Set up OCaml

Set up an OCaml and opam environment and add to PATH.

Usage

If you are new, this section is worth reading.

How to specify the version

There is a point that is particularly easy to misunderstand. It's where you specify the version of the action itself.

- name: Use OCaml ${{ matrix.ocaml-version }}
  uses: avsm/setup-ocaml@v1
  #                     ^^^
  with:
    ocaml-version: ${{ matrix.ocaml-version }}

We recommend that you include the version of the action. We adhere to semantic versioning, it's safe to use the major version (v1) in your workflow. If you use the master branch, this could break your workflow when we publish a breaking update and increase the major version.

steps:
  # Reference the major version of a release (most recommended)
  - uses: avsm/setup-ocaml@v1
  # Reference a specific commit (most strict)
  - uses: avsm/setup-ocaml@ab6ba4d
  # Reference a semver version of a release (not recommended)
  - uses: avsm/setup-ocaml@v1.0.1
  # Reference a branch (most dangerous)
  - uses: avsm/setup-ocaml@master

Example workflow

See the Hello World OCaml Action that uses Dune and opam to build a simple library.

name: Main workflow

on:
  - push
  - pull_request

jobs:
  build:
    strategy:
      fail-fast: false
      matrix:
        os:
          - macos-latest
          - ubuntu-latest
          - windows-latest
        ocaml-version:
          - 4.10.0
          - 4.09.1
          - 4.08.1

    runs-on: ${{ matrix.os }}

    steps:
      - name: Checkout code
        uses: actions/checkout@v2

      - name: Use OCaml ${{ matrix.ocaml-version }}
        uses: avsm/setup-ocaml@v1
        with:
          ocaml-version: ${{ matrix.ocaml-version }}

      - run: opam pin add hello.dev . --no-action

      - run: opam depext hello --yes --with-doc --with-test

      - run: opam install . --deps-only --with-doc --with-test

      - run: opam exec -- dune build

      - run: opam exec -- dune runtest

What is the difference between opam dependencies and depext dependencies?

• opam dependencies: opam packages installed by opam install.
• depext dependencies: System packages installed by apt install, yum install, brew install, etc.

For example, the opam package called ocurl requires libcurl4-gnutls-dev on the Ubuntu VM, and depext handles the distribution-specific installation of opam packages' external dependencies for such opam packages.

Inputs

• ocaml-version: the full version of the OCaml compiler (default 4.08.1)

Action

The action does the following:

• Ubuntu: Installs the latest opam with sandboxing active
• macOS: Installs the latest opam from Homebrew with sandboxing active
• Windows: Installs Cygwin and the fdopen fork with mingw64c

The repository is initialised to the default one, and then the following plugins are installed:

• opam-depext

The opam binary is added to the PATH for subsequent actions, so that executing opam commands will just work after that.

Roadmap

This action aims to provide an OS-neutral interface to opam, and so will not add features that only work on one operating system. It will also track the latest stable release of opam.

Discussions: https://discuss.ocaml.org/t/github-actions-for-ocaml-opam-now-available/4745