CONTRIBUTING.md

Contributing

Thanks for your help! Due to BuckleScript's nature, the contribution setup isn't all straightforward (though well documentated). If something isn't working, please file an issue or ping us in Discord!

Setup

Prerequisites:

• OPAM, the OCaml package manager
• NodeJS
• Make
• Go to run tests
• OS: Mac/Linux (BuckleScript works on Windows, but developing the repo in Windows isn't tested. Contribution welcome!)

# Use the correct opam switch for working on BuckleScript
opam update
opam switch 4.02.3+buckle-master
opam switch reinstall 4.02.3+buckle-master # do this if you get errors even from a clean compilation
opam install camlp4 cppo
eval `opam config env`

# Install dev-time npm dependencies
npm install

# Build BuckleScript's forked OCaml
cd vendor/ocaml
./configure -prefix `pwd`
make world.opt
make install

# Build BuckleScript itself
cd ../../
make
make install

# install this local bs globally
npm -g install .

Test on a Dummy Project

Go somewhere else and do this:

bsb -init foo -theme basic-reason
cd foo
npm run build

And whenever you modify a file in bucklescript, run this inside jscomp/:

make ../lib/bsc.exe && ./install-bsc.sh # build the compiler and make it available globally
make ../lib/bsb.exe && ./install-bsb.sh # build the build system and make it available globally

This will substitute the global bsc.exe & bsb.exe you just installed with the newly built one. Then run npm run build again in the dummy project and see the changes! The iteration cycle for testing these should be around 2 seconds =).

Troubleshooting

Did any of the above step not work?

• If you get compilation errors even from a supposedly clean compilation, you might have skipped the opam reinstall step above: opam switch reinstall 4.02.3+buckle-master
• Make sure you did eval `opam config env` In your CLI/bashrc/zshrc
• If the vendored ocaml changed between when you last iterated on the repo and now, you probably skipped the opam switch reinstall 4.02.3+buckle-master part. You'll have to do git clean -xdf and then restart with the build instructions. Careful, as git clean removes your uncommitted changes.
• If these fail too, make sure you do have the correct ocamlopt in your environment: which ocamlopt should show an opam path, not reason-cli path. If you see the latter, this means it overrode the global ocamlopt BuckleScript needed. In this case, either temporarily uninstall reason-cli or make sure your opam PATH overrides the reason-cli PATH (and not the other way around) in your bashrc/zshrc.

Whenever there are dependencies changes: do make depend in the specific directory, when available. This allows the makefile to track new dependencies.

Change the Vendored OCaml Compiler

This section is reserved for when you're making a change to the vendored ocaml compiler itself, in vendor/ocaml, and then testing on super-errors changes at the same time. If you're doing this for whatever reason, then the previous quick iteration workflow wouldn't work. Here's what you have to do after each change:

# at project root
cd jscomp
make force-snapshotml # make sure your changes are reflected in jscomp/bin/whole_compiler.ml
make -C ../lib bsc.exe && ./install-bsc.sh
make -C ../lib bsb.exe && ./install-bsb.sh

Contributing to the runtime

BuckleScript runtime implementation is currently a mix of OCaml and JavaScript. (jscomp/runtime directory). The JavaScript code is defined in the .ml file using the bs.raw syntax extension.

The goal is to implement the runtime purely in OCaml and you can help!

Each new PR should include appropriate testing.

Currently all tests are in jscomp/test directory and you should either add/modify a test file which covers the part of the compiler you modified.

• Add the filename in jscomp/test/test.mllib

• Add a test suite. The specification is in jscomp/test/mt.ml. For example some simple tests would be like:

  let suites : _ Mt.pair_suites =
     ["hey", (fun _ -> Eq(true, 3 > 2));
         "hi", (fun _ -> Neq(2,3));
         "hello", (fun _ -> Approx(3.0, 3.0));
         "throw", (fun _ -> ThrowAny(fun _ -> raise 3))
         ]
  let () = Mt.from_pair_suites __FILE__ suites

• Run the tests: mocha -R list jscomp/test/your_test_file.js To build libs, tests and run all tests: make libs && make -C jscomp/test all && npm test

• See the coverage: npm run cover

Contributing to Documentation

See https://github.com/BuckleScript/bucklescript.github.io

Contributing to the API Reference

The API reference is generated from doc comments in the source code. Here's a good example

Some tips and guidelines:

• The first sentence or line should be a very short summary. This is used in indexes and by tools like merlin.
• Ideally, every function should have at least one @example.
• Cross-reference another definition with {! identifier}. But use them sparingly, they’re a bit verbose (currently, at least).
• Wrap non-cross-referenced identifiers and other code in [ ... ].
• Escape {, }, [, ] and @ using \.
• It’s possible to use {%html ...} to generate custom html, but use this very, very sparingly.
• A number of "documentation tags" are provided that would be nice to use, but unfortunately they’re often not supported for `external`s. Which is of course most of the API.
• @param usually doesn’t work. Use {b <param>} ... instead
• @returns usually doesn’t work. Use {b returns} ... instead.
• Always use @deprecated when applicable.
• Always use @raise when applicable.
• Always provide a @see tag pointing to MDN for more information when available.

See Ocamldoc documentation for more details.

To generate the html, run make docs in jscomp/.

Html generation uses a custom generator located in odoc_gen/ and custom styles located in docs/api_static.

Make a Release

In release mode, assuming you have NodeJS and OCaml compiler with the right version installed:

node scripts/install.js

The build process will generate configure file with correct LIBDIR path, build all binaries and libraries and install the binaries into bin and lib files into lib.

First it will try to generate bin/config_whole_compiler.ml based on existing OCaml installation, if it fails, it will try to invoke buildocaml.sh to install an OCaml compiler from scratch, and retry again.

Publish Process

• Run make force-snapshotml
• Bump the compiler version

Code structure

The highlevel architecture is illustrated as below:

Lambda IR (OCaml compiler libs) ---+
  |   ^                            |
  |   |                     Lambda Passes (lam_* files)
  |   |             Optimization/inlining/dead code elimination
  |   \                            |
  |    \ --------------------------+
  |
  |  Self tail call elimination
  |  Constant folding + propagation
  V
JS IR (J.ml)  ---------------------+
  |   ^                            |
  |   |                     JS Passes (js_* files)
  |   |            Optimization/inlining/dead code elimination
  |   \                            |
  |    \  -------------------------+
  |
  |  Smart printer includes scope analysis
  |
  V
Javascript Code

Note that there is one design goal to keep in mind, never introduce any meaningless symbol unless real necessary, we do optimizations, however, it should also compile readable output code.

Contribution Licensing

Since BuckleScript is distributed under the terms of the LGPL Version 3, contributions that you make are licensed under the same terms. In order for us to be able to accept your contributions, we will need explicit confirmation from you that you are able and willing to provide them under these terms, and the mechanism we use to do this is called a Developer's Certificate of Origin DCO. This is very similar to the process used by the Linux(R) kernel, Samba, and many other major open source projects.

To participate under these terms, all that you must do is include a line like the following as the last line of the commit message for each commit in your contribution:

Signed-Off-By: Random J. Developer <random@developer.example.org>

You must use your real name (sorry, no pseudonyms, and no anonymous contributions).