Contributing to Js_of_ocaml

Reporting issues

If you encounter a problem or have questions, please open a GitHub issue.

1. Check if your issue has already been reported
2. Include version information (ocamlc -version, js_of_ocaml --version)
3. Describe the expected and actual behavior
4. Provide a minimal reproducible example if possible

Development setup

Install dependencies

opam install --deps-only -t js_of_ocaml js_of_ocaml-lwt \
  js_of_ocaml-compiler js_of_ocaml-toplevel js_of_ocaml-ppx \
  js_of_ocaml-ppx_deriving_json js_of_ocaml-tyxml

Build

dune build @all

Pull requests

1. Discuss significant changes in an issue first
2. Fork the repository and create your branch from master
3. Write tests for new code
4. Ensure tests pass (make tests)
5. Update CHANGES.md with an entry describing your change

Code style

OCaml

Code is formatted with ocamlformat 0.29.0. Run before committing:

make fmt

JavaScript

JavaScript runtime files are formatted and linted with Biome:

make fmt-js
make lint-js

Documentation

Code examples in the .mli doc-comments and the manual/ pages are checked by the test suite: OCaml code blocks are type-checked against the real API, so examples cannot silently drift out of sync. An illustrative snippet that is not meant to compile can be marked to be only syntax-checked, or skipped entirely. See manual/examples-check/ for the markers.

Testing

# Run all tests
make tests

# Run WebAssembly tests
make tests-wasm

# Run a specific test directory
dune build @compiler/tests-jsoo/runtest
dune build @compiler/tests-ocaml/runtest-js
WASM_OF_OCAML=true dune build @compiler/tests-ocaml/runtest-wasm

# Run javascript parser tests
cd compiler/tests-js-parser
git clone https://github.com/tc39/test262.git test262
dune build @runtest-parser

# Update expected test output after intentional changes
dune promote

Test directories:

• compiler/tests-jsoo/ - JavaScript and WebAssembly tests
• compiler/tests-wasm_of_ocaml/ - JavaScript and WebAssembly tests
• compiler/tests-compiler/ - Compiler unit tests
• compiler/tests-ocaml/ - Tests from the OCaml compiler codebase
• compiler/tests-full/ - Full integration tests

Project structure

• compiler/ - Compiler implementation

  • lib/ - Core compiler library
  • lib-wasm/ - WebAssembly backend
  • bin-js_of_ocaml/ - js_of_ocaml entry point
  • bin-wasm_of_ocaml/ - wasm_of_ocaml entry point
• lib/ - Library packages (js_of_ocaml, lwt, tyxml bindings)
• ppx/ - PPX syntax extensions
• runtime/ - JavaScript and WebAssembly runtime files
• toplevel/ - Web-based OCaml toplevel
• examples/ - Example projects

See also

• GitHub repository
• Issue tracker
• Pull requests