Fromager

Fromager helps you format your codebase by enforcing a common configuration (ocamlformat version, files and directories to ignore).

Note that fromager actually doesn't add much besides perhaps a better error message or a nicer configuration format (toml) than ocamlformat. For this reason, I give indications on how to do the same things with .ocamlformat in this README.

Installation & Usage

If you have Opam, the package manager of OCaml, simply do:

$ opam install fromager
$ fromager

It's that simple! You don't even need an .ocamlformat file.

Configuring Fromager

By default, fromager ignores any directory starting with an underscore (e.g. _opam) or with a dot (e.g. .git).

You can optionally create a fromage.toml file at the root of your project:

[config]
ocamlformat_version = "0.18.0"
ignored_files = []
ignored_dirs = [ "./some", "./ignored/directories" ]

By design, you can't tweak ocamlformat as it is discouraged.

To do this with ocamlformat directly:

• create an .ocamlformat file with version=0.18.0 as content
• create an .ocamlformat-ignore file with files or folders you want to ignore

Enforce formatting in CI by adding a Fromager Github action

name: Run Fromager

on:
  [pull_request]

jobs:
  run_fromager:
    strategy:
      fail-fast: false
      matrix:
        os:
          - macos-latest
          - ubuntu-latest
        ocaml-version:
          - 4.07.1

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

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

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

      - name: Build
        run: |
          eval $(opam env)
          opam pin add . -y

      - name: Format
        run: |
          eval $(opam env)
          opam install fromager
          fromager
          git diff --exit-code

to do this with ocamlformat, replace the format step with:

-name: Format
run: |
  eval $(opam env)
  opam install ocamlformat
  dune build @fmt
  dune promote
  git diff --exit-code