the generated MoonBit file given that it imports the runtime library with the alias lib.

This will be simplified in the future development.

Known Issues

• Deprecated group is not supported
• Extensions and custom options are ignored

Supported

See spec

Developing

moon build -C cli
mkdir gen-proto3
cp cli/target/native/release/build/protoc-gen-mbt.exe .
# Project name must match the directory name
protoc --plugin=protoc-gen-mbt=protoc-gen-mbt.exe --mbt_out=. --mbt_opt=paths=source_relative,project_name=gen-proto3 test/reader/proto3.proto

The generated MoonBit file (e.g., proto3_pb.mbt) will be placed in the specified output directory (e.g., gen-proto3).

Arguments

You can pass project parameters using --mbt_opt, separated by commas:

Name	Type	Description	Default Value
json	bool	Generate additional JSON serialization code	true
derive	string	Comma-separated list of derive traits for generated types (Show, Eq, Hash, Compare, Arbitrary)	Show,Eq
async	bool	Generate async read/write code	true
username	string	Username to be used in moon.mod.json	username
project_name	string	Project name to be used in moon.mod.json & moon.pkg.json	protoc-gen-mbt

Example usage:

protoc --plugin=protoc-gen-mbt=protoc-gen-mbt.exe --mbt_out=. --mbt_opt=json=true,derive=Show,Eq,Hash,username=yourname,project_name=yourproject input.proto

Project Structure

• cli/ - Protocol Buffer compiler plugin that generates MoonBit code from .proto files
• lib/ - MoonBit protobuf runtime library with serialization/deserialization support
• plugin/ - Generated MoonBit code from the protoc plugin interface definition
• test/ - Integration and snapshot tests
• doc/ - Project documentation (see spec.md for protobuf to MoonBit type mappings)
• scripts/ - Development and testing scripts

Development Scripts

Key scripts in the scripts/ directory:

snapshot_test.py

Tests code generation by comparing output with snapshots:

# Run snapshot tests
python3 scripts/snapshot_test.py

# Update snapshots after intentional changes
python3 scripts/snapshot_test.py --update

reader_test.py

Tests protobuf reader functionality:

python3 scripts/reader_test.py

generate_plugin.py

Regenerates plugin code from plugin.proto:

python3 scripts/generate_plugin.py

Other scripts (common.py, workflow.py) provide shared utilities for the above tools.